draft-ietf-smime-cms-rsaes-oaep-01.txt   draft-ietf-smime-cms-rsaes-oaep-02.txt 
S/MIME Working Group R. Housley S/MIME Working Group R. Housley
Internet Draft SPYRUS Internet Draft SPYRUS
expires in six months June 2000 expires in six months November 2000
Use of the RSAES-OAEP Key Transport Algorithm in CMS Use of the RSAES-OAEP Key Transport Algorithm in CMS
<draft-ietf-smime-cms-rsaes-oaep-01.txt> <draft-ietf-smime-cms-rsaes-oaep-02.txt>
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract Abstract
This document describes the use of the RSAES-OAEP key transport This document describes the use of the RSAES-OAEP key transport
method of key management within the Cryptographic Message Syntax method of key management within the Cryptographic Message Syntax
[CMS]. [CMS].
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[PKCS#1v2.0]. This new document supersedes RFC 2313. PKCS #1 [PKCS#1v2.0]. This new document supersedes RFC 2313. PKCS #1
Version 2.0 preserves support for the encryption padding format Version 2.0 preserves support for the encryption padding format
defined in PKCS #1 Version 1.5 [PKCS#1v1.5], and it also defines a defined in PKCS #1 Version 1.5 [PKCS#1v1.5], and it also defines a
new alternative. To resolve the adaptive chosen ciphertext new alternative. To resolve the adaptive chosen ciphertext
vulnerability, the PKCS #1 Version 2.0 specifies and recommends use vulnerability, the PKCS #1 Version 2.0 specifies and recommends use
of Optimal Asymmetric Encryption Padding (OAEP) when RSA encryption of Optimal Asymmetric Encryption Padding (OAEP) when RSA encryption
is used to provide confidentiality, such as key transport. is used to provide confidentiality, such as key transport.
This document specifies the use of RSAES-OAEP key transport algorithm This document specifies the use of RSAES-OAEP key transport algorithm
in the Cryptographic Message Syntax (CMS) [CMS]. CMS can be used in in the Cryptographic Message Syntax (CMS) [CMS]. CMS can be used in
either a store-and-forward or an interactibe request-response either a store-and-forward or an interactive request-response
environment. environment.
CMS supports variety of architectures for certificate-based key CMS supports variety of architectures for certificate-based key
management, particularly the one defined by the PKIX working group management, particularly the one defined by the PKIX working group
[PROFILE]. [PROFILE]. PKCS #1 Version 1.5 and PKCS #1 Version 2.0 require the
same RSA public key information. Thus, a certified RSA public key
may be used with either RSA key transport technique.
CMS values are generated using ASN.1 [X.208-88], using the Basic CMS values are generated using ASN.1 [X.208-88], using the Basic
Encoding Rules (BER) [X.209-88] and the Distinguished Encoding Rules Encoding Rules (BER) [X.209-88] and the Distinguished Encoding Rules
(DER) [X.509-88]. (DER) [X.509-88].
Throughout this document, when the terms MUST, MUST NOT, SHOULD and Throughout this document, when the terms MUST, MUST NOT, SHOULD and
MAY are used in capital letters, their use conforms to the MAY are used in capital letters, their use conforms to the
definitions in [MUSTSHOULD]. [MUSTSHOULD] defines these key words to definitions in [MUSTSHOULD]. [MUSTSHOULD] defines these key words to
help make the intent of standards track documents as clear as help make the intent of standards track documents as clear as
possible. The same key words are used in this document to help possible. The same key words are used in this document to help
skipping to change at page 3, line 23 skipping to change at page 3, line 25
2 Enveloped-data Conventions 2 Enveloped-data Conventions
The CMS enveloped-data content type consists of encrypted content and The CMS enveloped-data content type consists of encrypted content and
wrapped content-encryption keys for one or more recipients. The wrapped content-encryption keys for one or more recipients. The
RSAES-OAEP key transport algorithm is used to wrap the content- RSAES-OAEP key transport algorithm is used to wrap the content-
encryption key for one recipient. encryption key for one recipient.
Compliant software MUST meet the requirements for constructing an Compliant software MUST meet the requirements for constructing an
enveloped-data content type stated in [CMS] Section 6, "Enveloped- enveloped-data content type stated in [CMS] Section 6, "Enveloped-
data Content Type". [CMS] Section 6 should be studied before reading data Content Type".
this section, because this section does not repeat the [CMS] text.
A content-encryption key MUST be randomly generated for each instance A content-encryption key MUST be randomly generated for each instance
of an enveloped-data content type. The content-encryption key is of an enveloped-data content type. The content-encryption key is
used to encipher the content. used to encipher the content.
2.1 EnvelopedData Fields 2.1 EnvelopedData Fields
The enveloped-data content type is ASN.1 encoded using the The enveloped-data content type is ASN.1 encoded using the
EnvelopedData syntax. The fields of the EnvelopedData syntax must be EnvelopedData syntax. The fields of the EnvelopedData syntax must be
populated as follows: populated as follows:
The EnvelopedData version MUST be either 0 or 2. The EnvelopedData version MUST be either 0 or 2.
The EnvelopedData originatorInfo field MUST be absent. 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 The EnvelopedData recipientInfos CHOICE MUST be
KeyTransRecipientInfo. See section 2.2 for further discussion of KeyTransRecipientInfo. See section 2.2 for further discussion of
KeyTransRecipientInfo. KeyTransRecipientInfo.
The EnvelopedData encryptedContentInfo contentEncryptionAlgorithm The EnvelopedData encryptedContentInfo contentEncryptionAlgorithm
field MUST be specify a symmetric encryption algorithm. field MUST be specify a symmetric encryption algorithm.
Implementations MUST support the encryption of Triple-DES content- Implementations MUST support the encryption of Triple-DES content-
encryption keys, but implementations MAY support other algorithms as encryption keys, but implementations MAY support other algorithms as
well. well.
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The KeyTransRecipientInfo encryptedKey is the result of encrypting The KeyTransRecipientInfo encryptedKey is the result of encrypting
the content-encryption key in the recipient's RSA public key using the content-encryption key in the recipient's RSA public key using
the RSAES-OAEP algorithm. When using a Triple-DES content-encryption the RSAES-OAEP algorithm. When using a Triple-DES content-encryption
key, implementations MUST adjust the parity bits for each DES key key, implementations MUST adjust the parity bits for each DES key
comprising the Triple-DES key prior to RSAES-OAEP encryption. comprising the Triple-DES key prior to RSAES-OAEP encryption.
3 RSAES-OAEP Algorithm Identifiers and Parameters 3 RSAES-OAEP Algorithm Identifiers and Parameters
The RSAES-OAEP key transport algorithm is the RSA encryption scheme The RSAES-OAEP key transport algorithm is the RSA encryption scheme
defined in RFC 2347 [PKCS#1v2.0], where the message to be encrypted defined in RFC 2437 [PKCS#1v2.0], where the message to be encrypted
is the content-encryption key. The algorithm identifier for RSAES- is the content-encryption key. The algorithm identifier for RSAES-
OAEP is: OAEP is:
id-RSAES-OAEP OBJECT IDENTIFIER ::= { id-RSAES-OAEP OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 7 } iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 7 }
The AlgorithmIdentifier parameters field must be present, and the The AlgorithmIdentifier parameters field must be present, and the
parameters field must contain RSAES-OAEP-params. RSAES-OAEP-params parameters field must contain RSAES-OAEP-params. RSAES-OAEP-params
have the following syntax: have the following syntax:
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comprised of the id-sha1 object identifier and a parameter of comprised of the id-sha1 object identifier and a parameter of
NULL. Implementations that perform encryption MUST omit the NULL. Implementations that perform encryption MUST omit the
hashFunc field when SHA-1 is used, indicating that the default hashFunc field when SHA-1 is used, indicating that the default
algorithm was used. Implementations that perform decryption MUST algorithm was used. Implementations that perform decryption MUST
recognize both the id-sha1 object identifier and an absent recognize both the id-sha1 object identifier and an absent
hashFunc field as an indication that SHA-1 was used. hashFunc field as an indication that SHA-1 was used.
maskGenFunc identifies the mask generation function. maskGenFunc identifies the mask generation function.
Implementations MUST support MFG1 [PKCS#1v2.0]. MFG1 requires a Implementations MUST support MFG1 [PKCS#1v2.0]. MFG1 requires a
one-way hash function, and it is identified in the parameter field one-way hash function, and it is identified in the parameter field
of the algorithm identifier. Implementations MUST support SHA-1 of the MFG1 algorithm identifier. Implementations MUST support
[SHA1]. The MFG1 algorithm identifier is comprised of the id-mgf1 SHA-1 [SHA1]. The MFG1 algorithm identifier is comprised of the
object identifier and a parameter of the SHA-1 algorithm id-mgf1 object identifier and a parameter that contains the
identifier. Again, the SHA-1 algorithm identifier is comprised of algorithm identifier of the one-way hash function employed with
the id-sha1 object identifier and a parameter of NULL. MFG1. The SHA-1 algorithm identifier is comprised of the id-sha1
Implementations that perform encryption MUST omit the maskGenFunc object identifier and a parameter of NULL. Implementations that
field when MFG1 with SHA-1 is used, indicating that the default perform encryption MUST omit the maskGenFunc field when MFG1 with
algorithm was used. Implementations that perform decryption MUST SHA-1 is used, indicating that the default algorithm was used.
recognize both the id-mgf1 and id-sha1 object identifiers as well Implementations that perform decryption MUST recognize both the
as an absent maskGenFunc field as an indication that MFG1 with id-mgf1 and id-sha1 object identifiers as well as an absent
SHA-1 was used. maskGenFunc field as an indication that MFG1 with SHA-1 was used.
pSourceFunc identifies the source (and possibly the value) of the pSourceFunc identifies the source (and possibly the value) of the
encoding parameters, commonly called P. Implementations MUST encoding parameters, commonly called P. Implementations MUST
represent P by an algorithm identifier, id-pSpecified, indicating represent P by an algorithm identifier, id-pSpecified, indicating
that P is explicitly provided as an OCTET STRING in the that P is explicitly provided as an OCTET STRING in the
parameters. The default value for P is an empty string. In this 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. case, pHash in EME-OAEP contains the hash of a zero length string.
Implementations MUST support a zero length P value. Implementations MUST support a zero length P value.
Implementations that perform encryption MUST omit the pSourceFunc Implementations that perform encryption MUST omit the pSourceFunc
field when a zero length P value is used, indicating that the field when a zero length P value is used, indicating that the
default value was used. Implementations that perform decryption default value was used. Implementations that perform decryption
MUST recognize both the id-pSpecified object identifier and an MUST recognize both the id-pSpecified object identifier and an
absent pSourceFunc field as an indication that a zero length P absent pSourceFunc field as an indication that a zero length P
value was used. value was used.
4 SMIMECapabilities Attribute Conventions 4 SMIMECapabilities Attribute Conventions
RFC 2633, Section 2.5.2 defines the SMIMECapabilities signed RFC 2633, Section 2.5.2 defines the SMIMECapabilities signed
attribute (defined as a SEQUENCE of SMIMECapability SEQUNCEs) 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
RSAES-OAEP algorithm. RSAES-OAEP algorithm.
The SMIMECapability SEQUENCE representing RSAES-OAEP MUST include the The SMIMECapability SEQUENCE representing RSAES-OAEP MUST include the
id-RSAES-OAEP object identifier in the capabilityID field and MUST id-RSAES-OAEP object identifier in the capabilityID field and MUST
include the RSAES-OAEP-Default-Identifier SEQUENCE in the parameters include the RSAES-OAEP-Default-Identifier SEQUENCE in the parameters
field. field.
RSAES-OAEP-Default-Identifier ::= AlgorithmIdentifier { RSAES-OAEP-Default-Identifier ::= AlgorithmIdentifier {
id-RSAES-OAEP, { id-RSAES-OAEP, {
sha1Identifier, mgf1SHA1Identifier, pSpecifiedEmptyIdentifier } } sha1Identifier, mgf1SHA1Identifier, pSpecifiedEmptyIdentifier } }
When all of the default settings are selected, the SMIMECapability When all of the default settings are selected, the SMIMECapability
SEQUENCE representing RSAES-OAEP MUST be DER-encoded as: 30 length SEQUENCE representing RSAES-OAEP MUST be DER-encoded as:
[id-RSAES-OAEP OID encoding] [30 00].
30 0D 06 09 2A 86 48 86 F7 0D 01 01 07 30 00
References References
CMS Housley, R. Cryptographic Message Syntax. RFC 2630. CMS Housley, R. Cryptographic Message Syntax. RFC 2630.
June 1999. June 1999.
CRYPTO98 Bleichenbacher, D. "Chosen Ciphertext Attacks Against CRYPTO98 Bleichenbacher, D. "Chosen Ciphertext Attacks Against
Protocols Based on the RSA Encryption Standard PKCS #1," Protocols Based on the RSA Encryption Standard PKCS #1,"
in H. Krawczyk (editor), Advances in Cryptology - CRYPTO '98 in H. Krawczyk (editor), Advances in Cryptology - CRYPTO '98
Proceedings, Lecture Notes in Computer Science 1462 (1998), Proceedings, Lecture Notes in Computer Science 1462 (1998),
Springer-Verlag, pp. 1-12. Springer-Verlag, pp. 1-12.
MUSTSHOULD Bradner, S. Key Words for Use in RFCs to Indicate MUSTSHOULD Bradner, S. Key Words for Use in RFCs to Indicate
Requirement Levels. BCP 14, RFC 2119. March 1997. Requirement Levels. BCP 14, RFC 2119. March 1997.
PKCS#1v1.5 Kaliski, B. PKCS #1: RSA Encryption, Version 1.5. PKCS#1v1.5 Kaliski, B. PKCS #1: RSA Encryption, Version 1.5.
RFC 2313. March 1998. RFC 2313. March 1998.
PKCS#1v2.0 Kaliski, B. PKCS #1: RSA Encryption, Version 2.0. PKCS#1v2.0 Kaliski, B. PKCS #1: RSA Encryption, Version 2.0.
RFC 2347. October 1998. RFC 2437. October 1998.
PROFILE Housley, R., W. Ford, W. Polk, and D. Solo. Internet PROFILE Housley, R., W. Ford, W. Polk, and D. Solo. Internet
X.509 Public Key Infrastructure: Certificate and CRL X.509 Public Key Infrastructure: Certificate and CRL
Profile. RFC 2459. January 1999. Profile. RFC 2459. January 1999.
RANDOM Eastlake, D., S. Crocker, and J. Schiller. Randomness RANDOM Eastlake, D., S. Crocker, and J. Schiller. Randomness
Recommendations for Security. RFC 1750. December 1994. Recommendations for Security. RFC 1750. December 1994.
RSALABS Daniel Bleichenbacher, D., B. Kaliski, and J. Staddon. RSALABS Bleichenbacher, D., B. Kaliski, and J. Staddon.
Recent Results on PKCS #1: RSA Encryption Standard. RSA Recent Results on PKCS #1: RSA Encryption Standard.
Laboratories' Bulletin No. 7, June 26, 1998. RSA Laboratories' Bulletin No. 7, June 26, 1998.
[Available at http://www.rsasecurity.com/rsalabs/bulletins] [Available at http://www.rsasecurity.com/rsalabs/bulletins]
SHA1 National Institute of Standards and Technology. SHA1 National Institute of Standards and Technology.
FIPS Pub 180-1: Secure Hash Standard. 17 April 1995. FIPS Pub 180-1: Secure Hash Standard. 17 April 1995.
SSL Freier, A., P. Karlton, and P. Kocher. The SSL Protocol, SSL Freier, A., P. Karlton, and P. Kocher. The SSL Protocol,
Version 3.0. Netscape Communications. November 1996. Version 3.0. Netscape Communications. November 1996.
[Available at http://draft-freier-ssl-version3-02.txt] [Available at http://draft-freier-ssl-version3-02.txt]
TLS Dierks, T. and C. Allen. The TLS Protocol Version 1.0. TLS Dierks, T. and C. Allen. The TLS Protocol Version 1.0.
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