TLS_AES_128_CCM_8_SHA256

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_AES_128_CCM_8_SHA256 combines the AES-128-CCM-8 AEAD with the SHA256 hash. Each part is explained below with its known weaknesses; for the bigger picture see how cipher suites work.

TLS 1.3 suites only describe the symmetric part. The TLS 1.3 specification (RFC 9846) says its suites specify only the symmetric ciphers and cannot be used with TLS 1.2. Key exchange is negotiated separately through the supported_groups and key_share extensions (for example X25519, P-256 or the hybrid X25519MLKEM768) and is always ephemeral (EC)DHE unless a client resumes in the PSK-only psk_ke mode, so a full handshake always has forward secrecy. The certificate signature algorithm (for example RSA-PSS, ECDSA or Ed25519) is negotiated with signature_algorithms. In TLS_AES_128_CCM_8_SHA256, SHA256 is the hash behind the HKDF key schedule and the handshake transcript hash.

Encryption: AES with a 128-bit key, the 128-bit block cipher of FIPS 197 (2001). Most server and phone CPUs have AES instructions (AES-NI on x86, the ARMv8 cryptography extensions), which make it fast and avoid the cache-timing leaks of table-based software implementations.

Mode: CCM_8, AES-CCM with the authentication tag cut from 16 to 8 bytes (RFC 6655). That saves 8 bytes per record on constrained links, but a forged record now passes with probability 2^-64 per attempt instead of 2^-128, and no CCM_8 suite is marked Recommended in the IANA registry.

Why this rating

ssl.sh rating: Secure. The reasons:

• A TLS 1.3 AEAD suite, but IANA doesn't mark it "Recommended" (truncated tag, national or experimental algorithm, or limited client support).

How ssl.sh rates cipher suites

Which TLS libraries support it

Support for TLS_AES_128_CCM_8_SHA256 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. Also implemented by: OpenSSL 3.5 and GnuTLS.

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_AES_128_CCM_8_SHA256 (0x13,0x05) is registered in the IANA TLS Cipher Suites registry with RFC 9846, “The Transport Layer Security (TLS) Protocol Version 1.3” (July 2026, Standards Track) as its specification. The registry also cites an IESG action dated 16 August 2018 for this entry. TLS 1.3 was first published as RFC 8446 (2018) and republished as RFC 9846 (2026), which obsoletes RFC 8446. 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

Enable

Both servers use OpenSSL names. The snippet keeps a modern list and adds this suite; TLS 1.3 suites are configured separately from the TLS 1.2 list.

# Nginx
ssl_protocols TLSv1.2 TLSv1.3;
# nginx 1.19.4+ with OpenSSL 1.1.1+
ssl_conf_command Ciphersuites TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256:TLS_AES_128_CCM_8_SHA256;

# Apache httpd (mod_ssl)
SSLProtocol -all +TLSv1.2 +TLSv1.3
SSLCipherSuite TLSv1.3 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256:TLS_AES_128_CCM_8_SHA256

Disable

Either leave the suite out of your list or exclude it explicitly with a leading "!". Reload the server afterwards (nginx -s reload, apachectl graceful).

# Nginx
ssl_conf_command Ciphersuites TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256;

# Apache httpd (mod_ssl)
SSLCipherSuite TLSv1.3 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256

How to test whether a server accepts it

Offer only TLS_AES_128_CCM_8_SHA256 with openssl s_client; if the handshake completes, the server accepts it:

openssl s_client -connect example.com:443 -tls1_3 -ciphersuites TLS_AES_128_CCM_8_SHA256 </dev/null

If the handshake succeeds, the server accepts the suite; "no cipher match" or a handshake failure means it doesn't.

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_AES_128_CCM_8_SHA256 in its output:

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

If your nmap build doesn't print a TLS 1.3 section, rely on the openssl command instead.

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.