TLS_RSA_PSK_WITH_NULL_SHA384

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_RSA_PSK_WITH_NULL_SHA384 combines RSA key exchange, PSK authentication, NULL encryption and SHA384 integrity protection. Each part is explained below with its known weaknesses; for the bigger picture see how cipher suites work.

Key exchange: RSA_PSK (RFC 4279). The server authenticates with an RSA certificate and the client with a pre-shared key; the client encrypts part of the premaster secret with the server's RSA public key. Like plain RSA key exchange it has no forward secrecy.

Encryption: none. Records are only protected by the SHA384 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-SHA384 over each record, computed before encryption (MAC-then-encrypt). In TLS 1.2 the SHA384 in the name also selects the PRF hash. Because of that, the suite needs TLS 1.2 and cannot be used with older versions.

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_RSA_PSK_WITH_NULL_SHA384 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_RSA_PSK_WITH_NULL_SHA384 (0x00,0xB9) is registered in the IANA TLS Cipher Suites registry with RFC 5487, “Pre-Shared Key Cipher Suites for TLS with SHA-256/384 and AES Galois Counter Mode” (March 2009, Standards Track) as its specification. RFC 9325 (2022), part of BCP 195, says implementations MUST NOT negotiate suites with NULL encryption. RFC 10015 (2026) now says clients MUST NOT offer and servers MUST NOT select RSA key-exchange 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:!RSA-PSK-NULL-SHA384';

# 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:!RSA-PSK-NULL-SHA384

How to test whether a server accepts it

Offer only TLS_RSA_PSK_WITH_NULL_SHA384 with openssl s_client; if the handshake completes, the server accepts it:

openssl s_client -connect example.com:443 -tls1_2 -cipher RSA-PSK-NULL-SHA384 </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_RSA_PSK_WITH_NULL_SHA384 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.