Use of the RSA-KEM Key Transport Algorithm in the Cryptographic Message Syntax (CMS)
RFC 5990

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Internet Engineering Task Force (IETF)                        J. Randall
Request for Comments: 5990                            Randall Consulting
Category: Standards Track                                     B. Kaliski
ISSN: 2070-1721                                                      EMC
                                                             J. Brainard
                                                                     RSA
                                                               S. Turner
                                                                    IECA
                                                          September 2010

               Use of the RSA-KEM Key Transport Algorithm
               in the Cryptographic Message Syntax (CMS)

Abstract

   The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward)
   mechanism for transporting keying data to a recipient using the
   recipient's RSA public key.  ("KEM" stands for "key encapsulation
   mechanism".)  This document specifies the conventions for using the
   RSA-KEM Key Transport Algorithm with the Cryptographic Message Syntax
   (CMS).  The ASN.1 syntax is aligned with an expected forthcoming
   change to American National Standard (ANS) X9.44.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5990.

Randall, et al.              Standards Track                    [Page 1]
RFC 5990                  Use of RSA-KEM in CMS           September 2010

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
      1.1. Conventions Used in This Document ..........................4
   2. Use in CMS ......................................................4
      2.1. Underlying Components ......................................4
      2.2. RecipientInfo Conventions ..................................5
      2.3. Certificate Conventions ....................................5
      2.4. SMIMECapabilities Attribute Conventions ....................6
   3. Security Considerations .........................................7
   4. IANA Considerations .............................................9
   5. Acknowledgements ................................................9
   6. References .....................................................10
      6.1. Normative References ......................................10
      6.2. Informative References ....................................11
   Appendix A.  RSA-KEM Key Transport Algorithm ......................12
      A.1.  Underlying Components ....................................12
      A.2.  Sender's Operations ......................................12
      A.3.  Recipient's Operations ...................................13
   Appendix B.  ASN.1 Syntax .........................................15
      B.1.  RSA-KEM Key Transport Algorithm ..........................16
      B.2.  Selected Underlying Components ...........................18
         B.2.1.  Key Derivation Functions ............................18
         B.2.2.  Symmetric Key-Wrapping Schemes ......................19
      B.3.  ASN.1 Module .............................................20
      B.4.  Examples .................................................25

Randall, et al.              Standards Track                    [Page 2]
RFC 5990                  Use of RSA-KEM in CMS           September 2010

1.  Introduction

   The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward)
   mechanism for transporting keying data to a recipient using the
   recipient's RSA public key.

   Most previous key transport algorithms based on the RSA public-key
   cryptosystem (e.g., the popular PKCS #1 v1.5 algorithm [PKCS1]) have
   the following general form: