Network Working Group M. Suignard, Ed. Internet-Draft Microsoft Corporation Intended status: Standards Track M. Davis Expires: June 23, 2007 Google A. Freytag ASMUS Inc. December 20, 2006 Preparation of Internationalized Strings (stringprep) draft-suignard-stringprep-bis-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on June 23, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document describes a framework for preparing Unicode text strings in order to increase the likelihood that string input and string comparison work in ways that make sense for typical users throughout the world. The stringprep protocol is useful for protocol identifier values, company and personal names, internationalized Suignard, et al. Expires June 23, 2007 [Page 1] Internet-Draft stringprep December 2006 domain names, and other text strings. This document does not specify how protocols should prepare text strings. Protocols must create profiles of stringprep in order to fully specify the processing options. This document updates RFC3454 (stringprep). Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 1.2. Using stringprep in protocols . . . . . . . . . . . . . . 7 2. Preparation Overview . . . . . . . . . . . . . . . . . . . . . 8 3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. Commonly mapped to nothing . . . . . . . . . . . . . . . . 10 3.2. Case folding . . . . . . . . . . . . . . . . . . . . . . . 11 4. Normalization . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1. Choice of normalization form . . . . . . . . . . . . . . . 13 4.2. Normalization version . . . . . . . . . . . . . . . . . . 13 5. Prohibited Output . . . . . . . . . . . . . . . . . . . . . . 14 5.1. Space characters . . . . . . . . . . . . . . . . . . . . . 15 5.2. Control characters . . . . . . . . . . . . . . . . . . . . 15 5.3. Private use . . . . . . . . . . . . . . . . . . . . . . . 15 5.4. Non-character code points . . . . . . . . . . . . . . . . 16 5.5. Surrogate codes . . . . . . . . . . . . . . . . . . . . . 16 5.6. Inappropriate for plain text . . . . . . . . . . . . . . . 16 5.7. Inappropriate for canonical representation . . . . . . . . 16 5.8. Change display properties or are deprecated . . . . . . . 16 5.9. Tagging characters . . . . . . . . . . . . . . . . . . . . 17 5.10. Hangul filler characters . . . . . . . . . . . . . . . . . 17 5.11. Non Identifier code points . . . . . . . . . . . . . . . . 17 5.12. Archaic characters . . . . . . . . . . . . . . . . . . . . 17 6. Combining Marks . . . . . . . . . . . . . . . . . . . . . . . 17 7. Bidirectional Characters . . . . . . . . . . . . . . . . . . . 18 8. Unassigned Code Points in Stringprep Profiles . . . . . . . . 20 8.1. Categories of code points . . . . . . . . . . . . . . . . 21 8.2. Reasons for the difference between stored strings and queries . . . . . . . . . . . . . . . . . . . . . . . . . 22 8.3. Versions of applications and stored strings . . . . . . . 23 9. Security Considerations . . . . . . . . . . . . . . . . . . . 24 9.1. Stringprep-specific security considerations . . . . . . . 24 9.2. Generic Unicode security considerations . . . . . . . . . 24 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 11. Compatibility between stringprep and stringprep-bis-00 . . . . 26 11.1. Compatibility using Unicode 3.2 code points . . . . . . . 27 11.2. Compatibility using the Identifier repertoire . . . . . . 27 Suignard, et al. Expires June 23, 2007 [Page 2] Internet-Draft stringprep December 2006 12. Considerations concerning IDN revision . . . . . . . . . . . . 28 12.1. Permitted Character Identification . . . . . . . . . . . . 29 12.2. Strinprep mapping based on Unicode properties . . . . . . 29 12.3. Normalization stability . . . . . . . . . . . . . . . . . 29 12.4. Case folding . . . . . . . . . . . . . . . . . . . . . . . 29 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30 Appendix A. Unicode repertoires . . . . . . . . . . . . . . . 30 Appendix A.1. Unassigned code points in Unicode 3.2 . . . . . . 30 Appendix A.2. Unassigned code points in Unicode 5.0 . . . . . . 30 Appendix A.3. Identifier repertoire . . . . . . . . . . . . . . 30 Appendix B. Mapping Tables . . . . . . . . . . . . . . . . . . 30 Appendix B.1. Commonly mapped to nothing . . . . . . . . . . . . 31 Appendix B.1.1. Commonly mapped to nothing with ZWJ/ZWNJ special processing . . . . . . . . . . . . . . . . 31 Appendix B.2. Mapping for case-folding used with NFKC . . . . . 32 Appendix B.3. Mapping for case-folding used with no normalization . . . . . . . . . . . . . . . . . . 32 Appendix B.4. Reverse mapping for compability mode . . . . . . . 33 Appendix C. Prohibition tables . . . . . . . . . . . . . . . . 33 Appendix C.1. Space characters . . . . . . . . . . . . . . . . . 33 Appendix C.1.1. ASCII space character . . . . . . . . . . . . . . 33 Appendix C.1.2. Non-ASCII space characters . . . . . . . . . . . . 33 Appendix C.1.3. Non-ASCII space characters - Compatibility mode . 33 Appendix C.2. Control characters . . . . . . . . . . . . . . . . 34 Appendix C.2.1. ASCII control character . . . . . . . . . . . . . 34 Appendix C.2.2. Non-ASCII control character . . . . . . . . . . . 34 Appendix C.2.3. Non-ASCII control character - Compatibility mode . . . . . . . . . . . . . . . . . . . . . . . 34 Appendix C.3. Private use . . . . . . . . . . . . . . . . . . . 35 Appendix C.4. Non-characters code points . . . . . . . . . . . . 35 Appendix C.5. Surrogate codes . . . . . . . . . . . . . . . . . 35 Appendix C.6. Inappropriate for plain text . . . . . . . . . . . 35 Appendix C.7. Inappropriate for canonical representation . . . . 35 Appendix C.8. Change display properties or are deprecated . . . 35 Appendix C.9. Tagging characters . . . . . . . . . . . . . . . . 35 Appendix C.10. Hangul filler characters . . . . . . . . . . . . . 36 Appendix C.11. Non identifier code points . . . . . . . . . . . . 36 Appendix C.12. Archaic scripts . . . . . . . . . . . . . . . . . 36 Appendix D. Bidirectional tables . . . . . . . . . . . . . . . 36 Appendix D.1. Characters with bidirectional property R or AL . . 36 Appendix D.2. Characters with bidirectional property L . . . . . 37 Appendix D.3. Characters with bidirectional property L . . . . . 37 Appendix E. Combining marks . . . . . . . . . . . . . . . . . 37 Appendix E.1. Combining mark table . . . . . . . . . . . . . . . 37 Appendix F. Normalization tables . . . . . . . . . . . . . . . 37 Appendix F.1. Pre normalization mapping . . . . . . . . . . . . 37 Appendix F.2. Characters added since the previous stringprep version . . . . . . . . . . . . . . . . . . . . . 38 Suignard, et al. Expires June 23, 2007 [Page 3] Internet-Draft stringprep December 2006 Appendix F.3. Character sequences reordering . . . . . . . . . . 39 Appendix G. Differences between stringprep and stringprep-bis-00 . . . . . . . . . . . . . . . . 40 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 46 14.1. Normative References . . . . . . . . . . . . . . . . . . . 46 14.2. Informative References . . . . . . . . . . . . . . . . . . 47 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 48 Intellectual Property and Copyright Statements . . . . . . . . . . 50 Suignard, et al. Expires June 23, 2007 [Page 4] Internet-Draft stringprep December 2006 1. Introduction Application programs can display text in many different ways. Similarly, a user can enter text into an application program in a myriad of fashions. Internationalized text (that is, text that is not restricted to the narrow set of US-ASCII characters) has many input and display behaviors that make it difficult to compare text in a consistent fashion. This document specifies a framework of processing rules for Unicode text. Other protocols can create profiles of these rules; these profiles will allow users to enter internationalized text strings in applications and have the highest chance of getting the content of the strings correct. In this case, "correct" means that if two different people enter what they think is the same string into two different input mechanisms, the strings should match on a character- by-character basis. This framework does not describe how data is transcoded from other character sets into Unicode. In systems that use non-Unicode character sets, the transcoding algorithm is a critical part of enabling secure and "correct" operation of internationalized text strings. In addition to helping string matching, profiles of stringprep can also exclude characters that should not normally appear in text that is used in the protocol. The profile can prevent such characters by changing the characters to be excluded to other characters, by removing those characters, or by causing an error if the characters would appear in the output. For example, because the backspace character can cause unpredictable display results, a profile can specify that a string containing a backspace character would cause an error. A profile of stringprep converts a single string of input characters to a string of output characters, or returns an error if the output string would contain a prohibited character. Stringprep profiles cannot both emit a string and return an error. Stringprep profiles cannot account for all of the variations that might occur or that a user might expect. In particular, a profile will not be able to account for choice of spellings in all languages for all scripts because the number of alternative spellings of words and phrases is immense. Users would probably expect all spelling equivalents to be made equivalent, or none of them to be. Examples of spelling equivalents include "theater" vs. "theatre", and "hemoglobin" vs. "hU+00E6moglobin" in American vs. British English. Other examples are simplified Chinese spellings of names (for Suignard, et al. Expires June 23, 2007 [Page 5] Internet-Draft stringprep December 2006 example,"") vs. the equivalent traditional Chinese spelling (for example, ""). Language-specific equivalences such as "Aepfel" vs. "U+00C4pfel", which are sometimes considered equivalent in German, may not be considered equivalent in other languages. This document intends to replace the current version of stringprep [RFC3454]. It covers issues that were raised in the context of Internationalized Domain Names in Applications [RFC3490]. Some of these issues are about bidirectional strings[IDNABidi], others about repertoire[IDNARepertoire], others in all aspects of stringprep [IDNABis]. Issues are addressed in relevant sections of this document. Much more than previous version of stringprep[RFC3454], this document uses Unicode character properties to group these characters in classes, instead of using enumerated lists of characters. Certain key Unicode properties are guaranteed to always be backward compatible. For the properties that may see modification, stability of this specification is provided by using exception lists. 1.1. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119[RFC2119]. Note: A glossary of terms used in the Unicode Standard [Unicode5.0] and ISO/IEC 10646 [ISO10646]can be found in [Glossary]. Information on the 10646/Unicode character encoding model can be found in [CharModel]. The character repertoires of the Unicode Standard and ISO/IEC 10646, and many other features such as the Bidirectional Algorithm and Normalizations are synchronized. Further references to the common set will be done using the Unicode versions. Only features that are unique to either standard will be referenced as such. Character names in this document use the notation for code points and names from the Unicode Standard. For example, the letter "a" may be represented as either "U+0061" or "LATIN SMALL LETTER A". In the lists of mappings and the prohibited characters, the "U+" is left off to make the lists easier to read. Sequences of characters may be represented using the UCS Sequence Identifiers or USI specified in ISO/IEC 10646 [ISO10646]. A USI has the form: Suignard, et al. Expires June 23, 2007 [Page 6] Internet-Draft stringprep December 2006 where the UIDi represents the short identifiers for code points -- most commonly the U+ notation mentioned above. The comments for character ranges are shown in square brackets (such as "[CONTROL CHARACTERS]") and do not come from the standards. 1.2. Using stringprep in protocols The stringprep protocol does not stand on its own; it has to be used by other protocols at precisely-defined places in those other protocols. For example, a protocol that has strings that come from the entire Unicode [Unicode5.0] character repertoire might specify that only strings that have been processed with a particular profile of stringprep are legal. Another example would be a protocol that does string comparison as a step in the protocol; that protocol might specify that such comparison is done only after processing the strings with a specific profile of stringprep. When two protocols that use different profiles of stringprep interoperate, there may be conflict about what characters are and are not allowed in the final string. Thus, protocol developers should strongly consider re-using existing profiles of stringprep. When developers wish to allow users as wide of a range of characters as possible in input text strings, they should, where possible, cause stringprep to convert characters from the input string to a canonical form instead of prohibiting them. Although it would be easy to use the stringprep process to "correct" perceived mis-features or bugs in the current character standards, stringprep profiles SHOULD NOT do so. A profile of stringprep can create tables different from those in the appendixes of this document, but it will be an exception when they do. The intention of stringprep is to define the tables and have the profiles of stringprep select among those defined tables. A profile of stringprep MUST include all of the following: o The intended applicability of the profile o The character repertoire that is the input and output to stringprep (which is Unicode 5.0 for this version of stringprep) o The mapping tables from this document used (as described in section 3) o Any additional mapping tables specific to the profile Suignard, et al. Expires June 23, 2007 [Page 7] Internet-Draft stringprep December 2006 o The Unicode normalization used, if any (as described in section 4) o The tables from this document of characters that are prohibited as output (as described in section 5) o The bidirectional string testing used, if any (as described in section 6) o Any additional characters that are prohibited as output specific to the profile Each profile MUST state the character repertoire on which the profile will operate. Appendix A lists the Unicode repertoire that can be selected. No repertoire is ever complete, and it is expected that characters will be added to the Unicode repertoire for the foreseeable future. Section 7 of this document describes how to handle characters that are assigned in later versions of the Unicode repertories. A Subsection of appendix A also references unassigned code points for the Unicode repertoire. This document is for Unicode version 5.0, and should not be considered to automatically apply to later Unicode versions. The IETF, through an explicit standards action, may update this document as appropriate to handle later Unicode versions. This document references the unassigned code points in the range 0 to 10FFFF for Unicode 5.0 in appendix A. It also references in the same appendix unassigned code points for Unicode 3.2 to allow profiles to emulate behavior specified by previous version of stringprep[RFC3454] Each profile of stringprep MUST be registered with IANA. The registration procedure is described in the IANA Considerations appendix; basically, the IESG must review each profile of stringprep. Protocol developers are strongly encouraged to look through the IANA profile registry when creating new profiles for stringprep, and to re-use logic from earlier profiles where possible in new profiles. In some cases, an existing profile can be reused by a different protocol. 2. Preparation Overview The steps for preparing strings are: 1. Map -- For each character in the input, check if it has a mapping and, if so, replace it with its mapping. This is described in section 3. Suignard, et al. Expires June 23, 2007 [Page 8] Internet-Draft stringprep December 2006 2. Normalize -- Possibly normalize the result of step 1 using Unicode normalization. This is described in section 4. 3. Prohibit -- Check for any characters that are not allowed in the output. If any are found, return an error. This is described in section 5. 4. Check combining marks -- Check for any starting combining marks. If such an occurence is found, return an error. This is described in section 6. 5. Check bidi -- Possibly check for right-to-left characters, and if any are found, make sure that the whole string satisfies the requirements for bidirectional strings. If the string does not satisfy the requirements for bidirectional strings, return an error. This is described in section 7. The above steps MUST be performed in the order given to comply with this specification. The mappings described in section 3, and the optional Unicode normalization described in section 4, can be one-to-none, one-to-one, one-to-many, many-to-one, or many-to-many. That is, some characters might be eliminated or replaced by more than one character, and the output of this step might be shorter or longer than the input. Because of this, the system using stringprep MUST be prepared to receive a longer or shorter string than the one input in the stringprep algorithm. A profile MAY elect to simplify the preparation by using a Unicode repertoire which is stable through the mapping and normalization processes and does not contain any prohibited characters. In such case the preparation steps become: 1. Map -- All characters map to themselves by definition. 2. Normalize -- If normalized output is required by the profile, this step is still required even if the repertoire is stable through normalization. There are several reasons for this (combining marks, Hangul syllables, etc...). 3. Prohibit -- No characters are prohibited by definition. 4. Check combining marks -- As specified above. 5. Check bidi -- As specificied above. Appendix A.3 describes such an Unicode repertoire named "Identifier Suignard, et al. Expires June 23, 2007 [Page 9] Internet-Draft stringprep December 2006 repertoire" which can be conveniently referenced by profiles used for identifiers. For convenience, this document references its own definition of the repertoire in A.3, but the intent is to track the developments made by [IDNARepertoire] or similar initiatives when they become finalized. 3. Mapping Each character in the input stream MUST be checked against a mapping table. The mapping table SHOULD come from this document, although the mapping table MAY be added to or altered by the profile. The mapping tables are subsections of appendix B. The lists in appendix B MUST be used by implementations of this specification. If there are any discrepancies between the lists in appendix B and subsections below, the lists in appendix B always takes precedence. For any individual character, the mapping table MAY specify that a character be mapped to nothing, or mapped to one other character, or mapped to a string of other characters. Mapped characters are not re-scanned during the mapping step. That is, if character A at position X is mapped to character B, character B which is now at position X is not checked against the mapping table. 3.1. Commonly mapped to nothing Some characters are commonly deleted from the input (that is, they are mapped to nothing) because their presence or absence in protocol identifiers should not typically make two strings different. The list is referenced in appendix B.1. Typically, U+200C ZERO WIDTH NON-JOINER (ZWNJ) and U+200D ZERO WIDTH JOINER (ZWJ) should not make two strings different and as such are part of the list referenced in appendix B.1. However, because in certain languages U+200C ZERO WIDTH NON-JOINER (ZWNJ) and U+200D ZERO WIDTH JOINER (ZWJ) may carry meaning, some profiles MAY want to adopt a special rule by preserving the ZWNJ or ZWJ in the following contexts: ZWNJ breaking a cursive connection in Arabic-- An Arabic Right- Joining character, followed by zero or more Transparent characters, followed by a ZWNJ, followed by zero or more Transparent characters, followed by a Left-Joining character. Suignard, et al. Expires June 23, 2007 [Page 10] Internet-Draft stringprep December 2006 ZWNJ used in a conjunct context-- A Letter, followed by zero or more Combining Marks, followed by a Virama, followed by a ZWNJ, followed by zero or more Combining Marks, followed by a Letter. ZWJ used in a conjunct context-- A Letter, followed by zero or more Combining Marks, followed by a Virama, followed by a ZWJ, followed by zero or more Combining Marks, followed by a Letter. These contexts imply that a single script is used within the expression, excluding the Combining Marks and Viramas which may use "Common" or "Inherited" script values. The character script value is determined by the "Scripts.txt" file in the Unicode Character Database[UCD]. The character properties "Right-Joining" (R), "Transparent" (T), and "Left-Joining" (L) are specified by the ArabicShaping.txt file in the Unicode Character Database[UCD]. The character property "Letter" is the union of all General Category values: "Lu", "Ll", "Lt", "Lm", and "Lo" specified in the UnicodeData.txt file in the Unicode Character Database[UCD]. The character property "Combining Mark" is the concatenation of all General Category values: "Mc", "Mn", and "Me" specified in the UnicodeData.txt file in the Unicode Character Database[UCD]. The character property "Virama" is determined by having the Canonical_Combining_Class value equal to 9. That class is specified in the UnicodeData.txt file in the Unicode Character Database[UCD]. The profiles that MAY want to process the ZWJ and ZWNJ according to these contexts while mapping the other characters to nothing MUST use the table and property referencing specified in appendix B.1.1. 3.2. Case folding If a profile is going to map characters for case-insensitive comparison, that profile SHOULD map using either appendix B.2 or appendix B.3. appendix B.2 is for profiles that also use Unicode normalization form KC, while appendix B.3 is for profiles that do not use Unicode normalization. The referenced tables map from uppercase to lowercase characters. Note that this could have been "change all lowercase characters into uppercase characters". However, the upper- to-lower folding was chosen because there is a tradition of using lowercase in current Internet applications and protocols. If a profile creates its own mapping tables for case folding, they Suignard, et al. Expires June 23, 2007 [Page 11] Internet-Draft stringprep December 2006 SHOULD be based on the Case Mappings specified by the Unicode Standard[Unicode5.0], and SHOULD map from uppercase characters to lowercase. The "CaseFolding.txt" file from the Unicode Character Database[UCD] SHOULD be used to prepare the mapping table. The profile SHOULD do full case mapping (that is, using statuses C and F). If the profile is using Unicode normalization form KC (as described in section 4 of this document), an additional property, FC_NFKC_Closure, is required. The values specified in the "DerivedNormalizationProps.txt" file in the Unicode Character Database[NormProps]provides the set of mappings that constitute the FC_NFKC_Closure list. Appendix B.3 references the CaseFolding.txt file associated with Unicode 5.0; appendix B.2 also references the CaseFolding.txt file from the Unicode Character Database[UCD], but augmented by the entries in the "DerivedNormalizationProps.txt" file[NormProps] with a FC_NFKC value. Authors of profiles of this document need to consider the effects of changing the mapping of any currently-assigned character when updating their profiles. Adding a new mapping for a currently- assigned character, or changing an existing mapping, could cause a variance between the behavior of systems that have been updated and systems that have not been updated. Appendix B.4 specifies a reverse mapping table for Unicode 3.2 characters which have a new case folding as a result of applying Unicode 5.0 case folding tables. Applying that mapping table after the previous mapping provides a result compatible with Unicode 3.2 case folding. 4. Normalization The output of the mapping step is optionally normalized using one of the Unicode normalization forms, as described in [UAX15]. A profile can specify one of three options for Unicode normalization: o no normalization o Unicode normalization with form C using the Normalization Process for Stable Strings (NPSS). This process adds further stability requirements on normalization. o Unicode normalization with form KC using the Normalization Process for Stable Strings (NPSS). This process add further stability Suignard, et al. Expires June 23, 2007 [Page 12] Internet-Draft stringprep December 2006 requirements on normalization. A profile MAY choose to do no normalization. However, such a profile can easily yield results that will be surprising to typical users, depending on the input mechanism they use. For example, some input mechanisms enter compatibility characters that look exactly like the underlying characters, but have different code points. Another example of where Unicode normalization helps create predictable results is with characters that have multiple combining diacritics: normalization orders those diacritics in a predictable fashion. On the other hand, Unicode normalization requires fairly large tables and somewhat complicated character reordering logic. The size and complexity should not be considered daunting except in the most restricted of environments, and needs to be weighed against the problems of user surprise from comparing un-normalized strings. Note that the tables used for normalization are not given in this document, but instead must be derived from the Unicode Character Database, as described in [UAX15] and [UCD]. 4.1. Choice of normalization form If a profile is going to use a Unicode normalization as one of the options mentioned above, it MUST use Unicode normalization form C or KC (NFC or NFKC). Form KC maps many "compatibility characters" to their equivalents. Some user interface systems make it possible to enter compatibility characters instead of the base equivalents. Thus, using form KC instead of form C will cause more strings that users would expect to match to actually match. For most cases involving string preparation in the context of identifier (such as domain names), the form KC is preferred. However, there are cases where the compatibility mapping provided by the form KC may not be desirable because it prevents full representation of some national character set and of some special purpose repertoire (for example the mathematical letters). In addition, NFC is the preferred normalization form for Internationalized Resource Identifiers (IRIs)[RFC3987]. For all these reasons, some profiles may use form C instead of form KC. Finally, because case folding is not closed under form KC, the case folding required in the stringprep mapping step is more complex when that normalization form is used. See section 3.2. 4.2. Normalization version A profile that specifies Unicode normalization SHOULD use the normalization in [UAX15] that is associated with the version of the Suignard, et al. Expires June 23, 2007 [Page 13] Internet-Draft stringprep December 2006 Unicode character set specified for the profile. However, because the normalization associated with Unicode 3.2 has some well known issues identified in [UAX15] (see its corrigendum section), it is recommended to use the version 5.0 of the normalization even for Unicode 3.2 repertoire. The composition process described in [UAX15] requires a fixed composition version of Unicode to ensure that strings normalized under one version of Unicode remain normalized under all future versions of Unicode. In addition, the NPSS required by stringprep insures that processing unassigned code points through the normalization returns an error. Despite best efforts, the Unicode normalization has seen changes that may introduce compatibility issues between this version of stringprep and older version[RFC3454] if not handled correctly. A profile MAY elect to emulate old behavior while still using the latest version of the Unicode normalization by following these steps prior to the normalization process: o Map the characters specified in appendix F.1. o Filter out characters that were not assigned by the previous version. Appendix F.2 lists characters added since Unicode 3.2 which should be filtered out. o Reorder the sequences listed in appendix F.3 as described in the same appendix. None of these steps are needed if the profile is only applicable to the Unicode 5.0 repertoire. 5. Prohibited Output Before the text can be emitted, it MUST be checked for prohibited code points. There are a variety of prohibited code points, as described in this section. A profile of this document MAY use all or some of the tables in appendix C. The stringprep process never emits both an error and a string. If an error is detected during the checking for prohibited code points, only an error is returned. Note that the subsections below describe how the tables in appendix C were formed. They are here for people who want to understand more, but they should be ignored by implementers. Implementations that use tables MUST map based on the tables themselves, not based on the Suignard, et al. Expires June 23, 2007 [Page 14] Internet-Draft stringprep December 2006 descriptions in this section of how the tables were created. The lists in appendix C MUST be used by implementations of this specification. If there are any discrepancies between the lists in appendix C and subsections below, the lists in appendix C always take precedence. Some code points listed in one section may also appear in other sections. It is important to note that a profile of this document MAY prohibit additional characters. Each subsection of this section has a matching subsection in appendix C. For example, the characters listed in section 5.1 are listed in appendix C.1. 5.1. Space characters Space characters can make accurate visual transcription of strings nearly impossible and could lead to user entry errors in many ways. Note that the list below is split into two tables in appendix C: Table C.1.1 contains the ASCII code points, while Table C.1.2 contains the non-ASCII code points. Most profiles of this document that want to prohibit space characters will want to include both tables. For compatibility with the previous version of stringprep, Table C.1.3 is an alternate to C.1.2 containing the non-ASCII code points with some characters removed or added. 5.2. Control characters Control characters (or characters with control function) cannot be seen and can cause unpredictable results when displayed. Note that the list below is split into two tables in appendix C: Table C.2.1 contains the ASCII code points, while Table C.2.2 contains the non- ASCII code points. Most profiles of this document that want to prohibit control characters will want to include both tables. For compatibility with the previous version of stringprep, Table C.2.3 is an alternate to C.2.2 containing the non-ASCII code points with some characters removed or added. 5.3. Private use Because private-use characters do not have defined meanings, they are likely to be prohibited. The private-use characters are specified in Suignard, et al. Expires June 23, 2007 [Page 15] Internet-Draft stringprep December 2006 appendix C.3. 5.4. Non-character code points Non-character code points are code points that have been allocated in Unicode but are not assigned to characters. They are private use code points not intended for interchange. They are described in appendix C.4. 5.5. Surrogate codes The surrogate code points are permanently reserved for use as surrogate code values in the UTF-16 encoding, will never be assigned to characters in the Unicode repertoire, and are therefore prohibited. They are described in appendix C.5. 5.6. Inappropriate for plain text The interlinear annotation characters U+FFF9-U+FFFB do not appear in regular text. Note that there are also control characters. (see 5.2) The Object Replacement character (U+FFFC) is a placeholder for an an otherwise unspecified object. The replacement character (U+FFFD) might be used when a string is displayed on a system with incomplete rendering capabilities. Based on these considerations, all these characters are likely to be prohibited. They are referenced in appendix C.6. 5.7. Inappropriate for canonical representation The ideographic description characters provide a mechanism for the standard interchange of text referencing unencoded ideographs. They cannot be used to represent an alternate formal encoding of an ideograph. Based on this, most profiles should exclude them. These characters are described in appendix C.7. 5.8. Change display properties or are deprecated These characters can cause changes in display or the order in which characters appear when rendered, or are deprecated in Unicode. These characters are described in appendix C.8. Some of these characters are also part of the Control character category. (see 5.2) Suignard, et al. Expires June 23, 2007 [Page 16] Internet-Draft stringprep December 2006 5.9. Tagging characters The tagging characters are format characters (General Category = "Cf"), included in the TAG code point range (E0000-E007F). Some profiles may want to treat them separately from control characters. These characters are described in appendix C.9. 5.10. Hangul filler characters The Hangul filler characters are letter characters (General Category = "Lo"), that stands for missing Jamos to make a well-formed Korean syllable. Most profiles may want to exclude them as they are used in context inappropriate for identifiers. These characters are described in appendix C.10. 5.11. Non Identifier code points Some profiles may want to further restrict their Unicode repertoire by removing all characters that should not be used in identifiers according to the Unicode UAX#31 Identifier and Pattern Syntax. These non identifier code points are determined by not having the XID_Continue property in the Unicode Character Database[UCD]. These characters are described in appendix C.11. This definition of non identifier code points includes all other categories of prohibited code points specified up to this point. 5.12. Archaic characters Some profiles may want to exclude characters which are rarely found or not all in modern use. This is determined by their script property. Appendix C.12 provides a list of these archaic scripts. 6. Combining Marks Combining mark is a special character class that typically combines with its possible preceding combining marks back to the first non combining character. See the Unicode Standard[Unicode5.0] for further details. In most contexts, it is undesirable to have a combining mark appear as the first character of a string as it may combine with a character preceding the string, therefore out of context. A profile MAY choose to exclude combining marks. However many scripts and writing systems requires them even for their most basic support. Therefore excluding the combining marks and ignoring the Suignard, et al. Expires June 23, 2007 [Page 17] Internet-Draft stringprep December 2006 requirement below is stringly discouraged. For the purpose of the requirement below, a "MCat" character is a character that has the Unicode General Category value of either Spacing Combining Mark (Mc), or Nonspacing Mark (Mn), or Enclosing Mark (Me) In any profile that includes these characters, the following requirement MUST be met: o A string must not start with a MCat character. The stringprep process never emits both an error and a string. If an error is detected during the checking of that requirement, only an error is returned. Table E.1 references all these combining marks. 7. Bidirectional Characters Most characters are displayed from left to right, but some are displayed from right to left. This feature of Unicode is called "bidirectional text", or "bidi" for short. The Unicode standard has an extensive discussion of how to reorder glyphs for display when dealing with bidirectional text such as Arabic or Hebrew. See [UAX9] for more information. In particular, all Unicode text is stored in logical order. A profile MAY choose to ignore bidirectional text. However, ignoring bidirectional text can cause display ambiguities. For example, it is quite easy to create two different strings with the same characters (but in different order) that are correctly displayed identically. Therefore, in order to avoid most problems with ambiguous bidirectional text display, profile creators should strongly consider including the bidirectional character handling described in this section in their profile. The stringprep process never emits both an error and a string. If an error is detected during the checking of bidirectional strings, only an error is returned. [Unicode5.0] defines several bidirectional categories; each character has one bidirectional category assigned to it. For the purposes of the requirements below, the following categories are specified: Suignard, et al. Expires June 23, 2007 [Page 18] Internet-Draft stringprep December 2006 RCat character It is a character that has Unicode bidirectional categories "R" or "AL". These are characters belonging to right to left scripts such as Hebrew, Arabic, Thaana, etc... LCat character It is a character that has Unicode bidirectional category "L". These are characters belonging to left to right script such as Latin, Greek, Cyrillic, etc... NSMCat It is a character that has Unicode bidirectional category "NSM". These are combining marks. Note that there are many characters which fall in neither of the above definitions; Latin digits (U+0030 through U+0039) are examples of this because they have bidirectional category "EN". In any profile that specifies bidirectional character handling, all three of the following requirements MUST be met: 1. The characters in section 5.8 MUST be prohibited. 2. If a string contains any RCat character, the string MUST NOT contain any LCat character. 3. If a string contains any RCat character, a RCat character MUST be the first character of the string, and a RCat character MUST be either the last character of the string or followed only by NSMCat characters. Note that requirement 3 prohibits strings such as ("aleph 1") but allows strings such as ("aleph 1 beh"), and ("Divehi in Thaana script ending with a NSMCat character). [UAX9] goes into great detail about the display order of strings that contain particular categories of characters in particular sequences. Table D.1 references the characters that belong to Unicode bidirectional categories "R" and "AL". Table D.2 references all the characters that belong to Unicode bidirectonal category "L". Table D.3 references all the characters that belong to Unicode category "NSM". These tables are derived from [Unicode5.0]. Compared to the previous version of stringprep[RFC3454], this version adds the NSMCat category which addresses the right to left issue described in section 2 and 3 of [IDNABidi] and section 9 of [IDNABis]. As recognized by the former document in section 5, addressing that problem creates a new backward compatibility issues in as much as previously invalid strings are now valid. However, in agreement with it, it is felt that it will be less harmful than Suignard, et al. Expires June 23, 2007 [Page 19] Internet-Draft stringprep December 2006 denying use of words commonly used in languages affected by that previous restriction. Note that the document [IDNABidi] also describes a confusable string issue in its section 4 which can better addressed by a repertoire restriction which is an IDNA generic issue covered elsewhere in stringprep. 8. Unassigned Code Points in Stringprep Profiles This section describes two different types of strings in typical protocols where internationalized strings are used: "stored strings" and "queries". Of course, different Internet protocols use strings very differently, so these terms cannot be used exactly in every protocol that needs to use stringprep. In general, "stored strings" are strings that are used in protocol identifiers and named entities, such as names in digital certificates and DNS domain name parts. "Queries" are strings that are used to match against strings that are stored identifiers, such as user-entered names for digital certificate authorities and DNS lookups. All code points not assigned in the character repertoire named in a stringprep profile are called "unassigned code points". Stored strings using the profile MUST NOT contain any unassigned code points. Queries for matching strings MAY contain unassigned code points. Note that this is the only part of this document where the requirements for queries differs from the requirements for stored strings. Using two different policies for where unassigned code points can appear removes the need for versioning in protocols that use stringprep profiles. This is very useful since it makes the overall processing simpler and does not impose a "protocol" to handle versioning. It is expected that the Unicode repertoire will be updated fairly frequently; at the time that this document is being written, it has happened approximately once a year. Each time a new version of a repertoire appears, a new version of a profile MAY be created. Some end users will want to use the new code points as soon as they are defined. The list of unassigned code points MUST be given in a profile, and that list MUST be used by implementations of the profile. The goal of the requirements in this section is to prevent comparisons between two strings that were both permitted to contain unassigned code points. When two strings X and Y are compared and string Y was prepared in a way that permits unassigned code points, a Suignard, et al. Expires June 23, 2007 [Page 20] Internet-Draft stringprep December 2006 negative result to the comparison is not definitive; it's possible that the strings don't match even though they would match if a more recent version of the profile were used for Y. However, if both X and Y were prepared in a way that permits unassigned code points, something worse can happen: even a positive result for the comparison is not definitive. It is possible that the strings do match even though they would not match if a more recent version of the profile were used (one that prohibits a code point appearing in both X and Y). Due to the way that versioning is handled in this section, stored strings that are embedded in structures that cannot be changed (such as the signed parts of digital certificates) MUST NOT contain any unassigned code points. 8.1. Categories of code points Each code point in a repertoire named by a profile of stringprep can be categorized by how it acts in the process described in earlier sections of this document: o AO -- Code points that can be in the output o MN -- Code points that cannot be in the output because they never appear as output from mapping or normalization o D -- Code points that cannot be in the output because they are disallowed in the prohibition step o U -- Unassigned code points A subsequent version of a profile that references a newer version of a repertoire with new code points will inherently have some code points move from category U to either D, MN, or AO. For backwards compatibility, the following rules are provided for a subsequent version of a profile concerning the other code points: o D code points MUST NOT move to another category. o AO and MN code points SHOULD NOT move to another category. Exceptions should be clearly documented in the new versions. Stored strings MUST NOT contain any code points outside of AO for the latest version of a profile. That is, they are forbidden to contain code points from the MN, D, or U categories. Applications creating queries MUST treat U code points as if they were AO when preparing the query to be entered in the process Suignard, et al. Expires June 23, 2007 [Page 21] Internet-Draft stringprep December 2006 described by a profile of stringprep. Those applications MAY optionally have a preprocessor that provide stricter checks: treating unassigned code points in the input as errors, or warning the user about the fact that the code point is unassigned in the version of a profile that the software is based on; such a choice is a local matter for the software. It should be noted that the code point categories described above are not the only way code point sequences are analyzed during the string preparation process. The 'check bidi' and 'check combining marks' steps use additional code point properties to determine the validity of an input string. Furthermore, the position of a code point within a string may also determine that validity. A subsequent version of a profile SHOULD minimize code point property changes and positional behavior that modify the result of these preparation steps. If such changes are made, they MUST be identified in the new version of the profile. In general, a profile should minimize its set of AO code points to what is strictly required for its usage. A subsequent version can easily enlarge its repertoire while the opposite is always problematic. Using a repertoire that is stable through mapping and normalization is also preferred. The Identifier repertoire referenced in appendix A.3 is such a case. 8.2. Reasons for the difference between stored strings and queries Different software using different versions of a stringprep profile need to interoperate with maximal compatibility. The scheme described in this section (stored strings MUST NOT contain unassigned code points, queries MAY include unassigned code points) allows that compatibility without introducing any known security or interoperability issues. The list below shows what happens if a query contains a code point from category U that is allowed in a newer version of a profile. The query either matches the string that was intended, or matches no string at all. In this list, the query comes from an application using version "oldVersion" of a profile, the stored string was created using version "newVersion" of the same profile, and the code point X was in category U in oldVersion, and has changed category to AO, MN, or D. There are 3 possible scenarios: 1. X is assigned to AO -- In newVersion, X is in category AO. Because the application passed X through, it gets back a positive match with the stored string. There is one exceptional case, where X is a combining mark. Suignard, et al. Expires June 23, 2007 [Page 22] Internet-Draft stringprep December 2006 The order of combining marks is normalized, so if another combining mark Y has a lower combining class than X then XY will be put in the canonical order YX. (Unassigned code points are never reordered, so this doesn't happen in oldVersion). If the query contains YX, the query will get positive match with the stored string. However, no string can be stored with XY, so a query with XY will get a negative answer to the test for matching. 2. X is assigned to MN -- In newVersion, X is normalized to code point "nX" and therefore X is now put in category MN. This cannot exist in any stored string, so any query containing X will get a negative answer to the test for matching. Note, however, if the query had contained the letter nX, it would have positively matched. 3. X is assigned to D -- In newVersion, X is in category D. This cannot exist in any stored string, so any query containing X will get a negative answer to the test for matching. In none of the cases does the query get data for a stored string other than the one it actually tried to match against. Profiles are stable between versions in the following sense: If a string S has been prepared using newVersion, then it will not change if it is subsequently prepared using oldVersion. 8.3. Versions of applications and stored strings Another way to see that this versioning system works is to compare what happens when an application uses a newer or older version of a profile. Newer query application -- Suppose that a querying application is using version newVersion and the stored string was created using version oldVersion. This case is simple: there will be no characters in the stored string that cannot be queried by the application because the new profile uses a superset of the code points used for making the stored string. Newer stored string -- Suppose that a querying application is using oldVersion and the stored string was created using a profile that uses newVersion. Because the querying application let unassigned code points pass through, the user can query on stored strings that use code points in newVersion. No stored strings can have code points that are unassigned in newVersion, since that is illegal. In order to get a match, the querying application has to enter the unassigned code points in the proper order, and has to use unassigned code points that would make it through both the mapping and the Suignard, et al. Expires June 23, 2007 [Page 23] Internet-Draft stringprep December 2006 normalization steps. 9. Security Considerations Stringprep is used with Unicode characters. There are security considerations that are specific to stringprep, and others that are generic to using Unicode. 9.1. Stringprep-specific security considerations The Unicode repertoire has many characters that look similar. In many cases, users of security protocols might do visual matching, such as when comparing the names of trusted third parties. Because it is impossible to map similar-looking characters without a great deal of context such as knowing the fonts used, stringprep does nothing to map similar-looking characters together nor to prohibit some characters because they look like others. User applications can help disambiguate some similar-looking characters by showing the user when a string changes between scripts. Most profiles of stringprep can cause changes in strings that are input to stringprep. Because of this, protocols that have sets of non-allowed characters or sequences MUST check for the non-allowed characters or sequences after the stringprep processing. This document does not mandate the checking of bidirectional characters in section 6. If the requirements in section 6 are not used in a profile of stringprep, it is easy to create many strings whose characters are in different order but are displayed identically. This can cause security-related user confusion similar to look-alike characters, as described above. Stringprep does not do anything to assure that any algorithms translating characters from non-Unicode into Unicode produce the same output in all implementations. Some Unicode codepoints are invisible. Protocols that allow these characters (that is, do not map them out or prohibit them in stringprep) can cause users confusion when two identical-looking strings do not match. 9.2. Generic Unicode security considerations Using Unicode characters explicitly forces applications to use multi- octet characters. Converting an application from one that uses single-octet characters to one that uses multi-octet characters must be done very carefully, particularly in an application that checks Suignard, et al. Expires June 23, 2007 [Page 24] Internet-Draft stringprep December 2006 for values of characters or sorts characters. Protocols that use stringprep usually also use encodings of Unicode, such as UTF-8 or UTF-16. Some applications using those encodings have been known to not check for ill-formed sequences in the encodings, and thereby have not detected sequences of octets that would have been detected if they used just ASCII. For example, in UTF-8 the octet sequence "0xC0 0xAB" is an ill-formed sequence for U+002B (plus sign). All programs MUST reject any string that is an ill-formed octet sequence for the encoding being used. Both Unicode normalization and conversion between Unicode encodings can cause strings to grow or shrink. Programs that used fixed-size buffers, or that make assumptions that buffers will always be greater than or less than particular sizes, are likely to fail in insecure fashions when using Unicode normalization or encoding conversions. Covering an extensive list of security threats and considerations on the use of current and future versions of Unicode is outside of the scope of this document. Additional considerations are available in [UTR36] and [UTS39]. 10. IANA Considerations Stringprep profiles MUST have IETF consensus as described in [RFC2434]. Each profile MUST be reviewed by the IESG before it is registered. The IESG MAY change a profile before registration. IANA has set up a registry of stringprep profiles. This registry is a single text file that lists the known profiles. Each entry in the registry has three fields: o Profile name o RFC in which the profile is defined o Indicator whether or not this is the newest version of the profile Each version of a profile will remain listed in the registry forever. That is, if a new version of a profile supersedes an earlier version, both versions will continue to be listed in the registry, but the current version indicator will be turned off for the earlier version and turned on for the newer version. It is probably harmful if a large number of profiles of stringprep proliferate. Therefore, the IESG may reject proposals for new profiles and instead suggest that protocols reuse existing profiles. Suignard, et al. Expires June 23, 2007 [Page 25] Internet-Draft stringprep December 2006 11. Compatibility between stringprep and stringprep-bis-00 Despite the migration from Unicode 3.2[Unicode3.2] to Unicode 5.0[Unicode5.0] and related properties updates, this framework can be used to create a new version of a profile referencing the previous stringprep version[RFC3454]. The tables referenced in appendices A to F were updated from the previous version in a way to minimize compatibility issues with the previous version of stringprep[RFC3454]. Even when the previous version of the profile classified erroneously code points into either space characters (map to nothing) or control characters, these classification were maintained if they did not significantly impact the preparation results. For example: o U+200B ZERO WIDTH SPACE is not a space character and should not be part of appendix B.1. But the alternative is to classify it as a control code where it is prohibited. In both cases it is not part of the output set. o U+180E MONGOLIAN VOWEL SEPARATOR is actually a space character and should have been part of appendix B.1, but its classification as either a space character or a control character (compatibility mode) makes it prohibited. In addition, most profiles treat the set of prohibited characters described from appendix C.1 to C.9 as a whole, making classification in a particular appendix less critical as long these prohibited characters are included in the union set. Finally, some appendices were created to make easier to describe preparation steps aligned with the previous version of stringprep[RFC3454]. o appendix B.4 Reverse mapping for compatibility mode o appendix C.1.3 Non-ASCII space characters - Compatibility mode o appendix C.2.3 Non-ASCII control characters - Compatibility mode o appendix F.1 Pre normalization mapping o appendix F.2 Characters added since the previous stringprep version[RFC3454] o appendix F.3 Character sequence reordering Suignard, et al. Expires June 23, 2007 [Page 26] Internet-Draft stringprep December 2006 11.1. Compatibility using Unicode 3.2 code points By restricting its repertoire to Unicode 3.2[Unicode3.2] a profile may limit significantly compatibility issues. For example, a new version of the nameprep profile[RFC3491] could do the following: o use the Unicode 3.2 repertoire as specified in A.1. o use the mapping tables defined in B.1 and B.2 followed by the mapping in B.4. o normalize according to the compatibility mode using appendix F.1, F.2 and F.3 (see section 4). o prohibit output according to appendix/tables C.1.3, C.2.3, C.3, C.4, C.5, C.6, C.7, C.8, and C.9. o check combining marks according to section 6. o check bidi according to section 7. Following these steps provides the results: o all previous prohibited characters stay prohibited o additional characters are prohibited 17B4-17B5 [KHMER INHERENT VOWELS] (deprecated) 17A3 KHMER INDEPENDENT VOWEL QAQ 17D3 KHMER SIGN BATHAMASAT o any starting combining mark(s) result in an error. o mixing of RCat characters (see section 7.) with U+0cBF KANNADA VOWEL SIGN I, or U+0CC6 KANNADA VOWEL SIGN E, or U+2800-U+28FF [BRAILLE PATTERNS] is now invalid. o a RCat string may now end with NSMCat character(s). This combination would have been prohibited with the previous version of stringprep with the bidi option. 11.2. Compatibility using the Identifier repertoire A profile using a restricted repertoire such as the Identifier repertoire referenced in appendix A.3 can reasonably be perceived as a new version of an existing profile based on the prior version of stringprep[RFC3454] without using the compatibility mode tables. Suignard, et al. Expires June 23, 2007 [Page 27] Internet-Draft stringprep December 2006 For example, such a new version of nameprep profile[RFC3491] could do the following: o use the Identifier repertoire as specified in A.3. o no mapping, all characters map to themselves. o normalize according to the regular NFKC, no special processing or tables since the repertoire is stable through normalization. o No prohibit, since the repertoire contains no prohibited code points o check combining marks according to section 6. o check bidi according to section 7. If the preparation of this repertoire is compared with the original preparation of the same set through the original nameprep[RFC3491] (using the unassigned flag), the following differences should be found: o any starting combining mark(s) would result in an error. o mixing of RCat characters (see section 7.) with U+0cBF KANNADA VOWEL SIGN I, or U+0CC6 KANNADA VOWEL SIGN E is now invalid. o a RCat string may now end with NSMCat character(s). This would have been prohibited before. Therefore, using a restricted repertoire yields the same compatibility benefit that the restriction to a Unicode 3.2 subset but without the complex compatibility steps required in the first example. The appendix G shows more in details all the differences introduced by this new version of stringprep. 12. Considerations concerning IDN revision Although stringprep is not just covering IDN needs, it is an important part of its mandate. And because many concerns have been raised in that aspect, especially in [IDNABis], it is important to describe how this new version addresses these issues. The following text address point by point all issues pertinent to stringprep. Suignard, et al. Expires June 23, 2007 [Page 28] Internet-Draft stringprep December 2006 12.1. Permitted Character Identification By offering the choice of the "Identifier repertoire" referenced in appendix A.3, this version of strinprep offers an inclusion-based option. Furthermore the repertoire is stable under mapping and normalization which makes its implementation much simpler. Note however that the normalization step is still necessary for reasons explained in section 2. 12.2. Strinprep mapping based on Unicode properties As mentioned in the introduction, this has been one of the clear goal of this revision of stringprep. This version relies very little on list of Unicode characters, and makes an extensive usage of Unicode properties. The remaining characters lists are mostly to provide backward compatibility with the previous version of stringprep[RFC3454]. 12.3. Normalization stability Many concerns have been raised concerning the real or perceived lack of stability of the Unicode normalization process through its successive versions. The description of the normalization step in section 4 addresses these concerns in details. It covers several new mechanisms: o Usage of the newly introduced "normalization Process for Stable Strings (NPSS). This process returns an error for unassigned code points. o Usage of special tables (F.1, F.2, and F.3) to duplicate the behavior provided by implementation following Unicode 3.2[Unicode3.2]. These various mechanisms provides ways for profile using stringprep to pick and choose behavior based on strict backward compatibility while offering a way for application to interact with platforms offering various level of normalization services. 12.4. Case folding The case folding which is part of the mapping step cannot be fully separated from the normalization step, because case folding is not closed under compatibility normalization such as NFKC. While the previous version of stringprep was addressing this correctly, it was using hard coded lists of characters derived from original Unicode tables, making transition to a new version unnecessarily difficult. This version references directly the Unicode Character Database[UCD] Suignard, et al. Expires June 23, 2007 [Page 29] Internet-Draft stringprep December 2006 files in appendix B.2, making any further upgrade to a new version of Unicode much easier. 13. Acknowledgements TBD Appendix A. Unicode repertoires The following are the only repertoires covered in this document: o Unicode 3.2, as defined in Unicode 3.2[Unicode3.2] o Unicode 5.0, as defined in Unicode 5.0[Unicode5.0] o Identifier repertoire Appendix A.1. Unassigned code points in Unicode 3.2 The table A.1 is made of all unassigned code points in Unicode 5.0 (see appendix A.2) augmented by all characters specified in appendix F.2 which contains all characters added between Unicode 3.2 and 5.0. Appendix A.2. Unassigned code points in Unicode 5.0 The table A.2 is made of all unassigned code points in Unicode 5.0 specified as all code points with general category Gc=Cn except for code points which are listed in the PropList.txt file from the Unicode Character Database in the category: "NonCharacter_Code_Point"[UCD]. Appendix A.3. Identifier repertoire The table A.3 is made of all characters that have the XID_Continue property as referenced by the DerivedCoreProperties.txt file in the Unicode Character Database[UCD] and which map to themselves according to a mapping done using the table described in appendix B.2. Appendix B. Mapping Tables The following are the combination of tables and references for the mapping process from section 3. When explicitly specified the tables have three columns: Suignard, et al. Expires June 23, 2007 [Page 30] Internet-Draft stringprep December 2006 o the code point that is mapped from o the zero or more code points that it is mapped to o Character name The columns are separated by semicolons. Note that the second column may be empty, or it may have one code point, or it may have more than one code point, with each code point separated by a space. Appendix B.1. Commonly mapped to nothing The table B.1 is created by first using the following table: 00AD; ; SOFT HYPHEN 034F; ; COMBINING GRAPHEME JOINER 1806; ; MONGOLIAN TODO SOFT HYPHEN 200B; ; ZERO WIDTH SPACE 200C; ; ZERO WIDTH NON JOINER 200D; ; ZERO WIDTH JOINER 2060; ; WORD JOINER FEFF; ; ZERO WIDTH NO-BREAK SPACE In addition, the variation selector code points listed in the PropList.txt file from the Unicode Character Database[UCD] in the category: "Variation_Selector" are also added to the table B.1. Appendix B.1.1. Commonly mapped to nothing with ZWJ/ZWNJ special processing The table B.1.1 is created by first using the following table: 00AD; ; SOFT HYPHEN 034F; ; COMBINING GRAPHEME JOINER 1806; ; MONGOLIAN TODO SOFT HYPHEN 200B; ; ZERO WIDTH SPACE 2060; ; WORD JOINER FEFF; ; ZERO WIDTH NO-BREAK SPACE In addition, the variation selector code points listed in the PropList.txt file from the Unicode Character Database[UCD] in the category: "Variation_Selector" are also added to the table B.1.1. The additional requirements expressed in 5.1 use the following Unicode properties: o The character script value is determined by the "Scripts.txt" file in the Unicode Character Database[UnicodeScripts]. Suignard, et al. Expires June 23, 2007 [Page 31] Internet-Draft stringprep December 2006 o The character properties "Right-Joining" (R), "Transparent" (T), and "Left-Joining" (L) are specified by the ArabicShaping.txt file in the Unicode Character Database. o The character property "Letter" is the union of all General Category values: "Lu", "Ll", "Lt", "Lm", and "Lo" specified in the UnicodeData.txt file in the Unicode Character Database[UCD]. o The character property "Combining Mark" is the concatenation of all General Category values: "Mc", "Mn", and "Me" specified in the UnicodeData.txt file in the Unicode Character Database[UCD]. o The character property "Virama" is determined by having the Canonical_Combining_Class value equal to 9. That class is specified in the UnicodeData.txt file in the Unicode Character Database[UCD]. Appendix B.2. Mapping for case-folding used with NFKC The mapping table is constructed as by using the following steps: 1. For each code point entry in the "CaseFolding.txt" file from the Unicode Character Database[UCD] with either a "C" or "F" status field, replace the entry code point with the sequence of code points specified in the third field. 2. For each code point entry in the "DerivedNormalizationProps.txt" file[NormProps] with a "CF_NFKC", replace the entry code point with the sequence of code points specified in the third field. 3. Other code points map to themselves. If a code point entry is present in both the "CaseFolding.txt" file and the "DerivedNormalizationProps.txt" file, the latter entry supersedes the former (example: U+03F9 GREEK CAPITAL LUNATE SIGMA SYMBOL). Appendix B.3. Mapping for case-folding used with no normalization The mapping table is constructed as following: 1. For each code point entry in the "CaseFolding.txt" file from the Unicode Character Database[UCD]with either a "C" or "F" status field, replace the entry code point with the sequence of code points specified in the third field. 2. Other code points map to themselves. Suignard, et al. Expires June 23, 2007 [Page 32] Internet-Draft stringprep December 2006 Appendix B.4. Reverse mapping for compability mode The mapping table is constructed for the following code points: 04CF CYRILLIC SMALL LETTER PALOCHKA 214E TURNED SMALL F 2184 LATIN SMALL LETTER REVERSED C 2D00-2D25 [GEORGIAN SUPPLEMENT KHUTSURI] by mapping them back to their Simple_Uppercase_Mapping value as specified in the UnicodeData.txt file in the Unicode Character Database[UCD]. Appendix C. Prohibition tables The tables in this appendix consist of lines with one prohibited code point per line. The format of the lines are the value of the code point, a semicolon, and a comment which is the name of the code point. Appendix C.1. Space characters Appendix C.1.1. ASCII space character The table C.1.1 consists of a single code point: 0020; SPACE Appendix C.1.2. Non-ASCII space characters The table C.1.2 consists of all character code points with General Category value (Gc) equal to "Zs" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD], with the following exception: 0020; SPACE Appendix C.1.3. Non-ASCII space characters - Compatibility mode The table C.1.3 consists of all character code points with General Category value (Gc) equal to "Zs" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD], with the following addition: 200B ZERO WIDTH SPACE Suignard, et al. Expires June 23, 2007 [Page 33] Internet-Draft stringprep December 2006 and exceptions: 0020; SPACE 180E; MONGOLIAN VOWEL SEPARATOR Appendix C.2. Control characters Appendix C.2.1. ASCII control character The table C.2.1 consists of all character code points with General Category value (Gc) equal to "Cc" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD], within the ASCII range (0000-007F). Appendix C.2.2. Non-ASCII control character The table C.2.2 consists of all character code pointss with General Category value (Gc) equal to "Cc", "Cf", "Zl", and "Zp" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD], with the following exceptions: 0000-001F; [CONTROL CHARACTERS] 007F; DELETE 00AD; SOFT HYPHEN E0001; LANGUAGE TAG E0020-E007F; [TAGGING CHARACTERS] Appendix C.2.3. Non-ASCII control character - Compatibility mode The table C.2.2 consists of all character code pointss with General Category value (Gc) equal to "Cc", "Cf", "Zl", and "Zp" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD], with the following additions: 180E; MONGOLIAN VOWEL SEPARATOR (not a control) FFFC; OBJECT REPLACEMENT CHARACTER (not a control) and exceptions: 0000-001F; [CONTROL CHARACTERS] 007F; DELETE 00AD; SOFT HYPHEN E0001; LANGUAGE TAG E0020-E007F; [TAGGING CHARACTERS] Suignard, et al. Expires June 23, 2007 [Page 34] Internet-Draft stringprep December 2006 Appendix C.3. Private use The table C.3 consists of the following code points: E000-F8FF; [PRIVATE USE, PLANE 0] F0000-FFFFD; [PRIVATE USE, PLANE 15] 100000-10FFFD; [PRIVATE USE, PLANE 16] Appendix C.4. Non-characters code points The table C.4 is made of the non-character code points as referenced by the PropList.txt file from the Unicode Character Database[UCD] in the category: "Noncharacter_Code_Point". Appendix C.5. Surrogate codes The table C.5 consists of the following code points: D800-DFFF; [SURROGATE CODES] Appendix C.6. Inappropriate for plain text The table C.6 consists of the following code points: FFF9; INTERLINEAR ANNOTATION ANCHOR FFFA; INTERLINEAR ANNOTATION SEPARATOR FFFB; INTERLINEAR ANNOTATION TERMINATOR FFFC; OBJECT REPLACEMENT CHARACTER FFFD; REPLACEMENT CHARACTER Appendix C.7. Inappropriate for canonical representation The table C.7 is made of the code points as referenced by the PropList.txt file from the Unicode Character Database[UCD] in the categories: "IDS_Binary_Operator" and "IDS_Trinary_Operator". Appendix C.8. Change display properties or are deprecated The table C.8 is made of the code points as referenced by the PropList.txt file from the Unicode Character Database[UCD] in the categories: "Bidi_Control" and "Deprecated". Appendix C.9. Tagging characters The table C.9 consists of all characters with General Category value (Gc) equal to "Cf" as determined by the file UnicodeData.txt, from the Unicode Character Database [UCD]and included within the TAG range (E0000-E007F). Suignard, et al. Expires June 23, 2007 [Page 35] Internet-Draft stringprep December 2006 Appendix C.10. Hangul filler characters The table C.10 consists of the following code points: 115F ; HANGUL CHOSEONG FILLER 1160 ; HANGUL JUNGSEONG FILLER 3164 ; HANGUL FILLER FFA0 ; HALFWIDTH HANGUL FILLER Appendix C.11. Non identifier code points The table C.11 consists of all characters that do not have the XID_Continue property as referenced by the DerivedCoreProperties.txt file in the Unicode Character Database[UCD]. These are characters that are not letters, marks, or decimal numbers. Appendix C.12. Archaic scripts The table C.12 consists of all characters that have the following script values as referenced by the Scripts.txt file in the Unicode Character Database[UnicodeScripts]. Cprt; Cypriot syllabary Dsrt; Deseret alphabet Glag; Glagolitic alphabet Goth; Gothic alphabet Ital; Old Italic alphabet Khar; Kharoshthi abjad Linb; Linear-B syllabary Xpeo; Old Persian cuneiform Phag; Phags-pa alphabet Phnx; Phoenician alphabet Runr; Runic alphabet Shaw; Shavian alphabet Ugar; Ugaritic cuneiform Appendix D. Bidirectional tables Appendix D.1. Characters with bidirectional property R or AL The table D.1 consists of all character code points with Bidi_Class value equal to "R" and "Al" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD]. Suignard, et al. Expires June 23, 2007 [Page 36] Internet-Draft stringprep December 2006 Appendix D.2. Characters with bidirectional property L The table D.2 consists of all character code points with Bidi_Class value equal to "L" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD]. Appendix D.3. Characters with bidirectional property L The table D.3 consists of all character code points with Bidi_Class value equal to "NSM" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD]. Appendix E. Combining marks The following specifies the combining marks. Appendix E.1. Combining mark table The table E.1 consists of all character code points with General Category value (Gc) equal to "Mc", "Mn", and "Me" as determined by the file UnicodeData.txt in the Unicode Character Database[UCD]. Appendix F. Normalization tables The following tables provide the data set to ensure full compatibility with previous version of this framework. Appendix F.1. Pre normalization mapping The following is the mapping table from section 4. The table has two columns: o the code point that is mapped from o the code point that is mapped to o comment 2F868;2136A; would be mapped to 36FC since Unicode 4.0 2F874; 5F33; would be mapped to 5F53 since Unicode 4.0 2F91F; 43AB; would be mapped to 243AB since Unicode 4.0 2F95F; 7AAE; would be mapped to 7AEE since Unicode 4.0 2F9BF; 4D57; would be mapped to 45D7 since Unicode 4.0 Suignard, et al. Expires June 23, 2007 [Page 37] Internet-Draft stringprep December 2006 Appendix F.2. Characters added since the previous stringprep version The following is the list in code points and code point ranges of all characters added since Unicode 3.2. Some of them are inappropriate for use in stringprep, such as the variation selectors in the range U+E0100-U+E01FF which are mapped to nothing in the mapping process. 0221, 0234-024F, 02AE-02AF, 02EE-02FF, 0350-035F, 037B-037D, 03F7-03FF, 04CF, 04F6-04F7, 04FA-04FF, 0510-0513, 05A2, 05BA, 05C5-05C7, 0600-0603, 060B, 060D-0615, 061E, 0656-065E, 06EE-06EF, 06FF, 072D-072F, 074D-076D, 07C0-07FA, 0904, 097B-097F, 09BD, 09CE, 0A01, 0A03, 0A8C, 0AE1-0AE3, 0AF1, 0B35, 0B71, 0BB6, 0BE6, 0BF3-0BFA, 0CBC-0CBD, 0CE2-0CE3, 0CF1-0CF2, 0FD0-0FD1, 10F9-10FA, 10FC, 1207, 1247, 1287, 12AF, 12CF, 12EF, 130F, 131F, 1347, 135F-1360, 1380-1399, 17DD, 17F0-17F9, 1900-191C, 1920-192B, 1930-193B, 1940, 1944-194F, 1950-196D, 1970-1974, 1980-19A9, 19B0-19C9, 19D0-19D9, 19DE-19FF, 1A00-1A1B, 1A1E-1A1F, 1B00-1B4B, 1B50-1B7C, 1D00-1DCA, 1DFE-1DFF, 2053-2056, 2058-205E, 2090-2094, 20B2-20B5, 20EC-20EF, 213B-213C, 214E, 2184, 23CF-23E7, 24FF, 2614-2615, 2618, 267E-267F, 268A-269C, 26A0-26B2, 27C0-27CA, 2B00-2B1A, 2B20-2B23, 2C00-2C2E, 2C30-2C5E, 2C60-2C6C, 2C74-2C77, 2C80-2CEA, 2CF9-2CFF, 2D00-2D25, 2D30-2D65, 2D6F, 2D80-2D96, 2DA0-2DA6, 2DA8-2DAE, 2DB0-2DB6, 2DB8-2DBE, 2DC0-2DC6, 2DC8-2DCE, 2DD0-2DD6, 2DD8-2DDE, 2E00-2E17, 2E1C-2E1D, 31C0-31CF, 321D-321E, 3250, 327C-327E, 32CC-32CF, 3377-337A, 33DE-33DF, 33FF, 4DC0-4DFF, 9FA6-9FBB, A700-A71A, A720-A721, A800-A82B, A840-A877, FA70-FAD9, FDFD, FE10-FE19, FE47-FE48, Suignard, et al. Expires June 23, 2007 [Page 38] Internet-Draft stringprep December 2006 10000-1000B, 1000D-10026, 10028-1003A, 1003C-1003D, 1003F-1004D, 10050-1005D, 10080-100FA, 10100-10102, 10107-10133, 10137-1013F, 10140-1018A, 10380-1039D, 103C3, 103C8-103D5, 10426-10427, 1044E-1047F, 10480-1049D, 104A0-104A9, 10800-10805, 10808, 1080A-10835, 10837-10838, 1083C, 1083F, 10900-10919, 1091F, 10A00-10A03, 10A05-10A06, 10A0C-10A13, 10A15-10A17, 10A19-10A33, 10A38-10A3A, 10A3F-10A47, 10A50-10A58, 12000-1236E, 12400-12462, 12470-12473, 1D200-1D245, 1D300-1D356, 1D360-1D371 1D4C1, 1D6A4-1D6A5, 1D7CA-1D7CB, E0100-E01EF Appendix F.3. Character sequences reordering To ensure full compatibility with previous version of this framework some profiles may elect, prior to normalization, to reorder the sequences made of a character from the "First character" column, followed by one or more characters with a non-zero Canonical Combining Class property (intervening characters), followed by the character from the 'Last character" column located in the same row. +---------------------------+---------------------------------------+ | First character | Last character | +---------------------------+---------------------------------------+ | 09C7 BENGALI VOWEL SIGN E | 09BE BENGALI VOWEL SIGN AA or 09D7 | | | BENGALI AU LENGTH MARK | | 0B47 ORIYA VOWEL SIGN E | 0B3E ORIYA VOWEL SIGN AA or 0B56 | | | ORIYA AI LENGTH MARK or 0B57 ORIYA AU | | | LENGTH MARK | | 0BC6 TAMIL VOWEL SIGN E | 0BBE TAMIL VOWEL SIGN AA or 0BD7 | | | TAMIL AU LENGTH MARK | | 0BC7 TAMIL VOWEL SIGN EE | 0BBE TAMIL VOWEL SIGN AA | | 0B92 TAMIL LETTER O | 0BD7 TAMIL AU LENGTH MARK | | 0CC6 KANNADA VOWEL SIGN E | 0CC2 KANNADA VOWEL SIGN UU or 0CD5 | | | KANNADA LENGTH MARK or 0CD6 KANNADA | | | AI LENGTH MARK | | 0CBF KANNADA VOWEL SIGN I | 0CD5 KANNADA LENGTH MARK | | or 0CCA KANNADA VOWEL | | | SIGN O | | | 0D47 MALAYALAM VOWEL SIGN | 0D3E MALAYALAM VOWEL SIGN AA | | EE | | | 0D46 MALAYALAM VOWEL SIGN | 0D3E MALAYALAM VOWEL SIGN AA or 0D57 | | E | MALAYALAM AU LENGTH MARK | Suignard, et al. Expires June 23, 2007 [Page 39] Internet-Draft stringprep December 2006 | 1025 MYANMAR LETTER U | 102E MYANMAR VOWEL SIGN II | | 0DD9 SINHALA VOWEL SIGN | 0DCF SINHALA VOWEL SIGN AELA-PILLA or | | KOMBUVA | 0DDF SINHALA VOWEL SIGN GAYANUKITTA | | 1100-1112 HANGUL CHOSEONG | 1161-1175 HANGUL JUNGSEONG A..I [21 | | KIYEOK..HIEUH [19 | instances] | | instances] | | | [HangulSyllableType=LV] | 11A8-11C2 HANGUL JONGSEONG | | | KIYEOK..HIEUH [27 instances] | +---------------------------+---------------------------------------+ [:HangulSyllableType=LV:] is specified as the set of Hangul syllables that do not have a syllable-final character (also known as Jongseong). The determination of the structure of a Hangul syllable is done by following the process specified by the Hangul Syllable Decomposition in the Unicode standard [Unicode5.0]. The reordering consists in moving the intervening combining marks after the character from the "Last character" column. The Canonical Combining Class property value for each code point is specified by the Canonical_Combining_Class value within the UnicodeData.txt file in the Unicode Character Database[UCD]. Appendix G. Differences between stringprep and stringprep-bis-00 This appendix describes in details differences with the previous version of stringprep[RFC3454]. Unicode repertoire Added a Unicode 5.0 repertoire and an Identifier repertoire. Map to nothing o Added E0100-E01FF [VARIATION SELECTOR-17 TO 256] (new) to the list. Case Folding o 04C0 CYRILLIC LETTER PALOCHKA now maps to 04CF CYRILLIC SMALL LETTER PALOCHKA (new) instead of itself. o 10A0..10C5 [GEORGIAN CAPITAL LETTERS] now map to 2D00-2D25 [GEORGIAN SUPPLEMENT KHUTSURI] (new) instead of themselves. o 2132 TURNED CAPITAL F now maps to 214E TURNED SMALL F (new) instead of itself. Suignard, et al. Expires June 23, 2007 [Page 40] Internet-Draft stringprep December 2006 o 2183 ROMAN NUMERAL REVERSED ONE HUNDRED now maps to 2184 LATIN SMALL LETTER REVERSED C (new) instead of itself. o Case mapping added for new characters: 023A, 023B, 023D, 0241, 0243-0236, 0248, 024A, 024C, 024E,03F7, 03F9-03FA, 03FD-03FF, 04F6, 04FA, 04FC, 04FE, 0510, 0512, 1D2C-1D2E, 1D30-1D3A, 1D3C- 1D42, 213B, 2C00-2C2E, 2C60, 2C62-2C64, 2C67, 2C69, 2C6B, 2C75, 2C80, 2C82, 2C84, 2C86, 2C88, 2C8A, 2C8C, 2C8E, 2C90, 2C92, 2C94, 2C96, 2C98, 2C9A, 2C9C, 2C9E, 2CA0, 2CA2, 2CA4, 2CA6, 2CA8, 2CAA, 2CAC, 2CAE, 2CB0, 2CB2, 2CB4, 2CB6, 2CB8, 2CBA, 2CBC, 2CBE, 2CC0, 2CC2, 2CC4, 2CC6, 2CC8, 2CCA, 2CCC, 2CCE, 2CD0, 2CD2, 2CD4, 2CD6, 2CD8, 2CDA, 2CDC, 2CDE, 2CE0, 2CE2, 3250, 32CC, 32CE-32CF, 337A, 33DE, 33DF, 10426-10427, 1D7CA. Note that Unicode 3.2 did not guarantee the stability of case folding. Unicode 5.0 does guarantee the future stability, so that subsequent versions will only add case foldings for new characters. Space characters. In compatibility mode (C.1.3), there is no change. In regular mode (C.1.2), changes are as follows: o Added 180E MONGOLIAN VOWEL SEPARATOR (space) o Removed 200B ZERO WIDTH SPACE (not a space but control) Control characters. In compatibility mode (C.2.3), only additions are made to the Control character list. In regular mode (C.2.2), both additions and removals are done. o Added the following characters: 0600-0603 [ARABIC SUBTENDING MARKS] (new) 17B4-17B5 [KHMER INHERENT VOWELS] (deprecated) 200B ZERO WIDTH SPACE (not a space but control) 200E LEFT-TO-RIGHT MARK (bidi control) 200F RIGHT-TO-LEFT MARK (bidi control) 202A LEFT-TO-RIGHT EMBEDDING (bidi control) 202B RIGHT-TO-LEFT EMBEDDING (bidi control) 202C POP DIRECTIONAL FORMATTING (bidi control) 202D LEFT-TO-RIGHT OVERRIDE (bidi control) 202E RIGHT-TO-LEFT OVERRIDE (bidi control) Suignard, et al. Expires June 23, 2007 [Page 41] Internet-Draft stringprep December 2006 o Removed the following characters: 180E MONGOLIAN VOWEL SEPARATOR (not a control) FFFC OBJECT REPLACEMENT CHARACTER (not a control) Deprecated characters (C.8) o Added the following characters: 17A3 KHMER INDEPENDENT VOWEL QAQ 17D3 KHMER SIGN BATHAMASAT Character with bidirectional property R or AL (D.1) o Added the following characters with property R (new): 05C6 HEBREW PUNCTUATION NUN HAFUKHA 07C0-07C9 [NKO DIGITS] 07CA-07E7 [NKO LETTERS] 07E8-07EA [NKO ARCHAIC LETTERS] 07F4 NKO HIGH TONE APOSTROPHE 07F5 NKO LOW TONE APOSTROPHE 07FA NKO LAJANYALAN 10800-10805 [CYPRIOT SYLLABLES A to JA] 10808 CYPRIOT SYLLABLE JO 1080A-10835 [CYPRIOT SYLLABLES KA to WO] 10837-10838 [CYPRIOT SYLLABLES XA to XE] 1083C CYPRIOT SYLLABLE ZA 1083F CYPRIOT SYLLABLE ZO 10900-10919 [PHOENICIAN LETTERS] 10A00 KHAROSHTHI LETTER A 10A10-10A13 [KHAROSHTHI LETTERS KA to GHA] 10A15-10A17 [KHAROSHTHI LETTERS CA to JA] 10A19-10A33 [KHAROSHTHI LETTERS NYA to TTTHA] 10A40-10A43 [KHAROSHTHI DIGITS] 10A44-10A47 [KHAROSHTHI NUMBERS] 10A50-10A58 [KHAROSHTHI PUNCTUATION] o Added the following characters with property AL (new): 0600-0603 [ARABIC SUBTENDING MARKS] 060B AFGHANI SIGN 060D ARABIC DATE SEPARATOR 061E ARABIC TRIPLE DOT PUNCTUATION MARK 06EE-06EF [EXTENDED ARABIC LETTERS FOR PARKARI] 06FF ARABIC LETTER HEH WITH INVERTED V 072D-072F [SYRIAC PERSIAN LETTERS] 074D-074F [SYRIAC SODGIAN LETTERS] Suignard, et al. Expires June 23, 2007 [Page 42] Internet-Draft stringprep December 2006 0750-076D [EXTENDED ARABIC LETTERS] Character with bidirectional property L (D.2) o Changed the bidirectional property to L for the following characters: 0CBF KANNADA VOWEL SIGN I (from NSM in 3.2) 0CC6 KANNADA VOWEL SIGN E (from NSM in 3.2) 2800-28FF [BRAILLE PATTERNS] (from ON in 3.2) o Added the following new COMMON characters with property L: 213C, 26AC, 10100, 10102, 10107-10133, 10137-1013F, 1D360-1D371, 1D4C1, 1D6A4-1D6A5, 1D7CA-1D7CB o Added the following new LATIN characters with property L: 0221, 0234-024F, 02AE-02AF, 1D00-1D25, 1D2C-1D5C, 1D62-1D65, 1D6B-1D77, 1D79-1DBE, 2090-2094, 2132, 214E, 2184, 2C60-2C6C, 2C74-2C77 o Added the following new GREEK characters with property L: 037B-037D, 03F7-03FF, 1D26-1D2A, 1D5D-1D61, 1D66-1D6A, 1DBF o Added the following new CYRILLIC characters with property L: 04CF, 04F6-04F7, 04FA-04FF, 0510-0513, 1D2B, 1D78 o Added the following new DEVANAGARI characters with property L: 0904, 097B-097F o Added the following new BENGALI characters with property L: 09BD, 09CE o Added the following new GURMUKHI characters with property L: 0A03 o Added the following new GUJARATI characters with property L: 0A8C, 0AE1 Suignard, et al. Expires June 23, 2007 [Page 43] Internet-Draft stringprep December 2006 o Added the following new ORIYA characters with property L: 0B35,0B71 o Added the following new TAMIL characters with property L: 0BB6, 0BE6 o Added the following new KANNADA characters with property L: 0CBD o Added the following new TIBETAN characters with property L: 0FD0-0FD1 o Added the following new GEORGIAN characters with property L: 10F9-10FA, 10FC, 2D00-2D25 o Added the following new ETHIOPIC characters with property L: 1207, 1247, 1287, 12AF, 12CF, 12EF, 130F, 131F, 1347, 1360, 1380-138F, 2D80-2D96, 2DA0-2DA6, 2DA8-2DAE, 2DB0-2DB6, 2DB8-2DBE, 2DC0-2DC6, 2DC8-2DCE, 2DD0-2DD6, 2DD8-2DDE o Added the following new script LIMBU characters with property L: 1900-191C, 1923-1926, 1930-1931, 1933-1938, 1946-194F o Added the following new script TAI LE characters with property L: 1950-196D, 1970-1974 o Added the following new script NEW TAI LUE characters with property L: 1980-19A9, 19B0-19C9, 19D0-19D9 o Added the following new scripT BUGINESE characters with property L: 1A00-1A16, 1A19-1A1B, 1A1E-1A1F o Added the following new script BALINESE characters with property L: 1B04-1B33, 1B35, 1B3B, 1B3D-1B41, 1B43-1B4B, 1B50-1B6A, 1B74-1B7C Suignard, et al. Expires June 23, 2007 [Page 44] Internet-Draft stringprep December 2006 o Added the following new script GLAGOLITIC characters with property L: 2C00-2C2E, 2C30-2C5E o Added the following new script COPTIC characters with property L: 2C80-2CE4 o Added the following new script TIFINAGH characters with property L: 2D30-2D65, 2D6F o Added the following new HAN characters with property L: 9FA6-9FBB, FA70-FAD9 o Added the following new script SYLOTI NAGRI characters with property L: A800-A801, A803-A805, A807-A80A, A80C-A824, A827 o Added the following new script PHAGS-PA characters with property L: A840-A873 o Added the following new script LINEAR B characters with property L: 10000-1000B, 1000D-10026, 10028-1003A, 1003C-1003D, 1003F-1004D, 10050-1005D, 10080-100FA o Added the following new script UGARATIC characters with property L: 10380-1039D, 1039F o Added the following new script OLD PERSIAN characters with property L: 103A0-103C3, 103C8-103D5 o Added the following new DESERET characters with property L: 10426-10427, 1044E-1044F Suignard, et al. Expires June 23, 2007 [Page 45] Internet-Draft stringprep December 2006 o Added the following new script SHAVIAN characters with property L: 10450-1047F o Added the following new script OSMANYA characters with property L: 10480-1049D, 104A0-104A9 o Added the following new script CUNEIFORM characters with property L: 12000-1236E, 12400-12462, 12470-12473 Check combining marks. This is a preparation step in stringprep. This will obviously restrict any repertoire containing NSMCat characters further than any profile based on the former version of stringprep[RFC3454]. Check Bidi. Allowing NSMCat at the end of Rcat string relaxes restrictions. 14. References 14.1. Normative References [NormProps] The Unicode Consortium, "Unicode Derived Normalization Properties", , June 2006, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [UAX15] Davis, M. and M. Duerst, "Unicode Normalization Forms", Unicode Standard Annex #15, March 2001, . [UAX9] Davis, M., "The Bidirectional Algorithm", Unicode Standard Annex #9, September 2006, . [UCD] The Unicode Consortium, "Unicode Character Database", , July 2006, . [Unicode3.2] Suignard, et al. Expires June 23, 2007 [Page 46] Internet-Draft stringprep December 2006 The Unicode Consortium, "The Unicode Standard Version 3.2", is defined by The Unicode Standard, Version 3.0 (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5), as amended by the Unicode Standard Annex #27: Unicode 3.1 (http://www.unicode.org/reports/tr27/) and by the Unicode Standard Annex #28: Unicode 3.2 (http://www.unicode.org/reports/tr28/)., March 2002. [Unicode5.0] The Unicode Consortium, "The Unicode Standard Version 5.0", Addison-Wesley, Reading, MA , October 2006. [UnicodeScripts] The Unicode Consortium, "Unicode Scripts data file", , March 2006, . 14.2. Informative References [CharModel] Whistler, K., Davis, M., and A. Freytag, "Character Encoding Model.", Unicode Technical Report #17, September 2004, . [Glossary] The Unicode Consortium, "Unicode Glossary", Unicode Glossary , September 2006, . [IDNABidi] Alvestrand, H. and C. Karp, "An IDNA problem in right-to- left scripts", Internet-Draft , October 2006, . [IDNABis] Klensin, J., "Proposed Issues and Changes for IDNA - An Overview", Internet-Draft , October 2006, . [IDNARepertoire] Falstrom, P., "The Unicode Codepoints and IDN", Internet- Draft , October 2006, . [ISO10646] International Organization for Standardization, Suignard, et al. Expires June 23, 2007 [Page 47] Internet-Draft stringprep December 2006 "Information Technology - Universal Multiple-Octet Coded Character Set (UCS)", ISO Standard 10646-1, with amendments 1 and 2, 2003. [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [RFC3454] Hoffman, P. and M. Blanchet, "Preparation of Internationalized Strings ("stringprep")", RFC 3454, December 2002. [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing Domain Names in Applications (IDNA)", RFC 3490, March 2003. [RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)", RFC 3491, March 2003. [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, January 2005. [UTR36] Davis, M. and M. Suignard, "Unicode Security Considerations", Unicode Technical Report #36, August 2006, . [UTS39] Davis, M. and M. Suignard, "Unicode Security Mechanisms", Unicode Technical Standard #36, August 2006, . Authors' Addresses Michel Suignard (editor) Microsoft Corporation One Microsoft Way Redmond, WA 98052 U.S.A. Phone: +1 425 882-8080 Email: michelsu@microsoft.com URI: http://www.suignard.com Suignard, et al. Expires June 23, 2007 [Page 48] Internet-Draft stringprep December 2006 Mark Davis Google U.S.A. Email: mark.davis@macchiato.com or mark.davis@google.com Asmus Freytag ASMUS Inc. U.S.A. Email: asmus@unicode.org URI: http://home.ix.netcom.com/~asmus-inc/ Suignard, et al. Expires June 23, 2007 [Page 49] Internet-Draft stringprep December 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Suignard, et al. Expires June 23, 2007 [Page 50]