draft-ietf-smime-compression-01.txt   draft-ietf-smime-compression-02.txt 
Internet Draft Editor: Peter Gutmann Internet Draft Editor: Peter Gutmann
draft-ietf-smime-compression-01.txt University of Auckland draft-ietf-smime-compression-02.txt University of Auckland
August 29, 2000 October 25, 2000
Expires February 2001 Expires April 2001
Compressed Data Content Type for S/MIME Compressed Data Content Type for S/MIME
Status of this memo Status of this memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other Force (IETF), its areas, and its working groups. Note that other
skipping to change at line 30 skipping to change at line 30
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
The Cryptographic Message Syntax data format doesn't currently contain The Cryptographic Message Syntax data format doesn't currently
any provisions for compressing data before processing it. Compressing contain any provisions for compressing data before processing it.
data before transmission provides a number of advantages including the Compressing data before transmission provides a number of advantages
elimination of data redundancy which could help an attacker, speeding including the elimination of data redundancy which could help an
up processing by reducing the amount of data to be processed by later attacker, speeding up processing by reducing the amount of data to be
steps such as signing or encryption, and reducing overall message size. processed by later steps such as signing or encryption, and reducing
Although there have been proposals for adding compression at other overall message size. Although there have been proposals for adding
levels (for example at the MIME or SSL level) these don't address the compression at other levels (for example at the MIME or SSL level)
problem of compression of CMS content unless the compression is these don't address the problem of compression of CMS content unless
supplied by an external means (for example by intermixing MIME and the compression is supplied by an external means (for example by
CMS). This document defines a format for using compressed data as a intermixing MIME and CMS). This document defines a format for using
CMS content type. compressed data as a CMS content type.
1. Introduction 1. Introduction
This document describes a compressed data content encryption type for This document describes a compressed data content encryption type for
S/MIME. This is implemented as a new ContentInfo type and is an S/MIME. This is implemented as a new ContentInfo type and is an
extension to the types currently defined in CMS [RFC 2630]. Future extension to the types currently defined in CMS [RFC 2630]. Future
implementations of CMS SHOULD include this extension. implementations of CMS SHOULD include this extension.
The format of the messages are described in ASN.1:1994 [ASN1]. The format of the messages are described in ASN.1 [ASN1].
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in [RFC2119]. interpreted as described in [RFC2119].
1.1 Compressed Data Content Type 1.1 Compressed Data Content Type
The compressed-data content type consists of content of any type The compressed-data content type consists of content of any type
compressed using a specified algorithm. The following object compressed using a specified algorithm. The following object
identifier identifies the compressed-data content type: identifier identifies the compressed-data content type:
id-ct-compressedData OBJECT IDENTIFIER ::= { iso(1) member-body(2) id-ct-compressedData OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) ct(1) 9 } us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) ct(1) 9 }
The compressed-data content type shall have ASN.1 type CompressedData: The compressed-data content type shall have ASN.1 type
CompressedData:
CompressedData ::= SEQUENCE { CompressedData ::= SEQUENCE {
version CMSVersion, version CMSVersion,
compressionAlgorithm CompressionAlgorithmIdentifier, compressionAlgorithm CompressionAlgorithmIdentifier,
encapContentInfo EncapsulatedContentInfo encapContentInfo EncapsulatedContentInfo
} }
The fields of type CompressedData have the following meanings: The fields of type CompressedData have the following meanings:
version is the syntax version number. It shall be 0. version is the syntax version number. It shall be 0.
compressionAlgorithm is a compression algorithm identifier, as compressionAlgorithm is a compression algorithm identifier, as
defined in section 2. defined in section 2.
encapContentInfo is the content which is compressed. encapContentInfo is the content which is compressed.
Implementations SHOULD use the SMIMECapabilities attribute to indicate Implementations SHOULD use the SMIMECapabilities attribute to
their ability to process compressed content types. A compression indicate their ability to process compressed content types. A
SMIMECapability consists of the AlgorithmIdentifier for the supported compression SMIMECapability consists of the AlgorithmIdentifier for
compression algorithm, in the case of the algorithm specified in this the supported compression algorithm, in the case of the algorithm
document this is id-alg-zlibCompression with parameters NULL. specified in this document this is id-alg-zlibCompression with
Alternatively, the use of compression may be handled by prior parameters NULL. Alternatively, the use of compression may be handled
arrangement (for example as part of an interoperability profile). by prior arrangement (for example as part of an interoperability
profile).
2. Compression Types 2. Compression Types
CMS implementations should include ZLIB [RFC 1950] [RFC 1951], which is CMS implementations should include ZLIB [RFC 1950] [RFC 1951], which
free of any intellectual property restrictions and has a freely- is free of any intellectual property restrictions and has a freely-
available, portable and efficient reference implementation. The available, portable and efficient reference implementation. The
following object identifier identifies ZLIB: following object identifier identifies ZLIB:
id-alg-zlibCompress OBJECT IDENTIFIER ::= { iso(1) member-body(2) id-alg-zlibCompress OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) alg(3) 8 } us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) alg(3) 8 }
The parameters for this algorithm are NULL. The parameters for this algorithm are NULL.
3. Security Considerations 3. Security Considerations
This RFC is not concerned with security, except for the fact that This RFC is not concerned with security, except for the fact that
compressing data before encryption can enhance the security provided by compressing data before encryption can enhance the security provided
other processing steps by reducing the quantity of known plaintext by other processing steps by reducing the quantity of known plaintext
available to an attacker. available to an attacker.
Author Address Author Address
Peter Gutmann Peter Gutmann
University of Auckland University of Auckland
Private Bag 92019 Private Bag 92019
Auckland, New Zealand Auckland, New Zealand
pgut001@cs.auckland.ac.nz pgut001@cs.auckland.ac.nz
References References
ASN1 Recommendation X.680: Specification of Abstract Syntax Notation ASN1 Recommendation X.680: Specification of Abstract Syntax
One (ASN.1), 1994. Notation One (ASN.1), 1994.
RFC2119 Key Words for Use in RFC's to Indicate Requirement Levels, RFC2119 Key Words for Use in RFC's to Indicate Requirement Levels,
S.Bradner, March 1997. S.Bradner, March 1997.
RFC1950 ZLIB Compressed Data Format Specification version 3.3, RFC1950 ZLIB Compressed Data Format Specification version 3.3,
P.Deutsch and J-L Gailly, May 1996. P.Deutsch and J-L Gailly, May 1996.
RFC1951 DEFLATE Compressed Data Format Specification version 1.3, RFC1951 DEFLATE Compressed Data Format Specification version 1.3,
P.Deutsch, May 1996. P.Deutsch, May 1996.
skipping to change at line 161 skipping to change at line 163
compressionAlgorithm CompressionAlgorithmIdentifier, compressionAlgorithm CompressionAlgorithmIdentifier,
encapContentInfo EncapsulatedContentInfo encapContentInfo EncapsulatedContentInfo
} }
CompressionAlgorithmIdentifer ::= AlgorithmIdentifier CompressionAlgorithmIdentifer ::= AlgorithmIdentifier
END END
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society 1999. All Rights Reserved. Copyright (C) The Internet Society 2000. All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it or others, and derivative works that comment on or otherwise explain it
assist in its implementation may be prepared, copied, published and or assist in its implementation may be prepared, copied, published
distributed, in whole or in part, without restriction of any kind, and distributed, in whole or in part, without restriction of any
provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing the document itself may not be modified in any way, such as by removing
copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of developing Internet organizations, except as needed for the purpose of
Internet standards in which case the procedures for copyrights defined developing Internet standards in which case the procedures for
in the Internet Standards process must be followed, or as required to copyrights defined in the Internet Standards process must be
translate it into languages other than English. followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns. revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
FITNESS FOR A PARTICULAR PURPOSE. MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 End of changes. 

This html diff was produced by rfcdiff 1.25, available from http://www.levkowetz.com/ietf/tools/rfcdiff/