Preparation of Internationalized Strings ("stringprep")
RFC 3454

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Network Working Group                                         P. Hoffman
Request for Comments: 3454                                    IMC & VPNC
Category: Standards Track                                    M. Blanchet
                                                                Viagenie
                                                           December 2002

        Preparation of Internationalized Strings ("stringprep")

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

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
   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.

Table of Contents

   1. Introduction....................................................3
     1.1 Terminology..................................................4
     1.2 Using stringprep in protocols................................4
   2. Preparation Overview............................................6
   3. Mapping.........................................................7
     3.1 Commonly mapped to nothing...................................7
     3.2 Case folding.................................................8
   4. Normalization...................................................9
   5. Prohibited Output..............................................10
     5.1 Space characters............................................11
     5.2 Control characters..........................................11
     5.3 Private use.................................................12

Hoffman & Blanchet          Standards Track                     [Page 1]
RFC 3454        Preparation of Internationalized Strings   December 2002

     5.4 Non-character code points...................................12
     5.5 Surrogate codes.............................................13
     5.6 Inappropriate for plain text................................13
     5.7 Inappropriate for canonical representation..................13
     5.8 Change display properties or deprecated.....................13
     5.9 Tagging characters..........................................14
   6. Bidirectional Characters.......................................14
   7. Unassigned Code Points in Stringprep Profiles..................15
     7.1 Categories of code points...................................16
     7.2 Reasons for difference between stored strings and queries...17
     7.3 Versions of applications and stored strings.................18
   8. References.....................................................19
     8.1 Normative references........................................19
     8.2 Informative references......................................19
   9. Security Considerations........................................19
     9.1 Stringprep-specific security considerations.................19
     9.2 Generic Unicode security considerations.....................20
   10. IANA Considerations...........................................21
   11. Acknowledgements..............................................22
   A. Unicode repertoires............................................23
     A.1 Unassigned code points in Unicode 3.2.......................23
   B. Mapping Tables.................................................31
     B.1 Commonly mapped to nothing..................................31
     B.2 Mapping for case-folding used with NFKC.....................32
     B.3 Mapping for case-folding used with no normalization.........61
   C. Prohibition tables.............................................78
     C.1 Space characters............................................78
       C.1.1 ASCII space characters..................................78
       C.1.2 Non-ASCII space characters..............................79
     C.2 Control characters..........................................79
       C.2.1 ASCII control characters................................79
       C.2.2 Non-ASCII control characters............................79
     C.3 Private use.................................................80
     C.4 Non-character code points...................................80
     C.5 Surrogate codes.............................................80