ffdhe3072
ffdhe3072 is a named 3072-bit finite-field Diffie-Hellman group from RFC 7919, offered by libraries after ffdhe2048.
What it is
ffdhe3072 (group 257) is the 3072-bit named finite-field Diffie-Hellman group from RFC 7919. It is larger than ffdhe2048 and gives about 125 bits of security according to that RFC, similar to x25519 and P-256, but with much larger keys and slower computation.
Like the other named groups, it lets a client say which finite-field parameters it accepts, instead of trusting whatever prime a TLS 1.2 server picks for its DHE suites. In TLS 1.3 it can be used directly for the key exchange through key_share.
RFC 7919 also defines ffdhe4096, ffdhe6144 and ffdhe8192. Clients seldom offer the larger ones because each step makes the handshake noticeably slower.
In TLS 1.3, a server that picks a group without a matching key share from the client must send a HelloRetryRequest first, which costs an extra round trip.
Who sends it
Measured on 2026-10-25 against our own test server: sent by 7 of 12 clients. Position counts from 1 and ignores GREASE values.
Why it matters for fingerprinting
The same clients that offer ffdhe2048 offer ffdhe3072 right after it: Python requests, httpx, Node.js fetch, Guzzle, Debian curl and the Firefox profile of curl-impersonate. Debian curl is the only measured client that goes on to list ffdhe4096, ffdhe6144 and ffdhe8192 as well.
Check whether your client sends it
Open the test from your browser, or call it from your script, and look for ffdhe3072 in the TLS details.
Run the TLS fingerprint test