draft-ietf-smime-aes-alg-03.txt   draft-ietf-smime-aes-alg-04.txt 
S/MIME Working Group J. Schaad S/MIME Working Group J. Schaad
Internet Draft Soaring Hawk Consulting Internet Draft Soaring Hawk Consulting
Document: draft-ietf-smime-aes-alg-03.txt R. Housley Document: draft-ietf-smime-aes-alg-04.txt R. Housley
Expires: May 2001 RSA Laboratories Expires: July 2002 RSA Laboratories
November 2001 January 2002
Use of the AES Encryption Algorithm and RSA-OAEP Key Transport in CMS Use of the AES Encryption Algorithm and RSA-OAEP Key Transport in CMS
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026. all provisions of Section 10 of RFC 2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at line 37 skipping to change at line 37
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Comments or suggestions for improvement may be made on the "ietf- Comments or suggestions for improvement may be made on the "ietf-
smime" mailing list, or directly to the author. smime" mailing list, or directly to the author.
Abstract Abstract
This document specifies the conventions for using the Advanced This document specifies the conventions for using the Advanced
Encryption Standard (AES) algorithm [AES] for encryption and the Encryption Standard (AES) algorithm [AES] for encryption and the
RSAES-OAEP key transport method [PKCS#1v2.0] for key management with RSAES-OAEP key transport algorithm [PKCS#1v2.0] for key management
the Cryptographic Message Syntax (CMS) [CMS]. with the Cryptographic Message Syntax (CMS) [CMS].
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 document are to be interpreted as described in RFC 2119 this document are to be interpreted as described in RFC 2119
[MUSTSHOULD]. [MUSTSHOULD].
1 Overview 1 Overview
This document specifies the conventions for using the RSAES-OAEP key This document specifies the conventions for using the RSAES-OAEP key
transport algorithm and Advanced Encryption Standard (AES) content transport algorithm and Advanced Encryption Standard (AES) content
encryption algorithm with the Cryptographic Message Syntax [CMS] encryption algorithm with the Cryptographic Message Syntax [CMS]
enveloped-data and encrypted-data content types. enveloped-data and encrypted-data content types.
Schaad, Housley 1 Schaad, Housley 1
Use of the AES Algorithm in CMS November 2000 Use of the AES Algorithm in CMS February 2002
This document presents the use of the two algorithms together, since This document presents the use of the two algorithms together, since
we anticipate that they will be used together. However, the two we anticipate that they will be used together. However, the two
algorithms can be used independently. For example, RSA-OAEP could be algorithms can be used independently. For example, RSA-OAEP could be
used to transport Triple-DES keys, and AES keys could be distributed used to transport Triple-DES keys, and AES keys could be distributed
out-of-band for use with mail lists. out-of-band for use with mail lists.
1.1 AES CMS values are generated using ASN.1 [X.208-88], using the Basic
Encoding Rules (BER) [X.209-88] and the Distinguished Encoding Rules
(DER) [X.509-88].
The Advanced Encryption Standard (AES) is being developed to replace 1.1 AES
DES [DES]. The AES will be a new Federal Information Processing
Standard (FIPS) Publication that will specify a cryptographic
algorithm for use by U.S. Government organizations. However, the AES
will also be widely used by organizations, institutions, and The Advanced Encryption Standard (AES) [AES] was developed to replace
individuals outside of the U.S. Government.
NIST has posted the Draft FIPS for the AES (see DES [DES]. The AES Federal Information Processing Standard (FIPS)
http://csrc.nist.gov/encryption/aes). The AES will become official Publication specifies a cryptographic algorithm for use by U.S.
after a 90-day public comment period, NIST makes appropriate changes Government organizations. However, the AES will also be widely used
to the Draft FIPS, and the Secretary of Commerce approves the FIPS. by organizations, institutions, and individuals outside of the U.S.
Current estimates place this sometime in late 2001. In other words, Government.
any day now.
Two researchers who developed and submitted the Rijndael algorithm Two researchers who developed and submitted the Rijndael algorithm
for consideration are both cryptographers from Belgium: Dr. Joan for consideration are both cryptographers from Belgium: Dr. Joan
Daemen of Proton World International and Dr. Vincent Rijmen, a Daemen of Proton World International and Dr. Vincent Rijmen, a
postdoctoral researcher in the Electrical Engineering Department of postdoctoral researcher in the Electrical Engineering Department of
Katholieke Universiteit Leuven. Katholieke Universiteit Leuven.
NIST selected the Rijndael algorithm for AES because it offers a The National Institute of Standards and technology (NIST) selected
combination of security, performance, efficiency, ease of the Rijndael algorithm for AES because it offers a combination of
implementation, and flexibility. Specifically, Rijndael appears to security, performance, efficiency, ease of implementation, and
be consistently a very good performer in both hardware and software flexibility. Specifically, Rijndael appears to be consistently a
across a wide range of computing environments regardless of its use very good performer in both hardware and software across a wide range
in feedback or non-feedback modes. Its key setup time is excellent,
and its key agility is good. The very low memory requirements of the
Rijndael algorithm make it very well suited for restricted-space of computing environments regardless of its use in feedback or non-
environments, in which it also demonstrates excellent performance. feedback modes. Its key setup time is excellent, and its key agility
The Rijndael algorithm operations are among the easiest to defend
against power and timing attacks. Additionally, it appears that some
defense can be provided against such attacks without significantly is good. The very low memory requirements of the Rijndael algorithm
impacting the algorithm's performance. Finally, the algorithm's make it very well suited for restricted-space environments, in which
internal round structure appears to have good potential to benefit it also demonstrates excellent performance. The Rijndael algorithm
from instruction-level parallelism. operations are among the easiest to defend against power and timing
attacks. Additionally, it appears that some defense can be provided
against such attacks without significantly impacting the algorithm's
performance. Finally, the algorithm's internal round structure
appears to have good potential to benefit from instruction-level
parallelism.
The AES specifies three key sizes: 128, 192 and 256 bits. The AES specifies three key sizes: 128, 192 and 256 bits.
1.2 RSA-OAEP 1.2 RSA-OAEP
When the variant of the RSA key transport algorithm specified in PKCS When the variant of the RSA key transport algorithm specified in PKCS
#1 Version 1.5 [PKCS#1v1.5] is used for key management, it is #1 Version 1.5 [PKCS#1v1.5] is used for key management, it is
vulnerable to adaptive chosen ciphertext attacks. This attack is vulnerable to adaptive chosen ciphertext attacks. This attack is
described in [RSALAB] and [CRYPTO98]. The use of PKCS #1 Version 1.5 described in [RSALAB] and [CRYPTO98]. The use of PKCS #1 Version 1.5
key transport in interactive applications is especially vulnerable, key transport in interactive applications is especially vulnerable,
but countermeasures are described in [MMA]. . Exploitation of this but countermeasures are described in [MMA]. Exploitation of this
Schaad, Housley 2
Use of the AES Algorithm in CMS November 2000
identified vulnerability, revealing the result of a particular RSA identified vulnerability, revealing the result of a particular RSA
decryption, requires access to an oracle which will respond to decryption, requires access to an oracle which will respond to
Schaad, Housley 2
Use of the AES Algorithm in CMS February 2002
hundreds of thousands of ciphertexts, which are constructed hundreds of thousands of ciphertexts, which are constructed
adaptively in response to previously-received replies providing adaptively in response to previously-received replies providing
information on the successes or failures of attempted decryption information on the successes or failures of attempted decryption
operations. operations.
The attack appears significantly less feasible in store-and-forward The attack appears significantly less feasible in store-and-forward
environments, such as S/MIME. When PKCS #1 Version 1.5 key transport environments, such as S/MIME. When PKCS #1 Version 1.5 key transport
is applied as an intermediate encryption layer within an interactive is applied as an intermediate encryption layer within an interactive
request-response communications environment, exploitation could be request-response communications environment, exploitation could be
more feasible. However, Secure Sockets Layer (SSL) [SSL] and more feasible. However, Secure Sockets Layer (SSL) [SSL] and
Transport Layer Security (TLS) [TLS] protocol implementations could Transport Layer Security (TLS) [TLS] protocol implementations could
include countermeasures that detect and prevent Bleichenbacher's and include countermeasures that detect and prevent Bleichenbacher's and
other chosen-ciphertext attacks, without changing the way the RSA key other chosen-ciphertext attacks, without changing the way the RSA key
transport algorithm is used. These countermeasures are performed transport algorithm is used. These countermeasures are performed
within the protocol level. In the interest of long-term security within the protocol level. In the interest of long-term security
assurance, it is prudent to adopt an improved cryptographic technique assurance, it is prudent to adopt an improved cryptographic technique
rather than embedding countermeasures within protocols. rather than embedding countermeasures in protocols.
An updated version of PKCS #1 has been published, PKCS #1 Version 2.0 An updated version of PKCS #1 has been published: PKCS #1 Version 2.0
[PKCS#1v2.0]. This new document supersedes RFC 2313 [PKCS#1v1.5]. [PKCS#1v2.0]. This new document supersedes RFC 2313 [PKCS#1v1.5].
PKCS #1 Version 2.0 preserves support for the encryption padding PKCS #1 Version 2.0 preserves support for the encryption padding
format defined in PKCS #1 Version 1.5 [PKCS#1v1.5], and it also format defined in PKCS #1 Version 1.5 [PKCS#1v1.5], and it also
defines a new alternative. To resolve the adaptive chosen ciphertext defines a 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.
skipping to change at line 166 skipping to change at line 164
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 interactive 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]. PKCS #1 Version 1.5 and PKCS #1 Version 2.0 require the [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 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.
CMS values are generated using ASN.1 [X.208-88], using the Basic
Encoding Rules (BER) [X.209-88] and the Distinguished Encoding Rules
(DER) [X.509-88].
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. The AES algorithm is used to encryption key for one recipient. The AES algorithm is used to
encrypt the content. encrypt the content.
Schaad, Housley 3
Use of the AES Algorithm in CMS November 2000
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". data Content Type".
A content-encryption key MUST be randomly generated for each instance An AES content-encryption key MUST be randomly generated for each
instance of an enveloped-data content type. The content-encryption
key (CEK) is used to encrypt the content.
of an enveloped-data content type. The content-encryption key is Schaad, Housley 3
used to encrypt the content. Use of the AES Algorithm in CMS February 2002
AES can be used with the enveloped-data content type using any of the AES can be used with the enveloped-data content type using any of the
following key management techniques defined in [CMS] Section 6. following key management techniques defined in [CMS] Section 6.
1) Key Transport: The AES CEK is uniquely wrapped for each recipient 1) Key Transport: The AES CEK is uniquely wrapped for each recipient
using the recipient's public RSA key and other values. Section 2.2 using the recipient's public RSA key and other values. Section 2.2
provides additional details. provides additional details.
2) Key Agreement: The AES CEK is uniquely wrapped for each recipient 2) Key Agreement: The AES CEK is uniquely wrapped for each recipient
using a pairwise symmetric key-encryption key (KEK) generated using using a pairwise symmetric key-encryption key (KEK) generated using
DH-ES using the a randomly generated private key value for the DH-ES [DH] using the originator's randomly generated private key, the
originator, the recipient's public DH key and other values. Section
2.3 provides additional details.
3) "Previously Distributed" Symmetric KEK: The AES CEK is wrapped recipient's public DH key, and other values. Section 2.3 provides
using a "previously distributed" symmetric KEK (such as a Mail List additional details.
3) Previously Distributed Symmetric KEK: The AES CEK is wrapped
using a previously distributed symmetric KEK (such as a Mail List
Key). The methods by which the symmetric KEK is generated and Key). The methods by which the symmetric KEK is generated and
distributed are beyond the scope of this document. Section 2.4 distributed are beyond the scope of this document. Section 2.4
provides additional details. provides additional details.
4) Password Encryption: The AES CEK is wrapped using a KEK derived 4) Password Encryption: The AES CEK is wrapped using a KEK derived
from a password or other shared-secret value. Section 2.5 provides from a password or other shared secret. Section 2.5 provides
additional details. additional details.
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 is determined based on a number of factors. The EnvelopedData version is determined based on a number of factors.
See [CMS] section 6.1 for the algorithm to determine this value. See [CMS] section 6.1 for the algorithm to determine this value.
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
support recipients using other key management algorithms. support recipients using other key management algorithms.
The EnvelopedData recipientInfos CHOICE is dependent on the key The EnvelopedData recipientInfos CHOICE is dependent on the key
management technique used. Section 2.2, 2.3 and 2.4 provide management technique used. Section 2.2, 2.3, 2.4 and 2.5 provide
additional information. additional information.
The EnvelopedData encryptedContentInfo contentEncryptionAlgorithm The EnvelopedData encryptedContentInfo contentEncryptionAlgorithm
field MUST specify a symmetric encryption algorithm. Implementations field MUST specify a symmetric encryption algorithm. Implementations
MUST support the encryption of AES keys, but implementations MAY MUST support content encryption with AES, but implementations MAY
support other algorithms as well. support other algorithms as well.
The EnvelopedData unprotectedAttrs MAY be present. The EnvelopedData unprotectedAttrs MAY be present.
Schaad, Housley 4
Use of the AES Algorithm in CMS November 2000
2.2 KeyTransRecipientInfo Fields 2.2 KeyTransRecipientInfo 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:
Schaad, Housley 4
Use of the AES Algorithm in CMS February 2002
The KeyTransRecipientInfo version MUST be either 0 or 2. If the The KeyTransRecipientInfo version MUST be either 0 or 2. If the
RecipientIdentifier is the CHOICE issuerAndSerialNumber, then the RecipientIdentifier is the CHOICE issuerAndSerialNumber, then the
version MUST be 0. If the RecipientIdentifier is version MUST be 0. If the RecipientIdentifier is
subjectKeyIdentifier, then the version MUST be 2. subjectKeyIdentifier, then the version MUST be 2.
The KeyTransRecipientInfo RecipientIdentifier provides two The KeyTransRecipientInfo RecipientIdentifier provides two
alternatives for specifying the recipient's certificate, and thereby alternatives for specifying the recipient's certificate, and thereby
the recipient's public key. The recipient's certificate MUST contain the recipient's public key. The recipient's certificate MUST contain
a RSA public key. The content-encryption key is encrypted with the a RSA public key. The CEK is encrypted with the recipient's RSA
recipient's RSA public key. The issuerAndSerialNumber alternative public key. The issuerAndSerialNumber alternative identifies the
identifies the recipient's certificate by the issuer's distinguished recipient's certificate by the issuer's distinguished name and the
name and the certificate serial number; the subjectKeyIdentifier certificate serial number; the subjectKeyIdentifier identifies the
identifies the recipient's certificate by the X.509 recipient's certificate by the X.509 subjectKeyIdentifier extension
subjectKeyIdentifier extension value. value.
The KeyTransRecipientInfo keyEncryptionAlgorithm field specifies the The KeyTransRecipientInfo keyEncryptionAlgorithm field specifies the
RSAES-OAEP algorithm, and the associated parameters used to encrypt RSAES-OAEP algorithm, and the associated parameters used to encrypt
the content-encryption key for the recipient. The key-encryption the CEK for the recipient. The key encryption process is described
process is described in [PKCS#1v2.0]. See section 4.1 of this in [PKCS#1v2.0]. See section 4.2 of this document for the algorithm
document for the algorithm identifier and the parameter syntax. 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 CEK with the recipient's RSA public key using the RSAES-OAEP
the RSAES-OAEP algorithm. algorithm.
Note: When using a Triple-DES content-encryption key, implementations Note: When using a Triple-DES CEK, implementations MUST adjust the
parity bits for each DES key comprising the Triple-DES key prior to
RSAES-OAEP encryption.
MUST adjust the parity bits for each DES key comprising the Triple- Note: The same key wrap algorithm is used for both Two-key Triple-DES
DES key prior to RSAES-OAEP encryption.
and Three-key Triple-DES CEK keys. When a Two-key Triple-DES key is
to be wrapped, a third DES key with the same value as the first DES
key is created. Thus, all wrapped Triple-DES keys include three DES
keys.
2.3 KeyAgreeRecipientInfo Fields 2.3 KeyAgreeRecipientInfo Fields
This section describes the conventions for using ES-DH and AES with This section describes the conventions for using ES-DH and AES with
the CMS enveloped-data content type to support key agreement. When the CMS enveloped-data content type to support key agreement. When
key agreement is used, then the RecipientInfo keyAgreeRecipientInfo key agreement is used, then the RecipientInfo keyAgreeRecipientInfo
CHOICE MUST be used. CHOICE MUST be used.
The KeyAgreeRecipient version MUST be 3. The KeyAgreeRecipient version MUST be 3.
The EnvelopedData originatorInfo field must be the originatorKey The EnvelopedData originatorInfo field MUST be the originatorKey
alternative. The originatoryKey algorithm fields MUST contain the alternative. The originatoryKey algorithm fields MUST contain the
dh-public-number object identifier with absent parameters. The dh-public-number object identifier with absent parameters. The
originatorKey publicKey MUST contain the sender's ephemeral public originatorKey publicKey MUST contain the originator's ephemeral
key. public key.
The EnvelopedData ukm MAY be absent.
Schaad, Housley 5 The EnvelopedData ukm MAY be present.
Use of the AES Algorithm in CMS November 2000
The EnvelopedData keyEncrytionAlgorithm MUST be the id-alg-ESDH The EnvelopedData keyEncrytionAlgorithm MUST be the id-alg-ESDH
algorithm identifier. algorithm identifier [CMSALG].
Schaad, Housley 5
Use of the AES Algorithm in CMS February 2002
2.3.1 ES-DH/AES Key Derivation 2.3.1 ES-DH/AES Key Derivation
Generation of the an AES key used in doing AES-KeyWrap is done using Generation of the AES KEK to be used with the AES -key wrap algorithm
the method in [DH] with the following modifications:
The Hash function H will be [SHA-256] rather than SHA-1. is done using the method described in [DH].
2.3.1.1 Example 1 2.3.1.1 Example 1
ZZ is the 20 bytes 00 01 02 03 04 05 06 07 08 09 ZZ is the 20 bytes 00 01 02 03 04 05 06 07 08 09
0a 0b 0c 0d 0e 0f 10 11 12 13 0a 0b 0c 0d 0e 0f 10 11 12 13
The key wrap algorithm is AES-128 wrap, so we need 128 bits (20 The key wrap algorithm is AES-128 wrap, so we need 128 bits (16
bytes) of keying material. bytes) of keying material.
No partyAInfo is used. No partyAInfo is used.
Consequently, the input to the first invocation of SHA-256 is: Consequently, the input to SHA-1 is:
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 ; ZZ 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 ; ZZ
30 1b 30 1b
30 11 30 11
06 09 60 86 48 01 65 03 04 01 05 ; AES-128 wrap OID 06 09 60 86 48 01 65 03 04 01 05 ; AES-128 wrap OID
04 04 04 04
00 00 00 01 ; Counter 00 00 00 01 ; Counter
a2 06 a2 06
04 04 04 04
00 00 00 80 ; key length 00 00 00 80 ; key length
And the output is the 32 bytes: And the output is the 32 bytes:
79 66 a0 38 22 28 1e a3 eb 08 d9 bc 69 5b d8 ff d6 d6 b0 94 c1 02 7a 7d e6 e3 11 72 94 a3 53 64 49 08 50 f9
89 23 26 4d 2b ef ee 73 99 c0 a7 91 18 60 44 c1
Consenquently, Consenquently,
K=79 66 a0 38 22 28 1e a3 eb 08 d9 bc 69 5b d8 ff 89 23 26 4d K= d6 d6 b0 94 c1 02 7a 7d e6 e3 11 72 94 a3 53 64
2.3.1.2 Example 2 2.3.1.2 Example 2
ZZ is the 20 bytes 00 01 02 03 04 05 06 07 08 09 ZZ is the 20 bytes 00 01 02 03 04 05 06 07 08 09
0a 0b 0c 0d 0e 0f 10 11 12 13 0a 0b 0c 0d 0e 0f 10 11 12 13
The key wrap algorithm is AES-256 key wrap, so we need 256 bits (32 The key wrap algorithm is AES-256 key wrap, so we need 256 bits (32
bytes) of keying material. bytes) of keying material.
The partyAInfo used is the 64 bytes The partyAInfo used is the 64 bytes
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
Schaad, Housley 6
Use of the AES Algorithm in CMS November 2000
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
Consequently, the input to SHA-256 is: Consequently, the input to first invocation of SHA-1 is:
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 ; ZZ 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 ; ZZ
Schaad, Housley 6
Use of the AES Algorithm in CMS February 2002
30 5f 30 5f
30 11 30 11
06 09 60 86 48 01 65 03 04 01 2c ; AES-256 wrap OID 06 09 60 86 48 01 65 03 04 01 2c ; AES-256 wrap OID
04 04 04 04
00 00 00 01 ; Counter 00 00 00 01 ; Counter
a0 42
04 40
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 ; partyAInfo
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
a2 06
04 04
00 00 01 00 ; key length
And the output is the 20 bytes:
6f da b9 fa 67 09 30 3e 7e 2f 68 50 29 6f 28 fb 1b a6 4e 2a
The input to second invocation of SHA-1 is:
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 ; ZZ
30 5f
30 11
06 09 60 86 48 01 65 03 04 01 2c ; AES-256 wrap OID
04 04
00 00 00 02 ; Counter
a0 42 a0 42
04 40 04 40
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 ; partyAInfo 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 ; partyAInfo
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 01
a2 06 a2 06
04 04 04 04
00 00 01 00 ; key length 00 00 01 00 ; key length
And the output is the 32 bytes: And the output is the 20 bytes:
4f cd e4 58 60 0b 85 fb 47 f4 5a c8 1c 23 a9 4a 73 36 a5 ae 90 33 31 39 cb 3f 0e 90 cd d8 03 96 66 36 61 b0
3e 64 4b 79 82 9d 98 66 df a5 ee 80 2c 80 99 bb
Consequently, Consequently,
K=4f cd e4 58 60 0b 85 fb 47 f4 5a c8 1c 23 a9 4a K = 6f da b9 fa 67 09 30 3e 7e 2f 68 50 29 6f 28 fb 1b a6 4e 2a
3e 64 4b 79 82 9d 98 66 df a5 ee 80 2c 80 99 bb 73 36 a5 ae 90 33 31 39 cb 3f 0e 90
2.3.2 AES CEK Wrap Process 2.3.2 AES CEK Wrap Process
The AES key-wrap algorithm encrypts one AES key in another AES key. The AES key wrap algorithm encrypts one AES key in another AES key.
The algorithm inputs are a value in a multiple of 64-bits (in this The algorithm produces an output 64-bits longer than the input AES
case, the AES CEK) and an AES KEK of standard size. The algorithm CEK, the additional bits are a checksum. The algorithm uses 6*n AES
produces an output 64-bits longer than the input, the additional bits encryption/decryption operations where n is number of 64-bit blocks
acting as a checksum for the original data. The algorithm uses 6*n Schaad, Housley 7
AES encryption/decryption operations where n is number of 64-bit Use of the AES Algorithm in CMS February 2002
blocks. Full details of the AES key-wrap algorithm are available at
[AES-KEYWRAP].
NIST has assigned the following OIDs to define the key-wrap in the AES CEK. Full details of the AES key wrap algorithm are
available at [AES-WRAP].
NIST has assigned the following OIDs to define the AES key wrap
algorithm. algorithm.
id-aes128-wrap OBJECT IDENTIFIER ::= { aes 5 } id-aes128-wrap OBJECT IDENTIFIER ::= { aes 5 }
id-aes192-wrap OBJECT IDENTIFIER ::= { aes 25 } id-aes192-wrap OBJECT IDENTIFIER ::= { aes 25 }
id-aes256-wrap OBJECT IDENTIFIER ::= { aes 45 } id-aes256-wrap OBJECT IDENTIFIER ::= { aes 45 }
In all cases the parameters field MUST be absent. The OID gives the In all cases the parameters field MUST be absent. The OID gives the
KEK key size, but does not make any statements as to the size of the KEK key size, but does not make any statements as to the size of the
wrapped CEK. Implementations MAY use different size KEK and CEK wrapped AES CEK. Implementations MAY use different KEK and CEK
values. Implements MUST support the CEK and the KEK having the same sizes. Implements MUST support the CEK and the KEK having the same
Schaad, Housley 7
Use of the AES Algorithm in CMS November 2000
length. If different lengths are supported, the KEK MUST be of equal length. If different lengths are supported, the KEK MUST be of equal
or greater length then the CEK. or greater length than the CEK.
2.4 KEKRecipientInfo Fields 2.4 KEKRecipientInfo Fields
This section describes the conventions for using AES with the CMS This section describes the conventions for using AES with the CMS
enveloped-data content type to support previously distributed enveloped-data content type to support previously distributed
symmetric KEKs. When a previously distributed symmetric KEK is used symmetric KEKs. When a previously distributed symmetric KEK is used
to wrap the AES CEK, then the RecipientInfo KEKRecipientInfo CHOICE to wrap the AES CEK, then the RecipientInfo KEKRecipientInfo CHOICE
MUST be used. The methods used to generate and distribute the MUST be used. The methods used to generate and distribute the
symmetric KEK are beyond the scope of this document. One possible symmetric KEK are beyond the scope of this document. One possible
method of distributing keys is documented in [SYMKEYDIST]. method of distributing keys is documented in [SYMKEYDIST].
skipping to change at line 463 skipping to change at line 478
RecipientInfo PasswordRecipientInfo CHOICE MUST be used. RecipientInfo PasswordRecipientInfo CHOICE MUST be used.
The keyEncryptionAlgorithm algorithm field MUST be one of the OIDs The keyEncryptionAlgorithm algorithm field MUST be one of the OIDs
defined in section 2.3.2 indicating the AES wrap function is used to defined in section 2.3.2 indicating the AES wrap function is used to
wrap the AES CEK. The keyEncryptionAlgorithm parameters field MUST wrap the AES CEK. The keyEncryptionAlgorithm parameters field MUST
be absent. be absent.
The encryptedKey field MUST be the result of the AES key wrap The encryptedKey field MUST be the result of the AES key wrap
algorithm applied to the AES CEK value. algorithm applied to the AES CEK value.
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Use of the AES Algorithm in CMS February 2002
3 Encrypted-data Conventions 3 Encrypted-data Conventions
The encrypted-data content type is ASN.1 encoded using the The encrypted-data content type is ASN.1 encoded using the
EncryptededData syntax. The fields of the EncryptedData syntax MUST EncryptededData syntax. The fields of the EncryptedData syntax MUST
be populated as follows: be populated as follows:
The EncryptedData version is determined based on a number of factors. The EncryptedData version is determined based on a number of factors.
See [CMS] section 9.1 for the algorithm to determine this value. See [CMS] section 9.1 for the algorithm to determine this value.
The EncryptedData encryptedContentInfo contentEncryptionAlgorithm The EncryptedData encryptedContentInfo contentEncryptionAlgorithm
field MUST specify a symmetric encryption algorithm. Implementations field MUST specify a symmetric encryption algorithm. Implementations
MUST support encryption using AES, but implementations MAY support MUST support encryption using AES, but implementations MAY support
other algorithms as well. other algorithms as well.
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The EncryptedData unprotectedAttrs MAY be present. The EncryptedData unprotectedAttrs MAY be present.
4 Algorithm Identifiers and Parameters 4 Algorithm Identifiers and Parameters
This section specified algorithm identifiers for the AES encryption This section specified algorithm identifiers for the AES encryption
algorithm and the RSAES-OAEP key transport algorithm. algorithm and the RSAES-OAEP key transport algorithm.
4.1 AES Algorithm Identifiers and Parameters 4.1 AES Algorithm Identifiers and Parameters
The AES algorithm is defined in [AES]. RSA #1 v1.5 [PKCS#1v1.5] The AES algorithm is defined in [AES]. RSA #1 v1.5 [PKCS#1v1.5]
MUST NOT be used to transport AES keys. RSAES-OAEP [PKCS#1v2.0] MAY MUST NOT be used to transport AES keys. RSAES-OAEP [PKCS#1v2.0] MAY
be used to transport AES keys. be used to transport AES keys.
AES is added to the set of symmetric content encryption algorithms in AES is added to the set of symmetric content encryption algorithms
defined in [CMSALG]. The AES content-encryption algorithm, in Cipher
CMS. The AES content-encryption algorithm in Cipher Block Chaining Block Chaining (CBC) mode, for the three different key sizes are
(CBC) mode for the three different key sizes are identified by the identified by the following object identifiers:
following object identifiers:
id-aes128-CBC OBJECT IDENTIFIER ::= { aes 2 } id-aes128-CBC OBJECT IDENTIFIER ::= { aes 2 }
id-aes192-CBC OBJECT IDENTIFIER ::= { aes 22 } id-aes192-CBC OBJECT IDENTIFIER ::= { aes 22 }
id-aes256-CBC OBJECT IDENTIFIER ::= { aes 42 } id-aes256-CBC OBJECT IDENTIFIER ::= { aes 42 }
The AlgorithmIdentifier parameters field MUST be present, and the The AlgorithmIdentifier parameters field MUST be present, and the
parameters field MUST contain a AES-IV: parameters field MUST contain a AES-IV:
AES-IV ::= OCTET STRING (SIZE(16)) AES-IV ::= OCTET STRING (SIZE(16))
skipping to change at line 524 skipping to change at line 540
Content encryption algorithms are used to encrypt the content located Content encryption algorithms are used to encrypt the content located
in the EnvelopedData EncryptedContentInfo encryptedContent and the in the EnvelopedData EncryptedContentInfo encryptedContent and the
EncryptedData EncryptedContentInfo encryptedContent fields. EncryptedData EncryptedContentInfo encryptedContent fields.
4.2 RSAES-OAEP Algorithm Identifiers and Parameters 4.2 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 2437 [PKCS#1v2.0], where the message to be encrypted
is the content-encryption key. is the content-encryption key.
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Use of the AES Algorithm in CMS February 2002
The RSA key is identified in a certificate using the rsaEncryption The RSA key is identified in a certificate using the rsaEncryption
object identifier: object identifier:
pkcs-1 OBJECT IDENTIFIER ::= { pkcs-1 OBJECT IDENTIFIER ::= {
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) }
rsaEncryption OBJECT IDENTIFIER ::= { pkcs-1 1 } rsaEncryption OBJECT IDENTIFIER ::= { pkcs-1 1 }
Note: This is the same algorithm identifier used by RSAES-PKCS1-v1_5. Note: This is the same algorithm identifier used by RSAES-PKCS1-v1_5.
This means that the existence of an RSA key in a certificate cannot This means that the existence of an RSA key in a certificate cannot
be used to infer that a recipient can decrypt an RSAES-OAEP encrypted be used to infer that a recipient can decrypt an RSAES-OAEP encrypted
content-encryption key. content-encryption key.
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Use of the AES Algorithm in CMS November 2000
The object identifier for RSAES-OAEP is: The object identifier for RSAES-OAEP is:
id-RSAES-OAEP OBJECT IDENTIFIER ::= { pkcs-1 7 } id-RSAES-OAEP OBJECT IDENTIFIER ::= { pkcs-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:
RSAES-OAEP-params ::= SEQUENCE { RSAES-OAEP-params ::= SEQUENCE {
skipping to change at line 564 skipping to change at line 580
pSourceFunc [2] AlgorithmIdentifier pSourceFunc [2] AlgorithmIdentifier
DEFAULT pSpecifiedEmptyIdentifier } DEFAULT pSpecifiedEmptyIdentifier }
sha1Identifier ::= AlgorithmIdentifier { sha1Identifier ::= AlgorithmIdentifier {
id-sha1, NULL } id-sha1, NULL }
mgf1SHA1Identifier ::= AlgorithmIdentifier { mgf1SHA1Identifier ::= AlgorithmIdentifier {
id-mgf1, sha1Identifier } id-mgf1, sha1Identifier }
pSpecifiedEmptyIdentifier ::= AlgorithmIdentifier { pSpecifiedEmptyIdentifier ::= AlgorithmIdentifier {
id-pSpecified, OCTET STRING SIZE (0) } id-pSpecified, nullOctetString }
id-sha1 OBJECT IDENTIFIER ::= { id-sha1 OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) oiw(14) secsig(3) iso(1) identified-organization(3) oiw(14) secsig(3)
algorithms(2) 26 } algorithms(2) 26 }
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 }
nullOctetString OCTET STRING (SIZE (0)) ::= { ''H }
The fields of type RSAES-OAEP-params have the following meanings: The fields of type RSAES-OAEP-params have the following meanings:
hashFunc identifies the one-way hash function. Implementations MUST hashFunc identifies the one-way hash function. Implementations MUST
support SHA-1 [SHA1]. The SHA-1 algorithm identifier is comprised of support SHA-1 [SHA1]. The SHA-1 algorithm identifier is comprised of
the id-sha1 object identifier and a parameter of NULL. the id-sha1 object identifier and a parameter of NULL.
Implementations that perform key encryption MUST omit the hashFunc Implementations that perform key encryption MUST omit the hashFunc
field when SHA-1 is used, indicating that the default algorithm was field when SHA-1 is used, indicating that the default algorithm was
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Use of the AES Algorithm in CMS February 2002
used. Implementations that perform key decryption MUST recognize used. Implementations that perform key decryption MUST recognize
both the id-sha1 object identifier and an absent hashFunc field as an both the id-sha1 object identifier and an absent hashFunc field as an
indication that SHA-1 was used. indication that SHA-1 was used.
maskGenFunc identifies the mask generation function. Implementations maskGenFunc identifies the mask generation function. Implementations
MUST support MFG1 [PKCS#1v2.0]. MFG1 requires a one-way hash MUST support MFG1 [PKCS#1v2.0]. MFG1 requires a one-way hash
function, and it is identified in the parameter field of the MFG1 function, and it is identified in the parameter field of the MFG1
algorithm identifier. Implementations MUST support SHA-1 [SHA1]. algorithm identifier. Implementations MUST support SHA-1 [SHA1].
The MFG1 algorithm identifier is comprised of the id-mgf1 object The MFG1 algorithm identifier is comprised of the id-mgf1 object
identifier and a parameter that contains the algorithm identifier of identifier and a parameter that contains the algorithm identifier of
the one-way hash function employed with MFG1. The SHA-1 algorithm the one-way hash function employed with MFG1. The SHA-1 algorithm
identifier is comprised of the id-sha1 object identifier and a identifier is comprised of the id-sha1 object identifier and a
parameter of NULL. Implementations that perform key encryption MUST parameter of NULL. Implementations that perform key encryption MUST
omit the maskGenFunc field when MFG1 with SHA-1 is used, indicating omit the maskGenFunc field when MFG1 with SHA-1 is used, indicating
that the default algorithm was used. Implementations that perform that the default algorithm was used. Implementations that perform
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Use of the AES Algorithm in CMS November 2000
key decryption MUST recognize both the id-mgf1 and id-sha1 object key decryption MUST recognize both the id-mgf1 and id-sha1 object
identifiers as well as an absent maskGenFunc field as an indication identifiers as well as an absent maskGenFunc field as an indication
that MFG1 with SHA-1 was used. 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 parameters. that P is explicitly provided as an OCTET STRING in the parameters.
The default value for P is an empty string. In this case, pHash in The default value for P is an empty string. In this case, pHash in
EME-OAEP contains the hash of a zero length string. Implementations EME-OAEP contains the hash of a zero length string. Implementations
skipping to change at line 646 skipping to change at line 664
5.1 RSAES-OEAP SMIMECapability Attribute 5.1 RSAES-OEAP SMIMECapability Attribute
When constructing a signedData object, compliant software MAY include When constructing a 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. the 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
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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, { sha1Identifier, mgf1SHA1Identifier, id-RSAES-OAEP, { sha1Identifier, mgf1SHA1Identifier,
pSpecifiedEmptyIdentifier } } 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: SEQUENCE representing RSAES-OAEP MUST be DER-encoded as:
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
5.2 AES S/MIME Capability Attributes 5.2 AES S/MIME Capability Attributes
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Use of the AES Algorithm in CMS November 2000
If an S/MIME client is required to support symmetric encryption with If an S/MIME client is required to support symmetric encryption with
AES, the capabilities attribute MUST contain the AES object AES, the capabilities attribute MUST contain the AES object
identifier specified above in the category of symmetric algorithms. identifier specified above in the category of symmetric algorithms.
The parameter associated with this object identifier MUST is The parameter associated with this object identifier MUST is
AESSMimeCapability. AESSMimeCapability.
AESSMimeCapabilty ::= NULL AESSMimeCapabilty ::= NULL
The encodings for the mandatory key sizes are: The encodings for the mandatory key sizes are:
skipping to change at line 690 skipping to change at line 708
process involves information obtained from the capabilities lists process involves information obtained from the capabilities lists
included in messages received from the recipient, as well as other included in messages received from the recipient, as well as other
information such as private agreements, user preferences, legal information such as private agreements, user preferences, legal
restrictions, and so on. If users require AES for symmetric restrictions, and so on. If users require AES for symmetric
encryption, the S/MIME clients on both the sending and receiving side encryption, the S/MIME clients on both the sending and receiving side
MUST support it, and it MUST be set in the user preferences. MUST support it, and it MUST be set in the user preferences.
6 Security Considerations 6 Security Considerations
If RSA-OAEP and RSA #1 v1.5 are both used to transport the same If RSA-OAEP and RSA #1 v1.5 are both used to transport the same CEK,
content-encryption key, then an attacker can still use the then an attacker can still use the Bleichenbacher attack against the
Bleichenbacher attack against the RSA #1 v1.5 encrypted key. It is RSA #1 v1.5 encrypted key. It is generally unadvisable to mix both
generally unadvisable to mix both RSA-OAEP and RSA #1 v1.5 in the RSA-OAEP and RSA #1 v1.5 in the same set of recipients.
same set of recipients.
Implementations must protect the RSA private key and the content-
encryption key. Compromise of the RSA private key may result in the
disclosure of all messages protected with that key. Compromise of
the content-encryption key may result in disclosure of the associated
encrypted content.
The generation of RSA public/private key pairs and MGF seeds rely on
random numbers. The use of inadequate pseudo-random number
generators (PRNGs) to generate these values can result in little or
no security. An attacker may find it much easier to reproduce the
PRNG environment that produced the keys, searching the resulting
small set of possibilities, rather than brute force searching the
whole key space. The generation of quality random numbers is
difficult. RFC 1750 [RANDOM] offers important guidance in this area.
When wrapping a content-encryption key with a key-encryption key, the Implementations must protect the RSA private key and the CEK.
Compromise of the RSA private key may result in the disclosure of all
key-encryption key should always be at least the same length as the messages protected with that key. Compromise of the CEK may result
content -encryption key. An attacker will generally work at the in disclosure of the associated encrypted content.
weakest point in an encryption system. This would be the smaller of
the two key sizes for a brute force attack.
The generation of AES CEKs, RSA public/private key pairs, and MGF
seeds rely on random numbers. The use of inadequate pseudo-random
number generators (PRNGs) to generate these values can result in
little or no security. An attacker may find it much easier to
Schaad, Housley 12 Schaad, Housley 12
Use of the AES Algorithm in CMS November 2000 Use of the AES Algorithm in CMS February 2002
7 Open Issues reproduce the PRNG environment that produced the keys, searching the
resulting small set of possibilities, rather than brute force
searching the whole key space. The generation of quality random
numbers is difficult. RFC 1750 [RANDOM] offers important guidance in
- References to each algorithm that would be acceptable to the RFC this area.
editor. We have a FIPS number for AES (but it is not yet officially
published). We have no document for the key wrap algorithm yet and When wrapping a CEK with a KEK, the KEK MUST always be at least the
need to work out the details with NIST for publishing. same length as the CEK. An attacker will generally work at the
- Does the oid for key derivation need to be changed since we are weakest point in an encryption system. This would be the smaller of
using SHA-256 not SHA-1? the two key sizes for a brute force attack.
- Need to provide an ASN.1 module as [PKCS#1v2.0] is not 1988 syntax.
References References
AES J. Daemen, V. Rijmen, "The Rijndael Block Cipher", FIPS AES National Institute of Standards.
197, <To Be Published>. FIPS Pub 197: Advanced Encryption Standard (AES).
26 November 2001.
AES-KEYWRAP NIST, "AES Key-Wrap Algorithm", TBD. AES-WRAP Schaad, J., R. Housley, "AES Key Wrap Algorithm",
< http://www.nist.gov/kms/key-wrap.pdf> Draft-ietf-smime-aes-key-wrap-00.txt
CMS Housley, R. Cryptographic Message Syntax. RFC 2630. CMS Housley, R., Cryptographic Message Syntax.
June 1999. draft-ietf-smime-rfc2630bis-06.txt.
CRYPTO98 Bleichenbacher, D. "Chosen Ciphertext Attacks Against CMSALG Housley, R., Cryptographic Message Syntax (CMS) Algorithms,
draft-ietf-smime-cmsalg-07.txt.
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 in H. Krawczyk (editor), Advances in Cryptology - CRYPTO'98
'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.
DES National Institute of Standards and Technology. DES National Institute of Standards and Technology.
FIPS Pub 46: Data Encryption Standard. 15 January 1977. FIPS Pub 46: Data Encryption Standard. 15 January 1977.
DH Rescorla, E. Diffie-Hellman Key Agreement Method, RFC DH Rescorla, E., Diffie-Hellman Key Agreement Method, RFC
2631, June 1999. 2631, June 1999.
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.
MMA Rescorla, E. Preventing the Million Message Attack MMA Rescorla, E., Preventing the Million Message Attack
on CMS, RFC TBD, Date TBD. on CMS, RFC 3218, January 2002.
<draft-ietf-smime-pkcs1-01.txt>
MSG Ramsdell, B., Editor. S/MIME Version 3 Message MSG Ramsdell, B., Editor. S/MIME Version 3 Message
Specification. RFC 2633. June 1999. Specification. RFC 2633. June 1999.
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 2437. October 1998. RFC 2437. October 1998.
Schaad, Housley 13
Use of the AES Algorithm in CMS February 2002
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. <draft-ietf-smime-new-part1.txt>.
Schaad, Housley 13
Use of the AES Algorithm in CMS November 2000
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 Bleichenbacher, D., B. Kaliski, and J. Staddon. RSALABS Bleichenbacher, D., B. Kaliski, and J. Staddon.
Recent Results on PKCS #1: RSA Encryption Standard. Recent Results on PKCS #1: RSA Encryption Standard.
RSA Laboratories' Bulletin No. 7, June 26, 1998. RSA Laboratories' Bulletin No. 7, June 26, 1998.
[Available at http://www.rsasecurity.com/rsalabs/bulletins] [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] [At http://www.netscape.com/eng/ssl3/draft302.txt]
SYMKEYDIST Turner, S. CMS Symmetric Key Management and Distribution. SYMKEYDIST Turner, S. CMS Symmetric Key Management and Distribution.
RFC TDB. Date TBD. RFC TDB. Date TBD.
< draft-ietf-smime-symkeydist-06.txt> < draft-ietf-smime-symkeydist-06.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.
RFC 2246. January 1999. RFC 2246. January 1999.
X.208-88 CCITT. Recommendation X.208: Specification of Abstract X.208-88 CCITT. Recommendation X.208: Specification of Abstract
Syntax Notation One (ASN.1). 1988. Syntax Notation One (ASN.1). 1988.
skipping to change at line 828 skipping to change at line 836
Author's Addresses Author's Addresses
Jim Schaad Jim Schaad
Soaring Hawk Consulting Soaring Hawk Consulting
Email: jimsch@exmsft.com Email: jimsch@exmsft.com
Russell Housley Russell Housley
RSA Laboratories RSA Laboratories
918 Spring Knoll Drive 918 Spring Knoll Drive
Schaad, Housley 14
Use of the AES Algorithm in CMS February 2002
Herndon, VA 20170 Herndon, VA 20170
USA USA
Schaad, Housley 14
Use of the AES Algorithm in CMS November 2000
Email: rhousley@rsasecurity.com Email: rhousley@rsasecurity.com
Appendix A ASN.1 Module
CMSAesRsaesOaep {iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs-9(9) smime(16) modules(0) aes-rsaes-oaep(19) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- EXPORTS ALL --
IMPORTS
-- PKIX
AlgorithmIdentifier
FROM PKIXExplicit88 {iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
id-pkix1-explicit(18)};
-- AES information object identifiers --
aes OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840)
organization(1) gov(101) csor(3)_ nistAlgorithms(4) 1 }
-- AES using CBC-chaining mode for key sizes of 128, 192, 256
id-aes128-CBC OBJECT IDENTIFIER ::= { aes 2 }
id-aes192-CBC OBJECT IDENTIFIER ::= { aes 22 }
id-aes256-CBC OBJECT IDENTIFIER ::= { aes 42 }
-- AES-IV is a the parameter for all the above object identifiers.
AES-IV ::= OCTET STRING (SIZE(16))
-- AES S/MIME Capabilty parameter for all the above object identifiers
AESSMimeCapability ::= NULL
-- Definitions for RSA-OAEP
pkcs-1 OBJECT IDENTIFIER ::= {iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-1(1) }
id-RSAES-OAEP OBJECT IDENTIFIER ::= { pkcs-1 7 }
RSAES-OAEP-params ::= SEQUENCE {
hashFunc [0] AlgorithmIdentifier DEFAULT sha1Identifier,
maskGenFunc [1] AlgorithmIdentifier DEFAULT mgf1SHA1Identifier,
pSourceFunc [2] AlgorithmIdentifier
DEFAULT pSpecifiedEmptyIdentifier }
sha1Identifier AlgorithmIdentifier ::= { id-sha1, NULL }
Schaad, Housley 15 Schaad, Housley 15
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mgf1SHA1Identifier AlgorithmIdentifier ::= {id-mgf1, sha1Identifier }
nullOctetString OCTET STRING (SIZE (0)) ::= { ''H }
pSpecifiedEmptyIdentifier AlgorithmIdentifier ::= { id-pSpecified,
nullOctetString }
id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
oiw(14) secsig(3) algorithms(2) 26 }
id-mgf1 OBJECT IDENTIFIER ::= { pkcs-1 8 }
id-pSpecified OBJECT IDENTIFIER ::= { pkcs-1 9 }
rSAES-OAEP-Default-Identifier AlgorithmIdentifier ::= {
id-RSAES-OAEP, { sha1Identifier, mgf1SHA1Identifier,
pSpecifiedEmptyIdentifier } }
END
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