PuTTY wish aes-gcm

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summary: AES Galois Counter Mode (GCM) ciphers for SSH
class: wish: This is a request for an enhancement.
difficulty: tricky: Needs many tuits.
priority: low: We aren't sure whether to fix this or not.
fixed-in: c1a2114b28125572cf54c393bd51a6a39c4f00bd (0.78)

A combined cipher/MAC scheme using AES in a Galois Counter Mode (GCM) is defined for SSH by RFC 5647.

OpenSSH defines and implements its own versions, aes256-gcm@openssh.com and aes128-gcm@openssh.com (described in their protocol extension documentation), which use the same cryptography but avoid the badly-specified negotiation semantics in the RFC.

As of August 2022, PuTTY implements this - only the OpenSSH variants, so PuTTY won't use this cipher/MAC with SSH servers that only offer the unsuffixed aes256-gcm and aes128-gcm protocol IDs (if any such servers exist). (PuTTY's implementation makes basic use of processor cryptographic acceleration where available, although it could probably be improved upon.)

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Audit trail for this wish.

(last revision of this bug record was at 2022-09-11 23:46:37 +0100)