TLS_DH_DSS_WITH_AES_128_CBC_SHA

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_DH_DSS_WITH_AES_128_CBC_SHA combines DH key exchange, DSS authentication, AES-128-CBC encryption and SHA1 integrity protection. Each part is explained below with its known weaknesses; for the bigger picture see how cipher suites work.

Key exchange: static (non-ephemeral) Diffie-Hellman. The server's DH public key is fixed in its certificate instead of being generated per handshake, so there is no forward secrecy, and the server needs a certificate that carries a DH key rather than an ordinary RSA or ECDSA key. The DSS in the name only says which algorithm the CA used to sign that certificate.

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: CBC with MAC-then-encrypt. TLS 1.2 and earlier compute the HMAC over the plaintext, then pad and encrypt, so a receiver has to decrypt before it can check integrity. That ordering produced a long run of padding-oracle attacks: BEAST (CVE-2011-3389) against TLS 1.0's predictable IVs, Lucky Thirteen (CVE-2013-0169, 2013), which times the MAC check, and POODLE (CVE-2014-3566, 2014) against SSL 3.0's unchecked padding. RFC 9325 (2022) says CBC suites SHOULD NOT be used unless the encrypt_then_mac extension (RFC 7366) is also negotiated.

Integrity: HMAC-SHA1. SHA-1 collisions are practical (SHAttered, 2017), but HMAC does not rely on collision resistance, so HMAC-SHA1 record MACs are not considered broken; this suite's weak points lie elsewhere. When TLS 1.2 is negotiated, keys are derived with the SHA-256 PRF, which RFC 5246 (2008) applies to every cipher suite defined before it.

Why this rating

ssl.sh rating: Weak. The reasons:

• CBC mode with a separate MAC (MAC-then-encrypt), the construction behind padding-oracle attacks such as Lucky Thirteen; prefer an AEAD cipher.
• 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_DH_DSS_WITH_AES_128_CBC_SHA 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_DH_DSS_WITH_AES_128_CBC_SHA (0x00,0x30) is registered in the IANA TLS Cipher Suites registry with RFC 5246, “The Transport Layer Security (TLS) Protocol Version 1.2” (August 2008, Standards Track) as its specification. RFC 5246 has since been obsoleted by RFC 8446 (2018) and RFC 9846 (2026). RFC 9325 (2022), part of BCP 195, says implementations SHOULD NOT negotiate static DH or ECDH key agreement because neither has forward secrecy. RFC 10015 (2026) now says clients MUST NOT offer and servers MUST NOT select non-ephemeral FFDH suites in (D)TLS 1.2, and IANA changed this entry's Recommended value to D.

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_DH_DSS_WITH_AES_128_CBC_SHA, 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_DH_DSS_WITH_AES_128_CBC_SHA 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.