TLS_DHE_PSK_WITH_AES_128_CCM

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_DHE_PSK_WITH_AES_128_CCM combines DHE key exchange, PSK authentication, AES-128-CCM encryption and AEAD integrity protection. Each part is explained below with its known weaknesses; for the bigger picture see how cipher suites work.

Key exchange: DHE_PSK. A pre-shared key authenticates both sides and an ephemeral finite-field Diffie-Hellman exchange is mixed into the premaster secret, so a PSK leaked later does not expose recorded sessions (forward secrecy). It was specified in RFC 4279 (2005) together with plain PSK and RSA_PSK.

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 (counter mode with CBC-MAC), an AEAD with a 16-byte authentication tag. It only uses the block cipher's encryption function, so it suits small devices that have a hardware block cipher but no GCM support. RFC 6655 (2012) defined the AES-CCM suites for TLS 1.2 and RFC 7251 (2014) added the ECDHE-ECDSA variants.

Integrity: there is no separate MAC because the AEAD tag authenticates every record. The SHA256 at the end of the name selects the TLS 1.2 PRF hash used to derive keys and compute the Finished messages.

Why this rating

ssl.sh rating: Secure. The reasons:

• Ephemeral key exchange (forward secrecy) plus an AEAD cipher, the combination TLS 1.2 best practice asks for.

How ssl.sh rates cipher suites

Which TLS libraries support it

Support for TLS_DHE_PSK_WITH_AES_128_CCM 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_DHE_PSK_WITH_AES_128_CCM (0xC0,0xA6) is registered in the IANA TLS Cipher Suites registry with RFC 6655, “AES-CCM Cipher Suites for Transport Layer Security (TLS)” (July 2012, Standards Track) as its specification. RFC 9325 (2022), part of BCP 195, says TLS 1.2 implementations SHOULD NOT negotiate TLS_DHE_* suites, citing the Raccoon attack and the poor uptake of negotiated groups. RFC 10015 (2026) now says clients MUST NOT offer and servers MUST NOT select FFDHE suites in (D)TLS 1.2, and IANA changed this entry's Recommended value to D.

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;
ssl_ciphers 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-PSK-AES128-CCM';
ssl_prefer_server_ciphers off;

# Apache httpd (mod_ssl)
SSLProtocol -all +TLSv1.2 +TLSv1.3
SSLCipherSuite ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-PSK-AES128-CCM
SSLHonorCipherOrder off

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_ciphers 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:!DHE-PSK-AES128-CCM';

# Apache httpd (mod_ssl)
SSLCipherSuite ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:!DHE-PSK-AES128-CCM

How to test whether a server accepts it

Offer only TLS_DHE_PSK_WITH_AES_128_CCM with openssl s_client; if the handshake completes, the server accepts it:

openssl s_client -connect example.com:443 -tls1_2 -cipher DHE-PSK-AES128-CCM </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_DHE_PSK_WITH_AES_128_CCM 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.