Generic String Encoding Rules (GSER) for ASN.1 Types
RFC 3641

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 04

Network Working Group                                            S. Legg
Request for Comments: 3641                           Adacel Technologies
Category: Standards Track                                   October 2003

          Generic String Encoding Rules (GSER) for ASN.1 Types

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 (2003).  All Rights Reserved.

Abstract

   This document defines a set of Abstract Syntax Notation One (ASN.1)
   encoding rules, called the Generic String Encoding Rules (GSER), that
   produce a human readable text encoding for values of any given ASN.1
   data type.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Conventions. . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Generic String Encoding Rules. . . . . . . . . . . . . . . . .  3
       3.1.  Type Referencing Notations . . . . . . . . . . . . . . .  3
       3.2.  Restricted Character String Types. . . . . . . . . . . .  4
       3.3.  ChoiceOfStrings Types. . . . . . . . . . . . . . . . . .  5
       3.4.  Identifiers. . . . . . . . . . . . . . . . . . . . . . .  6
       3.5.  BIT STRING . . . . . . . . . . . . . . . . . . . . . . .  7
       3.6.  BOOLEAN. . . . . . . . . . . . . . . . . . . . . . . . .  7
       3.7.  ENUMERATED . . . . . . . . . . . . . . . . . . . . . . .  8
       3.8.  INTEGER. . . . . . . . . . . . . . . . . . . . . . . . .  8
       3.9.  NULL . . . . . . . . . . . . . . . . . . . . . . . . . .  8
       3.10. OBJECT IDENTIFIER and RELATIVE-OID . . . . . . . . . . .  8
       3.11. OCTET STRING . . . . . . . . . . . . . . . . . . . . . .  9
       3.12. CHOICE . . . . . . . . . . . . . . . . . . . . . . . . .  9
       3.13. SEQUENCE and SET . . . . . . . . . . . . . . . . . . . . 10
       3.14. SEQUENCE OF and SET OF . . . . . . . . . . . . . . . . . 10
       3.15. CHARACTER STRING . . . . . . . . . . . . . . . . . . . . 11
       3.16. EMBEDDED PDV . . . . . . . . . . . . . . . . . . . . . . 11
       3.17. EXTERNAL . . . . . . . . . . . . . . . . . . . . . . . . 11

Legg                        Standards Track                     [Page 1]
RFC 3641             Generic String Encoding Rules          October 2003

       3.18. INSTANCE OF. . . . . . . . . . . . . . . . . . . . . . . 11
       3.19. REAL . . . . . . . . . . . . . . . . . . . . . . . . . . 11
       3.20. Variant Encodings. . . . . . . . . . . . . . . . . . . . 12
   4.  GSER Transfer Syntax . . . . . . . . . . . . . . . . . . . . . 13
   5.  Security Considerations. . . . . . . . . . . . . . . . . . . . 13
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
       6.1.  Normative References . . . . . . . . . . . . . . . . . . 13
       6.2.  Informative References . . . . . . . . . . . . . . . . . 14
   7.  Intellectual Property Notice . . . . . . . . . . . . . . . . . 15
   8.  Author's Address . . . . . . . . . . . . . . . . . . . . . . . 15
   9.  Full Copyright Statement . . . . . . . . . . . . . . . . . . . 16

1.  Introduction

   This document defines a set of ASN.1 [8] encoding rules, called the
   Generic String Encoding Rules or GSER, that produce a human readable
   UTF-8 [6] character string encoding of ASN.1 values of any given
   arbitrary ASN.1 type.

   Note that "ASN.1 value" does not mean a Basic Encoding Rules (BER)
   [12] encoded value.  The ASN.1 value is an abstract concept that is
   independent of any particular encoding.  BER is just one possible
   encoding of an ASN.1 value.

   GSER is based on ASN.1 value notation [8], with changes to
   accommodate the notation's use as a transfer syntax, and to support
   well established ad-hoc string encodings for Lightweight Directory
   Access Protocol (LDAP) [14] directory data types.

   Though primarily intended for defining the LDAP-specific encoding of
   new LDAP attribute syntaxes and assertion syntaxes, these encoding
   rules could also be used in other domains where human readable
   renderings of ASN.1 values would be useful.

   Referencing GSER is sufficient to define a human readable text
   encoding for values of a specific ASN.1 type, however other
   specifications may wish to provide a customized Augmented Backus-Naur
   Form (ABNF) [3] description, independent of the ASN.1, as a
   convenience for the implementor (equivalent ABNF for the GSER
   encodings for ASN.1 types commonly occurring in LDAP syntaxes is
   provided in a separate document [15]).  Such a specification SHOULD
   state that if there is a discrepancy between the customized ABNF and
   the GSER encoding defined by this document, that the GSER encoding