nx_tls13_server_session_derive_traffic.nx

nx_tls13_server_session_derive_traffic.nx -- 5th TLS server stone. After derive_hs_secrets produced the Handshake-Secret, derive the per-direction handshake traffic secrets + their AEAD key + IV per RFC 8446 §7.1: c_hs_traffic = Derive-Secret(HS, "c hs traffic", ClientHello..ServerHello) s_hs_traffic = Derive-Secret(HS, "s hs traffic", ClientHello..ServerHello) *_hs_key = HKDF-Expand-Label(*_hs_traffic, "key", "", aead_key_len) *_hs_iv = HKDF-Expand-Label(*_hs_traffic, "iv", "", aead_iv_len) For ChaCha20-Poly1305: key=32 bytes, iv=12 bytes. This stone is the precondition for emit_ee_cert (next stone), which must AEAD-encrypt the EncryptedExtensions + Certificate messages under server_hs_key + server_hs_iv. State: requires EE_SENT (set by derive_hs_secrets); does not advance state -- it's a continuation of the key-schedule preparation. Subsequent emit_ee_cert advances state CERT_SENT. license_tier: ORIGINAL