draft-ietf-smime-cms-rsaes-oaep-07.txt   rfc3560.txt 
S/MIME Working Group R. Housley Network Working Group R. Housley
Internet Draft RSA Laboratories Request for Comments: 3560 Vigil Security
expires in six months December 2002 Category: Standards Track July 2003
Use of the RSAES-OAEP Key Transport Algorithm in CMS Use of the RSAES-OAEP Key Transport Algorithm in
<draft-ietf-smime-cms-rsaes-oaep-07.txt> the Cryptographic Message Syntax (CMS)
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This document describes the conventions for using the RSAES-OAEP key This document describes the conventions for using the RSAES-OAEP key
transport algorithm with the Cryptographic Message Syntax (CMS). The transport algorithm with the Cryptographic Message Syntax (CMS). The
CMS specifies the enveloped-data content type, which consists of an CMS specifies the enveloped-data content type, which consists of an
encrypted content and encrypted content-encryption keys for one or encrypted content and encrypted content-encryption keys for one or
more recipients. The RSAES-OAEP key transport algorithm can be used more recipients. The RSAES-OAEP key transport algorithm can be used
to encrypt content-encryption keys for intended recipients. to encrypt content-encryption keys for intended recipients.
1. Introduction Table of Contents
This draft is being discussed on the "ietf-smime" mailing list. To 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
join the list, send a message to <ietf-smime-request@imc.org> with 2. Enveloped-data Conventions . . . . . . . . . . . . . . . . . . 3
the single word "subscribe" in the body of the message. Also, there 2.1. EnvelopedData Fields . . . . . . . . . . . . . . . . . . 3
is a Web site for the mailing list at <http://www.imc.org/ietf- 2.2. KeyTransRecipientInfo Fields . . . . . . . . . . . . . . 4
smime/>. 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 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 of the RSA key transport algorithm. PKCS #1 Version 1.5 key
transport is vulnerable to adaptive chosen ciphertext attacks, transport is vulnerable to adaptive chosen ciphertext attacks,
especially when it is used to for key management in interactive especially when it is used to for key management in interactive
applications. This attack is often referred to as the "Million applications. This attack is often referred to as the "Million
Message Attack," and it explained in [RSALABS] and [CRYPTO98]. Message Attack," and it explained in [RSALABS] and [CRYPTO98].
Exploitation of this vulnerability, which reveals the result of a Exploitation of this vulnerability, which reveals the result of a
particular RSA decryption, requires access to an oracle which will particular RSA decryption, requires access to an oracle which will
respond to hundreds of thousands of ciphertexts, which are respond to hundreds of thousands of ciphertexts, which are
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communications environment, exploitation could be more feasible. communications environment, exploitation could be more feasible.
However, Secure Sockets Layer (SSL) [SSL] and Transport Layer However, Secure Sockets Layer (SSL) [SSL] and Transport Layer
Security (TLS) [TLS] protocol implementations could include Security (TLS) [TLS] protocol implementations could include
countermeasures that detect and prevent the Million Message Attack countermeasures that detect and prevent the Million Message Attack
and other chosen-ciphertext attacks. These countermeasures are and other chosen-ciphertext attacks. These countermeasures are
performed within the protocol level. performed within the protocol level.
In the interest of long-term security assurance, it is prudent to In the interest of long-term security assurance, it is prudent to
adopt an improved cryptographic technique rather than embedding adopt an improved cryptographic technique rather than embedding
countermeasures within protocols. To this end, an updated version of countermeasures within protocols. To this end, an updated version of
PKCS #1 has been published. PKCS #1 Version 2.0 [PKCS#1v2.0] PKCS #1 has been published. PKCS #1 Version 2.1 [PKCS#1v2.1]
supersedes RFC 2313. It preserves support for the PKCS #1 Version supersedes RFC 2313. It preserves support for the PKCS #1 Version
1.5 encryption padding format, and it also defines a new one. To 1.5 encryption padding format, and it also defines a new one. To
resolve the adaptive chosen ciphertext vulnerability, the PKCS #1 resolve the adaptive chosen ciphertext vulnerability, the PKCS #1
Version 2.0 specifies and recommends use of Optimal Asymmetric Version 2.1 specifies and recommends use of Optimal Asymmetric
Encryption Padding (OAEP) for RSA key transport. Encryption Padding (OAEP) for RSA 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 CMS. The CMS can be used in either a store-and-forward or an in the CMS. The CMS can be used in either a store-and-forward or an
interactive request-response environment. interactive request-response environment.
The CMS supports variety of architectures for certificate-based key The 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]. PKCS #1 Version 1.5 and PKCS #1 Version 2.0 require the [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 same RSA public key information. Thus, a certified RSA public key
may be used with either RSA key transport technique. may be used with either RSA key transport technique.
The CMS uses ASN.1 [X.208-88], the Basic Encoding Rules (BER) 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]. [X.209-88], and the Distinguished Encoding Rules (DER) [X.509-88].
Throughout this document, when the terms "MUST," "MUST NOT," Throughout this document, when the terms "MUST", "MUST NOT",
"SHOULD," and "MAY" are used in capital letters, their use conforms "SHOULD", and "MAY" are used in capital letters, their use conforms
to the definitions in RFC 2119 [STDWORDS]. These key word to the definitions in RFC 2119 [STDWORDS]. These key word
definitions help make the intent of standards documents as clear as definitions help make the intent of standards documents as clear as
possible. These key words are used in this document to help possible. These key words are used in this document to help
implementers achieve interoperability. implementers achieve interoperability.
2. Enveloped-data Conventions 2. Enveloped-data Conventions
The CMS enveloped-data content type consists of an encrypted content The CMS enveloped-data content type consists of an encrypted content
and wrapped content-encryption keys for one or more recipients. The and 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
encryption key for one recipient. content-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,
data Content Type". "Enveloped-data Content Type".
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 described in this section when RSAES-OAEP key transport populated as described in this section when RSAES-OAEP key transport
is employed for one or more recipients. is employed for one or more recipients.
The EnvelopedData version MUST be 0, 2, or 3. The EnvelopedData version MUST be 0, 2, or 3.
The EnvelopedData originatorInfo field is not used for the RSAES-OAEP The EnvelopedData originatorInfo field is not used for the RSAES-OAEP
key transport algorithm. However, this field MAY be present to key transport algorithm. However, this field MAY be present to
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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 a symmetric encryption algorithm identifier. field MUST be a symmetric encryption algorithm identifier.
The EnvelopedData unprotectedAttrs MAY be present. The EnvelopedData unprotectedAttrs MAY be present.
2.2. KeyTransRecipientInfo Fields 2.2. KeyTransRecipientInfo Fields
The fields of the KeyTransRecipientInfo syntax MUST be populated as The fields of the KeyTransRecipientInfo syntax MUST be populated as
described in this section when RSAES-OAEP key transport is employed described in this section when RSAES-OAEP key transport is employed
for one or more recipients. for one or more recipients.
The KeyTransRecipientInfo version MUST be 0 or 2. If the The KeyTransRecipientInfo version MUST be 0 or 2. If the
RecipientIdentifier uses the issuerAndSerialNumber alternative, then RecipientIdentifier uses the issuerAndSerialNumber alternative, then
the version MUST be 0. If the RecipientIdentifier uses the the version MUST be 0. If the RecipientIdentifier uses the
subjectKeyIdentifier alternative, then the version MUST be 2. subjectKeyIdentifier alternative, then the version MUST be 2.
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a RSA public key. The content-encryption key is encrypted with the a RSA public key. The content-encryption key is encrypted with the
recipient's RSA public key. The issuerAndSerialNumber alternative recipient's RSA public key. The issuerAndSerialNumber alternative
identifies the recipient's certificate by the issuer's distinguished identifies the recipient's certificate by the issuer's distinguished
name and the certificate serial number; the subjectKeyIdentifier name and the certificate serial number; the subjectKeyIdentifier
identifies the recipient's certificate by the X.509 identifies the recipient's certificate by the X.509
subjectKeyIdentifier extension value. subjectKeyIdentifier extension value.
The KeyTransRecipientInfo keyEncryptionAlgorithm specifies use of the The KeyTransRecipientInfo keyEncryptionAlgorithm specifies use of the
RSAES-OAEP algorithm, and its associated parameters, to encrypt the RSAES-OAEP algorithm, and its associated parameters, to encrypt the
content-encryption key for the recipient. The key-encryption process content-encryption key for the recipient. The key-encryption process
is described in [PKCS#1v2.0]. See section 3 of this document for the is described in [PKCS#1v2.1]. See section 3 of this document for the
algorithm identifier and the parameter syntax. algorithm identifier and the parameter syntax.
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. The RSA public key MUST be at least 1024 the RSAES-OAEP algorithm. The RSA public key MUST be at least 1024
bits in length. When using a Triple-DES [3DES] content-encryption bits in length. When using a Triple-DES [3DES] content-encryption
key, implementations MUST adjust the parity bits to ensure odd parity 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 for each octet of each DES key comprising the Triple-DES key prior to
RSAES-OAEP encryption. 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 2437 [PKCS#1v2.0], where the message to be encrypted defined in RFC 3447 [PKCS#1v2.1], 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
OAEP is: RSAES-OAEP is:
id-RSAES-OAEP OBJECT IDENTIFIER ::= { iso(1) member-body(2) id-RSAES-OAEP OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 7 } 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
has the following syntax: has the following syntax:
RSAES-OAEP-params ::= SEQUENCE { RSAES-OAEP-params ::= SEQUENCE {
hashFunc [0] AlgorithmIdentifier DEFAULT sha1Identifier, hashFunc [0] AlgorithmIdentifier DEFAULT sha1Identifier,
maskGenFunc [1] AlgorithmIdentifier DEFAULT mgf1SHA1Identifier, maskGenFunc [1] AlgorithmIdentifier DEFAULT mgf1SHA1Identifier,
pSourceFunc [2] AlgorithmIdentifier DEFAULT pSourceFunc [2] AlgorithmIdentifier DEFAULT
pSpecifiedEmptyIdentifier } pSpecifiedEmptyIdentifier }
sha1Identifier AlgorithmIdentifier ::= { id-sha1, NULL } sha1Identifier AlgorithmIdentifier ::= { id-sha1, NULL }
mgf1SHA1Identifier AlgorithmIdentifier ::= mgf1SHA1Identifier AlgorithmIdentifier ::=
{ id-mgf1, sha1Identifier } { id-mgf1, sha1Identifier }
pSpecifiedEmptyIdentifier AlgorithmIdentifier ::= pSpecifiedEmptyIdentifier AlgorithmIdentifier ::=
{ id-pSpecified, nullOctetString } { id-pSpecified, nullOctetString }
nullOctetString OCTET STRING (SIZE (0)) ::= { ''H } nullOctetString OCTET STRING (SIZE (0)) ::= { ''H }
id-sha1 OBJECT IDENTIFIER ::= { iso(1) id-sha1 OBJECT IDENTIFIER ::= { iso(1)
identified-organization(3) oiw(14) identified-organization(3) oiw(14)
secsig(3) algorithms(2) 26 } secsig(3) algorithms(2) 26 }
pkcs-1 OBJECT IDENTIFIER ::= { iso(1) member-body(2) pkcs-1 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-1(1) } us(840) rsadsi(113549) pkcs(1) pkcs-1(1) }
id-mgf1 OBJECT IDENTIFIER ::= { pkcs-1 8 } id-mgf1 OBJECT IDENTIFIER ::= { pkcs-1 8 }
id-pSpecified OBJECT IDENTIFIER ::= { pkcs-1 9 } id-pSpecified OBJECT IDENTIFIER ::= { pkcs-1 9 }
The fields within RSAES-OAEP-params have the following meanings: The fields within RSAES-OAEP-params have the following meanings:
hashFunc identifies the one-way hash function. Implementations hashFunc identifies the one-way hash function. Implementations MUST
MUST support SHA-1 [SHA1], and implementations MAY support other support SHA-1 [SHA1], and implementations MAY support other one-way
one-way hash functions. The SHA-1 algorithm identifier is hash functions. The SHA-1 algorithm identifier is comprised of the
comprised of the id-sha1 object identifier and a parameter of id-sha1 object identifier and a parameter of NULL. Implementations
NULL. Implementations that perform encryption MUST omit the that perform encryption MUST omit the hashFunc field when SHA-1 is
hashFunc field when SHA-1 is used, indicating that the default used, indicating that the default algorithm was used.
algorithm was used. Implementations that perform decryption MUST Implementations that perform decryption MUST recognize both the
recognize both the id-sha1 object identifier and an absent id-sha1 object identifier and an absent hashFunc field as an
hashFunc field as an indication that SHA-1 was used. indication that SHA-1 was used.
maskGenFunc identifies the mask generation function. maskGenFunc identifies the mask generation function. Implementations
Implementations MUST support MFG1 [PKCS#1v2.0]. MFG1 requires a MUST support MFG1 [PKCS#1v2.1]. MFG1 requires a one-way hash
one-way hash function, and it is identified in the parameter field function, and it is identified in the parameter field of the MFG1
of the MFG1 algorithm identifier. Implementations MUST support algorithm identifier. Implementations MUST support SHA-1 [SHA1], and
SHA-1 [SHA1], and implementations MAY support other one-way hash implementations MAY support other one-way hash functions. The MFG1
functions. The MFG1 algorithm identifier is comprised of the id- algorithm identifier is comprised of the id-mgf1 object identifier
mgf1 object identifier and a parameter that contains the algorithm and a parameter that contains the algorithm identifier of the one-way
identifier of the one-way hash function employed with MFG1. The hash function employed with MFG1. The SHA-1 algorithm identifier is
SHA-1 algorithm identifier is comprised of the id-sha1 object comprised of the id-sha1 object identifier and a parameter of NULL.
identifier and a parameter of NULL. Implementations that perform Implementations that perform encryption MUST omit the maskGenFunc
encryption MUST omit the maskGenFunc field when MFG1 with SHA-1 is field when MFG1 with SHA-1 is used, indicating that the default
used, indicating that the default algorithm was used. algorithm was used. Implementations that perform decryption MUST
Implementations that perform decryption MUST recognize both the recognize both the id-mgf1 and id-sha1 object identifiers as well as
id-mgf1 and id-sha1 object identifiers as well as an absent an absent maskGenFunc field as an indication that MFG1 with SHA-1 was
maskGenFunc field as an indication that MFG1 with SHA-1 was used. 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 the 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.
parameters. The default value for P is an empty string. In this The default value for P is an empty string. In this case, pHash in
case, pHash in EME-OAEP contains the hash of a zero length string. EME-OAEP contains the hash of a zero length string. Implementations
Implementations MUST support a zero length P value. MUST support a zero length P value. Implementations that perform
Implementations that perform encryption MUST omit the pSourceFunc encryption MUST omit the pSourceFunc field when a zero length P value
field when a zero length P value is used, indicating that the is used, indicating that the default value was used. Implementations
default value was used. Implementations that perform decryption that perform decryption MUST recognize both the id-pSpecified object
MUST recognize both the id-pSpecified object identifier and an identifier and an absent pSourceFunc field as an indication that a
absent pSourceFunc field as an indication that a zero length P zero length P value was used.
value was used.
4. Certificate Conventions 4. Certificate Conventions
RFC 3280 [PROFILE] specifies the profile for using X.509 Certificates RFC 3280 [PROFILE] specifies the profile for using X.509 Certificates
in Internet applications. When a RSA public key will be used for in Internet applications. When a RSA public key will be used for
RSAES-OAEP key transport, the conventions specified in this section RSAES-OAEP key transport, the conventions specified in this section
augment RFC 3280. augment RFC 3280.
Traditionally, the rsaEncryption object identifier is used to Traditionally, the rsaEncryption object identifier is used to
identify RSA public keys. However, to implement all of the identify RSA public keys. However, to implement all of the
recommendations described in the Security Considerations section of recommendations described in the Security Considerations section of
this document (see section 7), the certificate user needs to be able 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 to determine the form of key transport that the RSA private key owner
associates with the public key. associates with the public key.
The rsaEncryption object identifier continues to identify the subject The rsaEncryption object identifier continues to identify the subject
public key when the RSA private key owner does not wish to limit the 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 use of the public key exclusively to RSAES-OAEP. In this case, the
rsaEncryption object identifier MUST be used in the algorithm field rsaEncryption object identifier MUST be used in the algorithm field
within the subject public key information, and the parameters field within the subject public key information, and the parameters field
MUST contain NULL. MUST contain NULL.
rsaEncryption OBJECT IDENTIFIER ::= { pkcs-1 1 } rsaEncryption OBJECT IDENTIFIER ::= { pkcs-1 1 }
Further discussion of the conventions associated with use of the Further discussion of the conventions associated with use of the
rsaEncryption object identifier can be found in RFC 3279 (see rsaEncryption object identifier can be found in RFC 3279 (see
[CERTALGS], section 2.3.1). [CERTALGS], section 2.3.1).
When the RSA private key owner wishes to limit the use of the public 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 key exclusively to RSAES-OAEP, then the id-RSAES-OAEP object
identifier MUST be used in the algorithm field within the subject identifier MUST be used in the algorithm field within the subject
public key information, and the parameters field MUST contain public key information, and the parameters field MUST contain
RSAES-OAEP-params. The id-RSAES-OAEP object identifier value and RSAES-OAEP-params. The id-RSAES-OAEP object identifier value and the
the RSAES-OAEP-params syntax are fully described in section 3 of RSAES-OAEP-params syntax are fully described in section 3 of this
this document. document.
Regardless of the object identifier used, the RSA public key is Regardless of the object identifier 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 RSA public key MUST be encoded using the type RSAPublicKey type: The 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
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public key with the id-RSAES-OAEP object identifier, then the key public key with the id-RSAES-OAEP object identifier, then the key
usage extension MUST contain a combination of the following values: usage extension MUST contain a combination of the following values:
keyEncipherment; and keyEncipherment; and
dataEncipherment. dataEncipherment.
However, both keyEncipherment and dataEncipherment SHOULD NOT be However, both keyEncipherment and dataEncipherment SHOULD NOT be
present. present.
When a certificate that conveys an RSA public key with the When a certificate that conveys an RSA public key with the
id-RSAES-OAEP object identifier, the certificate user MUST only id-RSAES-OAEP object identifier, the certificate user MUST only use
use the certified RSA public key for RSAES-OAEP operations, and the certified RSA public key for RSAES-OAEP operations, and the
the certificate user MUST perform those operations using the certificate user MUST perform those operations using the parameters
parameters identified in the certificate. identified in the certificate.
5. SMIMECapabilities Attribute Conventions 5. SMIMECapabilities Attribute Conventions
RFC 2633 [MSG], Section 2.5.2 defines the SMIMECapabilities signed RFC 2633 [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
RSAES-OAEP algorithm. RSAES-OAEP algorithm.
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 include the id-RSAES-OAEP SEQUENCE representing RSAES-OAEP MUST include the id-RSAES-OAEP
object identifier in the capabilityID field and MUST include an empty object identifier in the capabilityID field and MUST include an empty
SEQUENCE in the parameters field. In this case, RSAES-OAEP is SEQUENCE in the parameters field. In this case, RSAES-OAEP is
represented by the rSAES-OAEP-Default-Identifier: represented by the rSAES-OAEP-Default-Identifier:
rSAES-OAEP-Default-Identifier AlgorithmIdentifier ::= rSAES-OAEP-Default-Identifier AlgorithmIdentifier ::=
{ id-RSAES-OAEP, { id-RSAES-OAEP,
{ sha1Identifier, { sha1Identifier,
mgf1SHA1Identifier, mgf1SHA1Identifier,
pSpecifiedEmptyIdentifier } } pSpecifiedEmptyIdentifier } }
The SMIMECapability SEQUENCE representing rSAES-OAEP-Default- The SMIMECapability SEQUENCE representing rSAES-OAEP-Default-
Identifier MUST be DER-encoded as the following hexadecimal string: 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 30 0D 06 09 2A 86 48 86 F7 0D 01 01 07 30 00
When settings other than the defaults are selected, the When settings other than the defaults are selected, the
SMIMECapability SEQUENCE representing RSAES-OAEP MUST include 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-params SEQUENCE that identifies the include the RSAES-OAEP-params SEQUENCE that identifies the
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the maskGenFunc, the SMIMECapability SEQUENCE representing RSAES-OAEP the maskGenFunc, the SMIMECapability SEQUENCE representing RSAES-OAEP
is the rSAES-OAEP-SHA512-Identifier, as specified in Appendix A. The is the rSAES-OAEP-SHA512-Identifier, as specified in Appendix A. The
SMIMECapability SEQUENCE representing rSAES-OAEP-SHA512-Identifier SMIMECapability SEQUENCE representing rSAES-OAEP-SHA512-Identifier
MUST be DER-encoded as the following hexadecimal string: 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 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 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 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 86 48 01 65 03 04 02 03 05 00
6. References 6. Security Considerations
This section provides normative and informative references.
6.1. 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. RFC <TBD>.
<TBD DATE>.
MSG Ramsdell, B. S/MIME Version 3 Message Specification.
RFC 2633. June 1999.
PKCS#1v2.0 Kaliski, B. PKCS #1: RSA Encryption, Version 2.0.
RFC 2437. October 1998.
PROFILE Housley, R., W. Polk, W. Ford, 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.
6.2. Informative References
CERTALGS Polk, W., R. Housley, and L. Bassham. "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., S. Crocker, 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.
7. Security Considerations
Implementations must protect the RSA private key and the content- Implementations must protect the RSA private key and the
encryption key. Compromise of the RSA private key may result in the content-encryption key. Compromise of the RSA private key may result
disclosure of all messages protected with that key. Compromise of in the disclosure of all messages protected with that key.
the content-encryption key may result in disclosure of the associated Compromise of the content-encryption key may result in disclosure of
encrypted content. the associated encrypted content.
The generation of RSA public/private key pairs relies on a random The generation of RSA public/private key pairs relies on a random
numbers. The use of inadequate pseudo-random number generators numbers. The use of inadequate pseudo-random number generators
(PRNGs) to generate cryptographic keys can result in little or no (PRNGs) to generate cryptographic keys can result in little or no
security. An attacker may find it much easier to reproduce the PRNG security. An attacker may find it much easier to reproduce the PRNG
environment that produced the keys, searching the resulting small set environment that produced the keys, searching the resulting small set
of possibilities, rather than brute force searching the whole key of possibilities, rather than brute force searching the whole key
space. The generation of quality random numbers is difficult. RFC space. The generation of quality random numbers is difficult. RFC
1750 [RANDOM] offers important guidance in this area. 1750 [RANDOM] offers important guidance in this area.
skipping to change at page 11, line 33 skipping to change at page 10, line 5
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. While PKCS #1 Version 1.5 essential to maintain provable security. While PKCS #1 Version 1.5
[PKCS#1v1.5] has been employed for both key transport and digital [PKCS#1v1.5] has been employed for both key transport and digital
signature without any known bad interactions, such a combined use of signature without any known bad interactions, such a combined use of
an RSA key pair is not recommended in the future. Therefore, an RSA 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 key pair used for RSAES-OAEP key transport should not also be used
for other purposes. For similar reasons, one RSA key pair should for other purposes. For similar reasons, one RSA key pair should
always be used with the same RSAES-OAEP parameters. always be used with the same RSAES-OAEP parameters.
This specification requires implementation to support the SHA-1 one- This specification requires implementation to support the SHA-1
way hash function for interoperability, but support for other one-way one-way hash function for interoperability, but support for other
hash function is permitted. At the time of this writing, the best one-way hash function is permitted. At the time of this writing, the
(known) collision attacks against SHA-1 are generic attacks with 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 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 value. When a one-way hash function is used with a digital signature
scheme, a collision attack is easily translated into a signature scheme, a collision attack is easily translated into a signature
forgery. Therefore, the use of SHA-1 in a digital signature scheme 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 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 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 with a longer hash value is needed. SHA-256, SHA-384, and SHA-512
are likely candidates [SHA2]. are likely candidates [SHA2].
The metrics for choosing a one-way hash function for use in digital The metrics for choosing a one-way hash function for use in digital
skipping to change at page 12, line 20 skipping to change at page 10, line 40
length of the hash value is at least twice as long as the desired length of the hash value is at least twice as long as the desired
security level in bits. security level in bits.
A 1024-bit RSA public key and SHA-1 both provide a security level of 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 about 80 bits. In [NISTGUIDE], the National Institute of Standards
and Technology suggests that a security level of 80 bits is adequate and Technology suggests that a security level of 80 bits is adequate
for most applications until 2015. If a security level greater than 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 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, 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 SHA-384, and SHA-512 are likely candidates for such a one-way hash
function. For this reason, the algorithm identifiers for these one- function. For this reason, the algorithm identifiers for these
way hash functions are included in the ASN.1 module in Appendix A. 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 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 and the maskGenFunc, but it is not required. Using the same one-way
hash function reduces the potential for implementation errors. hash function reduces the potential for implementation errors.
8. IANA Considerations 7. IANA Considerations
Within the CMS, algorithms are identified by object identifiers Within the CMS, algorithms are identified by object identifiers
(OIDs). All of the OIDs used in this document were assigned in (OIDs). All of the OIDs used in this document were assigned in
Public-Key Cryptography Standards (PKCS) documents or by the National Public-Key Cryptography Standards (PKCS) documents or by the National
Institute of Standards and Technology (NIST). No further action by Institute of Standards and Technology (NIST). No further action by
the IANA is necessary for this document or any anticipated updates. the IANA is necessary for this document or any anticipated updates.
9. Acknowledgments 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. This document is the result of contributions from many professionals.
I appreciate the hard work of all members of the IETF S/MIME Working 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 Group. Further, I extend a special thanks to Burt Kaliski, Jakob
Jonsson, Francois Rousseau, and Jim Schaad. Jonsson, Francois Rousseau, and Jim Schaad.
10. Author Address 10. References
Russell Housley This section provides normative and informative references.
RSA Laboratories
918 Spring Knoll Drive
Herndon, VA 20170
USA
rhousley@rsasecurity.com
Appendix A. ASN.1 Module 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 CMS-RSAES-OAEP
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) modules(0) cms-rsaes-oaep(20) } pkcs-9(9) smime(16) modules(0) cms-rsaes-oaep(20) }
DEFINITIONS IMPLICIT TAGS ::= DEFINITIONS IMPLICIT TAGS ::= BEGIN
BEGIN
-- EXPORTS ALL -- -- EXPORTS ALL --
IMPORTS IMPORTS
AlgorithmIdentifier AlgorithmIdentifier
FROM PKIX1Explicit88 -- RFC 3280 FROM PKIX1Explicit88 -- RFC 3280
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) security(5) mechanisms(5) pkix(7) id-mod(0)
id-pkix1-explicit(18) }; id-pkix1-explicit(18) };
skipping to change at page 15, line 13 skipping to change at page 17, line 5
pSpecifiedEmptyIdentifier } } pSpecifiedEmptyIdentifier } }
rSAES-OAEP-SHA512-Identifier AlgorithmIdentifier ::= rSAES-OAEP-SHA512-Identifier AlgorithmIdentifier ::=
{ id-RSAES-OAEP, { id-RSAES-OAEP,
{ sha512Identifier, { sha512Identifier,
mgf1SHA512Identifier, mgf1SHA512Identifier,
pSpecifiedEmptyIdentifier } } pSpecifiedEmptyIdentifier } }
END END
Author's Address
Russell Housley
Vigil Security, LLC
918 Spring Knoll Drive
Herndon, VA 20170
USA
EMail: housley@vigilsec.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. In addition, the included on all such copies and derivative works. However, this
ASN.1 module presented in Appendix A may be used in whole or in part document itself may not be modified in any way, such as by removing
without inclusion of the copyright notice. However, this document the copyright notice or references to the Internet Society or other
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 Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process shall be copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than followed, or as required to translate it into languages other than
English. English.
The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns. This revoked by the Internet Society or its successors or assignees.
document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK This document and the information contained herein is provided on an
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
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MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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