https://nalar.dev/tags/tls-1.3/ Recent content in TLS 1.3 on Nalar Hugo en-us Tue, 15 Sep 2026 00:00:00 +0700 https://nalar.dev/tls-1-3-early-data-trades-a-round-trip-for-replay-exposure/ Tue, 15 Sep 2026 00:00:00 +0700 https://nalar.dev/tls-1-3-early-data-trades-a-round-trip-for-replay-exposure/ <h1 id="tls-13-early-data-trades-a-round-trip-for-replay-exposure">TLS 1.3 Early Data Trades a Round Trip for Replay Exposure</h1> <p>A resumed TLS 1.3 connection can carry application bytes before the server has completed the new handshake. That latency reduction is attractive on paths where a round trip is expensive, but it changes a security property that applications often assume without naming it: a protected request is not necessarily fresh merely because the server decrypted it successfully.</p> <p>TLS 1.3 calls this facility early data, commonly described as 0-RTT. It is available when the client and server share a pre-shared key, including one established through a prior connection. The client can derive keys and send application data in its first flight rather than waiting for the server&rsquo;s handshake messages.</p>