Using the Boneh-Franklin and Boneh-Boyen Identity-Based Encryption Algorithms with the Cryptographic Message Syntax (CMS)
RFC 5409

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Network Working Group                                          L. Martin
Request for Comments: 5409                              Voltage Security
Category: Informational                                     M. Schertler
                                                                   Axway
                                                            January 2009

  Using the Boneh-Franklin and Boneh-Boyen Identity-Based Encryption
        Algorithms with the Cryptographic Message Syntax (CMS)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (c) 2009 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
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   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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Abstract

   This document describes the conventions for using the Boneh-Franklin
   (BF) and Boneh-Boyen (BB1) identity-based encryption algorithms in
   the Cryptographic Message Syntax (CMS) to encrypt content-encryption
   keys.  Object identifiers and the convention for encoding a
   recipient's identity are also defined.

Martin & Schertler           Informational                      [Page 1]
RFC 5409                   Using IBE with CMS               January 2009

Table of Contents

   1. Introduction ....................................................2
      1.1. Terminology ................................................3
      1.2. IBE Overview ...............................................3
   2. Using Identity-Based Encryption .................................3
   3. Key Encryption Algorithm Identifiers ............................6
   4. Processing by the Sender ........................................7
   5. Processing by the Receiver ......................................7
   6. ASN.1 Module ....................................................8
   7. Security Considerations .........................................9
      7.1. Attacks outside the Scope of This Document .................9
      7.2. Attacks within the Scope of This Document .................10
      7.3. Attacks to Which the Protocols Defined in This Document
           Are Susceptible............................................11
   8. References .....................................................12
      8.1. Normative References ......................................12
      8.2. Informative References ....................................12

1.  Introduction

   This document defines the way to use the Boneh-Franklin [IBCS] and
   Boneh-Boyen [IBCS] identity-based encryption (IBE) public-key
   algorithms in the Cryptographic Message Syntax (CMS) [CMS].  IBE is a
   public-key technology for encrypting content-encryption keys (CEKs)
   that can be implemented within the framework of the CMS: the
   recipient's identity is incorporated into the EnvelopedData CMS
   content type using the OtherRecipientInfo CHOICE in the RecipientInfo
   field as defined in Section 6.2.5 of [CMS].  This document does not
   describe the implementation of the BF and BB1 algorithms, which are
   described in detail in [IBCS].

   IBE algorithms are a type of public-key cryptographic algorithm in
   which the public key is calculated directly from a user's identity
   instead of being generated randomly.  This requires a different set
   of steps for encryption and decryption than would be used with other
   public-key algorithms, and these steps are defined in Sections 4 and
   5 of this document, respectively.

   This document also defines the object identifiers and syntax of the
   object that is used to define the identity of a message recipient.

   CMS values and identity objects are defined using ASN.1 [ASN1].

Martin & Schertler           Informational                      [Page 2]
RFC 5409                   Using IBE with CMS               January 2009

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [KEYWORDS].

1.2.  IBE Overview

   In addition to the client components that are described in this
   document, the following additional components are required for a
   complete IBE messaging system.

      o  A Private-Key Generator (PKG).  The PKG contains the
         cryptographic material, known as a master secret, for
         generating an individual's IBE private key.  A PKG accepts an
         IBE user's private key request and, after successfully
         authenticating them in some way, returns their IBE private key.