TLS_DHE_PSK_WITH_NULL_SHA

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_DHE_PSK_WITH_NULL_SHA combines DHE key exchange, PSK authentication, NULL 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: 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: none. Records are only protected by the SHA1 MAC, so anyone on the path can read the plaintext. RFC 9325 (2022) says implementations MUST NOT negotiate NULL-encryption suites, while noting they can still be useful for testing and debugging.

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:

• No encryption (NULL cipher): traffic is sent in clear text.

How ssl.sh rates cipher suites

Which TLS libraries support it

Support for TLS_DHE_PSK_WITH_NULL_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: 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_NULL_SHA (0x00,0x2D) is registered in the IANA TLS Cipher Suites registry with RFC 4785, “Pre-Shared Key (PSK) Ciphersuites with NULL Encryption for Transport Layer Security (TLS)” (January 2007, Standards Track) as its specification. RFC 9325 (2022), part of BCP 195, says implementations MUST NOT negotiate suites with NULL encryption. 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

This suite is rated insecure, so we don't show how to enable it. Make sure it's excluded.

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-NULL-SHA';

# 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-NULL-SHA

How to test whether a server accepts it

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

openssl s_client -connect example.com:443 -tls1_2 -cipher DHE-PSK-NULL-SHA </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_NULL_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.