TLS_PSK_WITH_3DES_EDE_CBC_SHA

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_PSK_WITH_3DES_EDE_CBC_SHA combines PSK key exchange, PSK authentication, 3DES-EDE-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 and authentication: pre-shared key (PSK), defined in RFC 4279 (2005). Both sides already hold the same symmetric secret, provisioned out of band, and the handshake only names which key to use (the PSK identity). No certificates and no public-key operations are needed, which is why PSK suites appear in constrained devices and closed systems rather than on the public web. Plain PSK has no forward secrecy: whoever learns the key can decrypt every session made with it.

Encryption: 3DES (Triple DES, EDE) in CBC mode. Meet-in-the-middle attacks reduce its nominal 168-bit key to about 112 bits of security, and its 64-bit block is the real problem: Sweet32 (CVE-2016-2183, Bhargavan and Leurent, 2016) recovered an HTTP cookie after capturing about 785 GB on one long-lived connection, because block collisions become likely after roughly 2^32 blocks. NIST disallowed Triple DES for encryption after 2023.

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: Insecure. The reasons:

• Uses 3DES, a 64-bit block cipher vulnerable to the Sweet32 birthday attack (CVE-2016-2183).

How ssl.sh rates cipher suites

Which TLS libraries support it

Support for TLS_PSK_WITH_3DES_EDE_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. Also implemented by: 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_PSK_WITH_3DES_EDE_CBC_SHA (0x00,0x8B) is registered in the IANA TLS Cipher Suites registry with RFC 4279, “Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)” (December 2005, Standards Track) as its specification. RFC 9325 (2022), part of BCP 195, says implementations SHOULD NOT negotiate suites using algorithms with less than 128 bits of security, and counts 3DES at 112 bits. 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_PSK_WITH_3DES_EDE_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_PSK_WITH_3DES_EDE_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.