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Internet Engineering Task Force (IETF)                         M. SalterRequest for Comments: 6460                      National Security AgencyObsoletes:5430                                               R. HousleyCategory: Informational                                   Vigil SecurityISSN: 2070-1721                                             January 2012Suite B Profile for Transport Layer Security (TLS)Abstract   The United States government has published guidelines for "NSA Suite   B Cryptography" that define cryptographic algorithm policy for   national security applications.  This document defines a profile of   Transport Layer Security (TLS) version 1.2 that is fully compliant   with Suite B.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6460.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://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.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Salter & Housley              Informational                     [Page 1]

RFC 6460                     Suite B for TLS                January 2012   This document may contain material from IETF Documents or IETF   Contributions published or made publicly available before November   10, 2008.  The person(s) controlling the copyright in some of this   material may not have granted the IETF Trust the right to allow   modifications of such material outside the IETF Standards Process.   Without obtaining an adequate license from the person(s) controlling   the copyright in such materials, this document may not be modified   outside the IETF Standards Process, and derivative works of it may   not be created outside the IETF Standards Process, except to format   it for publication as an RFC or to translate it into languages other   than English.Table of Contents1. Introduction ....................................................22. Conventions Used in This Document ...............................33. Suite B Requirements ............................................33.1. Minimum Levels of Security (minLOS) for Suite B TLS ........43.2. Suite B TLS Authentication .................................54. Suite B Compliance and Interoperability Requirements ............54.1. Acceptable Curves ..........................................64.2. Certificates ...............................................74.3. signature_algorithms Extension .............................74.4. CertificateRequest Message .................................84.5. CertificateVerify Message ..................................84.6. ServerKeyExchange Message Signature ........................85. Security Considerations .........................................86. Acknowledgments .................................................97. References ......................................................97.1. Normative References .......................................97.2. Informative References ....................................10   Annex A. A Transitional Suite B Profile for TLS 1.1 and 1.0 .......11   Annex B. Changes sinceRFC 5430 ...................................131.  Introduction   This document specifies the conventions for using National Security   Agency (NSA) Suite B Cryptography [SuiteB] with the Transport Layer   Security (TLS) protocol, and the Datagram Transport Layer Security   (DTLS) protocol.   This document does not define any new cipher suites; instead, it   defines a Suite B compliant profile for use with TLS version 1.2   [RFC5246], DTLS version 1.2 [RFC6347], and the cipher suites defined   in [RFC5289].  This profile uses only Suite B algorithms.Salter & Housley              Informational                     [Page 2]

RFC 6460                     Suite B for TLS                January 2012RFC 5430 defined an additional transitional profile for use with TLS   versions 1.0 [RFC2246] and 1.1 [RFC4346] or with DTLS version 1.0   [RFC4347] and the cipher suites defined in [RFC4492].  When either   the client or the server does not support TLS version 1.2 and DTLS   version 1.2, the transitional profile can be used to achieve   interoperability that is not Suite B compliant.  The description for   the transitional profile appears in Annex A of this document.2.  Conventions Used in This Document   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described in [RFC2119].   We will use the notation "ECDSA-256" to represent the use of the   Elliptic Curve Digital Signature Algorithm (ECDSA) with the P-256   curve and the SHA-256 hash function.  Similarly, "ECDSA-384" will   represent the use of the ECDSA with the P-384 curve and the SHA-384   hash function.3.  Suite B Requirements   The Fact Sheet on Suite B Cryptography requires key establishment and   authentication algorithms based on Elliptic Curve Cryptography and   encryption using AES [AES].  Suite B algorithms are defined to   support two minimum levels of security: 128 and 192 bits.   In particular, Suite B includes the following:      Encryption:         Advanced Encryption Standard (AES) [AES] --                          FIPS 197 (with key sizes of 128 and 256 bits)      Digital Signature:  Elliptic Curve Digital Signature Algorithm                          (ECDSA) [DSS] - FIPS 186-3 (using the curves                          with 256- and 384-bit prime moduli)      Key Exchange:       Elliptic Curve Diffie-Hellman (ECDH) - NIST                          Special Publication 800-56A [PWKE] (using the                          curves with 256- and 384-bit prime moduli)   The two elliptic curves used in Suite B each appear in the literature   under two different names.  For sake of clarity, we list both names   below:      Curve    NIST name   [SECG] name      --------------------------------      P-256    nistp256    secp256r1      P-384    nistp384    secp384r1Salter & Housley              Informational                     [Page 3]

RFC 6460                     Suite B for TLS                January 2012   The purpose of this document is to specify the requirements for a   Suite B compliant implementation of TLS (hereafter referred to as   "Suite B TLS").3.1.  Minimum Levels of Security (minLOS) for Suite B TLS   Suite B provides two levels of cryptographic security, namely a   128-bit minimum level of security (minLOS_128) and a 192-bit minimum   level of security (minLOS_192).  Each level defines a minimum   strength that all cryptographic algorithms must provide.   The following combination of algorithms and key sizes are used in   Suite B TLS:   Suite B Combination 1              Suite B Combination 2   --------------------------------   --------------------------------   AES with 128-bit key in GCM mode   AES with 256-bit key in GCM mode   ECDH using the 256-bit prime       ECDH using the 384-bit prime      modulus curve P-256 [DSS]          modulus curve P-384 [DSS]   TLS PRF with SHA-256 [SHS]         TLS PRF with SHA-384 [SHS]   Suite B TLS configured at a minimum level of security of 128 bits   MUST use a TLS cipher suite satisfying either SuiteB_Combination_1 in   its entirety or SuiteB_Combination_2 in its entirety.   Suite B TLS configured at a minimum level of security of 192 bits   MUST use a TLS cipher suite satisfying SuiteB_Combination_2 in its   entirety.   The specific Suite B compliant cipher suites for each combination are   listed inSection 4.   For Suite B TLS, ECDH uses the Ephemeral Unified Model Scheme with   cofactor set to 1 (see Section 6.1.2.2 in [PWKE]).   To accommodate backward compatibility, a Suite B TLS client or server   MAY be configured to accept a cipher suite that is not part of Suite   B.  However, whenever a Suite B TLS client and a Suite B TLS server   establish a TLS version 1.2 session, Suite B algorithms MUST be   employed.Salter & Housley              Informational                     [Page 4]

RFC 6460                     Suite B for TLS                January 20123.2 Suite B TLS Authentication   Suite B TLS MUST use ECDSA for digital signatures; authentication   methods other than ECDSA-256 and ECDSA-384 MUST NOT be used for TLS   authentication.  If a relying party receives a signature based on any   other authentication method, it MUST return a TLS error and stop the   TLS handshake.   A system compliant with the Suite B TLS and configured at a minimum   level of security of 128 bits MUST use either ECDSA-256 or ECDSA-384   for client or server authentication.  One party can authenticate with   ECDSA-256 when the other party authenticates with ECDSA-384.  This   flexibility allows interoperation between a client and a server that   have ECDSA authentication keys of different sizes.   Clients and servers in a system configured at a minimum level of   security of 128 bits MUST be able to verify ECDSA-256 signatures and   SHOULD be able to verify ECDSA-384 signatures unless it is absolutely   certain that the implementation will never need to verify   certificates originating from an authority that uses an ECDSA-384   signing key.   A system compliant with the Suite B TLS and configured at a minimum   level of security of 192 bits MUST use ECDSA-384 for client and   server authentication.   Clients and servers in a system configured at a minimum level of   security of 192 bits MUST be able to verify ECDSA-384 signatures.   In all cases, the client MUST authenticate the server.  The server   MAY authenticate the client, as needed by the specific application.4.  Suite B Compliance and Interoperability Requirements   TLS versions 1.1 [RFC4346] and earlier do not support Galois/ Counter   Mode (GCM) cipher suites [RFC5289].  However, TLS version 1.2   [RFC5246] and later do support GCM.  For Suite B TLS, GCM cipher   suites MUST be used; therefore, a Suite B TLS client MUST implement   TLS version 1.2 or later.   A Suite B TLS client configured at a minimum level of security of 128   bits MUST offer the TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 or the   TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 cipher suite in the   ClientHello message.  The TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256   cipher suite is preferred; if offered, it MUST appear before the   TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 cipher suite.Salter & Housley              Informational                     [Page 5]

RFC 6460                     Suite B for TLS                January 2012   If configured at a minimum level of security of 192 bits, the client   MUST offer the TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 cipher suite   and MUST NOT offer the TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 cipher   suite.   One of these two cipher suites MUST be the first (most preferred)   cipher suites in the ClientHello message.  A Suite B TLS client that   offers interoperability with servers that are not Suite B compliant   MAY offer additional cipher suites, but any additional cipher suites   MUST appear after the two Suite B compliant cipher suites in the   ClientHello message.   A Suite B TLS server MUST implement TLS version 1.2 or later.   A Suite B TLS server configured at a minimum level of security of 128   bits MUST accept either the TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256   cipher suite or the TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 cipher   suite if it is offered in the ClientHello message, with the   TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 cipher suite being preferred.   A Suite B TLS server configured at a minimum level of security of 192   bits MUST accept the TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 cipher   suite if it is offered in the ClientHello message.   If the server is not offered either of the Suite B cipher suites, and   interoperability with clients that are not Suite B compliant is   desired, then the Suite B TLS server MAY accept another offered   cipher suite that is considered acceptable by the server   administrator.4.1.  Acceptable CurvesRFC 4492 defines a variety of elliptic curves.  Suite B TLS   connections MUST use secp256r1(23) or secp384r1(24).  These are the   same curves that appear in FIPS 186-3 [DSS] as P-256 and P-384,   respectively.  Secp256r1 MUST be used for the key exchange in all   cipher suites in this specification using AES-128; secp384r1 MUST be   used for the key exchange in all cipher suites in this specification   using AES-256.RFC 4492 requires that the uncompressed(0) form be   supported.  The ansiX962_compressed_prime(1) point format MAY also be   supported.   Clients desiring to negotiate only a Suite B TLS connection MUST   generate a "Supported Elliptic Curves Extension" containing only the   allowed curves.  Clients operating at a minimum level of security of   128 bits MUST include secp256r1 and SHOULD include secp384r1 in the   extension.  Clients operating at a minimum level of security of 192   bits MUST include secp384r1 in the extension.  In order to be able toSalter & Housley              Informational                     [Page 6]

RFC 6460                     Suite B for TLS                January 2012   verify ECDSA signatures, a client and server in a system configured   at a minimum level of security of 128 bits MUST support secp256r1 and   SHOULD support secp384r1 unless it is absolutely certain that the   client and server will never need to use or verify certificates   originating from an authority which uses an ECDSA-384 signing key.  A   client and server in a system configured at a minimum level of 192   bits MUST support secp384r1.   TLS connections that offer options that are both compliant and non-   compliant with Suite B MAY omit the extension, or they MAY send the   extension but offer other curves as well as the appropriate Suite B   ones.   Servers desiring to negotiate a Suite B TLS connection SHOULD check   for the presence of the extension, but they MUST NOT select a curve   that is not Suite B even if it is offered by the client.  This allows   a client that is willing to do either Suite B or non-Suite B TLS   connections to interoperate with a server that will only do Suite B   TLS.  If the client does not advertise an acceptable curve, the   server MUST generate a fatal "handshake_failure" alert and terminate   the connection.  Clients MUST check the chosen curve to make sure   that it is one of the Suite B curves.4.2.  Certificates   Server and client certificates used to establish a Suite B TLS   connection MUST be signed with ECDSA and MUST be compliant with the   "Suite B  Certificate and Certificate Revocation List (CRL) Profile",   [RFC5759].4.3.  signature_algorithms Extension   The signature_algorithms extension is defined inSection 7.4.1.4.1 of   TLS version 1.2 [RFC5246].  A Suite B TLS version 1.2 or later client   MUST include the signature_algorithms extension.  A Suite B TLS   client configured at a minimum level of security of 128 bits MUST   offer SHA-256 with ECDSA and SHOULD offer ECDSA with SHA-384 in the   signature_algorithms extension unless it is absolutely certain that a   client will never need to use or verify certificates originating from   an authority that uses an ECDSA-384 signing key.  A Suite B TLS   client configured at a minimum level of 192 bits MUST offer ECDSA   with SHA-384 in the signature_algorithms extension.   Following the guidance in [RFC5759], Suite B TLS connections MUST   only accept signature algorithms ECDSA with either SHA-256 or SHA-384   for certification path validation.  (Note that this is a change from   [RFC5430].)Salter & Housley              Informational                     [Page 7]

RFC 6460                     Suite B for TLS                January 2012   Other offerings MAY be included to indicate the acceptable signature   algorithms in cipher suites that are offered for interoperability   with servers not compliant with Suite B and to indicate the signature   algorithms that are acceptable for certification path validation in   non-compliant Suite B TLS connections.4.4.  CertificateRequest Message   A Suite B TLS server configured at a minimum level of security of 128   bits MUST include ECDSA with SHA-256 and SHOULD include ECDSA with   SHA-384 in the supported_signature_algorithms field of the   CertificateRequest message unless it is absolutely certain that a   server will never need to verify certificates originating from an   authority that uses an ECDSA-384 signing key.  A Suite B TLS server   configured at a minimum level of security of 192 bits MUST include   ECDSA with SHA-384 in the supported_signature_algorithms field.4.5.  CertificateVerify Message   Using the definitions found inSection 3.2, a Suite B TLS client MUST   use ECDSA-256 or ECDSA-384 for the signature in the CertificateVerify   message.  A Suite B TLS client configured at a minimum security level   of 128 bits MUST use ECDSA-256 or ECDSA-384.  A Suite B TLS client   configured at a minimum security level of 192 bits MUST use   ECDSA-384.4.6.  ServerKeyExchange Message Signature   In the TLS_ECDHE_ECDSA-collection of cipher suites, the server sends   its ephemeral ECDH public key and a specification of the   corresponding curve in the ServerKeyExchange message.  These   parameters MUST be signed with ECDSA using the server's private key,   which corresponds to the public key in the server's certificate.   A Suite B TLS server MUST sign the ServerKeyExchange message using   either ECDSA-256 or ECDSA-384.  A system configured at a minimum   level of security of 128 bits MUST use either ECDSA-256 or ECDSA-384.   A system configured at a minimum level of security of 192-bits MUST   use ECDSA-384.5.  Security Considerations   Most of the security considerations for this document are described   in "The Transport Layer Security (TLS) Protocol Version 1.2"   [RFC5246], "Elliptic Curve Cryptography (ECC) Cipher Suites for   Transport Layer Security (TLS)" [RFC4492], "AES Galois Counter ModeSalter & Housley              Informational                     [Page 8]

RFC 6460                     Suite B for TLS                January 2012   (GCM) Cipher Suites for TLS" [RFC5288], and "TLS Elliptic Curve   Cipher Suites with SHA-256/384 and AES Galois Counter Mode (GCM)"   [RFC5289].  Readers should consult those documents.   In order to meet the goal of a consistent security level for the   entire cipher suite, Suite B TLS implementations MUST ONLY use the   curves defined inSection 4.1.  Otherwise, it is possible to have a   set of symmetric algorithms with much weaker or stronger security   properties than the asymmetric (ECC) algorithms.6.  Acknowledgments   The authors would like to thank Eric Rescorla for his work on the   originalRFC 5430.   This work was supported by the US Department of Defense.7.  References7.1.  Normative References   [AES]      National Institute of Standards and Technology,              "Specification for the Advanced Encryption Standard              (AES)", FIPS 197, November 2001.   [DSS]      National Institute of Standards and Technology, "Digital              Signature Standard", FIPS 186-3, June 2009.   [PWKE]     National Institute of Standards and Technology,              "Recommendation for Pair-Wise Key Establishment Schemes              Using Discrete Logarithm Cryptography (Revised)", NIST              Special Publication 800-56A, March 2007.   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer              Security",RFC 4347, April 2006.   [RFC4492]  Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.              Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites              for Transport Layer Security (TLS)",RFC 4492, May 2006.   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security              (TLS) Protocol Version 1.2",RFC 5246, August 2008.Salter & Housley              Informational                     [Page 9]

RFC 6460                     Suite B for TLS                January 2012   [RFC5289]  Rescorla, E., "TLS Elliptic Curve Cipher Suites with              SHA-256/384 and AES Galois Counter Mode (GCM)",RFC 5289,              August 2008.   [RFC5759]  Solinas, J. and L. Zieglar, "Suite B Certificate and              Certificate Revocation List (CRL) Profile",RFC 5759,              January 2010.   [SHS]      National Institute of Standards and Technology, "Secure              Hash Standard", FIPS 180-3, October 2008.   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer              Security Version 1.2",RFC 6347, January 2012.7.2.  Informative References   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",RFC 2246, January 1999.   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security              (TLS) Protocol Version 1.1",RFC 4346, April 2006.   [RFC5288]  Salowey, J., Choudhury, A., and D. McGrew, "AES Galois              Counter Mode (GCM) Cipher Suites for TLS",RFC 5288,              August 2008.   [RFC5430]  Salter, M., Rescorla, E., and R. Housley, "Suite B Profile              for Transport Layer Security (TLS)",RFC 5430, March 2009.   [SECG]     Brown, D., "SEC 2: Recommended Elliptic Curve Domain              Parameters",http://www.secg.org/download/aid-784/sec2-v2.pdf, February              2010.   [SuiteB]   National Security Agency, "Fact Sheet NSA Suite B              Cryptography", November 2010,http://www.nsa.gov/ia/programs/suiteb_cryptography/.Salter & Housley              Informational                    [Page 10]

RFC 6460                     Suite B for TLS                January 2012Annex A.  A Transitional Suite B Profile for TLS 1.1 and 1.0   A transitional profile is described for use with TLS version 1.0   [RFC2246], TLS version 1.1 [RFC4346], or DTLS version 1.0 [RFC4347]   and the cipher suites defined in [RFC4492].  This profile uses the   Suite B cryptographic algorithms to the greatest extent possible and   provides backward compatibility.  While the transitional profile is   not a Suite B Compliant implementation of TLS, it provides a   transitional path towards the Suite B compliant Profile.   The following combination of algorithms and key sizes are defined for   use with the Suite B TLS transitional profile:   Transitional Suite B Combination 1 Transitional Suite B Combination 2   ---------------------------------- ----------------------------------   AES with 128-bit key in CBC mode   AES with 256-bit key in CBC mode   ECDH using the 256-bit prime       ECDH using the 384-bit prime      modulus curve P-256 [DSS]          modulus curve P-384 [DSS]   Standard TLS PRF                   Standard TLS PRF      (with SHA-1 and MD5)               (with SHA-1 and MD5)   HMAC with SHA-1 for message        HMAC with SHA-1 for message      authentication                     authentication   A Transitional Suite B TLS system configured at a minimum level of   security of 128 bits MUST use a TLS cipher suite satisfying either   Transitional Suite B Combination 1 in its entirety or Transitional   Suite B Combination 2 in its entirety.   A Transitional Suite B TLS system configured at a minimum level of   security of 192 bits MUST use a TLS cipher suite satisfying   Transitional Suite B Combination 2 in its entirety.   TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA and   TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA satisfy the requirements of   Transitional Suite B Combination 1 and Transitional Suite B   Combination 2, respectively.   A Transitional Suite B TLS client MUST implement TLS version 1.1 or   earlier.   A Transitional Suite B TLS system configured at a minimum level of   security of 128 bits, MUST offer the   TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA cipher suite and/or the   TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA cipher suite in theSalter & Housley              Informational                    [Page 11]

RFC 6460                     Suite B for TLS                January 2012   ClientHello message.  The TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA cipher   suite is preferred; if it is offered, it MUST appear before the   TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA cipher suite (if present).   A Transitional Suite B TLS system configured at a minimum level of   security of 192 bits MUST offer the   TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA cipher suite in the ClientHello   message.   One of these Transitional Suite B cipher suites MUST be the first   (most preferred) in the ClientHello message.   A Transitional Suite B client that offers interoperability with   servers that are not Suite B transitional MAY offer additional cipher   suites.  If any additional cipher suites are offered, they MUST   appear after the Transitional Suite B cipher suites in the   ClientHello message.   A Transitional Suite B TLS server MUST implement TLS version 1.1 or   earlier.   A Transitional Suite B TLS server configured at a minimum level of   security of 128 bits MUST accept the   TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA cipher suite (preferred) or the   TLS_ECHDE_ECDSA_WITH_AES_256_CBC_SHA cipher suite if offered in the   ClientHello message.   A Transitional Suite B TLS server configured at a minimum level of   security of 192 bits MUST accept the   TLS_ECHDE_ECDSA_WITH_AES_256_CBC_SHA cipher suite if offered in the   ClientHello message.   If a Transitional Suite B TLS server is not offered the Transitional   Suite B cipher suites and interoperability with non-Transitional   Suite B clients is desired, then the server MAY accept another   offered cipher suite that is considered acceptable by the server   administrator.   A Transitional Suite B TLS server MUST sign the ServerKeyExchange   message using ECDSA with SHA-1.  The Transitional Suite B profile   does not impose any additional restrictions on the server certificate   signature or the signature schemes used elsewhere in the   certification path.  Likewise, the Transitional Suite B Profile does   not impose restrictions on signature schemes used in the   certification path for the client's certificate when mutual   authentication is employed.Salter & Housley              Informational                    [Page 12]

RFC 6460                     Suite B for TLS                January 2012Annex B.  Changes sinceRFC 5430   The changes fromRFC 5430 [RFC5430] are as follows:    - The transitional profile for use with TLS version 1.0, TLS version      1.1, and DTLS version 1.0 was moved to an annex.    - The requirement ofSection 4 of RFC 5430 that a Suite B TLS 1.2      Client offer the TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 or      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 cipher suites was removed.    - A Suite B TLS system configured at a minimum level of security of      128 bits MUST use either TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256      or TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, with the first being      preferred.    - A Suite B TLS system configured at a minimum level of security of      128 bits MUST use either ECDSA on the secp256r1 curve with SHA-256      or ECDSA on the secp384r1 curve with SHA-384.  One party can      authenticate with ECDSA on the secp256r1 curve and SHA-256 when      the other party authenticates with ECDSA on the secp384r1 curve      and SHA-384.    - A system desiring to negotiate a Suite B TLS connection at a      minimum level of security of 128 bits MUST generate a "Supported      Elliptic Curves Extension", MUST include secp256r1 in the      extension, and SHOULD include secp384r1 in the extension.    - A client and server, in order to verify digital signatures in a      Suite B TLS system configured at a minimum level of security of      128 bits, MUST support secp256r1 and SHOULD support secp384r1.    - A Suite B TLS client configured at a minimum level of security of      128 bits MUST offer SHA-256 with ECDSA and SHOULD offer SHA-384      with ECDSA in the signature_algorithms extension.    - Certification path validation MUST only include certificates      containing an ECDSA public key on the secp256r1 curve or on the      secp384r1 curve.  The ECDSA public keys used in the certification      path MUST be in non-descending order of size from the end entity      public key to the root public key.    - A Suite B TLS server configured at a minimum level of security of      128 bits MUST include ECDSA with SHA-256 and SHOULD include ECDSA      with SHA-384 in the supported_signature_algorithms field of the      CertificateRequest message.Salter & Housley              Informational                    [Page 13]

RFC 6460                     Suite B for TLS                January 2012    - A Suite B TLS client configured at a minimum level of security of      128 bits MUST use ECDSA on the secp256r1 curve and SHA-256 or      ECDSA on the secp384r1 curve and SHA-384.    - A Suite B TLS server configured at a minimum level of security of      128 bits MUST use either ECDSA on the secp256r1 curve and SHA-256      or ECDSA on the secp384r1 curve and SHA-384 when signing the      ServerKeyExchange message.Authors' Addresses   Margaret Salter   National Security Agency   9800 Savage Rd.   Fort Meade  20755-6709   USA   EMail: misalte@nsa.gov   Russ Housley   Vigil Security   918 Spring Knoll Drive   Herndon  21070   USA   EMail: housley@vigilsec.comSalter & Housley              Informational                    [Page 14]