Independent Submission M. Jenkins
Request for Comments: 8755 NSA
Category: Informational March 2020
ISSN: 2070-1721
Using Commercial National Security Algorithm Suite Algorithms in Secure/
Multipurpose Internet Mail Extensions
Abstract
The United States Government has published the National Security
Agency (NSA) Commercial National Security Algorithm (CNSA) Suite,
which defines cryptographic algorithm policy for national security
applications. This document specifies the conventions for using the
United States National Security Agency's CNSA Suite algorithms in
Secure/Multipurpose Internet Mail Extensions (S/MIME) as specified in
RFC 8551. It applies to the capabilities, configuration, and
operation of all components of US National Security Systems that
employ S/MIME messaging. US National Security Systems are described
in NIST Special Publication 800-59. It is also appropriate for all
other US Government systems that process high-value information. It
is made publicly available for use by developers and operators of
these and any other system deployments.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This is a contribution to the RFC Series, independently of any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not candidates for any level of Internet Standard;
see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8755.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.
Table of Contents
1. Introduction
1.1. Terminology
2. The Commercial National Security Algorithm Suite
3. Requirements and Assumptions
4. SHA-384 Message Digest Algorithm
5. Digital Signature
5.1. ECDSA Signature
5.2. RSA Signature
6. Key Establishment
6.1. Elliptic Curve Key Agreement
6.2. RSA Key Transport
7. Content Encryption
7.1. AES-GCM Content Encryption
7.2. AES-CBC Content Encryption
8. Security Considerations
9. IANA Considerations
10. References
10.1. Normative References
10.2. Informative References
Author's Address
1. Introduction
This document specifies the conventions for using the United States
National Security Agency's Commercial National Security Algorithm
(CNSA) Suite algorithms [CNSA] in Secure/Multipurpose Internet Mail
Extensions (S/MIME) [RFC8551]. It applies to the capabilities,
configuration, and operation of all components of US National
Security Systems that employ S/MIME messaging. US National Security
Systems are described in NIST Special Publication 800-59 [SP80059].
It is also appropriate for all other US Government systems that
process high-value information. It is made publicly available for
use by developers and operators of these and any other system
deployments.
S/MIME makes use of the Cryptographic Message Syntax (CMS) [RFC5652]
[RFC5083]. In particular, the signed-data, enveloped-data, and
authenticated-enveloped-data content types are used. This document
only addresses CNSA Suite compliance for S/MIME. Other applications
of CMS are outside the scope of this document.
This document does not define any new cryptographic algorithm suites;
instead, it defines a CNSA-compliant profile of S/MIME. Since many
of the CNSA Suite algorithms enjoy uses in other environments as
well, the majority of the conventions needed for these algorithms are
already specified in other documents. This document references the
source of these conventions, with some relevant details repeated to
aid developers that choose to support the CNSA Suite. Where details
have been repeated, the cited documents are authoritative.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. The Commercial National Security Algorithm Suite
The National Security Agency (NSA) profiles commercial cryptographic
algorithms and protocols as part of its mission to support secure,
interoperable communications for US Government National Security
Systems. To this end, it publishes guidance both to assist with the
US Government transition to new algorithms and to provide vendors --
and the Internet community in general -- with information concerning
their proper use and configuration.
Recently, cryptographic transition plans have become overshadowed by
the prospect of the development of a cryptographically relevant
quantum computer. The NSA has established the Commercial National
Security Algorithm (CNSA) Suite to provide vendors and IT users near-
term flexibility in meeting their cybersecurity interoperability
requirements. The purpose behind this flexibility is to avoid having
vendors and customers make two major transitions in a relatively
short timeframe, as we anticipate a need to shift to quantum-
resistant cryptography in the near future.
The NSA is authoring a set of RFCs, including this one, to provide
updated guidance concerning the use of certain commonly available
commercial algorithms in IETF protocols. These RFCs can be used in
conjunction with other RFCs and cryptographic guidance (e.g., NIST
Special Publications) to properly protect Internet traffic and data-
at-rest for US Government National Security Systems.
3. Requirements and Assumptions
CMS values are generated using ASN.1 [X208], the Basic Encoding Rules
(BER) [X209], and the Distinguished Encoding Rules (DER) [X509].
The elliptic curve used in the CNSA Suite is specified in [FIPS186]
and appears in the literature under two different names. For the
sake of clarity, we list both names below:
+----------+-----------+-----------+---------------+
| Curve | NIST Name | SECG Name | OID [FIPS186] |
+==========+===========+===========+===============+
| nistp384 | P-384 | secp384r1 | 1.3.132.0.34 |
+----------+-----------+-----------+---------------+
Table 1
For CNSA Suite applications, public key certificates used to verify
S/MIME signatures MUST be compliant with the CNSA Suite Certificate
and Certificate Revocation List (CRL) profile specified in [RFC8603].
Within the CMS signed-data content type, signature algorithm
identifiers are located in the signatureAlgorithm field of SignerInfo
structures contained within the SignedData. In addition, signature
algorithm identifiers are located in the SignerInfo
signatureAlgorithm field of countersignature attributes. Specific
requirements for digital signatures are given in Section 5; compliant
implementations MUST consider signatures not meeting these
requirements as invalid.
Implementations based on Elliptic Curve Cryptography (ECC) also
require specification of schemes for key derivation and key wrap.
Requirements for these schemes are in Sections 6.1.1 and 6.1.2,
respectively.
RSA key pairs (public, private) are identified by the modulus size
expressed in bits; RSA-3072 and RSA-4096 are computed using moduli of
3072 bits and 4096 bits, respectively.
RSA signature key pairs used in CNSA Suite-compliant implementations
are either RSA-3072 or RSA-4096. The RSA exponent e MUST satisfy
2^16
2^(16) < e < 2^256 2^(256) and be odd per [FIPS186].
It is recognized that, while the vast majority of RSA signatures are
currently made using the RSASSA-PKCS1-v1_5 algorithm, the preferred
RSA signature scheme for new applications is RSASSA-PSS. CNSA Suite-
compliant X.509 certificates will be issued in accordance with
[RFC8603], and while those certificates must be signed and validated
using RSASSA-PKCS1-v1_5, the subject's RSA key pair can be used to
generate and validate signatures appropriate for either signing
scheme. Where use of RSASSA-PSS is indicated in this document, the
parameters in Section 5.2.2 apply.
This document assumes that the required trust anchors have been
securely provisioned to the client.
All implementations use SHA-384 for hashing and either AES-CBC or
AES-GCM for encryption, the requirements for which are given in
Section 4 and Section 7, respectively.
4. SHA-384 Message Digest Algorithm
SHA-384 is the sole CNSA Suite message digest algorithm. [RFC5754]
specifies the conventions for using SHA-384 with the Cryptographic
Message Syntax (CMS). CNSA Suite-compliant S/MIME implementations
MUST follow the conventions in [RFC5754].
Within the CMS signed-data content type, message digest algorithm
identifiers are located in the SignedData digestAlgorithms field and
the SignerInfo digestAlgorithm field.
The SHA-384 message digest algorithm is defined in FIPS Pub 180
[FIPS180]. The algorithm identifier for SHA-384 is defined in
[RFC5754] as follows:
id-sha384 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistalgorithm(4) hashalgs(2) 2 }
For SHA-384, the AlgorithmIdentifier parameters field is OPTIONAL,
and if present, the parameters field MUST contain a NULL. As
specified in [RFC5754], implementations MUST generate SHA-384
AlgorithmIdentifiers with absent parameters. Implementations MUST
accept SHA-384 AlgorithmIdentifiers with absent parameters or with
NULL parameters.
5. Digital Signature
5.1. ECDSA Signature
The Elliptic Curve Digital Signature Algorithm (ECDSA) is the CNSA
Suite digital signature algorithm based on ECC. [RFC5753] specifies
the conventions for using ECDSA with the Cryptographic Message Syntax
(CMS). CNSA Suite-compliant S/MIME implementations MUST follow the
conventions in [RFC5753].
[RFC5480] defines the signature algorithm identifier used in CMS for
ECDSA with SHA-384 as follows:
ecdsa-with-SHA384 OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) ansi-X9-62(10045) signatures(4)
ecdsa-with-sha2(3) 3 }
When the ecdsa-with-SHA384 algorithm identifier is used, the
AlgorithmIdentifier parameters field MUST be absent.
When signing, the ECDSA algorithm generates two values, commonly
called r and s. These two values MUST be encoded using the ECDSA-
Sig-Value type specified in [RFC5480]:
ECDSA-Sig-Value ::= SEQUENCE {
r INTEGER,
s INTEGER }
5.2. RSA Signature
The RSA signature generation process and the encoding of the result
is either RSASSA-PKCS1-v1_5 or RSA-PSS, as described in detail in
PKCS #1 version 2.2 [RFC8017].
5.2.1. RSA-PKCS1-v1_5
[RFC5754] defines the signature algorithm identifier used in CMS for
an RSA signature with SHA-384 as follows:
sha384WithRSAEncryption OBJECT IDENTIFIER :== ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 12 }
When the sha384WithRSAEncryption algorithm identifier is used, the
parameters MUST be NULL. Implementations MUST accept the parameters
being absent as well as present.
5.2.2. RSA-PSS
[RFC4056] defines the signature algorithm identifier used in CMS for
an RSA-PSS signature as follows: follows (presented here in expanded form):
RSASSA-PSS OBJECT IDENTIFIER :== ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 10 }
The parameters field of an AlgorithmIdentifier that identifies
RSASSA-PSS is defined in [RFC4055] as follows:
RSASSA-PSS-params ::= SEQUENCE {
hashAlgorithm [0] HashAlgorithm DEFAULT
sha1Identifier,
maskGenAlgorithm [1] MaskGenAlgorithm DEFAULT
mgf1SHA1Identifier,
saltLength [2] INTEGER DEFAULT 20,
trailerField [3] INTEGER DEFAULT 1 }
The AlgorithmIdentifier parameters field MUST contain RSASSA-PSS-
params with the following values:
* The hash algorithm MUST be id-sha384 as defined in [RFC8017];
* The mask generation function MUST use the algorithm identifier
mfg1SHA384Identifier as defined in [RFC4055];
* The salt length MUST be 48 octets (the same length as the SHA-384
output); and
* The trailerField MUST have value 1.
6. Key Establishment
6.1. Elliptic Curve Key Agreement
Elliptic Curve Diffie-Hellman (ECDH) is the CNSA Suite key agreement
algorithm. Since S/MIME is used in store-and-forward communications,
ephemeral-static ECDH is always employed. This means that the
message originator possesses an ephemeral ECDH key pair and that the
message recipient possesses a static ECDH key pair whose public key
is provided in an X.509 certificate. The certificate used to obtain
the recipient's public key MUST be compliant with [RFC8603].
When a key agreement algorithm is used, the following steps are
performed:
1. A content-encryption key (CEK) for a particular content-
encryption algorithm is generated at random.
2. The recipient's public key and sender's private key are used with
a key agreement scheme to generate a shared secret (Z).
3. The shared secret is used with a key derivation function (KDF) to
produce a key-encryption key (KEK).
4. The KEK is used with a key wrap algorithm to encrypt the CEK.
Key derivation is discussed in Section 6.1.1. Key wrapping is
discussed in Section 6.1.2.
Section 3.1 of [RFC5753] specifies the conventions for using ECDH
with the CMS. CNSA Suite-compliant S/MIME implementations MUST
follow these conventions.
Within the CMS enveloped-data and authenticated-enveloped-data
content types, key agreement algorithm identifiers are located in the
EnvelopedData RecipientInfos KeyAgreeRecipientInfo
keyEncryptionAlgorithm field.
The keyEncryptionAlgorithm field comprises two fields, an algorithm
field and a parameter field. The algorithm field MUST identify
dhSinglePass-stdDH-sha384kdf-scheme. The algorithm identifier for
the dhSinglePass-stdDH-sha384kdf-scheme, repeated from Section 7.1.4
of [RFC5753], is: is (presented here in expanded form):
dhSinglePass-stdDH-sha384kdf-scheme OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) certicom(132)
schemes(1) 11 2 }
The keyEncryptionAlgorithm parameter field MUST be constructed as
described in Section 6.1.2.
6.1.1. Key Derivation Functions
KDFs based on SHA-384 are used to derive a pairwise key-encryption
key from the shared secret produced by ephemeral-static ECDH.
Sections 7.1.8 and 7.2 in [RFC5753] specify the CMS conventions for
using a KDF with the shared secret generated during ephemeral-static
ECDH. CNSA Suite-compliant S/MIME implementations MUST follow these
conventions.
As specified in Section 7.1.8 of [RFC5753], the ANSI-X9.63-KDF
described in Section 3.6.1 of [SEC1] and based on SHA-384 MUST be
used.
As specified in Section 7.2 of [RFC5753], when using ECDH with the
CMS enveloped-data or authenticated-enveloped-data content type, the
derivation of key-encryption keys makes use of the ECC-CMS-SharedInfo
type:
ECC-CMS-SharedInfo ::= SEQUENCE {
keyInfo AlgorithmIdentifier,
entityUInfo [0] EXPLICIT OCTET STRING OPTIONAL,
suppPubInfo [2] EXPLICIT OCTET STRING }
In the CNSA Suite for S/MIME, the fields of ECC-CMS-SharedInfo are
used as follows:
* keyInfo contains the object identifier of the key-encryption
algorithm used to wrap the content-encryption key. If AES-256 Key
Wrap is used, then the keyInfo will contain id-aes256-wrap-pad,
and the parameters will be absent.
* entityUInfo optionally contains a random value provided by the
message originator. If user keying material (ukm) is included in
the KeyAgreeRecipientInfo, then the entityUInfo MUST be present,
and it MUST contain the ukm value. If the ukm is not present,
then the entityUInfo MUST be absent.
* suppPubInfo contains the length of the generated key-encryption
key in bits, represented as a 32-bit unsigned number, as described
in [RFC2631]. When a 256-bit AES key is used, the length MUST be
0x00000100.
ECC-CMS-SharedInfo is DER encoded and is used as input to the key
derivation function, as specified in Section 3.6.1 of [SEC1]. Note
that ECC-CMS-SharedInfo differs from the OtherInfo specified in
[RFC2631]. Here, a counter value is not included in the keyInfo
field because the KDF specified in [SEC1] ensures that sufficient
keying data is provided.
The KDF specified in Section 3.6.1 of [SEC1] describes how to
generate an essentially arbitrary amount of keying material from a
shared secret, Z, produced by ephemeral-static ECDH. To generate an
L-bit key-encryption key (KEK), KM is computed: blocks of key material (KM) are
computed by incrementing Counter appropriately until enough material
has been generated:
KM(Counter) = Hash ( Z || Counter || ECC-CMS-SharedInfo )
incrementing Counter appropriately, until enough material has been
generated.
The KM blocks are concatenated left to right as they are generated,
and the first (leftmost) L bits are used as the KEK:
KEK = the leftmost L bits of
[KM ( counter=1 ) || KM ( counter=2 ) ...]
In the CNSA Suite for S/MIME, the elements of the KDF are defined as
follows:
* Hash is a one-way hash function. The SHA-384 hash MUST be used.
* Z is the shared secret value generated during ephemeral-static
ECDH. Z MUST be exactly 384 bits, i.e., leading zero bits MUST be
preserved.
* Counter is a 32-bit unsigned number represented in network byte
order. Its initial value MUST be 0x00000001 for any key
derivation operation.
* ECC-CMS-SharedInfo is composed as described above. It MUST be DER
encoded.
In the CNSA Suite for S/MIME, exactly one iteration is needed; the
Counter is not incremented. The key-encryption key (KEK) MUST be the
first (leftmost) 256 bits of the SHA-384 output value:
KEK = the leftmost 256 bits of
SHA-384 ( Z || 0x00000001 || ECC-CMS-SharedInfo )
Note that the only source of secret entropy in this computation is Z.
6.1.2. AES Key Wrap
The AES Key Wrap with Padding key-encryption algorithm, as specified
in [RFC5649] and [SP80038F], is used to encrypt the content-
encryption key with a pairwise key-encryption key that is generated
using ephemeral-static ECDH. Section 8 of [RFC5753] specifies the
CMS conventions for using AES Key Wrap with a pairwise key generated
through ephemeral-static ECDH. CNSA Suite-compliant S/MIME
implementations MUST follow these conventions.
Within the CMS enveloped-data content type, key wrap algorithm
identifiers are located in the KeyWrapAlgorithm parameters within the
EnvelopedData RecipientInfos KeyAgreeRecipientInfo
keyEncryptionAlgorithm field.
The KeyWrapAlgorithm MUST be id-aes256-wrap-pad. The required
algorithm identifier, specified in [RFC5649], is:
id-aes256-wrap-pad OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) aes(1) 48 }
6.2. RSA Key Transport
RSA encryption (RSA) is the CNSA Suite key transport algorithm. The
RSA key transport algorithm is the RSA encryption scheme defined in
[RFC8017], where the message to be encrypted is the content-
encryption key.
The recipient of an S/MIME message possesses an RSA key pair whose
public key is represented by an X.509 certificate. The certificate
used to obtain the recipient's public key MUST be compliant with
[RFC8603]. These certificates are suitable for use with either
RSAES-OAEP or RSAES-PKCS1-v1_5.
6.2.1. RSAES-PKCS1-v1_5
Section 4.2 of [RFC3370] specifies the conventions for using RSAES-
PKCS1-v1_5 with the CMS. S/MIME implementations employing this form
of key transport MUST follow these conventions.
Within the CMS enveloped-data and authenticated-enveloped-data
content types, key transport algorithm identifiers are located in the
EnvelopedData RecipientInfos KeyTransRecipientInfo
keyEncryptionAlgorithm field.
The algorithm identifier for RSA (PKCS #1 v1.5) is:
rsaEncryption OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 1 }
The AlgorithmIdentifier parameters field MUST be present, and the
parameters field MUST contain NULL.
6.2.2. RSAES-OAEP
[RFC3560] specifies the conventions for using RSAES-OAEP with the
CMS. CNSA Suite-compliant S/MIME implementations employing this form
of key transport MUST follow these conventions.
Within the CMS enveloped-data and authenticated-enveloped-data
content types, key transport algorithm identifiers are located in the
EnvelopedData RecipientInfos KeyTransRecipientInfo
keyEncryptionAlgorithm field.
The algorithm identifier for RSA (OAEP) is:
id-RSAES-OAEP OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 7 }
The parameters field of an AlgorithmIdentifier that identifies RSAES-
OAEP is defined in [RFC4055] as follows:
RSAES-OAEP-params ::= SEQUENCE {
hashFunc [0] AlgorithmIdentifier DEFAULT
sha1Identifier,
maskGenFunc [1] AlgorithmIdentifier DEFAULT
mgf1SHA1Identifier,
pSourceFunc [2] AlgorithmIdentifier DEFAULT
pSpecifiedEmptyIdentifier }
pSpecifiedEmptyIdentifier AlgorithmIdentifier ::=
{ id-pSpecified, nullOctetString }
nullOctetString OCTET STRING (SIZE (0)) ::= { ''H }
The AlgorithmIdentifier parameters field MUST be present, and the
parameters field MUST contain RSAES-OAEP-params with values as
follows:
* The hashFunc algorithm must be id-sha384 as defined in [RFC8017];
* The mask generation function must use the algorithm identifier
mfg1SHA384Identifier as defined in [RFC4055];
* The pSourceFunc field must be absent.
The SMIMECapabilities signed attribute is used to specify a partial
list of algorithms that the software announcing the SMIMECapabilities
can support. If the SMIMECapabilities signed attribute is included
to announce support for the RSAES-OAEP algorithm, it MUST be
constructed as defined in Section 5 of [RFC3560], with the sequence
representing the rSAES-OAEP-SHA384-Identifier.
7. Content Encryption
AES-GCM is the preferred mode for CNSA Suite applications, as
described in the Security Considerations (Section 8). AES-CBC is
acceptable where AES-GCM is not yet available.
7.1. AES-GCM Content Encryption
CNSA Suite-compliant S/MIME implementations using the authenticated-
enveloped-data content type [RFC5083] MUST use AES [FIPS197] in
Galois Counter Mode (GCM) [SP80038D] as the content-authenticated
encryption algorithm and MUST follow the conventions for using AES-
GCM with the CMS defined in [RFC5084].
Within the CMS authenticated-enveloped-data content type, content-
authenticated encryption algorithm identifiers are located in the
AuthEnvelopedData EncryptedContentInfo contentEncryptionAlgorithm
field. The content-authenticated encryption algorithm is used to
encipher the content located in the AuthEnvelopedData
EncryptedContentInfo encryptedContent field.
The AES-GCM content-authenticated encryption algorithm is described
in [FIPS197] and [SP80038D]. The algorithm identifier for AES-256 in
GCM mode is:
id-aes256-GCM OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) aes(1) 46 }
The AlgorithmIdentifier parameters field MUST be present, and the
parameters field must contain GCMParameters:
GCMParameters ::= SEQUENCE {
aes-nonce OCTET STRING,
aes-ICVlen AES-GCM-ICVlen DEFAULT 12 }
The authentication tag length (aes-ICVlen) SHALL be 16 (indicating a
tag length of 128 bits).
The initialization vector (aes-nonce) MUST be generated in accordance
with Section 8.2 of [SP80038D]. AES-GCM loses security
catastrophically if a nonce is reused with a given key on more than
one distinct set of input data. Therefore, a fresh content-
authenticated encryption key MUST be generated for each message.
7.2. AES-CBC Content Encryption
CNSA Suite-compliant S/MIME implementations using the enveloped-data
content type MUST use AES-256 [FIPS197] in Cipher Block Chaining
(CBC) mode [SP80038A] as the content-encryption algorithm and MUST
follow the conventions for using AES with the CMS defined in
[RFC3565].
Within the CMS enveloped-data content type, content-encryption
algorithm identifiers are located in the EnvelopedData
EncryptedContentInfo contentEncryptionAlgorithm field. The content-
encryption algorithm is used to encipher the content located in the
EnvelopedData EncryptedContentInfo encryptedContent field.
The AES-CBC content-encryption algorithm is described in [FIPS197]
and [SP80038A]. The algorithm identifier for AES-256 in CBC mode is:
id-aes256-CBC OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) aes(1) 42 }
The AlgorithmIdentifier parameters field MUST be present, and the
parameters field must contain AES-IV:
AES-IV ::= OCTET STRING (SIZE(16))
The 16-octet initialization vector is generated at random by the
originator. See [RFC4086] for guidance on generation of random
values.
8. Security Considerations
This document specifies the conventions for using the NSA's CNSA
Suite algorithms in S/MIME. All of the algorithms and algorithm
identifiers have been specified in previous documents.
See [RFC4086] for guidance on generation of random values.
The security considerations in [RFC5652] discuss the CMS as a method
for digitally signing data and encrypting data.
The security considerations in [RFC3370] discuss cryptographic
algorithm implementation concerns in the context of the CMS.
The security considerations in [RFC5753] discuss the use of elliptic
curve cryptography (ECC) in the CMS.
The security considerations in [RFC3565] discuss the use of AES in
the CMS.
The security considerations in [RFC8551] apply to this profile,
particularly the recommendation to use authenticated encryption modes
(i.e., use authenticated-enveloped-data with AES-GCM rather than
enveloped-data with AES-CBC).
9. IANA Considerations
This document has no IANA actions.
10. References
10.1. Normative References
[CNSA] Committee for National Security Systems, "Use of Public
Standards for Secure Information Sharing", CNSS Policy 15,
October 2016,
<https://www.cnss.gov/CNSS/Issuances/Policies.cfm>.
[FIPS180] National Institute of Standards and Technology, "Secure
Hash Standard (SHS)", Federal Information Processing
Standard 180-4, August 2015,
<https://csrc.nist.gov/publications/detail/fips/180/4/
final>.
[FIPS186] National Institute of Standards and Technology, "Digital
Signature Standard (DSS)", DOI 10.6028/NIST.FIPS.186-4,
FIPS PUB 186-4, July 2013,
<https://csrc.nist.gov/publications/detail/fips/186/4/
final>.
[FIPS197] National Institute of Standards and Technology, "Advanced
Encryption Standard (AES)", DOI 10.6028/NIST.FIPS.197,
FIPS PUB 197, November 2001,
<https://csrc.nist.gov/publications/detail/fips/197/
final>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2631] Rescorla, E., "Diffie-Hellman Key Agreement Method",
RFC 2631, DOI 10.17487/RFC2631, June 1999,
<https://www.rfc-editor.org/info/rfc2631>.
[RFC3370] Housley, R., "Cryptographic Message Syntax (CMS)
Algorithms", RFC 3370, DOI 10.17487/RFC3370, August 2002,
<https://www.rfc-editor.org/info/rfc3370>.
[RFC3560] Housley, R., "Use of the RSAES-OAEP Key Transport
Algorithm in Cryptographic Message Syntax (CMS)",
RFC 3560, DOI 10.17487/RFC3560, July 2003,
<https://www.rfc-editor.org/info/rfc3560>.
[RFC3565] Schaad, J., "Use of the Advanced Encryption Standard (AES)
Encryption Algorithm in Cryptographic Message Syntax
(CMS)", RFC 3565, DOI 10.17487/RFC3565, July 2003,
<https://www.rfc-editor.org/info/rfc3565>.
[RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional
Algorithms and Identifiers for RSA Cryptography for use in
the Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile", RFC 4055,
DOI 10.17487/RFC4055, June 2005,
<https://www.rfc-editor.org/info/rfc4055>.
[RFC4056] Schaad, J., "Use of the RSASSA-PSS Signature Algorithm in
Cryptographic Message Syntax (CMS)", RFC 4056,
DOI 10.17487/RFC4056, June 2005,
<https://www.rfc-editor.org/info/rfc4056>.
[RFC5083] Housley, R., "Cryptographic Message Syntax (CMS)
Authenticated-Enveloped-Data Content Type", RFC 5083,
DOI 10.17487/RFC5083, November 2007,
<https://www.rfc-editor.org/info/rfc5083>.
[RFC5084] Housley, R., "Using AES-CCM and AES-GCM Authenticated
Encryption in the Cryptographic Message Syntax (CMS)",
RFC 5084, DOI 10.17487/RFC5084, November 2007,
<https://www.rfc-editor.org/info/rfc5084>.
[RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Elliptic Curve Cryptography Subject Public Key
Information", RFC 5480, DOI 10.17487/RFC5480, March 2009,
<https://www.rfc-editor.org/info/rfc5480>.
[RFC5649] Housley, R. and M. Dworkin, "Advanced Encryption Standard
(AES) Key Wrap with Padding Algorithm", RFC 5649,
DOI 10.17487/RFC5649, September 2009,
<https://www.rfc-editor.org/info/rfc5649>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
[RFC5753] Turner, S. and D. Brown, "Use of Elliptic Curve
Cryptography (ECC) Algorithms in Cryptographic Message
Syntax (CMS)", RFC 5753, DOI 10.17487/RFC5753, January
2010, <https://www.rfc-editor.org/info/rfc5753>.
[RFC5754] Turner, S., "Using SHA2 Algorithms with Cryptographic
Message Syntax", RFC 5754, DOI 10.17487/RFC5754, January
2010, <https://www.rfc-editor.org/info/rfc5754>.
[RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
"PKCS #1: RSA Cryptography Specifications Version 2.2",
RFC 8017, DOI 10.17487/RFC8017, November 2016,
<https://www.rfc-editor.org/info/rfc8017>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", RFC 8551, DOI 10.17487/RFC8551,
April 2019, <https://www.rfc-editor.org/info/rfc8551>.
[RFC8603] Jenkins, M. and L. Zieglar, "Commercial National Security
Algorithm (CNSA) Suite Certificate and Certificate
Revocation List (CRL) Profile", RFC 8603,
DOI 10.17487/RFC8603, May 2019,
<https://www.rfc-editor.org/info/rfc8603>.
[SEC1] Standards for Efficient Cryptography Group, "SEC1:
Elliptic Curve Cryptography", May 2009,
<https://www.secg.org/sec1-v2.pdf>.
[SP80038A] Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: Methods and Techniques",
DOI 10.6028/NIST.SP.800-38A, Special Publication 800-38A,
December 2001, <https://csrc.nist.gov/publications/detail/
sp/800-38a/final>.
[SP80038D] Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: Galois/Counter Mode (GCM) and GMAC",
DOI 10.6028/NIST.SP.800-38D, Special Publication 800-38D,
November 2007, <https://csrc.nist.gov/publications/detail/
sp/800-38d/final>.
[SP80038F] Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: Methods for Key Wrapping",
DOI 10.6028/NIST.SP.800-38F, Special Publication 800-38F,
December 2012, <https://csrc.nist.gov/publications/detail/
sp/800-38f/final>.
[X208] CCITT, "Specification of Abstract Syntax Notation One
(ASN.1)", CCITT Recommendation X.208, 1988,
<https://www.itu.int/rec/T-REC-X.208-198811-W/en>.
[X209] CCITT, "Specification of Basic Encoding Rules for Abstract
Syntax Notation One (ASN.1)", CCITT Recommendation X.209,
1988, <https://www.itu.int/rec/T-REC-X.209-198811-W/en>.
[X509] CCITT, "The Directory - Authentication Framework", CCITT
Recommendation X.509, 1988,
<https://www.itu.int/rec/T-REC-X.509-198811-S>.
10.2. Informative References
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>.
[SP80059] Barker, W., "Guideline for Identifying an Information
System as a National Security System",
DOI 10.6028/NIST.SP.800-59, Special Publication 800-59,
August 2003, <https://csrc.nist.gov/publications/detail/
sp/800-59/final>.
Author's Address
Michael Jenkins
National Security Agency
Email: mjjenki@nsa.gov