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Independent Submission D. Cooley
Request for Comments: 9151 NSA
Category: Informational April 2022
ISSN: 2070-1721
Commercial National Security Algorithm (CNSA) Suite Profile for TLS and
DTLS 1.2 and 1.3
Abstract
This document defines a base profile for TLS protocol versions 1.2
and 1.3 as well as DTLS protocol versions 1.2 and 1.3 for use with
the US Commercial National Security Algorithm (CNSA) Suite.
The profile applies to the capabilities, configuration, and operation
of all components of US National Security Systems that use TLS or
DTLS. It is also appropriate for all other US Government systems
that process high-value information.
The profile is made publicly available here 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/rfc9151.
Copyright Notice
Copyright (c) 2022 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
2. CNSA
3. Terminology
4. CNSA Suites
4.1. CNSA (D)TLS Key Establishment Algorithms
4.2. CNSA TLS Authentication
5. CNSA Compliance and Interoperability Requirements
5.1. Acceptable Elliptic Curve Cryptography (ECC) Curves
5.2. Acceptable RSA Schemes, Parameters, and Checks
5.3. Acceptable Finite Field Groups
5.4. Certificates
6. (D)TLS 1.2 Requirements
6.1. The "extended_master_secret" Extension
6.2. The "signature_algorithms" Extension
6.3. The "signature_algorithms_cert" Extension
6.4. The CertificateRequest Message
6.5. The CertificateVerify Message
6.6. The Signature in the ServerKeyExchange Message
6.7. Certificate Status
7. (D)TLS 1.3 Requirements
7.1. The "signature_algorithms" Extension
7.2. The "signature_algorithms_cert" Extension
7.3. The "early_data" Extension
7.4. Resumption
7.5. Certificate Status
8. Security Considerations
9. IANA Considerations
10. References
10.1. Normative References
10.2. Informative References
Author's Address
1. Introduction
This document specifies a profile of TLS version 1.2 [RFC5246] and
TLS version 1.3 [RFC8446] as well as DTLS version 1.2 [RFC6347] and
DTLS version 1.3 [RFC9147] for use by applications that support the
National Security Agency's (NSA) Commercial National Security
Algorithm (CNSA) Suite [CNSA]. The profile applies to the
capabilities, configuration, and operation of all components of US
National Security Systems [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.
This document does not define any new cipher suites; instead, it
defines a CNSA-compliant profile of TLS and DTLS, and the cipher
suites defined in [RFC5288], [RFC5289], and [RFC8446]. This profile
uses only algorithms in the CNSA Suite.
The reader is assumed to have familiarity with the TLS 1.2 and 1.3 as
well as the DTLS 1.2 and 1.3 protocol specifications: [RFC5246],
[RFC8446], [RFC6347], and [RFC9147], respectively. All MUST-level
requirements from the protocol documents apply throughout this
profile; they are generally not repeated. This profile contains
changes that elevate some SHOULD-level options to MUST-level; this
profile also contains changes that elevate some MAY-level options to
SHOULD-level or MUST-level. All options that are not mentioned in
this profile remain at their original requirement level.
2. CNSA
The National Security Agency (NSA) profiles commercial cryptographic
algorithms and protocols as part of its mission to support secure,
interoperable communications for US 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 CNSA Suite to provide
vendors and IT users near-term flexibility in meeting their
Information Assurance (IA) 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 National Security Systems.
3. 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.
"ECDSA" and "ECDH" refer to the use of the Elliptic Curve Digital
Signature Algorithm (ECDSA) and Elliptic Curve Diffie Hellman (ECDH),
respectively. ECDSA and ECDH are used with the NIST P-384 curve
(which is based on a 384-bit prime modulus) and the SHA-384 hash
function. Similarly, "RSA" and "DH" refer to Rivest-Shamir-Adleman
(RSA) and Finite Field Diffie-Hellman (DH), respectively. RSA and DH
are used with a 3072-bit or 4096-bit modulus. When RSA is used for
digital signature, it is used with the SHA-384 hash function.
Henceforth, this document refers to TLS versions 1.2 and 1.3 and DTLS
versions 1.2 and 1.3 collectively as "(D)TLS".
4. CNSA Suites
[CNSA] approves the use of both Finite Field and elliptic curve
versions of the DH key agreement algorithm as well as RSA-based key
establishment. [CNSA] also approves certain versions of the RSA and
elliptic curve digital signature algorithms. The approved encryption
techniques include the Advanced Encryption Standard (AES) used with a
256-bit key in an Authenticated Encryption with Associated Data
(AEAD) mode.
In particular, CNSA includes the following:
Encryption:
AES [AES] (with key size 256 bits), operating in Galois/Counter
Mode (GCM) [GCM]
Digital Signature:
ECDSA [DSS] (using the NIST P-384 elliptic curve)
RSA [DSS] (with a modulus of 3072 bits or 4096 bits)
Key Establishment (includes key agreement and key transport):
ECDH [PWKE-A] (using the NIST P-384 elliptic curve)
DH [PWKE-A] (with a prime modulus of 3072 or 4096 bits)
RSA [PWKE-B] (with a modulus of 3072 or 4096 bits, but only in
(D)TLS 1.2)
[CNSA] also approves the use of SHA-384 [SHS] as the hash algorithm
for mask generation, signature generation, Pseudorandom Function
(PRF) in TLS 1.2 and HMAC-based Key Derivation Function (HKDF) in TLS
1.3.
4.1. CNSA (D)TLS Key Establishment Algorithms
The following combination of algorithms and key sizes are used in
CNSA (D)TLS:
AES with 256-bit key, operating in GCM mode
ECDH [PWKE-A] using the Ephemeral Unified Model Scheme with
cofactor set to 1 (see Section 6.1.2.2 in [PWKE-A])
TLS PRF/HKDF with SHA-384 [SHS]
Or
AES with 256-bit key, operating in GCM mode
RSA key transport using 3072-bit or 4096-bit modulus
[PWKE-B][RFC8017]
TLS PRF/HKDF with SHA-384 [SHS]
Or
AES with 256-bit key, operating in GCM mode
DH using dhEphem with domain parameters specified below in
Section 5.3 (see Section 6.1.2.1 in [PWKE-A])
TLS PRF/HKDF with SHA-384 [SHS]
The specific CNSA-compliant cipher suites are listed in Section 5.
4.2. CNSA TLS Authentication
For server and/or client authentication, CNSA (D)TLS MUST generate
and verify either ECDSA signatures or RSA signatures.
In all cases, the client MUST authenticate the server. The server
MAY also authenticate the client, as needed by the specific
application.
The public keys used to verify these signatures MUST be contained in
a certificate (see Section 5.4 for more information).
5. CNSA Compliance and Interoperability Requirements
CNSA (D)TLS MUST NOT use TLS versions prior to (D)TLS 1.2 in a CNSA-
compliant system. CNSA (D)TLS servers and clients MUST implement and
use either (D)TLS version 1.2 [RFC5246] [RFC6347] or (D)TLS version
1.3 [RFC8446] [RFC9147].
5.1. Acceptable Elliptic Curve Cryptography (ECC) Curves
The elliptic curves used in the CNSA Suite appear in the literature
under two different names [DSS] [SECG]. For the sake of clarity,
both names are listed below:
+=======+===========+===========+
| Curve | NIST name | SECG name |
+=======+===========+===========+
| P-384 | nistp384 | secp384r1 |
+-------+-----------+-----------+
Table 1: Elliptic Curves in
CNSA Suite
[RFC8422] defines a variety of elliptic curves. CNSA (D)TLS
connections MUST use secp384r1 (also called nistp384), and the
uncompressed form MUST be used, as required by [RFC8422] and
[RFC8446].
Key pairs MUST be generated following Section 5.6.1.2 of [PWKE-A].
5.2. Acceptable RSA Schemes, Parameters, and Checks
[CNSA] specifies a minimum modulus size of 3072 bits; however, only
two modulus sizes (3072 bits and 4096 bits) are supported by this
profile.
For (D)TLS 1.2:
For certificate signatures, RSASSA-PKCS1-v1_5 [RFC8017] MUST be
supported, and RSASSA-PSS [DSS] SHOULD be supported.
For signatures in TLS handshake messages, RSASSA-PKCS1-v1_5
[RFC8017] MUST be supported, and RSASSA-PSS [DSS] SHOULD be
supported.
For key transport, RSAES-PKCS1-v1_5 [RFC8017] MUST be supported.
For (D)TLS 1.3:
For certificate signatures, RSASSA-PKCS1-v1_5 [RFC8017] MUST be
supported, and RSASSA-PSS [DSS] SHOULD be supported.
For signatures in TLS handshake messages, RSASSA-PSS [DSS] MUST be
supported.
For key transport, TLS 1.3 does not support RSA key transport.
For all versions of (D)TLS:
RSA exponent e MUST satisfy 2^16<e<2^256 and be odd per [DSS].
If RSASSA-PSS is supported (using rsa_pss_rsae_sha384 for
example), then the implementation MUST assert rsaEncryption as the
public key algorithm, the hash algorithm (used for both mask
generation and signature generation) MUST be SHA-384, the mask
generation function 1 (MGF1) from [RFC8017] MUST be used, and the
salt length MUST be 48 octets.
5.3. Acceptable Finite Field Groups
[CNSA] specifies a minimum modulus size of 3072 bits; however, only
two modulus sizes (3072 bits and 4096 bits) are supported by this
profile.
Ephemeral key pairs MUST be generated following Section 5.6.1.1.1 of
[PWKE-A] using the approved safe prime groups specified in [RFC7919]
for DH ephemeral key agreement. The named groups are:
ffdhe3072 (ID=257)
ffdhe4096 (ID=258)
5.4. Certificates
Certificates used to establish a CNSA (D)TLS connection MUST be
signed with ECDSA or RSA and MUST be compliant with the CNSA Suite
Certificate and Certificate Revocation List (CRL) Profile [RFC8603].
6. (D)TLS 1.2 Requirements
Although TLS 1.2 has technically been obsoleted by the IETF in favor
of TLS 1.3, many implementations and deployments of TLS 1.2 will
continue to exist. For the cases where TLS 1.2 continues to be used,
implementations MUST use [RFC5246] and SHOULD implement the updates
specified in [RFC8446] (outlined in Section 1.3 of that document).
The CNSA (D)TLS 1.2 client MUST offer at least one of these cipher
suites:
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 [RFC5289] [RFC8422]
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 [RFC5289] [RFC8422]
TLS_RSA_WITH_AES_256_GCM_SHA384 [RFC5288]
TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 [RFC5288] [RFC7919]
The CNSA cipher suites listed above MUST be the first (most
preferred) cipher suites in the ClientHello message.
A CNSA (D)TLS client that offers interoperability with servers that
are not CNSA compliant MAY offer additional cipher suites, but any
additional cipher suites MUST appear after the CNSA cipher suites in
the ClientHello message.
A CNSA (D)TLS server MUST accept one of the CNSA Suites above if they
are offered in the ClientHello message before accepting a non-CNSA-
compliant suite.
If interoperability is not desired with non-CNSA-compliant clients or
servers, then the session MUST fail if no CNSA Suites are offered or
accepted.
6.1. The "extended_master_secret" Extension
A CNSA (D)TLS client SHOULD include and a CNSA (D)TLS server SHOULD
accept the "extended_master_secret" extension as specified in
[RFC7627]. See Section 1 of [RFC7627] for security concerns when
this extension is not used.
6.2. The "signature_algorithms" Extension
A CNSA (D)TLS client MUST include and a CNSA (D)TLS server MUST also
accept the "signature_algorithms" extension. The CNSA (D)TLS client
MUST offer and the CNSA (D)TLS server MUST also accept at least one
of the following values in the "signature_algorithms" extensions as
specified in [RFC8446]:
ecdsa_secp384r1_sha384
rsa_pkcs1_sha384
And, if supported, the client SHOULD offer and/or the server SHOULD
also accept:
rsa_pss_pss_sha384
rsa_pss_rsae_sha384
Following the guidance in [RFC8603], CNSA (D)TLS servers MUST only
accept ECDSA or RSA for signatures on ServerKeyExchange messages and
for certification path validation.
Other client offerings MAY be included to indicate the acceptable
signature algorithms in cipher suites that are offered for
interoperability with servers not compliant with CNSA and to indicate
the signature algorithms that are acceptable for ServerKeyExchange
messages and for certification path validation in non-compliant CNSA
(D)TLS connections. These offerings MUST NOT be accepted by a CNSA-
compliant (D)TLS server.
6.3. The "signature_algorithms_cert" Extension
A CNSA (D)TLS client MAY include the "signature_algorithms_cert"
extension. CNSA (D)TLS servers MUST process the
"signature_algorithms_cert" extension if it is offered per
Section 4.2.3 of [RFC8446].
Both CNSA (D)TLS clients and servers MUST use one of the following
values for certificate path validation:
ecdsa_secp384r1_sha384
rsa_pkcs1_sha384
And, if supported, SHOULD offer/accept:
rsa_pss_pss_sha384
rsa_pss_rsae_sha384
6.4. The CertificateRequest Message
When a CNSA (D)TLS server is configured to authenticate the client,
the server MUST include the following values in its
CertificateRequest.supported_signature_algorithms [RFC5246] offer:
ecdsa_secp384r1_sha384
rsa_pkcs1_sha384
And, if supported as specified in [RFC8446], SHOULD offer/accept:
rsa_pss_pss_sha384
rsa_pss_rsae_sha384
6.5. The CertificateVerify Message
A CNSA (D)TLS client MUST use ECDSA or RSA when sending the
CertificateVerify message. CNSA (D)TLS servers MUST only accept
ECDSA or RSA in the CertificateVerify message.
6.6. The Signature in the ServerKeyExchange Message
A CNSA (D)TLS server MUST sign the ServerKeyExchange message using
ECDSA or RSA.
6.7. Certificate Status
Certificate Authorities (CAs) providing certificates to a CNSA (D)TLS
server or client MUST provide certificate revocation status
information via a Certificate Revocation List (CRL) distribution
point or using the Online Certificate Status Protocol (OCSP). A CNSA
client SHOULD request it according to Section 4.4.2.1 of [RFC8446].
If OCSP is supported, the (D)TLS server SHOULD provide OCSP responses
in the CertificateStatus message.
7. (D)TLS 1.3 Requirements
The CNSA (D)TLS client MUST offer the following cipher suite in the
ClientHello:
TLS_AES_256_GCM_SHA384
The CNSA (D)TLS client MUST include at least one of the following
values in the "supported_groups" extension:
ECDHE: secp384r1
DHE: ffdhe3072
DHE: ffdhe4096
The CNSA cipher suite MUST be the first (most preferred) cipher suite
in the ClientHello message and in the extensions.
A CNSA (D)TLS client that offers interoperability with servers that
are not CNSA compliant MAY offer additional cipher suites, but any
additional cipher suites MUST appear after the CNSA-compliant cipher
suites in the ClientHello message.
A CNSA (D)TLS server MUST accept one of the CNSA algorithms listed
above if they are offered in the ClientHello message.
If interoperability is not desired with non-CNSA-compliant clients or
servers, then the session MUST fail if no CNSA Suites are offered or
accepted.
7.1. The "signature_algorithms" Extension
A CNSA (D)TLS client MUST include the "signature_algorithms"
extension. The CNSA (D)TLS client MUST offer at least one of the
following values in the "signature_algorithms" extension:
ecdsa_secp384r1_sha384
rsa_pss_pss_sha384
rsa_pss_rsae_sha384
Clients that allow negotiating TLS 1.2 MAY offer rsa_pkcs1_sha384 for
use with TLS 1.2. Other offerings MAY be included to indicate the
acceptable signature algorithms in cipher suites that are offered for
interoperability with servers not compliant with CNSA in non-
compliant CNSA (D)TLS connections. These offerings MUST NOT be
accepted by a CNSA-compliant (D)TLS server.
7.2. The "signature_algorithms_cert" Extension
A CNSA (D)TLS client SHOULD include the "signature_algorithms_cert"
extension. And, if offered, the CNSA (D)TLS client MUST offer at
least one of the following values in the "signature_algorithms_cert"
extension:
ecdsa_secp384r1_sha384
rsa_pkcs1_sha384
And, if supported, SHOULD offer:
rsa_pss_pss_sha384
rsa_pss_rsae_sha384
Following the guidance in [RFC8603], CNSA (D)TLS servers MUST only
accept ECDSA or RSA for certificate path validation.
Other offerings MAY be included to indicate the signature algorithms
that are acceptable for certification path validation in non-
compliant CNSA (D)TLS connections. These offerings MUST NOT be
accepted by a CNSA-compliant (D)TLS server.
7.3. The "early_data" Extension
A CNSA (D)TLS client or server MUST NOT include the "early_data"
extension. See Section 2.3 of [RFC8446] for security concerns.
7.4. Resumption
A CNSA (D)TLS server MAY send a CNSA (D)TLS client a NewSessionTicket
message to enable resumption. A CNSA (D)TLS client MUST request
"psk_dhe_ke" via the "psk_key_exchange_modes" ClientHello extension
to resume a session. A CNSA (D)TLS client MUST offer Ephemeral
Elliptic Curve Diffie-Hellman (ECDHE) with SHA-384 and/or Ephemeral
Diffie-Hellman (DHE) with SHA-384 in the "supported_groups" and/or
"key_share" extensions.
7.5. Certificate Status
Certificate Authorities (CAs) providing certificates to a CNSA (D)TLS
server or client MUST provide certificate revocation status
information via a Certificate Revocation List (CRL) distribution
point or using the Online Certificate Status Protocol (OCSP). A CNSA
client SHOULD request it according to Section 4.4.2.1 of [RFC8446].
If OCSP is supported, the (D)TLS server SHOULD provide OCSP responses
in the "CertificateEntry".
8. Security Considerations
Most of the security considerations for this document are described
in [RFC5246], [RFC8446], [RFC6347], and [RFC9147]. In addition, the
security considerations for Elliptic Curve Cryptography (ECC) related
to TLS are described in [RFC8422], [RFC5288], and [RFC5289]. Readers
should consult those documents.
In order to meet the goal of a consistent security level for the
entire cipher suite, CNSA (D)TLS implementations MUST only use the
elliptic curves, RSA schemes, and Finite Fields defined in
Section 5.1, Section 5.2, and Section 5.3, respectively. If this is
not the case, then security may be weaker than is required.
As noted in TLS version 1.3 [RFC8446], TLS does not provide inherent
replay protections for early data. For this reason, this profile
forbids the use of early data.
9. IANA Considerations
This document has no IANA actions.
10. References
10.1. Normative References
[AES] National Institute of Standards and Technology,
"Announcing the ADVANCED ENCRYPTION STANDARD (AES)",
FIPS 197, DOI 10.6028/NIST.FIPS.197, November 2001,
<https://nvlpubs.nist.gov/nistpubs/fips/
NIST.FIPS.197.pdf>.
[CNSA] Committee for National Security Systems, "Use of Public
Standards for Secure Information Sharing", CNSSP 15,
October 2016,
<https://www.cnss.gov/CNSS/issuances/Policies.cfm>.
[DSS] National Institute of Standards and Technology, "Digital
Signature Standard (DSS)", FIPS PUB 186-4,
DOI 10.6028/NIST.FIPS.186-4, July 2013,
<https://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.186-4.pdf>.
[GCM] Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: Galois/Counter Mode (GCM) and GMAC", NIST
Special Publication 800-38D, DOI 10.6028/NIST.SP.800-38D,
November 2007,
<https://nvlpubs.nist.gov/nistpubs/Legacy/SP/
nistspecialpublication800-38d.pdf>.
[PWKE-A] Barker, E., Chen, L., Roginsky, A., Vassilev, A., and R.
Davis, "Recommendation for Pair-Wise Key Establishment
Schemes Using Discrete Logarithm Cryptography", NIST
Special Publication 800-56A Revision 3,
DOI 10.6028/NIST.SP.800-56Ar3, April 2018,
<https://nvlpubs.nist.gov/nistpubs/SpecialPublications/
NIST.SP.800-56Ar3.pdf>.
[PWKE-B] Barker, E., Chen, L., Roginsky, A., Vassilev, A., Davis,
R., and S. Simon, "Recommendation for Pair-Wise Key
Establishment Schemes Using Integer Factorization
Cryptography", NIST Special Publication 800-56B Revision
2, DOI 10.6028/NIST.SP.800-56Br2, March 2019,
<https://nvlpubs.nist.gov/nistpubs/SpecialPublications/
NIST.SP.800-56Br2.pdf>.
[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>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
DOI 10.17487/RFC5288, August 2008,
<https://www.rfc-editor.org/info/rfc5288>.
[RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-
256/384 and AES Galois Counter Mode (GCM)", RFC 5289,
DOI 10.17487/RFC5289, August 2008,
<https://www.rfc-editor.org/info/rfc5289>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A.,
Langley, A., and M. Ray, "Transport Layer Security (TLS)
Session Hash and Extended Master Secret Extension",
RFC 7627, DOI 10.17487/RFC7627, September 2015,
<https://www.rfc-editor.org/info/rfc7627>.
[RFC7919] Gillmor, D., "Negotiated Finite Field Diffie-Hellman
Ephemeral Parameters for Transport Layer Security (TLS)",
RFC 7919, DOI 10.17487/RFC7919, August 2016,
<https://www.rfc-editor.org/info/rfc7919>.
[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>.
[RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
Curve Cryptography (ECC) Cipher Suites for Transport Layer
Security (TLS) Versions 1.2 and Earlier", RFC 8422,
DOI 10.17487/RFC8422, August 2018,
<https://www.rfc-editor.org/info/rfc8422>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[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>.
[RFC9147] Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
<https://www.rfc-editor.org/info/rfc9147>.
[SHS] National Institute of Standards and Technology (NIST),
"Secure Hash Standard (SHS)", DOI 10.6028/NIST.FIPS.180-4,
FIPS PUB 180-4, August 2015,
<https://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.180-4.pdf>.
10.2. Informative References
[SECG] Brown, D., "SEC 2: Recommended Elliptic Curve Domain
Parameters", Version 2.0, February 2010,
<https://www.secg.org/sec2-v2.pdf>.
[SP80059] Barker, W., "Guideline for Identifying an Information
System as a National Security System",
DOI 10.6028/NIST.SP.800-59, NIST Special
Publication 800-59, August 2003,
<https://nvlpubs.nist.gov/nistpubs/Legacy/SP/
nistspecialpublication800-59.pdf>.
Author's Address
Dorothy Cooley
National Security Agency
Email: decoole@nsa.gov