The TLS 1.3 Handshake: Certificate Chain, SNI, ALPN and Post-Quantum Key Exchange
TLS 1.3 sets up the encrypted channel in one RTT by putting the key_share in the ClientHello; ECDHE gives forward secrecy and X25519MLKEM768 adds post-quantum protection. The handshake with openssl s_client, a ClientHello growing from 285 to 1,525 bytes, certificate chain errors, SNI/ECH/ALPN, 0-RTT and .NET staying on TLS 1.2 on macOS.
8 Nov 2026
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11 min
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