TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC combines GOST key exchange, GOST authentication, Kuznyechik-CTR encryption and OMAC integrity protection. Each part is explained below with its known weaknesses; for the bigger picture see how cipher suites work.

Key exchange and authentication: GOST. The suite uses the Russian GOST R 34.10-2012 elliptic-curve algorithms with the 256-bit GOST R 34.11-2012 (Streebog) hash, as specified for TLS 1.2 in RFC 9189 (2022); the server authenticates with a GOST certificate.

Encryption: Kuznyechik, the Russian 128-bit block cipher from GOST R 34.12-2015, with a 256-bit key.

Mode: counter-mode encryption with a separate OMAC (CMAC) authenticator, as specified for TLS 1.2 in RFC 9189 (2022). Unlike an AEAD, encryption and integrity are two separate steps.

Why this rating

ssl.sh rating: Weak. The reasons:

• Not an AEAD cipher: confidentiality and integrity rely on a separate MAC construction.
• No forward secrecy: the session keys are protected by the server's long-term key (static RSA/DH/ECDH, PSK or Kerberos), so a leaked key decrypts recorded traffic.

How ssl.sh rates cipher suites

Which TLS libraries support it

Support for TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC as read from each library's own source code or official documentation on 2026-11-10. “Enabled by default” means the library negotiates it with no configuration; “off by default” means it is implemented but has to be switched on.

None of the 9 libraries tracked here enables it by default. None of them implements it.

NSS shows the library's own defaults; Firefox switches every NSS suite off at start-up and re-enables only those with a security.ssl3.* or security.tls13.* preference. Java defaults are derived from the jdk.tls.disabledAlgorithms value Oracle documents for JDK 21, which later updates may extend. The OpenSSL and GnuTLS rows only show whether the suite is implemented.

History and standards status

TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC (0xC1,0x00) is registered in the IANA TLS Cipher Suites registry with RFC 9189, “GOST Cipher Suites for Transport Layer Security (TLS) Protocol Version 1.2” (March 2022, Informational) as its specification. The registry marks it N, which per RFC 8447 (2018) means it either hasn't been through the IETF consensus process, has limited applicability or is meant only for specific use cases, not necessarily that it is flawed.

Enable or disable it in Nginx and Apache

OpenSSL 3.5 doesn't implement this suite, so stock Nginx and Apache httpd builds can't offer it and you don't need to disable it.

How to test whether a server accepts it

OpenSSL 3.5 cannot offer TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC, so openssl s_client can't test it directly; use a scanner that implements the suite itself.

nmap's ssl-enum-ciphers script connects repeatedly, trying one suite at a time, and lists every suite the server accepts with a grade from A to F. Look for TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC in its output:

nmap --script ssl-enum-ciphers -p 443 example.com

To decode a name or hex code, use the cipher suite lookup; the SSL checker shows which protocol versions a live server accepts and the cipher suite it negotiates.