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Security Transport Layer Security Internet-Draft This document updates the changes to TLS and DTLS IANA registries made in RFC 8447. It adds a new value "D" for discouraged to the Recommended column of the selected TLS registries and adds a "Comment" column to all active registries that do not already have a "Comment" column. Finally, it updates the registration request instructions. This document updates the following RFCs: 3749, 5077, 4680, 5246, 5705, 5878, 6520, 7301, and 8447. About This Document Status information for this document may be found at . Discussion of this document takes place on the Transport Layer Security Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .
Introduction This document instructs IANA to make changes to a number of the IANA registries related to Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS). These changes update the changes made in . This specification adds a new value "D" for discouraged to the Recommended column of the selected TLS registries and adds a "Comment" column to all active registries that do not already have a "Comment" column. This specication also updates the registration request instructions.
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 when, and only when, they appear in all capitals, as shown here.
Updating "Recommended" Column's Values The instructions in this document update the Recommended column, originally added in to add a third value, "D", indicating that a value is "Discouraged". The permitted values of the "Recommended" column are:
Y:
Indicates that the IETF has consensus that the item is RECOMMENDED. This only means that the associated mechanism is fit for the purpose for which it was defined. Careful reading of the documentation for the mechanism is necessary to understand the applicability of that mechanism. The IETF could recommend mechanisms that have limited applicability, but will provide applicability statements that describe any limitations of the mechanism or necessary constraints on its use.
N:
Indicates that the item has not been evaluated by the IETF and that the IETF has made no statement about the suitability of the associated mechanism. This does not necessarily mean that the mechanism is flawed, only that no consensus exists. The IETF might have consensus to leave an items marked as "N" on the basis of its having limited applicability or usage constraints.
D:
Indicates that the item is discouraged. This marking could be used to identify mechanisms that might result in problems if they are used, such as a weak cryptographic algorithm or a mechanism that might cause interoperability problems in deployment. When marking a registry entry as “D”, either the References or the Comments Column MUST include sufficient information to determine why the marking has been applied. Implementers and users SHOULD consult the linked references associated with the item to determine the conditions under which the item SHOULD NOT or MUST NOT be used.
Setting a value to "Y" or "D" or transitioning the value from "Y" or "D" in the "Recommended" column requires IETF Standards Action or IESG Approval . Not all items defined in Standards Track RFCs need to be set to "Y" or "D". Any item not otherwise specified is set to "N". The column is blank for values that are unassigned or reserved unless specifically set.
Recommended Note Existing registries have a note on the meaning of the Recommended column. For the registries discussed in the subsequent sections this note is updated with a sentence describing the "D" value as follows:
Note:
If "Recommended" column is set to "N", it does not necessarily mean that it is flawed; rather, it indicates that the item either has not been through the IETF consensus process, has limited applicability, or is intended only for specific use cases. If the "Recommended" column is set to "D" the item is discouraged and SHOULD NOT or MUST NOT be used, depending upon the situation; consult the item’s references for clarity.
TLS ExtensionType Values Registry In order to reflect the changes in the Recommended column allocation, IANA is requested to update the TLS ExtensionType Values registry as follows:
  • Adjust the registration procedure related to setting the “Recommended” column as follows:
  • Add a reference to this document under the reference heading.
  • Update the "Recommended" column with the changes as listed below. Entries keep their existing "Y" and "N" entries except for the entries in following table. IANA is requested to add a reference to this document for these entries.
Value Extension Recommended
4 truncated_hmac D
53 connection_id (deprecated) D
40 Reserved D
46 Reserved D
  • Update note on the Recommended column with text in .
  • For the truncated_hmac, add the following link to Reference column: https://www.iacr.org/archive/asiacrypt2011/70730368/70730368.pdf
  • For the two Reserved values above, add the following link in the Reference column: https://mailarchive.ietf.org/arch/msg/tls-reg-review/5BD62HBFjo_AsW-Y8ohVuWEe1gI/
TLS Cipher Suites Registry Several categories of ciphersuites are discouraged for general use and are marked as "D". Ciphersuites that use NULL encryption do not provide the confidentiality normally expected of TLS. Protocols and applications are often designed to require confidentiality as a security property. These ciphersuites MUST NOT be used in those cases. Ciphersuites marked as EXPORT use weak ciphers and were deprecated in TLS 1.1 . Cipher suites marked as anon do not provide any authentication and are vulnerable to on-path attacks and are deprecated in TLS 1.1 . RC4 is a weak cipher and is deprecated in . DES and IDEA are not considered secure for general use and are deprecated in . Nor is MD5 or SHA-1 and these are deprecated in . In order to reflect the changes in the Recommended column allocation, IANA is requested to update the TLS ExtensionType Values registry as follows:
  • Adjust the registration procedure related to setting the “Recommended” column as follows:
  • Add a reference to this document under the reference heading.
  • Update the "Recommended" column with the changes as listed below. Entries keep their existing "Y" and "N" entries except for the entries in following table. IANA is requested to add a reference to this document for these entries. This document does not make any changes to the DTLS-OK column.
Value Cipher Suite Name Recommended
0x00,0x1E TLS_KRB5_WITH_DES_CBC_SHA D
0x00,0x20 TLS_KRB5_WITH_RC4_128_SHA D
0x00,0x21 TLS_KRB5_WITH_IDEA_CBC_SHA D
0x00,0x22 TLS_KRB5_WITH_DES_CBC_MD5 D
0x00,0x24 TLS_KRB5_WITH_RC4_128_MD5 D
0x00,0x25 TLS_KRB5_WITH_IDEA_CBC_MD5 D
0x00,0x26 TLS_KRB5_EXPORT_WITH_DES_CBC_40_SHA D
0x00,0x27 TLS_KRB5_EXPORT_WITH_RC2_CBC_40_SHA D
0x00,0x28 TLS_KRB5_EXPORT_WITH_RC4_40_SHA D
0x00,0x29 TLS_KRB5_EXPORT_WITH_DES_CBC_40_MD5 D
0x00,0x2A TLS_KRB5_EXPORT_WITH_RC2_CBC_40_MD5 D
0x00,0x2B TLS_KRB5_EXPORT_WITH_RC4_40_MD5 D
0x00,0x2C TLS_PSK_WITH_NULL_SHA D
0x00,0x8A TLS_PSK_WITH_RC4_128_SHA D
0x00,0xB0 TLS_PSK_WITH_NULL_SHA256 D
0x00,0xB1 TLS_PSK_WITH_NULL_SHA384 D
0xC0,0x06 TLS_ECDHE_ECDSA_WITH_NULL_SHA D
0xC0,0x07 TLS_ECDHE_ECDSA_WITH_RC4_128_SHA D
0xC0,0x10 TLS_ECDHE_RSA_WITH_NULL_SHA D
0xC0,0x11 TLS_ECDHE_RSA_WITH_RC4_128_SHA D
0xC0,0x33 TLS_ECDHE_PSK_WITH_RC4_128_SHA D
0xC0,0x39 TLS_ECDHE_PSK_WITH_NULL_SHA D
0xC0,0x3A TLS_ECDHE_PSK_WITH_NULL_SHA256 D
0xC0,0x3B TLS_ECDHE_PSK_WITH_NULL_SHA384 D
0xC0,0xB4 TLS_SHA256_SHA256 D
0xC0,0xB5 TLS_SHA384_SHA384 D
  • Update note on the Recommended column with text in .
TLS Supported Groups Registry In order to reflect the changes in the Recommended column allocation, IANA is requested to update the TLS Supported Groups registry as follows:
  • Update the registration policy to include:
  • Add a reference to this document under the reference heading.
  • Update the "Recommended" column with the changes as listed below. Entries keep their existing "Y" and "N" entries except for the entries in following table. IANA is requested to add a reference to this document for these entries.
Value Curve Recommended
1 sect163k1 D
2 sect163r1 D
3 sect163r2 D
4 sect193r1 D
5 sect193r2 D
6 sect233k1 D
7 sect233r1 D
8 sect239k1 D
15 secp160k1 D
16 secp160r1 D
17 secp160r2 D
18 secp192k1 D
19 secp192r1 D
20 secp224k1 D
21 secp224r1 D
  • Update note on the Recommended column with text in .
  • Remove the "Elliptic curve groups" note from the registration procedures table.
  • For each of the entries above, add the following link to the Comment column: https://datatracker.ietf.org/meeting/118/materials/slides-118-tls-rfc8447bis-00
TLS Exporter Labels Registry This document updates the registration procedure for the TLS Exporter Labels registry and updates the Recommended column allocation. IANA is requested to update the TLS Exporter Labels Registry as follows:
  • Change the registration procedure from Specification Required to Expert Review and update it to include:
  • Add a reference to this document under the reference heading.
  • Entries keep their existing Recommended column "Y" and "N" entries
  • Update note on the Recommended column with text in .
  • Update the note on the role of the expert reviewer as follows.
Note:
The role of the designated expert is described in . Even though this registry does not require a specification, the designated expert will strongly encourage registrants to provide a link to a publicly available specification. An Internet-Draft (that is posted and never published as an RFC) or a document from another standards body, industry consortium, university site, etc. are suitable for these purposes. The expert may provide more in-depth reviews, but their approval should not be taken as an endorsement of the exporter label. The expert also verifies that the label is a string consisting of printable ASCII characters beginning with "EXPORTER". IANA MUST also verify that one label is not a prefix of any other label. For example, labels "key" or "master secretary" are forbidden.
TLS Certificate Types Registry In order to reflect the changes in the Recommended column allocation, IANA is requested to update the TLS Certificate Types registry as follows:
  • Adjust the registration procedure related to setting the “Recommended” column as follows:
  • Add a reference to this document under the reference heading.
  • Entries keep their existing Recommended column "Y" and "N" entries.
  • Update note on the Recommended column with text in .
TLS HashAlgorithm Registry Though TLS 1.0 and TLS 1.1 were deprecated , TLS 1.2 will be in use for some time. In order to reflect the changes in the Recommended column allocation, IANA is requested to update the TLS HashAlgorithm Registry as follows:
  • Update the registration procedure to include:
  • Add a reference to this document under the reference heading.
  • Update the TLS HashAlgorithm registry to add a "Recommended" column as follows:
Value Description Recommended
0 none Y
1 md5 D
2 sha1 D
3 sha224 D
4 sha256 Y
5 sha384 Y
6 sha512 Y
8 Intrinsic Y
  • Add note on the Recommended column with text in .
TLS SignatureAlgorithm Registry Though TLS 1.0 and TLS 1.1 were deprecated , TLS 1.2 will be in use for some time. In order to reflect the changes in the Recommended column allocation, IANA is requested to update the TLS SignatureAlgorithm registry as follows:
  • Update the registration procedure to include:
  • Add a reference to this document under the reference heading.
  • Update the TLS SignatureAlgorithm registry to add a "Recommended" column as follows:
Value Description Recommended
0 anonymous N
1 rsa Y
2 dsa N
3 ecdsa Y
7 ed25519 Y
8 ed448 Y
64 gostr34102012_256 N
65 gostr34102012_512 N
  • Add note on the Recommended column with text in .
TLS ClientCertificateType Identifiers Registry Though TLS 1.0 and TLS 1.1 were deprecated , TLS 1.2 will be in use for some time. In order to refect the changes in the Recommended column allocation, IANA is requested to update the TLS ClientCertificateType Identifiers registry as follows:
  • Update the registration procedure to include:
  • Add a reference to this document under the reference heading.
  • Update the TLS ClientCertificateType Identifiers registry to add a "Recommended" column as follows:
Value Description Recommended
1 rsa_sign Y
2 dss_sign N
3 rsa_fixed_dh N
4 dss_fixed_dh N
5 rsa_ephemeral_dh_RESERVED D
6 dss_ephemeral_dh_RESERVED D
20 fortezza_dms_RESERVED D
64 ecdsa_sign Y
65 rsa_fixed_ecdh N
66 ecdsa_fixed_ecdh N
67 gost_sign256 N
68 gost_sign512 N
  • Add note on the Recommended column with text in .
TLS PskKeyExchangeMode Registry In order to reflect the changes in the Recommended column allocation, IANA is requested to update the TLS PskKeyExchangeMode registry as follows:
  • Update the registration procedure to include:
  • Add a reference to this document under the reference heading.
  • Entries keep their existing Recommended column "Y" and "N" entries.
  • Update note on the Recommended column with text in .
TLS SignatureScheme Registry In order to reflect the changes in the Recommended column allocation, IANA is requested to update the TLS SignatureScheme registry as follows:
  • Update the registration procedure to include:
  • IANA is requested to add a reference to this document under the reference heading.
  • Entries keep their existing Recommended column "Y" and "N" entries.
  • Update note on the Recommended column with text in .
Adding "Comment" Column IANA is requested to add a "Comment" column to the following registries:
  • TLS ExtensionType Values
  • TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs
  • TLS CachedInformationType Values
  • TLS Certificate Compression Algorithm IDs
  • TLS Cipher Suites
  • TLS ContentType
  • TLS EC Point Formats
  • TLS EC Curve Types
  • TLS Supplemental Data Formats (SupplementalDataType)
  • TLS UserMappingType Values
  • TLS Authorization Data Formats
  • TLS Heartbeat Message Types
  • TLS Heartbeat Modes
  • TLS SignatureScheme
  • TLS PskKeyExchangeMode
  • TLS KDF Identifiers
This list of registries is all registries that do not already have a "Comment" or "Notes" column or that were not orphaned by TLS 1.3.
Expert Review of Current and Potential IETF and IRTF Documents The intent of the Specification Required choice for TLS code points is to allow for easy registration for code points associated with protocols and algorithms that are not being actively developed inside IETF or IRTF. When TLS-based technologies are being developed inside the IRTF/IETF they should be done in coordination with the TLS WG in order to provide appropriate review. For this reason, unless the TLS WG chairs indicate otherwise via email, designated experts should decline code point registrations for documents which have already been adopted or are being proposed for adoption by IETF working groups or IRTF research groups.
Registration Requests Registration requests MUST be submitted in one of two ways:
  1. By sending email to iana-prot-param@iana.org; this email SHOULD use an appropriate subject (e.g., "Request to register value in TLS bar registry").
  2. Using the online form at https://www.iana.org/form/protocol-assignment.
Specification Required registry requests are registered after a three-week review period on the advice of one or more designated experts. However, to allow for the allocation of values prior to publication, the designated experts may approve registration once they are satisfied that such a specification will be published.
Security Considerations The change to Specification Required from IETF Review lowers the amount of review provided for cipher suites and supported groups. This change reflects reality in that the TLS WG essentially provided no cryptographic review of the cipher suites or supported groups. This was especially true of national cipher suites. Recommended algorithms are regarded as secure for general use at the time of registration; however, cryptographic algorithms and parameters will be broken or weakened over time. It is possible that the "Recommended" status in the registry lags behind the most recent advances in cryptanalysis. Implementers and users need to check that the cryptographic algorithms listed continue to provide the expected level of security. Designated experts ensure the specification is publicly available. They may provide more in-depth reviews. Their review should not be taken as an endorsement of the cipher suite, extension, supported group, etc.
IANA Considerations This document is entirely about changes to TLS-related IANA registries.
Normative References IANA Registry Updates for TLS and DTLS This document describes a number of changes to TLS and DTLS IANA registries that range from adding notes to the registry all the way to changing the registration policy. These changes were mostly motivated by WG review of the TLS- and DTLS-related registries undertaken as part of the TLS 1.3 development process. This document updates the following RFCs: 3749, 5077, 4680, 5246, 5705, 5878, 6520, and 7301. Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Guidelines for Writing an IANA Considerations Section in RFCs Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA). To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry. This is the third edition of this document; it obsoletes RFC 5226. The Transport Layer Security (TLS) Protocol Version 1.1 This document specifies Version 1.1 of the Transport Layer Security (TLS) protocol. The TLS protocol provides communications security over the Internet. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery. Prohibiting RC4 Cipher Suites This document requires that Transport Layer Security (TLS) clients and servers never negotiate the use of RC4 cipher suites when they establish connections. This applies to all TLS versions. This document updates RFCs 5246, 4346, and 2246. DES and IDEA Cipher Suites for Transport Layer Security (TLS) Transport Layer Security (TLS) versions 1.0 (RFC 2246) and 1.1 (RFC 4346) include cipher suites based on DES (Data Encryption Standard) and IDEA (International Data Encryption Algorithm) algorithms. DES (when used in single-DES mode) and IDEA are no longer recommended for general use in TLS, and have been removed from TLS version 1.2 (RFC 5246). This document specifies these cipher suites for completeness and discusses reasons why their use is no longer recommended. This memo provides information for the Internet community. Deprecating MD5 and SHA-1 Signature Hashes in TLS 1.2 and DTLS 1.2 The MD5 and SHA-1 hashing algorithms are increasingly vulnerable to attack, and this document deprecates their use in TLS 1.2 and DTLS 1.2 digital signatures. However, this document does not deprecate SHA-1 with Hashed Message Authentication Code (HMAC), as used in record protection. This document updates RFC 5246. Deprecating TLS 1.0 and TLS 1.1 This document formally deprecates Transport Layer Security (TLS) versions 1.0 (RFC 2246) and 1.1 (RFC 4346). Accordingly, those documents have been moved to Historic status. These versions lack support for current and recommended cryptographic algorithms and mechanisms, and various government and industry profiles of applications using TLS now mandate avoiding these old TLS versions. TLS version 1.2 became the recommended version for IETF protocols in 2008 (subsequently being obsoleted by TLS version 1.3 in 2018), providing sufficient time to transition away from older versions. Removing support for older versions from implementations reduces the attack surface, reduces opportunity for misconfiguration, and streamlines library and product maintenance. This document also deprecates Datagram TLS (DTLS) version 1.0 (RFC 4347) but not DTLS version 1.2, and there is no DTLS version 1.1. This document updates many RFCs that normatively refer to TLS version 1.0 or TLS version 1.1, as described herein. This document also updates the best practices for TLS usage in RFC 7525; hence, it is part of BCP 195.