Require forward-secret ciphers

Why it matters

The server accepts ciphers where one stolen private key can decrypt all recorded past traffic. Forward-secret ciphers (ECDHE) are supported by every current client.

Staged change. Do this in stages and check each one before the next, so a mistake does not break your site or your mail.

The fix

1. Replace the cipher list with ECDHE-only AES-GCM and ChaCha20 suites, as in the snippets for your server. This removes RSA key exchange.
2. Stage it. Apply the change and test. Clients so old that they lack ECDHE (very old Android, Java 6 or Windows XP) will stop working, so roll back if you must support them.
3. Enable TLS 1.3 as well, since all its suites are forward secret.

nmap --script ssl-enum-ciphers -p 443 example.com

The examples use example.com. Replace it with your own domain.

Read the documentation ↗(opens in a new tab)

Related

• Reported by the cipher suites check
• Disable the RC4 cipher
• Disable the 3DES cipher
• Offer modern AEAD ciphers
• Retire the old TLS versions that use CBC ciphers