pub const NOISE_PATTERN_XXFALLBACK: &str = "Noise_XXfallback_25519_AESGCM_SHA256";Expand description
Noise XXfallback pattern name (36 bytes, hashed by Noise spec).
Used to recover gracefully when an in-flight IK handshake is rejected by
the server (server’s static rotated, cached pub key is stale). The client
reuses the ephemeral it already sent in the IK ClientHello and processes
the server’s XX-style ServerHello. Mirrors WA Web’s A constant.