RSAES-OAEP in CMS: Use of the RSAES-OAEP Key Transport Algorithm in Cryptographic Message Syntax (CMS)

Network Working Group                                         R. Housley
Request for Comments: 3560                                Vigil Security
Category: Standards Track                                      July 2003


            Use of the RSAES-OAEP Key Transport Algorithm in
                 the Cryptographic Message Syntax (CMS)

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 describes the conventions for using the RSAES-OAEP key
   transport algorithm with the Cryptographic Message Syntax (CMS).  The
   CMS specifies the enveloped-data content type, which consists of an
   encrypted content and encrypted content-encryption keys for one or
   more recipients.  The RSAES-OAEP key transport algorithm can be used
   to encrypt content-encryption keys for intended recipients.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Enveloped-data Conventions . . . . . . . . . . . . . . . . . .  3
       2.1.  EnvelopedData Fields . . . . . . . . . . . . . . . . . .  3
       2.2.  KeyTransRecipientInfo Fields . . . . . . . . . . . . . .  4
   3.  RSAES-OAEP Algorithm Identifiers and Parameters. . . . . . . .  4
   4.  Certificate Conventions. . . . . . . . . . . . . . . . . . . .  6
   5.  SMIMECapabilities Attribute Conventions. . . . . . . . . . . .  8
   6.  Security Considerations. . . . . . . . . . . . . . . . . . . .  9
   7.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 11
   8.  Intellectual Property Rights Statement . . . . . . . . . . . . 11
   9.  Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 11
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
       10.1.  Normative References. . . . . . . . . . . . . . . . . . 11
       10.2.  Informative References. . . . . . . . . . . . . . . . . 12
   Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . 14
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 18

1.  Introduction

   PKCS #1 Version 1.5 [PKCS#1v1.5] specifies a widely deployed variant
   of the RSA key transport algorithm.  PKCS #1 Version 1.5 key
   transport is vulnerable to adaptive chosen ciphertext attacks,
   especially when it is used to for key management in interactive
   applications.  This attack is often referred to as the "Million
   Message Attack," and it explained in [RSALABS] and [CRYPTO98].
   Exploitation of this vulnerability, which reveals the result of a
   particular RSA decryption, requires access to an oracle which will
   respond to hundreds of thousands of ciphertexts, which are
   constructed adaptively in response to previously received replies
   that provide information on the successes or failures of attempted
   decryption operations.

   The attack is significantly less feasible in store-and-forward
   environments, such as S/MIME.  RFC 3218 [MMA] discussed the
   countermeasures to this attack that are available when PKCS #1
   Version 1.5 key transport is used in conjunction with the
   Cryptographic Message Syntax (CMS) [CMS].

   When PKCS #1 Version 1.5 key transport is applied as an intermediate
   encryption layer within an interactive request-response
   communications environment, exploitation could be more feasible.
   However, Secure Sockets Layer (SSL) [SSL] and Transport Layer
   Security (TLS) [TLS] protocol implementations could include
   countermeasures that detect and prevent the Million Message Attack
   and other chosen-ciphertext attacks.  These countermeasures are
   performed within the protocol level.

   In the interest of long-term security assurance, it is prudent to
   adopt an improved cryptographic technique rather than embedding
   countermeasures within protocols.  To this end, an updated version of
   PKCS #1 has been published.  PKCS #1 Version 2.1 [PKCS#1v2.1]
   supersedes RFC 2313.  It preserves support for the PKCS #1 Version
   1.5 encryption padding format, and it also defines a new one.  To
   resolve the adaptive chosen ciphertext vulnerability, the PKCS #1
   Version 2.1 specifies and recommends use of Optimal Asymmetric
   Encryption Padding (OAEP) for RSA key transport.

   This document specifies the use of RSAES-OAEP key transport algorithm
   in the CMS.  The CMS can be used in either a store-and-forward or an
   interactive request-response environment.

   The CMS supports variety of architectures for certificate-based key
   management, particularly the one defined by the PKIX working group
   [PROFILE].  PKCS #1 Version 1.5 and PKCS #1 Version 2.1 require the
   same RSA public key information.  Thus, a certified RSA public key
   may be used with either RSA key transport technique.

   The CMS uses ASN.1 [X.208-88], the Basic Encoding Rules (BER)
   [X.209-88], and the Distinguished Encoding Rules (DER) [X.509-88].

   Throughout this document, when the terms "MUST", "MUST NOT",
   "SHOULD", and "MAY" are used in capital letters, their use conforms
   to the definitions in RFC 2119 [STDWORDS].  These key word
   definitions help make the intent of standards documents as clear as
   possible.  These key words are used in this document to help
   implementers achieve interoperability.

2.  Enveloped-data Conventions

   The CMS enveloped-data content type consists of an encrypted content
   and wrapped content-encryption keys for one or more recipients.  The
   RSAES-OAEP key transport algorithm is used to wrap the
   content-encryption key for one recipient.

   Compliant software MUST meet the requirements for constructing an
   enveloped-data content type stated in [CMS] Section 6,
   "Enveloped-data Content Type".

   A content-encryption key MUST be randomly generated for each instance
   of an enveloped-data content type.  The content-encryption key is
   used to encipher the content.

2.1.  EnvelopedData Fields

   The enveloped-data content type is ASN.1 encoded using the
   EnvelopedData syntax.  The fields of the EnvelopedData syntax MUST be
   populated as described in this section when RSAES-OAEP key transport
   is employed for one or more recipients.

   The EnvelopedData version MUST be 0, 2, or 3.

   The EnvelopedData originatorInfo field is not used for the RSAES-OAEP
   key transport algorithm.  However, this field MAY be present to
   support recipients using other key management algorithms.

   The EnvelopedData recipientInfos CHOICE MUST be
   KeyTransRecipientInfo.  See section 2.2 for further discussion of
   KeyTransRecipientInfo.

   The EnvelopedData encryptedContentInfo contentEncryptionAlgorithm
   field MUST be a symmetric encryption algorithm identifier.

   The EnvelopedData unprotectedAttrs MAY be present.

2.2.  KeyTransRecipientInfo Fields

   The fields of the KeyTransRecipientInfo syntax MUST be populated as
   described in this section when RSAES-OAEP key transport is employed
   for one or more recipients.

   The KeyTransRecipientInfo version MUST be 0 or 2.  If the
   RecipientIdentifier uses the issuerAndSerialNumber alternative, then
   the version MUST be 0.  If the RecipientIdentifier uses the
   subjectKeyIdentifier alternative, then the version MUST be 2.

   The KeyTransRecipientInfo RecipientIdentifier provides two
   alternatives for specifying the recipient's certificate, and thereby
   the recipient's public key.  The recipient's certificate MUST contain
   a RSA public key.  The content-encryption key is encrypted with the
   recipient's RSA public key.  The issuerAndSerialNumber alternative
   identifies the recipient's certificate by the issuer's distinguished
   name and the certificate serial number; the subjectKeyIdentifier
   identifies the recipient's certificate by the X.509
   subjectKeyIdentifier extension value.

   The KeyTransRecipientInfo keyEncryptionAlgorithm specifies use of the
   RSAES-OAEP algorithm, and its associated parameters, to encrypt the
   content-encryption key for the recipient.  The key-encryption process
   is described in [PKCS#1v2.1].  See section 3 of this document for the
   algorithm identifier and the parameter syntax.

   The KeyTransRecipientInfo encryptedKey is the result of encrypting
   the content-encryption key in the recipient's RSA public key using
   the RSAES-OAEP algorithm.  The RSA public key MUST be at least 1024
   bits in length.  When using a Triple-DES [3DES] content-encryption
   key, implementations MUST adjust the parity bits to ensure odd parity
   for each octet of each DES key comprising the Triple-DES key prior to
   RSAES-OAEP encryption.

3.  RSAES-OAEP Algorithm Identifiers and Parameters

   The RSAES-OAEP key transport algorithm is the RSA encryption scheme
   defined in RFC 3447 [PKCS#1v2.1], where the message to be encrypted
   is the content-encryption key.  The algorithm identifier for
   RSAES-OAEP is:

   id-RSAES-OAEP  OBJECT IDENTIFIER  ::=  { iso(1) member-body(2)
     us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 7 }

   The AlgorithmIdentifier parameters field MUST be present, and the
   parameters field MUST contain RSAES-OAEP-params.  RSAES-OAEP-params
   has the following syntax:

   RSAES-OAEP-params  ::=  SEQUENCE  {
     hashFunc    [0] AlgorithmIdentifier DEFAULT sha1Identifier,
     maskGenFunc [1] AlgorithmIdentifier DEFAULT mgf1SHA1Identifier,
     pSourceFunc [2] AlgorithmIdentifier DEFAULT
                         pSpecifiedEmptyIdentifier  }

   sha1Identifier  AlgorithmIdentifier  ::=  { id-sha1, NULL }

   mgf1SHA1Identifier  AlgorithmIdentifier  ::=
                         { id-mgf1, sha1Identifier }

   pSpecifiedEmptyIdentifier  AlgorithmIdentifier ::=
                         { id-pSpecified, nullOctetString }

   nullOctetString  OCTET STRING (SIZE (0))  ::=  { ''H }

   id-sha1  OBJECT IDENTIFIER  ::=  { iso(1)
                         identified-organization(3) oiw(14)
                         secsig(3) algorithms(2) 26 }

   pkcs-1  OBJECT IDENTIFIER  ::=  { iso(1) member-body(2)
                         us(840) rsadsi(113549) pkcs(1) pkcs-1(1) }

   id-mgf1  OBJECT IDENTIFIER  ::=  { pkcs-1 8 }

   id-pSpecified  OBJECT IDENTIFIER  ::=  { pkcs-1 9 }

   The fields within RSAES-OAEP-params have the following meanings:

   hashFunc identifies the one-way hash function.  Implementations MUST
   support SHA-1 [SHA1], and implementations MAY support other one-way
   hash functions.  The SHA-1 algorithm identifier is comprised of the
   id-sha1 object identifier and a parameter of NULL.  Implementations
   that perform encryption MUST omit the hashFunc field when SHA-1 is
   used, indicating that the default algorithm was used.
   Implementations that perform decryption MUST recognize both the
   id-sha1 object identifier and an absent hashFunc field as an
   indication that SHA-1 was used.

   maskGenFunc identifies the mask generation function.  Implementations
   MUST support MFG1 [PKCS#1v2.1].  MFG1 requires a one-way hash
   function, and it is identified in the parameter field of the MFG1
   algorithm identifier.  Implementations MUST support SHA-1 [SHA1], and
   implementations MAY support other one-way hash functions.  The MFG1
   algorithm identifier is comprised of the id-mgf1 object identifier
   and a parameter that contains the algorithm identifier of the one-way
   hash function employed with MFG1.  The SHA-1 algorithm identifier is
   comprised of the id-sha1 object identifier and a parameter of NULL.
   Implementations that perform encryption MUST omit the maskGenFunc
   field when MFG1 with SHA-1 is used, indicating that the default
   algorithm was used. Implementations that perform decryption MUST
   recognize both the id-mgf1 and id-sha1 object identifiers as well as
   an absent maskGenFunc field as an indication that MFG1 with SHA-1 was
   used.

   pSourceFunc identifies the source (and possibly the value) of the
   encoding parameters, commonly called P.  Implementations MUST
   represent P by the algorithm identifier, id-pSpecified, indicating
   that P is explicitly provided as an OCTET STRING in the parameters.
   The default value for P is an empty string.  In this case, pHash in
   EME-OAEP contains the hash of a zero length string.  Implementations
   MUST support a zero length P value.  Implementations that perform
   encryption MUST omit the pSourceFunc field when a zero length P value
   is used, indicating that the default value was used. Implementations
   that perform decryption MUST recognize both the id-pSpecified object
   identifier and an absent pSourceFunc field as an indication that a
   zero length P value was used.

4.  Certificate Conventions

   RFC 3280 [PROFILE] specifies the profile for using X.509 Certificates
   in Internet applications.  When a RSA public key will be used for
   RSAES-OAEP key transport, the conventions specified in this section
   augment RFC 3280.

   Traditionally, the rsaEncryption object identifier is used to
   identify RSA public keys.  However, to implement all of the
   recommendations described in the Security Considerations section of
   this document (see section 6), the certificate user needs to be able
   to determine the form of key transport that the RSA private key owner
   associates with the public key.

   The rsaEncryption object identifier continues to identify the subject
   public key when the RSA private key owner does not wish to limit the
   use of the public key exclusively to RSAES-OAEP.  In this case, the
   rsaEncryption object identifier MUST be used in the algorithm field
   within the subject public key information, and the parameters field
   MUST contain NULL.

      rsaEncryption  OBJECT IDENTIFIER  ::=  { pkcs-1 1 }

   Further discussion of the conventions associated with use of the
   rsaEncryption object identifier can be found in RFC 3279 (see
   [CERTALGS], section 2.3.1).

   When the RSA private key owner wishes to limit the use of the public
   key exclusively to RSAES-OAEP, then the id-RSAES-OAEP object
   identifier MUST be used in the algorithm field within the subject
   public key information, and the parameters field MUST contain
   RSAES-OAEP-params.  The id-RSAES-OAEP object identifier value and the
   RSAES-OAEP-params syntax are fully described in section 3 of this
   document.

   Regardless of the object identifier used, the RSA public key is
   encoded in the same manner in the subject public key information.
   The RSA public key MUST be encoded using the type RSAPublicKey type:

      RSAPublicKey ::= SEQUENCE {
         modulus            INTEGER,    -- n
         publicExponent     INTEGER  }  -- e

   Here, the modulus is the modulus n, and publicExponent is the public
   exponent e.  The DER encoded RSAPublicKey is carried in the
   subjectPublicKey BIT STRING within the subject public key
   information.

   The intended application for the key MAY be indicated in the key
   usage certificate extension (see [PROFILE], section 4.2.1.3).  If the
   keyUsage extension is present in a certificate that conveys an RSA
   public key with the id-RSAES-OAEP object identifier, then the key
   usage extension MUST contain a combination of the following values:

      keyEncipherment; and
      dataEncipherment.

   However, both keyEncipherment and dataEncipherment SHOULD NOT be
   present.

   When a certificate that conveys an RSA public key with the
   id-RSAES-OAEP object identifier, the certificate user MUST only use
   the certified RSA public key for RSAES-OAEP operations, and the
   certificate user MUST perform those operations using the parameters
   identified in the certificate.

5.  SMIMECapabilities Attribute Conventions

   RFC 2633 [MSG], Section 2.5.2 defines the SMIMECapabilities signed
   attribute (defined as a SEQUENCE of SMIMECapability SEQUENCEs) to be
   used to specify a partial list of algorithms that the software
   announcing the SMIMECapabilities can support.  When constructing a
   signedData object, compliant software MAY include the
   SMIMECapabilities signed attribute announcing that it supports the
   RSAES-OAEP algorithm.

   When all of the default settings are selected, the SMIMECapability
   SEQUENCE representing RSAES-OAEP MUST include the id-RSAES-OAEP
   object identifier in the capabilityID field and MUST include an empty
   SEQUENCE in the parameters field.  In this case, RSAES-OAEP is
   represented by the rSAES-OAEP-Default-Identifier:

   rSAES-OAEP-Default-Identifier  AlgorithmIdentifier  ::=
                         { id-RSAES-OAEP,
                            { sha1Identifier,
                              mgf1SHA1Identifier,
                              pSpecifiedEmptyIdentifier } }

   The SMIMECapability SEQUENCE representing rSAES-OAEP-Default-
   Identifier MUST be DER-encoded as the following hexadecimal string:

      30 0D 06 09 2A 86 48 86 F7 0D 01 01 07 30 00

   When settings other than the defaults are selected, the
   SMIMECapability SEQUENCE representing RSAES-OAEP MUST include the
   id-RSAES-OAEP object identifier in the capabilityID field and MUST
   include the RSAES-OAEP-params SEQUENCE that identifies the
   non-default settings in the parameters field.

   When SHA-256 is used in the hashFunc and SHA-256 is used with MGF1 in
   the maskGenFunc, the SMIMECapability SEQUENCE representing RSAES-OAEP
   is the rSAES-OAEP-SHA256-Identifier, as specified in Appendix A.  The
   SMIMECapability SEQUENCE representing rSAES-OAEP-SHA256-Identifier
   MUST be DER-encoded as the following hexadecimal string:

      30 38 06 09 2A 86 48 86 F7 0D 01 01 07 30 2B 30
      0D 06 09 60 86 48 01 65 03 04 02 01 05 00 30 1A
      06 09 2A 86 48 86 F7 0D 01 01 08 30 0D 06 09 60
      86 48 01 65 03 04 02 01 05 00

   When SHA-384 is used in the hashFunc and SHA-384 is used with MGF1 in
   the maskGenFunc, the SMIMECapability SEQUENCE representing RSAES-OAEP
   is the rSAES-OAEP-SHA384-Identifier, as specified in Appendix A.  The
   SMIMECapability SEQUENCE representing rSAES-OAEP-SHA384-Identifier
   MUST be DER-encoded as the following hexadecimal string:

      30 38 06 09 2A 86 48 86 F7 0D 01 01 07 30 2B 30
      0D 06 09 60 86 48 01 65 03 04 02 02 05 00 30 1A
      06 09 2A 86 48 86 F7 0D 01 01 08 30 0D 06 09 60
      86 48 01 65 03 04 02 02 05 00

   When SHA-512 is used in the hashFunc and SHA-512 is used with MGF1 in
   the maskGenFunc, the SMIMECapability SEQUENCE representing RSAES-OAEP
   is the rSAES-OAEP-SHA512-Identifier, as specified in Appendix A.  The
   SMIMECapability SEQUENCE representing rSAES-OAEP-SHA512-Identifier
   MUST be DER-encoded as the following hexadecimal string:

      30 38 06 09 2A 86 48 86 F7 0D 01 01 07 30 2B 30
      0D 06 09 60 86 48 01 65 03 04 02 03 05 00 30 1A
      06 09 2A 86 48 86 F7 0D 01 01 08 30 0D 06 09 60
      86 48 01 65 03 04 02 03 05 00

6.  Security Considerations

   Implementations must protect the RSA private key and the
   content-encryption key.  Compromise of the RSA private key may result
   in the disclosure of all messages protected with that key.
   Compromise of the content-encryption key may result in disclosure of
   the associated encrypted content.

   The generation of RSA public/private key pairs relies on a random
   numbers.  The use of inadequate pseudo-random number generators
   (PRNGs) to generate cryptographic keys can result in little or no
   security.  An attacker may find it much easier to reproduce the PRNG
   environment that produced the keys, searching the resulting small set
   of possibilities, rather than brute force searching the whole key
   space.  The generation of quality random numbers is difficult.  RFC
   1750 [RANDOM] offers important guidance in this area.

   Generally, good cryptographic practice employs a given RSA key pair
   in only one scheme.  This practice avoids the risk that vulnerability
   in one scheme may compromise the security of the other, and may be
   essential to maintain provable security.  While PKCS #1 Version 1.5
   [PKCS#1v1.5] has been employed for both key transport and digital
   signature without any known bad interactions, such a combined use of
   an RSA key pair is not recommended in the future.  Therefore, an RSA
   key pair used for RSAES-OAEP key transport should not also be used
   for other purposes.  For similar reasons, one RSA key pair should
   always be used with the same RSAES-OAEP parameters.

   This specification requires implementation to support the SHA-1
   one-way hash function for interoperability, but support for other
   one-way hash function is permitted.  At the time of this writing, the
   best (known) collision attacks against SHA-1 are generic attacks with
   complexity 2^80, where 80 is one-half the bit length of the hash
   value.  When a one-way hash function is used with a digital signature
   scheme, a collision attack is easily translated into a signature
   forgery.  Therefore, the use of SHA-1 in a digital signature scheme
   provides a security level of no more than 80 bits.  If a greater
   level of security is desired, then a secure one-way hash function
   with a longer hash value is needed.  SHA-256, SHA-384, and SHA-512
   are likely candidates [SHA2].

   The metrics for choosing a one-way hash function for use in digital
   signatures do not directly apply to the RSAES-OAEP key transport
   algorithm, since a collision attack on the one-way hash function does
   not directly translate into an attack on the key transport algorithm,
   unless the encoding parameters P varies (in which case a collision
   the hash value for different encoding parameters might be exploited).

   Nevertheless, for consistency with the practice for digital signature
   schemes, and in case the encoding parameters P is not the empty
   string, it is recommended that the same rule of thumb be applied to
   selection of a one-way hash function for use with RSAES-OAEP.  That
   is, the one-way hash function should be selected so that the bit
   length of the hash value is at least twice as long as the desired
   security level in bits.

   A 1024-bit RSA public key and SHA-1 both provide a security level of
   about 80 bits.  In [NISTGUIDE], the National Institute of Standards
   and Technology suggests that a security level of 80 bits is adequate
   for most applications until 2015.  If a security level greater than
   80 bits is needed, then a longer RSA public key and a secure one-way
   hash function with a longer hash value are needed.  Again, SHA-256,
   SHA-384, and SHA-512 are likely candidates for such a one-way hash
   function.  For this reason, the algorithm identifiers for these
   one-way hash functions are included in the ASN.1 module in Appendix
   A.

   The same one-way hash function should be employed for the hashFunc
   and the maskGenFunc, but it is not required.  Using the same one-way
   hash function reduces the potential for implementation errors.

7.  IANA Considerations

   Within the CMS, algorithms are identified by object identifiers
   (OIDs).  All of the OIDs used in this document were assigned in
   Public-Key Cryptography Standards (PKCS) documents or by the National
   Institute of Standards and Technology (NIST).  No further action by
   the IANA is necessary for this document or any anticipated updates.

8.  Intellectual Property Rights Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

9.  Acknowledgments

   This document is the result of contributions from many professionals.
   I appreciate the hard work of all members of the IETF S/MIME Working
   Group.  Further, I extend a special thanks to Burt Kaliski, Jakob
   Jonsson, Francois Rousseau, and Jim Schaad.

10.  References

   This section provides normative and informative references.

10.1.  Normative References

   [3DES]        American National Standards Institute.  ANSI X9.52-
                 1998, Triple Data Encryption Algorithm Modes of
                 Operation.  1998.

   [CMS]         Housley, R., "Cryptographic Message Syntax (CMS)", RFC
                 3369, August 2002.

   [MSG]         Ramsdell, B., "S/MIME Version 3 Message Specification",
                 RFC 2633, June 1999.

   [PKCS#1v2.1]  Jonsson, J. and B. Kaliski, "Public-Key Cryptography
                 Standards (PKCS) #1: RSA Cryptography Specifications,
                 Version 2.1", RFC 3447, February 2003.

   [PROFILE]     Housley, R., Polk, W., Ford, W. and D. Solo, "Internet
                 X.509 Public Key Infrastructure: Certificate and
                 Certificate Revocation List (CRL) Profile", RFC 3280,
                 April 2002.

   [SHA1]        National Institute of Standards and Technology.  FIPS
                 Pub 180-1: "Secure Hash Standard."  April 1995.

   [STDWORDS]    Bradner, S., "Key Words for Use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.

   [X.208-88]    CCITT.  Recommendation X.208: Specification of Abstract
                 Syntax Notation One (ASN.1).  1988.

   [X.209-88]    CCITT.  Recommendation X.209: Specification of Basic
                 Encoding Rules for Abstract Syntax Notation One
                 (ASN.1).  1988.

   [X.509-88]    CCITT.  Recommendation X.509: The Directory -
                 Authentication Framework.  1988.

10.2.  Informative References

   [CERTALGS]    Bassham, L., Polk, W. and R. Housley, "Algorithms and
                 Identifiers for the Internet X.509 Public Key
                 Infrastructure Certificate and Certificate Revocation
                 List (CRL) Profile", RFC 3279, April 2002.

   [CRYPTO98]    Bleichenbacher, D.  "Chosen Ciphertext Attacks Against
                 Protocols Based on the RSA Encryption Standard PKCS
                 #1", in H. Krawczyk (editor), Advances in Cryptology -
                 CRYPTO '98 Proceedings, Lecture Notes in Computer
                 Science 1462 (1998), Springer-Verlag, pp. 1-12.

   [MMA]         Rescorla, E., "Preventing the Million Message Attack on
                 Cryptographic Message Syntax", RFC 3218, January 2002.

   [NISTGUIDE]   National Institute of Standards and Technology.  Second
                 Draft: "Key Management Guideline, Part 1:  General
                 Guidance."  June 2002.
                 [http://csrc.nist.gov/encryption/kms/guideline-1.pdf]

   [PKCS#1v1.5]  Kaliski, B., "PKCS #1: RSA Encryption, Version 1.5",
                 RFC 2313, March 1998.

   [RANDOM]      Eastlake, D., Crocker, S. and J. Schiller, "Randomness
                 Recommendations for Security", RFC 1750, December 1994.

   [RSALABS]     Bleichenbacher, D., B. Kaliski, and J. Staddon.  Recent
                 Results on PKCS #1: RSA Encryption Standard.  RSA
                 Laboratories' Bulletin No. 7, June 26, 1998.
                 [http://www.rsasecurity.com/rsalabs/bulletins]

   [SHA2]        National Institute of Standards and Technology.  Draft
                 FIPS Pub 180-2: "Specifications for the Secure Hash
                 Standard."  May 2001.
                 [http://csrc.nist.gov/encryption/shs/dfips-180-2.pdf]

   [SSL]         Freier, A., P. Karlton, and P. Kocher.  The SSL
                 Protocol, Version 3.0.  Netscape Communications.
                 November 1996.
                 [http://wp.netscape.com/eng/ssl3/draft302.txt]

   [TLS]         Dierks, T. and C. Allen, "The TLS Protocol Version
                 1.0", RFC 2246, January 1999.

Appendix A.  ASN.1 Module

   CMS-RSAES-OAEP
      { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
        pkcs-9(9) smime(16) modules(0) cms-rsaes-oaep(20) }

   DEFINITIONS IMPLICIT TAGS ::= BEGIN

   -- EXPORTS ALL --

   IMPORTS
      AlgorithmIdentifier
          FROM PKIX1Explicit88 -- RFC 3280
          { iso(1) identified-organization(3) dod(6) internet(1)
            security(5) mechanisms(5) pkix(7) id-mod(0)
            id-pkix1-explicit(18) };

   pkcs-1  OBJECT IDENTIFIER  ::=  { iso(1) member-body(2) us(840)
                         rsadsi(113549) pkcs(1) pkcs-1(1) }

   rsaEncryption  OBJECT IDENTIFIER  ::=  { pkcs-1 1 }

   id-RSAES-OAEP  OBJECT IDENTIFIER  ::=  { pkcs-1 7 }

   RSAES-OAEP-params  ::=  SEQUENCE  {
      hashFunc    [0] AlgorithmIdentifier DEFAULT sha1Identifier,
      maskGenFunc [1] AlgorithmIdentifier DEFAULT mgf1SHA1Identifier,
      pSourceFunc [2] AlgorithmIdentifier DEFAULT

                         pSpecifiedEmptyIdentifier }

   sha1Identifier  AlgorithmIdentifier  ::=  { id-sha1, NULL }

   sha256Identifier  AlgorithmIdentifier  ::=  { id-sha256, NULL }

   sha384Identifier  AlgorithmIdentifier  ::=  { id-sha384, NULL }

   sha512Identifier  AlgorithmIdentifier  ::=  { id-sha512, NULL }

   mgf1SHA1Identifier  AlgorithmIdentifier  ::=
                         { id-mgf1, sha1Identifier }

   mgf1SHA256Identifier  AlgorithmIdentifier  ::=
                         { id-mgf1, sha256Identifier }

   mgf1SHA384Identifier  AlgorithmIdentifier  ::=
                         { id-mgf1, sha384Identifier }

   mgf1SHA512Identifier  AlgorithmIdentifier  ::=
                         { id-mgf1, sha512Identifier }

   pSpecifiedEmptyIdentifier  AlgorithmIdentifier ::=
                         { id-pSpecified, nullOctetString }

   nullOctetString  OCTET STRING (SIZE (0))  ::=  { ''H }

   id-sha1  OBJECT IDENTIFIER  ::=  { iso(1)
                         identified-organization(3) oiw(14)
                         secsig(3) algorithms(2) 26 }

   id-sha256  OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
                         country(16) us(840) organization(1) gov(101)
                         csor(3) nistalgorithm(4) hashalgs(2) 1 }

   id-sha384  OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
                         country(16) us(840) organization(1) gov(101)
                         csor(3) nistalgorithm(4) hashalgs(2) 2 }

   id-sha512  OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
                         country(16) us(840) organization(1) gov(101)
                         csor(3) nistalgorithm(4) hashalgs(2) 3 }

   id-mgf1  OBJECT IDENTIFIER  ::=  { pkcs-1 8 }

   id-pSpecified  OBJECT IDENTIFIER  ::=  { pkcs-1 9 }

   rSAES-OAEP-Default-Identifier  AlgorithmIdentifier  ::=
                         { id-RSAES-OAEP,
                            { sha1Identifier,
                              mgf1SHA1Identifier,
                              pSpecifiedEmptyIdentifier } }

   rSAES-OAEP-SHA256-Identifier  AlgorithmIdentifier  ::=
                         { id-RSAES-OAEP,
                            { sha256Identifier,
                              mgf1SHA256Identifier,
                              pSpecifiedEmptyIdentifier } }

   rSAES-OAEP-SHA384-Identifier  AlgorithmIdentifier  ::=
                         { id-RSAES-OAEP,
                            { sha384Identifier,
                              mgf1SHA384Identifier,
                              pSpecifiedEmptyIdentifier } }

   rSAES-OAEP-SHA512-Identifier  AlgorithmIdentifier  ::=
                         { id-RSAES-OAEP,
                            { sha512Identifier,
                              mgf1SHA512Identifier,
                              pSpecifiedEmptyIdentifier } }

   END

Author's Address

   Russell Housley
   Vigil Security, LLC
   918 Spring Knoll Drive
   Herndon, VA 20170
   USA

   EMail: housley@vigilsec.com

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