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'RFC 1951' on line 93 looks like a reference Summary: 6 errors (**), 0 flaws (~~), 4 warnings (==), 7 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Internet Draft Editor: Peter Gutmann 2 draft-ietf-smime-compression-00.txt University of Auckland 3 October 18, 1999 4 Expires April 2000 6 Compressed Data Content Type for S/MIME 8 Status of this memo 10 This document is an Internet-Draft and is in full conformance with all 11 provisions of Section 10 of RFC2026. 13 Internet-Drafts are working documents of the Internet Engineering Task 14 Force (IETF), its areas, and its working groups. Note that other 15 groups may also distribute working documents as Internet-Drafts. 17 Internet-Drafts are draft documents valid for a maximum of six months 18 and may be updated, replaced, or obsoleted by other documents at any 19 time. It is inappropriate to use Internet- Drafts as reference 20 material or to cite them other than as "work in progress." 22 The list of current Internet-Drafts can be accessed at 23 http://www.ietf.org/ietf/1id-abstracts.txt 25 The list of Internet-Draft Shadow Directories can be accessed at 26 http://www.ietf.org/shadow.html. 28 Abstract 30 The Cryptographic Message Syntax data format doesn't currently contain 31 any provisions for compressing data before processing it. Compressing 32 data before transmission provides a number of advantages including the 33 elimination of data redundancy which could help an attacker, speeding 34 up processing by reducing the amount of data to be processed by later 35 steps such as signing or encryption, and reducing overall message size. 36 This document defines a format for using compressed data as a CMS 37 content type. 39 This draft is being discussed on the "ietf-smime" mailing list. To 40 join the list, send a message to with the 41 single word "subscribe" in the body of the message. Also, there is a 42 Web site for the mailing list at . 44 1. Introduction 46 This document describes a compressed data content encryption type for 47 S/MIME. This is implemented as a new ContentInfo type and is an 48 extension to the types currently defined in CMS [CMS]. Future 49 implementations of CMS SHOULD include this extension. 51 The format of the messages are described in ASN.1:1994 [ASN1]. 53 The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", 54 "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be 55 interpreted as described in [RFC2119]. 57 1.1 Compressed Data Content Type 59 The compressed-data content type consists of content of any type 60 compressed using a specified algorithm. The following object 61 identifier identifies the compressed-data content type: 63 id-ct-compressedData OBJECT IDENTIFIER ::= { iso(1) member-body(2) 64 us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) ct(1) 3 } 66 The compressed-data content type shall have ASN.1 type CompressedData: 68 CompressedData ::= SEQUENCE { 69 version CMSVersion, 70 compressionAlgorithm CompressionAlgorithmIdentifier, 71 encapContentInfo EncapsulatedContentInfo 72 } 74 The fields of type CompressedData have the following meanings: 76 version is the syntax version number. It shall be 0. 78 compressionAlgorithm is a compression algorithm identifier, as 79 defined in section 2. 81 encapContentInfo is the content which is compressed. 83 Implementations SHOULD use the SMIMECapabilities attribute to indicate 84 their ability to process compressed content types. A compression 85 SMIMECapability consists of the AlgorithmIdentifier for the supported 86 compression algorithm, in the case of the algorithm specified in this 87 document this is is-alg-zlib with parameters NULL. Alternatively, the 88 use of compression may be handled by prior arrangement (for example as 89 part of an interoperability profile). 91 2. Compression Types 93 CMS implementations should include ZLIB [RFC 1950] [RFC 1951], which is 94 free of any intellectual property restrictions and has a 95 freely-available, portable and efficient reference implementation. The 96 following object identifier identifies ZLIB: 98 id-alg-zlib OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) 99 rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) alg(3) 8 } 101 The parameters for this algorithm are NULL. 103 3. Security Considerations 105 This RFC is not concerned with security, except for the fact that 106 compressing data before encryption can enhance the security provided by 107 other processing steps by reducing the quantity of known plaintext 108 available to an attacker. 110 Author Address 112 Peter Gutmann 113 University of Auckland 114 Private Bag 92019 115 Auckland, New Zealand 116 pgut001@cs.auckland.ac.nz 118 References 120 ASN1 Recommendation X.680: Specification of Abstract Syntax Notation 121 One (ASN.1), 1994. 123 CMS Cryptographic Message Syntax, draft-ietf-smime-cms-11.txt, Russ 124 Housley, April 1999. 126 RFC2119 Key Words for Use in RFC's to Indicate Requirement Levels, 127 S.Bradner, March 1997. 129 RFC1950 ZLIB Compressed Data Format Specification version 3.3, 130 P.Deutsch and J-L Gailly, May 1996. 132 RFC1951 DEFLATE Compressed Data Format Specification version 1.3, 133 P.Deutsch, May 1996. 135 Appendix A: ASN.1 Module 137 PasswordRecipientInfo 138 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 139 smime(16) modules(0) compression(n+1) } 141 DEFINITIONS IMPLICIT TAGS ::= 142 BEGIN 144 CompressedData ::= SEQUENCE { 145 version CMSVersion, -- Always set to 0 146 compressionAlgorithm CompressionAlgorithmIdentifier, 147 encapContentInfo EncapsulatedContentInfo 148 } 150 CompressionAlgorithmIdentifer ALGORITHM-IDENTIFIER ::= { 151 { SYNTAX NULL IDENTIFIED BY id-alg-ZLIB }, 152 ... 153 } 155 END 157 Full Copyright Statement 159 Copyright (C) The Internet Society 1999. All Rights Reserved. 161 This document and translations of it may be copied and furnished to 162 others, and derivative works that comment on or otherwise explain it or 163 assist in its implementation may be prepared, copied, published and 164 distributed, in whole or in part, without restriction of any kind, 165 provided that the above copyright notice and this paragraph are 166 included on all such copies and derivative works. However, this 167 document itself may not be modified in any way, such as by removing the 168 copyright notice or references to the Internet Society or other 169 Internet organizations, except as needed for the purpose of developing 170 Internet standards in which case the procedures for copyrights defined 171 in the Internet Standards process must be followed, or as required to 172 translate it into languages other than English. 174 The limited permissions granted above are perpetual and will not be 175 revoked by the Internet Society or its successors or assigns. 177 This document and the information contained herein is provided on an 178 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 179 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT 180 NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL 181 NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR 182 FITNESS FOR A PARTICULAR PURPOSE.