draft-ietf-smime-cms-rsa-kem-06.txt   draft-ietf-smime-cms-rsa-kem-07.txt 
S/MIME Working Group J. Randall S/MIME Working Group James Randall, Randall Consulting
Internet Draft RSA Internet Draft Burt Kaliski, EMC
Document: draft-ietf-smime-cms-rsa-kem-06.txt B.Kaliski John Brainard, RSA
Category: Standards EMC Corp. Sean Turner, IECA
Expires: March 2009 September 2008 Expires: January 7, 2010 Category: Standards
July 7, 2009
Use of the RSA-KEM Key Transport Algorithm in CMS Use of the RSA-KEM Key Transport Algorithm in CMS
<draft-ietf-smime-cms-rsa-kem-06.txt> <draft-ietf-smime-cms-rsa-kem-07.txt>
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Abstract Abstract
The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward) The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward)
mechanism for transporting keying data to a recipient using the mechanism for transporting keying data to a recipient using the
recipient's RSA public key. This document specifies the conventions recipient's RSA public key. This document specifies the conventions
for using the RSA-KEM Key Transport Algorithm with the Cryptographic for using the RSA-KEM Key Transport Algorithm with the Cryptographic
Message Syntax (CMS). The ASN.1 syntax is aligned with ANS X9.44 and Message Syntax (CMS). The ASN.1 syntax is aligned with ANS X9.44 and
ISO/IEC 18033-2. ISO/IEC 18033-2.
Conventions Used in This Document Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
this document are to be interpreted as described in RFC 2119 document are to be interpreted as described in RFC 2119 [STDWORDS].
[STDWORDS].
1. Introduction 1. Introduction
The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward) The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward)
mechanism for transporting keying data to a recipient using the mechanism for transporting keying data to a recipient using the
recipient's RSA public key. recipient's RSA public key.
Most previous key transport algorithms based on the 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 cryptosystem (e.g., the popular PKCS #1 v1.5 algorithm [PKCS1]) have
the following general form: the following general form:
skipping to change at page 2, line 53 skipping to change at page 3, line 20
The RSA-KEM Key Transport Algorithm takes a different approach that The RSA-KEM Key Transport Algorithm takes a different approach that
provides higher security assurance, by encrypting a _random_ integer provides higher security assurance, by encrypting a _random_ integer
with the recipient's public key, and using a symmetric key-wrapping with the recipient's public key, and using a symmetric key-wrapping
scheme to encrypt the keying data. It has the following form: scheme to encrypt the keying data. It has the following form:
1. Generate a random integer z between 0 and n-1. 1. Generate a random integer z between 0 and n-1.
2. Encrypt the integer z with the recipient's RSA public key: 2. Encrypt the integer z with the recipient's RSA public key:
c = z^e mod n. c = z^e mod n
3. Derive a key-encrypting key KEK from the integer z. 3. Derive a key-encrypting key KEK from the integer z.
4. Wrap the keying data using KEK to obtain wrapped keying data 4. Wrap the keying data using KEK to obtain wrapped keying data WK.
WK.
5. Output c and WK as the encrypted keying data. 5. Output c and WK as the encrypted keying data.
This different approach provides higher security assurance because This different approach provides higher security assurance because
(a) the input to the underlying RSA operation is effectively a (a) the input to the underlying RSA operation is effectively a random
random integer between 0 and n-1, where n is the RSA modulus, so it integer between 0 and n-1, where n is the RSA modulus, so it does not
does not have any structure that could be exploited by an adversary, have any structure that could be exploited by an adversary, and (b)
and (b) the input is independent of the keying data so the result of the input is independent of the keying data so the result of the RSA
the RSA decryption operation is not directly available to an decryption operation is not directly available to an adversary. As a
adversary. As a result, the algorithm enjoys a "tight" security result, the algorithm enjoys a "tight" security proof in the random
proof in the random oracle model. (In other padding schemes, such oracle model. (In other padding schemes, such as PKCS #1 v1.5, the
as PKCS #1 v1.5, the input has structure and/or depends on the input has structure and/or depends on the keying data, and the
keying data, and the provable security assurances are not as provable security assurances are not as strong.) The approach is also
strong.) The approach is also architecturally convenient because the architecturally convenient because the public-key operations are
public-key operations are separate from the symmetric operations on separate from the symmetric operations on the keying data. One
the keying data. One benefit is that the length of the keying data benefit is that the length of the keying data is bounded only by the
is bounded only by the symmetric key-wrapping scheme, not the size symmetric key-wrapping scheme, not the size of the RSA modulus.
of the RSA modulus.
The RSA-KEM Key Transport Algorithm in various forms is being adopted The RSA-KEM Key Transport Algorithm in various forms is being adopted
in several draft standards as well as in ANS-X9.44 and ISO/IEC in several draft standards as well as in ANS-X9.44 and ISO/IEC 18033-
18033-2. It has also been recommended by the NESSIE project [NESSIE]. 2. It has also been recommended by the NESSIE project [NESSIE].
For completeness, a specification of the algorithm is given in For completeness, a specification of the algorithm is given in
Appendix A of this document; ASN.1 syntax is given in Appendix B. Appendix A of this document; ASN.1 syntax is given in Appendix B.
NOTE: The term KEM stands for "key encapsulation mechanism" and NOTE: The term KEM stands for "key encapsulation mechanism" and
refers to the first three steps of the process above. The refers to the first three steps of the process above. The
formalization of key transport algorithms (or more generally, formalization of key transport algorithms (or more generally,
asymmetric encryption schemes) in terms of key encapsulation asymmetric encryption schemes) in terms of key encapsulation
mechanisms is described further in research by Victor Shoup leading mechanisms is described further in research by Victor Shoup leading
to the development of the ISO/IEC 18033-2 standard [SHOUP]. to the development of the ISO/IEC 18033-2 standard [SHOUP].
skipping to change at page 3, line 50 skipping to change at page 4, line 20
The RSA-KEM Key Transport Algorithm MAY be employed for one or more The RSA-KEM Key Transport Algorithm MAY be employed for one or more
recipients in the CMS enveloped-data content type (Section 6 of recipients in the CMS enveloped-data content type (Section 6 of
[CMS]), where the keying data processed by the algorithm is the CMS [CMS]), where the keying data processed by the algorithm is the CMS
content-encryption key. content-encryption key.
The RSA-KEM Key Transport Algorithm SHOULD be considered for new The RSA-KEM Key Transport Algorithm SHOULD be considered for new
CMS-based applications as a replacement for the widely implemented CMS-based applications as a replacement for the widely implemented
RSA encryption algorithm specified originally in PKCS #1 v1.5 (see RSA encryption algorithm specified originally in PKCS #1 v1.5 (see
[PKCS1] and Section 4.2.1 of [CMSALGS]), which is vulnerable to [PKCS1] and Section 4.2.1 of [CMSALGS]), which is vulnerable to
chosen-ciphertext attacks. The RSAES-OAEP Key Transport Algorithm chosen-ciphertext attacks. The RSAES-OAEP Key Transport Algorithm has
has also been proposed as a replacement (see [PKCS1] and [CMS- also been proposed as a replacement (see [PKCS1] and [CMS-OAEP]).
OAEP]). RSA-KEM has the advantage over RSAES-OAEP of a tighter RSA-KEM has the advantage over RSAES-OAEP of a tighter security
security proof, but the disadvantage of slightly longer encrypted proof, but the disadvantage of slightly longer encrypted keying data.
keying data.
2.1 Underlying Components 2.1. Underlying Components
A CMS implementation that supports the RSA-KEM Key Transport A CMS implementation that supports the RSA-KEM Key Transport
Algorithm MUST support at least the following underlying components: Algorithm MUST support at least the following underlying components:
* For the key derivation function, KDF2 or KDF3 (see [ANS-X9.44] o For the key derivation function, KDF2 (see [ANS-X9.44]) (see
[IEEE-P1363a]) based on SHA-1 (see [FIPS-180-2]) (this function [IEEE-P1363a]) based on SHA-1 (see [FIPS-180-2]) (this function is
is also specified as the key derivation function in also specified as the key derivation function in [ANS-X9.63]), and
[ANS-X9.63]). KDF3 (see [IEEE-P1363a]) based on SHA-256 (see [FIPS-180-2]).
* For the key-wrapping scheme, AES-Wrap-128, i.e., the AES Key o For the key-wrapping scheme, AES-Wrap-128, i.e., the AES Key Wrap
Wrap with a 128-bit key encrypting key (see [AES-WRAP]) with a 128-bit key encrypting key (see [AES-WRAP])
An implementation SHOULD also support KDF2 and KDF3 based on SHA-256 An implementation SHOULD also support KDF3 based on SHA-1 and KDF2
(see [FIPS-180-2]). The Camillia key wrap algorithm (see [CAMILLIA]) based on SHA-256. The Camellia key wrap algorithm (see [CAMELLIA])
should be supported, and, if 3DES is supported as a content- SHOULD be supported, and, if 3DES is supported as a content-
encryption cipher, then the Triple-DES Key Wrap (see [3DES-WRAP]) encryption cipher, then the Triple-DES Key Wrap (see [3DES-WRAP])
SHOULD also be supported. SHOULD also be supported.
It MAY support other underlying components. When AES or Camilla are It MAY support other underlying components. When AES or Camellia are
used the data block size is 128 bits while the key size can be 128, used the data block size is 128 bits while the key size can be 128,
192, or 256 bits while Triple DES requires a data block size of 64 192, or 256 bits while Triple DES requires a data block size of 64
bits and a key size of 112 or 168 bits. bits and a key size of 112 or 168 bits.
2.2 RecipientInfo Conventions 2.2. RecipientInfo Conventions
When the RSA-KEM Key Transport Algorithm is employed for a recipient, When the RSA-KEM Key Transport Algorithm is employed for a recipient,
the RecipientInfo alternative for that recipient MUST be the RecipientInfo alternative for that recipient MUST be
KeyTransRecipientInfo. The algorithm-specific fields of the KeyTransRecipientInfo. The algorithm-specific fields of the
KeyTransRecipientInfo value MUST have the following values: KeyTransRecipientInfo value MUST have the following values:
* keyEncryptionAlgorithm.algorithm MUST be id-ac-generic-hybrid o keyEncryptionAlgorithm.algorithm MUST be id-rsa-kem see Appendix
(see Appendix B) B)
* keyEncryptionAlgorithm.parameters MUST be a value of type o keyEncryptionAlgorithm.parameters MUST be a value of type
GenericHybridParameters, identifying the RSA-KEM key GenericHybridParameters, identifying the RSA-KEM key encapsulation
encapsulation mechanism (see Appendix B) mechanism (see Appendix B)
* encryptedKey MUST be the encrypted keying data output by the o encryptedKey MUST be the encrypted keying data output by the
algorithm, where the keying data is the content-encryption key. algorithm, where the keying data is the content-encryption
(see Appendix A) key.(see Appendix A)
2.3 Certificate Conventions 2.3. Certificate Conventions
The conventions specified in this section augment RFC 3280 [PROFILE]. The conventions specified in this section augment RFC 3280 [PROFILE].
A recipient who employs the RSA-KEM Key Transport Algorithm MAY A recipient who employs the RSA-KEM Key Transport Algorithm MAY
identify the public key in a certificate by the same identify the public key in a certificate by the same
AlgorithmIdentifier as for the PKCS #1 v1.5 algorithm, i.e., using AlgorithmIdentifier as for the PKCS #1 v1.5 algorithm, i.e., using
the rsaEncryption object identifier [PKCS1]. the rsaEncryption object identifier [PKCS1]. The fact that the user
will accept RSA-KEM with this public key is not indicated by the use
of this identifier. This may be signed by the use of the appropriate
SMIME Capabilities either in a message or in the certificate.
If the recipient wishes only to employ the RSA-KEM Key Transport If the recipient wishes only to employ the RSA-KEM Key Transport
Algorithm with a given public key, the recipient MUST identify the Algorithm with a given public key, the recipient MUST identify the
public key in the certificate using the id-ac-generic-hybrid object public key in the certificate using the id-rsa-kem object identifier
identifier (see Appendix B) where the associated (see Appendix B). The parameters are absent.
GenericHybridParameters value indicates the underlying components
with which the algorithm is to be employed. The certificate user MUST
perform the RSA-KEM Key Transport algorithm using only those
components.
Regardless of the AlgorithmIdentifier used, the RSA public key is Regardless of the AlgorithmIdentifier used, the RSA public key is
encoded in the same manner in the subject public key information. encoded in the same manner in the subject public key information. The
The RSA public key MUST be encoded using the type RSAPublicKey type: RSA public key MUST be encoded using the type RSAPublicKey type:
RSAPublicKey ::= SEQUENCE { RSAPublicKey ::= SEQUENCE {
modulus INTEGER, -- n modulus INTEGER, -- n
publicExponent INTEGER -- e publicExponent INTEGER -- e
} }
Here, the modulus is the modulus n, and publicExponent is the public Here, the modulus is the modulus n, and publicExponent is the public
exponent e. The DER encoded RSAPublicKey is carried in the exponent e. The DER encoded RSAPublicKey is carried in the
subjectPublicKey BIT STRING within the subject public key subjectPublicKey BIT STRING within the subject public key
information. information.
The intended application for the key MAY be indicated in the key The intended application for the key MAY be indicated in the key
usage certificate extension (see [PROFILE], Section 4.2.1.3). If the usage certificate extension (see [PROFILE], Section 4.2.1.3). If the
keyUsage extension is present in a certificate that conveys an RSA keyUsage extension is present in a certificate that conveys an RSA
public key with the id-ac-generic-hybrid object identifier as public key with the id-rsa-kem object identifier as discussed above,
discussed above, then the key usage extension MUST contain the then the key usage extension MUST contain the following value:
following value:
keyEncipherment. keyEncipherment.
dataEncipherment SHOULD NOT be present. That is, a key intended to be dataEncipherment SHOULD NOT be present. That is, a key intended to be
employed only with the RSA-KEM Key Transport Algorithm SHOULD NOT employed only with the RSA-KEM Key Transport Algorithm SHOULD NOT
also be employed for data encryption or for authentication such as in also be employed for data encryption or for authentication such as in
signatures. Good cryptographic practice employs a given RSA key pair signatures. Good cryptographic practice employs a given RSA key pair
in only one scheme. This practice avoids the risk that vulnerability in only one scheme. This practice avoids the risk that vulnerability
in one scheme may compromise the security of the other, and may be in one scheme may compromise the security of the other, and may be
essential to maintain provable security. essential to maintain provable security.
2.4 SMIMECapabilities Attribute Conventions 2.4. SMIMECapabilities Attribute Conventions
RFC 2633 [MSG], Section 2.5.2 defines the SMIMECapabilities signed RFC 3851 [MSG], Section 2.5.2 defines the SMIMECapabilities signed
attribute (defined as a SEQUENCE of SMIMECapability SEQUENCEs) to be attribute (defined as a SEQUENCE of SMIMECapability SEQUENCEs) to be
used to specify a partial list of algorithms that the software used to specify a partial list of algorithms that the software
announcing the SMIMECapabilities can support. When constructing a announcing the SMIMECapabilities can support. When constructing a
signedData object, compliant software MAY include the signedData object, compliant software MAY include the
SMIMECapabilities signed attribute announcing that it supports the SMIMECapabilities signed attribute announcing that it supports the
RSA-KEM Key Transport algorithm. RSA-KEM Key Transport algorithm.
The SMIMECapability SEQUENCE representing the RSA-KEM Key Transport The SMIMECapability SEQUENCE representing the RSA-KEM Key Transport
Algorithm MUST include the id-ac-generic-hybrid object identifier Algorithm MUST include the id-rsa-kem object identifier (see Appendix
(see Appendix B) in the capabilityID field and MUST include a B) in the capabilityID field and MUST include a
GenericHybridParameters value in the parameters field identifying the GenericHybridParameters value in the parameters field identifying the
components with which the algorithm is to be employed. components with which the algorithm is to be employed.
The DER encoding of a SMIMECapability SEQUENCE is the same as the DER The DER encoding of a SMIMECapability SEQUENCE is the same as the DER
encoding of an AlgorithmIdentifier. Example DER encodings for typical encoding of an AlgorithmIdentifier. Example DER encodings for typical
sets of components are given in Appendix B.4. sets of components are given in Appendix B.4.
3. Security Considerations 3. Security Considerations
The security of the RSA-KEM Key Transport Algorithm described in The security of the RSA-KEM Key Transport Algorithm described in this
this document can be shown to be tightly related to the difficulty document can be shown to be tightly related to the difficulty of
of either solving the RSA problem or breaking the underlying either solving the RSA problem or breaking the underlying symmetric
symmetric key-wrapping scheme, if the underlying key derivation key-wrapping scheme, if the underlying key derivation function is
function is modeled as a random oracle, and assuming that the modeled as a random oracle, and assuming that the symmetric key-
symmetric key-wrapping scheme satisfies the properties of a data wrapping scheme satisfies the properties of a data encapsulation
encapsulation mechanism [SHOUP]. While in practice a random-oracle mechanism [SHOUP]. While in practice a random-oracle result does not
result does not provide an actual security proof for any particular provide an actual security proof for any particular key derivation
key derivation function, the result does provide assurance that the function, the result does provide assurance that the general
general construction is reasonable; a key derivation function would construction is reasonable; a key derivation function would need to
need to be particularly weak to lead to an attack that is not be particularly weak to lead to an attack that is not possible in the
possible in the random oracle model. random oracle model.
The RSA key size and the underlying components should be selected The RSA key size and the underlying components should be selected
consistent with the desired symmetric security level for an consistent with the desired symmetric security level for an
application. Several security levels have been identified in [NIST- application. Several security levels have been identified in [NIST-
FIPS PUB 800-57]. For brevity, the first three levels are mentioned FIPS PUB 800-57]. For brevity, the first three levels are mentioned
here: here:
* 80-bit security. The RSA key size SHOULD be at least 1024 bits, o 80-bit security. The RSA key size SHOULD be at least 1024 bits,
the hash function underlying the KDF SHOULD be SHA-1 or above, the hash function underlying the KDF SHOULD be SHA-1 or above, and
and the symmetric key-wrapping scheme SHOULD be AES Key Wrap, the symmetric key-wrapping scheme SHOULD be AES Key Wrap, Triple-
Triple-DES Key Wrap, or Camillia Key Wrap. DES Key Wrap, or Camellia Key Wrap.
* 112-bit security. The RSA key size SHOULD be at least 2048 o 112-bit security. The RSA key size SHOULD be at least 2048 bits,
bits, the hash function underlying the KDF SHOULD be SHA-224 or the hash function underlying the KDF SHOULD be SHA-224 or above,
above, and the symmetric key-wrapping scheme SHOULD be AES Key and the symmetric key-wrapping scheme SHOULD be AES Key Wrap,
Wrap, Triple-DES Key Wrap, or Camillia Key Wrap. Triple-DES Key Wrap, or Camellia Key Wrap.
* 128-bit security. The RSA key size SHOULD be at least 3072 o 128-bit security. The RSA key size SHOULD be at least 3072 bits,
bits, the hash function underlying the KDF SHOULD be SHA-256 or the hash function underlying the KDF SHOULD be SHA-256 or above,
above, and the symmetric key-wrapping scheme SHOULD be AES Key and the symmetric key-wrapping scheme SHOULD be AES Key Wrap or
Wrap or Camillia Key Wrap. Camellia Key Wrap.
Note that the AES Key Wrap or Camillia Key Wrap MAY be used at all Note that the AES Key Wrap or Camellia Key Wrap MAY be used at all
three of these levels; the use of AES or Camillia does not require a three of these levels; the use of AES or Camellia does not require a
128-bit security level for other components. 128-bit security level for other components.
Implementations MUST protect the RSA private key and the content- Implementations MUST protect the RSA private key and the content-
encryption key. Compromise of the RSA private key may result in the encryption key. Compromise of the RSA private key may result in the
disclosure of all messages protected with that key. Compromise of the disclosure of all messages protected with that key. Compromise of the
content-encryption key may result in disclosure of the associated content-encryption key may result in disclosure of the associated
encrypted content. encrypted content.
Additional considerations related to key management may be found in Additional considerations related to key management may be found in
[NIST-GUIDELINE]. [NIST-GUIDELINE].
The security of the algorithm also depends on the strength of the The security of the algorithm also depends on the strength of the
random number generator, which SHOULD have a comparable security random number generator, which SHOULD have a comparable security
level. For further discussion on random number generation, please level. For further discussion on random number generation, please see
see [RANDOM]. [RANDOM].
Implementations SHOULD NOT reveal information about intermediate Implementations SHOULD NOT reveal information about intermediate
values or calculations, whether by timing or other "side channels", values or calculations, whether by timing or other "side channels",
or otherwise an opponent may be able to determine information about or otherwise an opponent may be able to determine information about
the keying data and/or the recipient's private key. Although not all the keying data and/or the recipient's private key. Although not all
intermediate information may be useful to an opponent, it is intermediate information may be useful to an opponent, it is
preferable to conceal as much information as is practical, unless preferable to conceal as much information as is practical, unless
analysis specifically indicates that the information would not be analysis specifically indicates that the information would not be
useful. useful.
skipping to change at page 7, line 47 skipping to change at page 8, line 39
SHOULD NOT be used with other key establishment schemes, or for data SHOULD NOT be used with other key establishment schemes, or for data
encryption, or with more than one set of underlying algorithm encryption, or with more than one set of underlying algorithm
components. components.
Parties MAY formalize the assurance that one another's Parties MAY formalize the assurance that one another's
implementations are correct through implementation validation, e.g. implementations are correct through implementation validation, e.g.
NIST's Cryptographic Module Validation Program (CMVP). NIST's Cryptographic Module Validation Program (CMVP).
4. References 4. References
4.1 Normative References 4.1. Normative References
[3DES-WRAP] Housley, R. Triple-DES and RC2 Key Wrapping. RFC [3DES-WRAP] Housley, R. Triple-DES and RC2 Key Wrapping. RFC
3217. December 2001. 3217. December 2001.
[AES-WRAP] Schaad, J. and R. Housley. Advanced Encryption [AES-WRAP] Schaad, J. and R. Housley. Advanced Encryption
Standard (AES) Key Wrap Algorithm. RFC 3394. Standard (AES) Key Wrap Algorithm. RFC 3394.
September 2002. September 2002.
[ANS-X9.63] American National Standard X9.63-2002: Public Key [ANS-X9.63] American National Standard X9.63-2002: Public Key
Cryptography for the Financial Services Industry: Cryptography for the Financial Services Industry:
skipping to change at page 8, line 4 skipping to change at page 9, line 7
[3DES-WRAP] Housley, R. Triple-DES and RC2 Key Wrapping. RFC [3DES-WRAP] Housley, R. Triple-DES and RC2 Key Wrapping. RFC
3217. December 2001. 3217. December 2001.
[AES-WRAP] Schaad, J. and R. Housley. Advanced Encryption [AES-WRAP] Schaad, J. and R. Housley. Advanced Encryption
Standard (AES) Key Wrap Algorithm. RFC 3394. Standard (AES) Key Wrap Algorithm. RFC 3394.
September 2002. September 2002.
[ANS-X9.63] American National Standard X9.63-2002: Public Key [ANS-X9.63] American National Standard X9.63-2002: Public Key
Cryptography for the Financial Services Industry: Cryptography for the Financial Services Industry:
Key Agreement and Key Transport Using Elliptic Key Agreement and Key Transport Using Elliptic
Curve Cryptography. Curve Cryptography.
[CAMILLIA] Kato, A., Moriai, S., and Kanda, M.: The Camellia [CAMELLIA] Kato, A., Moriai, S., and Kanda, M.: Use of the
Cipher Algorithm and Its Use With IPsec. RFC 3657. Camellia Encryption Algorithm in Cryptographic
December 2005. Message Syntax. RFC 3657. December 2005.
[CMS] Housley, R. Cryptographic Message Syntax. RFC [CMS] Housley, R. Cryptographic Message Syntax. RFC
3852. July 2004. 3852. July 2004.
[CMSALGS] Housley, R. Cryptographic Message Syntax (CMS) [CMSALGS] Housley, R. Cryptographic Message Syntax (CMS)
Algorithms. RFC 3370. August 2002. Algorithms. RFC 3370. August 2002.
[FIPS-180-2] National Institute of Standards and Technology [FIPS-180-2] National Institute of Standards and Technology
(NIST). FIPS 180-2: Secure Hash Standard. August (NIST). FIPS 180-2: Secure Hash Standard. August
2002. 2002.
[MSG] Ramsdell, B. S/MIME Version 3 Message [MSG] Ramsdell, B. S/MIME Version 3 Message
Specification. RFC 3851. July 2004. Specification. RFC 3851. July 2004.
[PROFILE] Housley, R., Polk, W., Ford, W. and D. Solo. [PROFILE] Cooper, D., Santesson, S., Farrell, S.,
Internet X.509 Public Key Infrastructure: Boeyen, S., Housley, R., and W. Polk. Internet
Certificate and Certificate Revocation List (CRL) X.509 Public Key Infrastructure Certificate
Profile. RFC 3280. April 2002. and Certificate Revocation List (CRL) Profile.
RFC 5280. May 2008.
[STDWORDS] Bradner, S. Key Words for Use in RFCs to Indicate [STDWORDS] Bradner, S. Key Words for Use in RFCs to Indicate
Requirement Levels. RFC 2119. March 1997. Requirement Levels. RFC 2119. March 1997.
4.2 Informative References 4.2. Informative References
[ANS-X9.44] ASC X9F1 Working Group. American National [ANS-X9.44] ASC X9F1 Working Group. American National
Standard X9.44: Public Key Cryptography for the Standard X9.44: Public Key Cryptography for the
Financial Services Industry -- Key Establishment Financial Services Industry -- Key Establishment
Using Integer Factorization Cryptography. 2007 Using Integer Factorization Cryptography. 2007
[CMS-OAEP] Housley, R. Use of the RSAES-OAEP Key Transport [CMS-OAEP] Housley, R. Use of the RSAES-OAEP Key Transport
Algorithm in the Cryptographic Message Syntax Algorithm in the Cryptographic Message Syntax
(CMS). RFC 3560. July 2003. (CMS). RFC 3560. July 2003.
skipping to change at page 8, line 57 skipping to change at page 10, line 18
[ISO-IEC-18033-2] ISO/IEC 18033-2:2005 Information technology -- [ISO-IEC-18033-2] ISO/IEC 18033-2:2005 Information technology --
Security techniques -- Encryption algorithms -- Security techniques -- Encryption algorithms --
Part 2: Asymmetric Ciphers. ISO/IEC, 2005. Part 2: Asymmetric Ciphers. ISO/IEC, 2005.
[NESSIE] NESSIE Consortium. Portfolio of Recommended [NESSIE] NESSIE Consortium. Portfolio of Recommended
Cryptographic Primitives. February 27, 2003. Cryptographic Primitives. February 27, 2003.
Available via http://www.cryptonessie.org/. Available via http://www.cryptonessie.org/.
[NIST-GUIDELINE] National Institute of Standards and Technology. [NIST-GUIDELINE] National Institute of Standards and Technology.
Special Publication 800-57: Recommendation for Key Special Publication 800-57: Recommendation for
Management. Part 1: General Guideline. August 2005. Key Management. Part 1: General Guideline.
August 2005. Available via:
Available via:
http://csrc.nist.gov/publications/index.html. http://csrc.nist.gov/publications/index.html.
[PKCS1] Jonsson, J. and B. Kaliski. PKCS #1: RSA [PKCS1] Jonsson, J. and B. Kaliski. PKCS #1: RSA
Cryptography Specifications Version 2.1. RFC 3447. Cryptography Specifications Version 2.1. RFC
February 2003. 3447. February 2003.
[RANDOM] Eastlake, D., S. Crocker, and J. Schiller. [RANDOM] Eastlake, D., S. Crocker, and J. Schiller.
Randomness Recommendations for Security. RFC 4086. Randomness Recommendations for Security. RFC
June 2005. 4086. June 2005.
[SHOUP] Shoup, V. A Proposal for an ISO Standard for [SHOUP] Shoup, V. A Proposal for an ISO Standard for
Public Key Encryption. Version 2.1, December 20, Public Key Encryption. Version 2.1, December 20,
2001. Available via http://www.shoup.net/papers/. 2001. Available via http://www.shoup.net/papers/.
5. IANA Considerations Appendix A.
RSA-KEM Key Transport Algorithm
Within the CMS, algorithms are identified by object identifiers
(OIDs). With one exception, all of the OIDs used in this document
were assigned in other IETF documents, in ISO/IEC standards
documents, by the National Institute of Standards and Technology
(NIST), and in Public-Key Cryptography Standards (PKCS) documents.
The one exception is that the ASN.1 module's identifier (see Appendix
B.3) is assigned in this document. No further action by the IANA is
necessary for this document or any anticipated updates.
6. Acknowledgments
This document is one part of a strategy to align algorithm standards
produced by ASC X9, ISO/IEC JTC1 SC27, NIST, and the IETF. We would
like to thank the members of the ASC X9F1 working group for their
contributions to drafts of ANS X9.44 which led to this specification.
Our thanks to Russ Housley as well for his guidance and
encouragement. We also appreciate the helpful direction we've
received from Blake Ramsdell and Jim Schaad in bringing this document
to fruition. A special thanks to Magnus Nystrom for his assistance on
Appendix B.
7. Authors' Addresses
James Randall
RSA, The Security Division of EMC
174 Middlesex Turnpike
Bedford, MA 01730
USA
e-mail: jrandall@rsa.com
Burt Kaliski
EMC
176 South Street
Hopkinton, MA 01748
USA
e-mail: kaliski_burt@emc.com
Appendix A. RSA-KEM Key Transport Algorithm
The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward) The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward)
mechanism for transporting keying data to a recipient using the mechanism for transporting keying data to a recipient using the
recipient's RSA public key. recipient's RSA public key.
With this type of algorithm, a sender encrypts the keying data using With this type of algorithm, a sender encrypts the keying data using
the recipient's public key to obtain encrypted keying data. The the recipient's public key to obtain encrypted keying data. The
recipient decrypts the encrypted keying data using the recipient's recipient decrypts the encrypted keying data using the recipient's
private key to recover the keying data. private key to recover the keying data.
A.1 Underlying Components A.1. Underlying Components
The algorithm has the following underlying components: The algorithm has the following underlying components:
* KDF, a key derivation function, which derives keying data of a o KDF, a key derivation function, which derives keying data of a
specified length from a shared secret value specified length from a shared secret value
* Wrap, a symmetric key-wrapping scheme, which encrypts keying o Wrap, a symmetric key-wrapping scheme, which encrypts keying Data
data using a key-encrypting key using a key-encrypting key
In the following, kekLen denotes the length in bytes of the key- In the following, kekLen denotes the length in bytes of the key-
encrypting key for the underlying symmetric key-wrapping scheme. encrypting key for the underlying symmetric key-wrapping scheme.
In this scheme, the length of the keying data to be transported MUST In this scheme, the length of the keying data to be transported MUST
be among the lengths supported by the underlying symmetric key- be among the lengths supported by the underlying symmetric key-
wrapping scheme. (Both the AES and Camillia Key Wraps, for instance, wrapping scheme. (Both the AES and Camellia Key Wraps, for instance,
require the length of the keying data to be a multiple of 8 bytes, require the length of the keying data to be a multiple of 8 bytes,
and at least 16 bytes.) Usage and formatting of the keying data and at least 16 bytes.) Usage and formatting of the keying data
(e.g., parity adjustment for Triple-DES keys) is outside the scope of (e.g., parity adjustment for Triple-DES keys) is outside the scope of
this algorithm. With some key derivation functions, it is possible to this algorithm. With some key derivation functions, it is possible to
include other information besides the shared secret value in the include other information besides the shared secret value in the
input to the function. Also, with some symmetric key-wrapping input to the function. Also, with some symmetric key-wrapping
schemes, it is possible to associate a label with the keying data. schemes, it is possible to associate a label with the keying data.
Such uses are outside the scope of this document, as they are not Such uses are outside the scope of this document, as they are not
directly supported by CMS. directly supported by CMS.
A.2 Sender's Operations A.2. Sender's Operations
Let (n,e) be the recipient's RSA public key (see [PKCS1] for details) Let (n,e) be the recipient's RSA public key (see [PKCS1] for
and let K be the keying data to be transported. details) and let K be the keying data to be transported.
Let nLen denote the length in bytes of the modulus n, i.e., the least Let nLen denote the length in bytes of the modulus n, i.e., the least
integer such that 2^{8*nLen} > n. integer such that 2^{8*nLen} > n.
The sender performs the following operations: The sender performs the following operations:
1. Generate a random integer z between 0 and n-1 (see Note), and 1. Generate a random integer z between 0 and n-1 (see Note), and
convert z to a byte string Z of length nLen, most significant convert z to a byte string Z of length nLen, most significant byte
byte first: first:
z = RandomInteger (0, n-1) z = RandomInteger (0, n-1)
Z = IntegerToString (z, nLen) Z = IntegerToString (z, nLen)
2. Encrypt the random integer z using the recipient's public key
(n,e) and convert the resulting integer c to a ciphertext C, a 2. Encrypt the random integer z using the recipient's public key n,e)
byte string of length nLen: and convert the resulting integer c to a ciphertext C, a byte
string of length nLen:
c = z^e mod n c = z^e mod n
C = IntegerToString (c, nLen) C = IntegerToString (c, nLen)
3. Derive a key-encrypting key KEK of length kekLen bytes from the 3. Derive a key-encrypting key KEK of length kekLen bytes from the
byte string Z using the underlying key derivation function: byte string Z using the underlying key derivation function:
KEK = KDF (Z, kekLen) KEK = KDF (Z, kekLen)
4. Wrap the keying data K with the key-encrypting key KEK using 4. Wrap the keying data K with the key-encrypting key KEK using the
the underlying key-wrapping scheme to obtain wrapped keying underlying key-wrapping scheme to obtain wrapped keying data WK:
data WK:
WK = Wrap (KEK, K) WK = Wrap (KEK, K)
5. Concatenate the ciphertext C and the wrapped keying data WK to 5. Concatenate the ciphertext C and the wrapped keying data WK to
obtain the encrypted keying data EK: obtain the encrypted keying data EK:
EK = C || WK EK = C || WK
6. Output the encrypted keying data EK. 6. Output the encrypted keying data EK.
NOTE: The random integer z MUST be generated independently at random NOTE: The random integer z MUST be generated independently at random
for different encryption operations, whether for the same or for different encryption operations, whether for the same or
different recipients. different recipients.
A.3 Recipient's Operations A.3. Recipient's Operations
Let (n,d) be the recipient's RSA private key (see [PKCS1]; other Let (n,d) be the recipient's RSA private key (see [PKCS1]; other
private key formats are allowed) and let EK be the encrypted keying private key formats are allowed) and let EK be the encrypted keying
data. data.
Let nLen denote the length in bytes of the modulus n. Let nLen denote the length in bytes of the modulus n.
The recipient performs the following operations: The recipient performs the following operations:
1. Separate the encrypted keying data EK into a ciphertext C of 1. Separate the encrypted keying data EK into a ciphertext C of
length nLen bytes and wrapped keying data WK: length nLen bytes and wrapped keying data WK:
C || WK = EK C || WK = EK
If the length of the encrypted keying data is less than nLen If the length of the encrypted keying data is less than nLen
bytes, output "decryption error" and stop. bytes, output "decryption error" and stop.
2. Convert the ciphertext C to an integer c, most significant 2. Convert the ciphertext C to an integer c, most significant byte
byte first. Decrypt the integer c using the recipient's first. Decrypt the integer c using the recipient's private key
private key (n,d) to recover an integer z (see Note): (n,d) to recover an integer z (see Note):
c = StringToInteger (C) c = StringToInteger (C)
z = c^d mod n z = c^d mod n
If the integer c is not between 0 and n-1, output "decryption If the integer c is not between 0 and n-1, output "decryption
error" and stop. error" and stop.
3. Convert the integer z to a byte string Z of length nLen, most 3. Convert the integer z to a byte string Z of length nLen, most
significant byte first (see Note): significant byte first (see Note):
Z = IntegerToString (z, nLen) Z = IntegerToString (z, nLen)
4. Derive a key-encrypting key KEK of length kekLen bytes from 4. Derive a key-encrypting key KEK of length kekLen bytes from
the byte string Z using the underlying key derivation function the byte string Z using the underlying key derivation function
skipping to change at page 12, line 15 skipping to change at page 13, line 31
error" and stop. error" and stop.
3. Convert the integer z to a byte string Z of length nLen, most 3. Convert the integer z to a byte string Z of length nLen, most
significant byte first (see Note): significant byte first (see Note):
Z = IntegerToString (z, nLen) Z = IntegerToString (z, nLen)
4. Derive a key-encrypting key KEK of length kekLen bytes from 4. Derive a key-encrypting key KEK of length kekLen bytes from
the byte string Z using the underlying key derivation function the byte string Z using the underlying key derivation function
(see Note): (see Note):
KEK = KDF (Z, kekLen) KEK = KDF (Z, kekLen)
5. Unwrap the wrapped keying data WK with the key-encrypting key 5. Unwrap the wrapped keying data WK with the key-encrypting key
KEK using the underlying key-wrapping scheme to recover the KEK using the underlying key-wrapping scheme to recover the
keying data K: keying data K:
K = Unwrap (KEK, WK) K = Unwrap (KEK, WK)
If the unwrapping operation outputs an error, output If the unwrapping operation outputs an error, output "decryption
"decryption error" and stop. error" and stop.
6. Output the keying data K. 6. Output the keying data K.
NOTE: Implementations SHOULD NOT reveal information about the integer NOTE: Implementations SHOULD NOT reveal information about the integer
z and the string Z, nor about the calculation of the exponentiation z and the string Z, nor about the calculation of the exponentiation
in Step 2, the conversion in Step 3, or the key derivation in Step 4, in Step 2, the conversion in Step 3, or the key derivation in Step 4,
whether by timing or other "side channels". The observable behavior whether by timing or other "side channels". The observable behavior
of the implementation SHOULD be the same at these steps for all of the implementation SHOULD be the same at these steps for all
ciphertexts C that are in range. (For example, IntegerToString ciphertexts C that are in range. (For example, IntegerToString
conversion should take the same amount of time regardless of the conversion should take the same amount of time regardless of the
actual value of the integer z.) The integer z, the string Z and other actual value of the integer z.) The integer z, the string Z and other
intermediate results MUST be securely deleted when they are no longer intermediate results MUST be securely deleted when they are no longer
needed. needed.
Appendix B. ASN.1 Syntax Appendix B.
ASN.1 Syntax
The ASN.1 syntax for identifying the RSA-KEM Key Transport Algorithm The ASN.1 syntax for identifying the RSA-KEM Key Transport Algorithm
is an extension of the syntax for the "generic hybrid cipher" in is an extension of the syntax for the "generic hybrid cipher" in
ISO/IEC 18033-2 [ISO-IEC-18033-2], and is the same as employed in ISO/IEC 18033-2 [ISO-IEC-18033-2], and is the same as employed in ANS
ANS X9.44 [ANS-X9.44]. The syntax for the scheme is given in Section X9.44 [ANS-X9.44]. The syntax for the scheme is given in Section B.1.
B.1. The syntax for selected underlying components including those The syntax for selected underlying components including those
mentioned above is given in B.2. mentioned above is given in B.2.
The following object identifier prefixes are used in the definitions The following object identifier prefixes are used in the definitions
below: below:
is18033-2 OID ::= { iso(1) standard(0) is18033(18033) part2(2) } is18033-2 OID ::= { iso(1) standard(0) is18033(18033) part2(2) }
nistAlgorithm OID ::= { nistAlgorithm OID ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1) joint-iso-itu-t(2) country(16) us(840) organization(1)
gov(101) csor(3) nistAlgorithm(4) gov(101) csor(3) nistAlgorithm(4)
skipping to change at page 13, line 17 skipping to change at page 15, line 38
NullParms is a more descriptive synonym for NULL when an algorithm NullParms is a more descriptive synonym for NULL when an algorithm
identifier has null parameters: identifier has null parameters:
NullParms ::= NULL NullParms ::= NULL
The material in this Appendix is based on ANS X9.44. The material in this Appendix is based on ANS X9.44.
B.1 RSA-KEM Key Transport Algorithm B.1 RSA-KEM Key Transport Algorithm
The object identifier for the RSA-KEM Key Transport Algorithm is the The object identifier for the RSA-KEM Key Transport Algorithm is id-
same as for the "generic hybrid cipher" in ISO/IEC 18033-2, rsa-kem, which is defined in the draft as:
id-ac-generic-hybrid, which is defined in the draft as:
id-ac-generic-hybrid OID ::= { id-rsa-kem OID ::= {
is18033-2 asymmetric-cipher(1) generic-hybrid(2) iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) alg(3) TBA
} }
The associated parameters for id-ac-generic-hybrid have type When id-rsa-kem is used in an AlgorithmIdentifier, the parameters
GenericHybridParameters: MUST employ the GenericHybridParameters syntax. The parameters MUST
be absent when used in the subjectPublicKeyInfo field The syntax for
GenericHybridParameters is as follows:
GenericHybridParameters ::= { GenericHybridParameters ::= {
kem KeyEncapsulationMechanism, kem KeyEncapsulationMechanism,
dem DataEncapsulationMechanism dem DataEncapsulationMechanism
} }
The fields of type GenericHybridParameters have the following The fields of type GenericHybridParameters have the following
meanings: meanings:
* kem identifies the underlying key encapsulation mechanism. For o kem identifies the underlying key encapsulation mechanism. For the
the RSA-KEM Key Transport Algorithm, the scheme is RSA-KEM from RSA-KEM Key Transport Algorithm, the scheme is RSA-KEM from
ISO/IEC 18033-2. ISO/IEC 18033-2.
The object identifier for RSA-KEM (as a key encapsulation The object identifier for RSA-KEM (as a key encapsulation
mechanism) is id-kem-rsa, which is defined in ISO/IEC 18033-2 mechanism) is id-kem-rsa, which is defined in ISO/IEC 18033-2 as
as
id-kem-rsa OID ::= { id-kem-rsa OID ::= {
is18033-2 key-encapsulation-mechanism(2) rsa(4) is18033-2 key-encapsulation-mechanism(2) rsa(4)
} }
The associated parameters for id-kem-rsa have type The associated parameters for id-kem-rsa have type
RsaKemParameters: RsaKemParameters:
RsaKemParameters ::= { RsaKemParameters ::= {
keyDerivationFunction KeyDerivationFunction, keyDerivationFunction KeyDerivationFunction,
keyLength KeyLength keyLength KeyLength
} }
The fields of type RsaKemParameters have the following The fields of type RsaKemParameters have the following meanings:
meanings:
* keyDerivationFunction identifies the underlying key * keyDerivationFunction identifies the underlying key
derivation function. For alignment with ANS X9.44, it derivation function. For alignment with ANS X9.44, it
MUST be KDF2 or KDF3. However, other key derivation MUST be KDF2 or KDF3. However, other key derivation
functions MAY be used with CMS. Please see B.2.1 for the functions MAY be used with CMS. Please see B.2.1 for
syntax for KDF2 and KDF3. the syntax for KDF2 and KDF3.
KeyDerivationFunction ::= KeyDerivationFunction ::=
AlgorithmIdentifier {{KDFAlgorithms}} AlgorithmIdentifier {{KDFAlgorithms}}
KDFAlgorithms ALGORITHM ::= { KDFAlgorithms ALGORITHM ::= {
kdf2 | kdf3, kdf2 | kdf3,
... -- implementations may define other methods ... -- implementations may define other methods
} }
* keyLength is the length in bytes of the key-encrypting * keyLength is the length in bytes of the key-encrypting
key, which depends on the underlying symmetric key- key, which depends on the underlying symmetric key-
wrapping scheme. wrapping scheme.
KeyLength ::= INTEGER (1..MAX)
* dem identifies the underlying data encapsulation mechanism. KeyLength ::= INTEGER (1..MAX)
For alignment with ANS X9.44, it MUST be an X9-approved o dem identifies the underlying data encapsulation mechanism. For
symmetric key-wrapping scheme. (See Note.) However, other alignment with ANS X9.44, it MUST be an X9-approved symmetric key-
symmetric key-wrapping schemes MAY be used with CMS. Please see wrapping scheme. (See Note.) However, other symmetric key-wrapping
B.2.2 for the syntax for the AES, Triple-DES, and Camillia Key schemes MAY be used with CMS. Please see B.2.2 for the syntax for
Wraps. the AES, Triple-DES, and Camellia Key Wraps.
DataEncapsulationMechanism ::= DataEncapsulationMechanism ::=
AlgorithmIdentifier {{DEMAlgorithms}} AlgorithmIdentifier {{DEMAlgorithms}}
DEMAlgorithms ALGORITHM ::= { DEMAlgorithms ALGORITHM ::= {
X9-SymmetricKeyWrappingSchemes, X9-SymmetricKeyWrappingSchemes,
Camillia-KeyWrappingSchemes, Camellia-KeyWrappingSchemes,
... -- implementations may define other methods ... -- implementations may define other methods
} }
X9-SymmetricKeyWrappingSchemes ALGORITHM ::= { X9-SymmetricKeyWrappingSchemes ALGORITHM ::= {
aes128-Wrap | aes192-Wrap | aes256-Wrap | tdes-Wrap, aes128-Wrap | aes192-Wrap | aes256-Wrap | tdes-Wrap,
... -- allows for future expansion ... -- allows for future expansion
} }
Camillia-KeyWrappingSchemes ALGORITHM ::= { Camellia-KeyWrappingSchemes ALGORITHM ::= {
camillia128-Wrap | camillia192-Wrap | camillia256-Wrap Camellia128-Wrap | Camellia192-Wrap | Camellia256-Wrap
} }
NOTE: The generic hybrid cipher in ISO/IEC 18033-2 can encrypt NOTE: The generic hybrid cipher in ISO/IEC 18033-2 can encrypt
arbitrary data, hence the term "data encapsulation mechanism". The arbitrary data, hence the term "data encapsulation mechanism". The
symmetric key-wrapping schemes take the role of data encapsulation symmetric key-wrapping schemes take the role of data encapsulation
mechanisms in the RSA-KEM Key Transport Algorithm. ISO/IEC 18033-2 mechanisms in the RSA-KEM Key Transport Algorithm. ISO/IEC 18033-2
allows only three specific data encapsulation mechanisms, not allows only three specific data encapsulation mechanisms, not
including any of these symmetric key-wrapping schemes. However, the including any of these symmetric key-wrapping schemes. However, the
ASN.1 syntax in that document expects that additional algorithms will ASN.1 syntax in that document expects that additional algorithms will
be allowed. be allowed.
B.2 Selected Underlying Components B.2
B.2.1 Key Derivation Functions B.2.1 Key Derivation Functions
The object identifier for KDF2 (see [ANS X9.44]) is: The object identifier for KDF2 (see [ANS X9.44]) is:
id-kdf-kdf2 OID ::= { x9-44-components kdf2(1) } id-kdf-kdf2 OID ::= { x9-44-components kdf2(1) }
The associated parameters identify the underlying hash function. For The associated parameters identify the underlying hash function. For
alignment with ANS X9.44, the hash function MUST be an ASC alignment with ANS X9.44, the hash function MUST be an ASC X9-
X9-approved hash function. However, other hash functions MAY be used approved hash function. However, other hash functions MAY be used
with CMS. with CMS.
kdf2 ALGORITHM ::= { OID id-kdf-kdf2 PARMS KDF2-HashFunction } kdf2 ALGORITHM ::= { OID id-kdf-kdf2 PARMS KDF2-HashFunction }
KDF2-HashFunction ::= AlgorithmIdentifier {{KDF2-
KDF2-HashFunction ::= AlgorithmIdentifier {{KDF2-HashFunctions}} HashFunctions}}
KDF2-HashFunctions ALGORITHM ::= { KDF2-HashFunctions ALGORITHM ::= {
X9-HashFunctions, X9-HashFunctions,
... -- implementations may define other methods ... -- implementations may define other methods
} }
X9-HashFunctions ALGORITHM ::= { X9-HashFunctions ALGORITHM ::= {
sha1 | sha224 | sha256 | sha384 | sha512, sha1 | sha224 | sha256 | sha384 | sha512,
... -- allows for future expansion ... -- allows for future expansion
} }
skipping to change at page 16, line 53 skipping to change at page 20, line 5
} }
This object identifier has a NULL parameter. This object identifier has a NULL parameter.
tdes-Wrap ALGORITHM ::= tdes-Wrap ALGORITHM ::=
{ OID id-alg-CMS3DESwrap PARMS NullParms } { OID id-alg-CMS3DESwrap PARMS NullParms }
NOTE: As of this writing, the AES Key Wrap and the Triple-DES Key NOTE: As of this writing, the AES Key Wrap and the Triple-DES Key
Wrap are in the process of being approved by ASC X9. Wrap are in the process of being approved by ASC X9.
The object identifiers for the Camillia Key Wrap depends on the size The object identifiers for the Camellia Key Wrap depend on the size
of the key encrypting key. There are three object identifiers: of the key encrypting key. There are three object identifiers:
id-camellia128-Wrap OBJECT IDENTIFIER ::= id-camellia128-Wrap OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) 392 200011 61 security(1) { iso(1) member-body(2) 392 200011 61 security(1)
algorithm(1) key-wrap-algorithm(3) algorithm(1) key-wrap-algorithm(3)
camellia128-wrap(2) } camellia128-wrap(2) }
id-camellia192-Wrap OBJECT IDENTIFIER ::= id-camellia192-Wrap OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) 392 200011 61 security(1) { iso(1) member-body(2) 392 200011 61 security(1)
algorithm(1) key-wrap-algorithm(3) algorithm(1) key-wrap-algorithm(3)
camellia192-wrap(3) } camellia192-wrap(3) }
id-camellia256-Wrap OBJECT IDENTIFIER ::= id-camellia256-Wrap OBJECT IDENTIFIER ::=
skipping to change at page 17, line 46 skipping to change at page 20, line 48
-- EXPORTS ALL -- EXPORTS ALL
-- IMPORTS None -- IMPORTS None
-- Useful types and definitions -- Useful types and definitions
OID ::= OBJECT IDENTIFIER -- alias OID ::= OBJECT IDENTIFIER -- alias
-- Unless otherwise stated, if an object identifier has associated -- Unless otherwise stated, if an object identifier has associated
-- parameters (i.e., the PARMS element is specified), the parameters
-- field shall be included in algorithm identifier values. The -- parameters (i.e., the PARMS element is specified), the
-- parameters field shall be omitted if and only if the object -- parameters field shall be included in algorithm identifier
-- identifier does not have associated parameters (i.e., the PARMS -- values. The parameters field shall be omitted if and only if
-- element is omitted), unless otherwise stated. -- the object identifier does not have associated parameters
-- (i.e., the PARMS element is omitted), unless otherwise stated.
ALGORITHM ::= CLASS { ALGORITHM ::= CLASS {
&id OBJECT IDENTIFIER UNIQUE, &id OBJECT IDENTIFIER UNIQUE,
&Type OPTIONAL &Type OPTIONAL
} }
WITH SYNTAX { OID &id [PARMS &Type] } WITH SYNTAX { OID &id [PARMS &Type] }
AlgorithmIdentifier { ALGORITHM:IOSet } ::= SEQUENCE { AlgorithmIdentifier { ALGORITHM:IOSet } ::= SEQUENCE {
algorithm ALGORITHM.&id( {IOSet} ), algorithm ALGORITHM.&id( {IOSet} ),
parameters ALGORITHM.&Type( {IOSet}{@algorithm} ) OPTIONAL parameters ALGORITHM.&Type( {IOSet}{@algorithm} ) OPTIONAL
} }
NullParms ::= NULL NullParms ::= NULL
-- ISO/IEC 18033-2 arc -- ISO/IEC 18033-2 arc
is18033-2 OID ::= { iso(1) standard(0) is18033(18033) part2(2) } is18033-2 OID ::= { iso(1) standard(0) is18033(18033) part2(2) }
-- NIST algorithm arc -- NIST algorithm arc
nistAlgorithm OID ::= { nistAlgorithm OID ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1) joint-iso-itu-t(2) country(16) us(840) organization(1)
skipping to change at page 18, line 27 skipping to change at page 21, line 37
joint-iso-itu-t(2) country(16) us(840) organization(1) joint-iso-itu-t(2) country(16) us(840) organization(1)
gov(101) csor(3) nistAlgorithm(4) gov(101) csor(3) nistAlgorithm(4)
} }
-- PKCS #1 arc -- PKCS #1 arc
pkcs-1 OID ::= { pkcs-1 OID ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1)
} }
-- RSA-KEM Key Transport Algorithm, based on Generic Hybrid Cipher -- RSA-KEM Key Transport Algorithm
id-ac-generic-hybrid OID ::= { id-rsa-kem OID ::= {
is18033-2 asymmetric-cipher(1) generic-hybrid(2) iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) alg(3) TBA
} }
GenericHybridParameters ::= SEQUENCE { GenericHybridParameters ::= SEQUENCE {
kem KeyEncapsulationMechanism, kem KeyEncapsulationMechanism,
dem DataEncapsulationMechanism dem DataEncapsulationMechanism
} }
KeyEncapsulationMechanism ::= AlgorithmIdentifier {{KEMAlgorithms}} KeyEncapsulationMechanism ::= AlgorithmIdentifier {{KEMAlgorithms}}
KEMAlgorithms ALGORITHM ::= {
... -- Don't know what you want in here
}
id-kem-rsa OID ::= { id-kem-rsa OID ::= {
is18033-2 key-encapsulation-mechanism(2) rsa(4) is18033-2 key-encapsulation-mechanism(2) rsa(4)
} }
RsaKemParameters ::= SEQUENCE { RsaKemParameters ::= SEQUENCE {
keyDerivationFunction KeyDerivationFunction, keyDerivationFunction KeyDerivationFunction,
keyLength KeyLength keyLength KeyLength
} }
KeyDerivationFunction ::= AlgorithmIdentifier {{KDFAlgorithms}} KeyDerivationFunction ::= AlgorithmIdentifier {{KDFAlgorithms}}
KDFAlgorithms ALGORITHM ::= { KDFAlgorithms ALGORITHM ::= {
kdf2 | kdf3, kdf2 | kdf3,
... -- implementations may define other methods ... -- implementations may define other methods
} }
KeyLength ::= INTEGER (1..MAX) KeyLength ::= INTEGER (1..MAX)
DataEncapsulationMechanism ::= AlgorithmIdentifier {{DEMAlgorithms}} DataEncapsulationMechanism ::=
AlgorithmIdentifier {{DEMAlgorithms}}
DEMAlgorithms ALGORITHM ::= { DEMAlgorithms ALGORITHM ::= {
X9-SymmetricKeyWrappingSchemes | X9-SymmetricKeyWrappingSchemes |
Camillia-KeyWrappingSchemes, Camellia-KeyWrappingSchemes,
... -- implementations may define other methods ... -- implementations may define other methods
} }
X9-SymmetricKeyWrappingSchemes ALGORITHM ::= { X9-SymmetricKeyWrappingSchemes ALGORITHM ::= {
aes128-Wrap | aes192-Wrap | aes256-Wrap | tdes-Wrap, aes128-Wrap | aes192-Wrap | aes256-Wrap | tdes-Wrap,
... -- allows for future expansion ... -- allows for future expansion
} }
X9-SymmetricKeyWrappingScheme ::= X9-SymmetricKeyWrappingScheme ::=
AlgorithmIdentifier {{ X9-SymmetricKeyWrappingSchemes }} AlgorithmIdentifier {{ X9-SymmetricKeyWrappingSchemes }}
Camillia-KeyWrappingSchemes ALGORITHM ::= { Camellia-KeyWrappingSchemes ALGORITHM ::= {
camellia128-Wrap | camellia192-Wrap | camellia256-Wrap, camellia128-Wrap | camellia192-Wrap | camellia256-Wrap,
... -- allows for future expansion ... -- allows for future expansion
} }
Camillia-KeyWrappingScheme ::= Camellia-KeyWrappingScheme ::=
AlgorithmIdentifier {{ Camellia-KeyWrappingSchemes }}
AlgorithmIdentifier {{ Camillia-KeyWrappingSchemes }}
-- Key Derivation Functions -- Key Derivation Functions
id-kdf-kdf2 OID ::= { x9-44-components kdf2(1) } id-kdf-kdf2 OID ::= { x9-44-components kdf2(1) }
-- Base arc -- Base arc
x9-44 OID ::= { x9-44 OID ::= {
iso(1) identified-organization(3) tc68(133) country(16) x9(840) iso(1) identified-organization(3) tc68(133) country(16) x9(840)
x9Standards(9) x9-44(44) x9Standards(9) x9-44(44)
} }
x9-44-components OID ::= { x9-44 components(1) } x9-44-components OID ::= { x9-44 components(1) }
kdf2 ALGORITHM ::= { OID id-kdf-kdf2 PARMS KDF2-HashFunction } kdf2 ALGORITHM ::= { OID id-kdf-kdf2 PARMS KDF2-HashFunction }
skipping to change at page 19, line 56 skipping to change at page 23, line 22
kdf2 ALGORITHM ::= { OID id-kdf-kdf2 PARMS KDF2-HashFunction } kdf2 ALGORITHM ::= { OID id-kdf-kdf2 PARMS KDF2-HashFunction }
KDF2-HashFunction ::= AlgorithmIdentifier {{ KDF2-HashFunctions }} KDF2-HashFunction ::= AlgorithmIdentifier {{ KDF2-HashFunctions }}
KDF2-HashFunctions ALGORITHM ::= { KDF2-HashFunctions ALGORITHM ::= {
X9-HashFunctions, X9-HashFunctions,
... -- implementations may define other methods ... -- implementations may define other methods
} }
-- id-kdf-kdf3 OID ::= { x9-44-components kdf3(2) } -- id-kdf-kdf3 OID ::= { x9-44-components kdf3(2) } kdf3 ALGORITHM
kdf3 ALGORITHM ::= { OID id-kdf-kdf2 PARMS KDF3-HashFunction } ::= { OID id-kdf-kdf2 PARMS KDF3-HashFunction } KDF3-HashFunction
::= AlgorithmIdentifier {{ KDF3-HashFunctions }}
KDF3-HashFunction ::= AlgorithmIdentifier {{ KDF3-HashFunctions }}
KDF3-HashFunctions ALGORITHM ::= { KDF3-HashFunctions ALGORITHM ::= {
X9-HashFunctions, X9-HashFunctions,
... -- implementations may define other methods ... -- implementations may define other methods
} }
-- Hash Functions -- Hash Functions
X9-HashFunctions ALGORITHM ::= { X9-HashFunctions ALGORITHM ::= {
sha1 | sha224 | sha256 | sha384 | sha512, sha1 | sha224 | sha256 | sha384 | sha512,
skipping to change at page 21, line 19 skipping to change at page 25, line 4
id-camellia256-Wrap OBJECT IDENTIFIER ::= id-camellia256-Wrap OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) 392 200011 61 security(1) { iso(1) member-body(2) 392 200011 61 security(1)
algorithm(1) key-wrap-algorithm(3) algorithm(1) key-wrap-algorithm(3)
camellia256-wrap(4) } camellia256-wrap(4) }
camellia128-Wrap ALGORITHM ::= { OID id-camellia128-Wrap } camellia128-Wrap ALGORITHM ::= { OID id-camellia128-Wrap }
camellia192-Wrap ALGORITHM ::= { OID id-camellia192-Wrap } camellia192-Wrap ALGORITHM ::= { OID id-camellia192-Wrap }
camellia256-Wrap ALGORITHM ::= { OID id-camellia256-Wrap } camellia256-Wrap ALGORITHM ::= { OID id-camellia256-Wrap }
END END
B.4 Examples B.4 Examples
As an example, if the key derivation function is KDF2 based on As an example, if the key derivation function is KDF2 based onSHA-256
SHA-256 and the symmetric key-wrapping scheme is the AES Key Wrap and the symmetric key-wrapping scheme is the AES Key Wrap with a 128-
with a 128-bit KEK, the AlgorithmIdentifier for the RSA-KEM Key bit KEK, the AlgorithmIdentifier for the RSA-KEM Key Transport
Transport Algorithm will have the following value: Algorithm will have the following value:
SEQUENCE { SEQUENCE {
id-ac-generic-hybrid, -- generic cipher id-rsa-kem, -- RSA-KEM cipher
SEQUENCE { -- GenericHybridParameters SEQUENCE { -- GenericHybridParameters
SEQUENCE { -- key encapsulation mechanism SEQUENCE { -- key encapsulation mechanism
id-kem-rsa, -- RSA-KEM id-kem-rsa, -- RSA-KEM
SEQUENCE { -- RsaKemParameters SEQUENCE { -- RsaKemParameters
SEQUENCE { -- key derivation function SEQUENCE { -- key derivation function
id-kdf-kdf2, -- KDF2 id-kdf-kdf2, -- KDF2
SEQUENCE { -- KDF2-HashFunction SEQUENCE { -- KDF2-HashFunction
id-sha256 -- SHA-256; no parameters (preferred) id-sha256 -- SHA-256; no parameters (preferred)
}, },
16 -- KEK length in bytes 16 -- KEK length in bytes
}, },
SEQUENCE { -- data encapsulation mechanism SEQUENCE { -- data encapsulation mechanism
id-aes128-Wrap -- AES-128 Wrap; no parameters id-aes128-Wrap -- AES-128 Wrap; no parameters
} }
} }
} }
This AlgorithmIdentifier value has the following DER encoding:
30 4f This AlgorithmIdentifier value has the following DER encoding (??
06 07 28 81 8c 71 02 01 02 -- id-ac-generic-hybrid indicates the algorithm number which is to be assigned):
30 53
06 0b 2a 86 48 86 f7 0d 01 09 10 03 ?? -- id-rsa-kem
30 44 30 44
30 25 30 25
06 07 28 81 8c 71 02 02 04 -- id-kem-rsa 06 07 28 81 8c 71 02 02 04 -- id-kem-rsa
30 1a 30 1a
30 16 30 16
06 07 28 81 8c 71 02 05 02 -- id-kdf-kdf2 06 07 28 81 8c 71 02 05 02 -- id-kdf-kdf2
30 0b 30 0b
06 09 60 86 48 01 65 03 04 02 01 -- id-sha256 06 09 60 86 48 01 65 03 04 02 01 -- id-sha256
02 10 -- 16 bytes 02 10 -- 16 bytes
30 0b 30 0b
skipping to change at page 22, line 19 skipping to change at page 26, line 4
30 25 30 25
06 07 28 81 8c 71 02 02 04 -- id-kem-rsa 06 07 28 81 8c 71 02 02 04 -- id-kem-rsa
30 1a 30 1a
30 16 30 16
06 07 28 81 8c 71 02 05 02 -- id-kdf-kdf2 06 07 28 81 8c 71 02 05 02 -- id-kdf-kdf2
30 0b 30 0b
06 09 60 86 48 01 65 03 04 02 01 -- id-sha256 06 09 60 86 48 01 65 03 04 02 01 -- id-sha256
02 10 -- 16 bytes 02 10 -- 16 bytes
30 0b 30 0b
06 09 60 86 48 01 65 03 04 01 05 -- id-aes128-Wrap 06 09 60 86 48 01 65 03 04 01 05 -- id-aes128-Wrap
The DER encodings for other typical sets of underlying components are The DER encodings for other typical sets of underlying components are
as follows: as follows:
* KDF2 based on SHA-384, AES Key Wrap with a 192-bit KEK o KDF2 based on SHA-384, AES Key Wrap with a 192-bit KEK
30 4f 06 07 28 81 8c 71 02 01 02 30 44 30 25 06 30 46 06 0b 2a 86 48 86 f7 0d 01 09 10 03 ?? 02
07 28 81 8c 71 02 02 04 30 1a 30 16 06 07 28 81 01 02 30 44 30 25 06 07 28 81 8c 71 02 02 04 30
8c 71 02 05 02 30 0b 06 09 60 86 48 01 65 03 04 1a 30 16 06 07 28 81 8c 71 02 05 02 30 0b 06 09
02 02 02 18 30 0b 06 09 60 86 48 01 65 03 04 01 60 86 48 01 65 03 04 02 02 02 18 30 0b 06 09 60
19 86 48 01 65 03 04 01 19
* KDF2 based on SHA-512, AES Key Wrap with a 256-bit KEK o KDF2 based on SHA-512, AES Key Wrap with a 256-bit KEK
30 4f 06 07 28 81 8c 71 02 01 02 30 44 30 25 06 30 46 06 0b 2a 86 48 86 f7 0d 01 09 10 03 ?? 02
07 28 81 8c 71 02 02 04 30 1a 30 16 06 07 28 81 01 02 30 44 30 25 06 07 28 81 8c 71 02 02 04 30
8c 71 02 05 02 30 0b 06 09 60 86 48 01 65 03 04 1a 30 16 06 07 28 81 8c 71 02 05 02 30 0b 06 09
02 03 02 20 30 0b 06 09 60 86 48 01 65 03 04 01 60 86 48 01 65 03 04 02 03 02 20 30 0b 06 09 60
2d 86 48 01 65 03 04 01 2d
* KDF2 based on SHA-1, Triple-DES Key Wrap with a 128-bit KEK o KDF2 based on SHA-1, Triple-DES Key Wrap with a 128-bit KEK (two-
(two-key triple-DES) key triple-DES)
30 4f 06 07 28 81 8c 71 02 01 02 30 44 30 21 06 30 46 06 0b 2a 86 48 86 f7 0d 01 09 10 03 ?? 02
07 28 81 8c 71 02 02 04 30 16 30 12 06 07 28 81 01 02 30 44 30 21 06 07 28 81 8c 71 02 02 04 30
8c 71 02 05 02 30 07 06 05 2b 0e 03 02 1a 02 10 16 30 12 06 07 28 81 8c 71 02 05 02 30 07 06 05
30 0f 06 0b 2a 86 48 86 f7 0d 01 09 10 03 06 05 2b 0e 03 02 1a 02 10 30 0f 06 0b 2a 86 48 86 f7
00 0d 01 09 10 03 06 05 00
Full Copyright Statement IANA Considerations
Copyright (C) The IETF Trust (2008). Within the CMS, algorithms are identified by object identifiers
(OIDs). With one exception, all of the OIDs used in this document
were assigned in other IETF documents, in ISO/IEC standards
documents, by the National Institute of Standards and Technology
(NIST), and in Public-Key Cryptography Standards (PKCS) documents.
The one exception is that the ASN.1 module's identifier (see Appendix
B.3) is assigned in this document. No further action by the IANA is
necessary for this document or any anticipated updates.
This document and translations of it may be copied and furnished to Acknowledgments
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be This document is one part of a strategy to align algorithm standards
revoked by the Internet Society or its successors or assigns. produced by ASC X9, ISO/IEC JTC1 SC27, NIST, and the IETF. We would
like to thank the members of the ASC X9F1 working group for their
contributions to drafts of ANS X9.44 which led to this specification.
Disclaimer Statement Our thanks to Russ Housley as well for his guidance and
encouragement. We also appreciate the helpful direction we've
received from Blake Ramsdell and Jim Schaad in bringing this document
to fruition. A special thanks to Magnus Nystrom for his assistance on
Appendix B. Thanks also to Bob Griffin and John Linn for both
editorial direction and procedural guidance.
This document and the information contained herein are provided on an Author Information
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND James Randall
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF Randall Consulting
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 55 Sandpiper Drive
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Dover, NH 03820
USA
Email: jdrandall@comcast.net
Burt Kaliski
EMC
176 South Street
Hopkinton, MA 01748
USA
Email: kaliski_burt@emc.com
John Brainard
RSA, The Security Division of EMC
174 Middlesex Turnpike
Bedford, MA 01730
USA
Email: jbrainard@rsa.com
Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA
Email: turners@ieca.com
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