SSL/TLS Handshake (SSL/TLS Handshake)
The Importance of SSL/TLS Handshake
The TLS handshake is where security decisions are made for every HTTPS connection. If the handshake allows weak cipher suites or outdated TLS versions, the entire connection is vulnerable. Misconfigured servers that accept TLS 1.0 can be exploited through downgrade attacks like POODLE, where an attacker forces the connection to use the weakest supported protocol.
Handshake performance directly affects user experience. A TLS 1.2 handshake requires two round trips between client and server before data can flow. TLS 1.3 reduces this to one round trip, and supports 0-RTT resumption for repeat visitors. For sites with global audiences, this latency difference is significant - especially on mobile connections with high latency.
Server configuration determines handshake behavior. The cipher suite order, supported TLS versions, and certificate type all affect both security and performance. Misconfiguration can result in handshake failures for certain clients, especially older devices or corporate proxies.
Key Parameters
| Handshake Step | TLS 1.2 | TLS 1.3 |
|---|---|---|
| ClientHello | Round trip 1 | Round trip 1 |
| ServerHello + Certificate | Round trip 1 | Round trip 1 |
| Key Exchange | Round trip 2 | Completed in round trip 1 |
| Application Data | After round trip 2 | After round trip 1 |
| 0-RTT Resumption | Not available | Available |
How to Test for SSL/TLS Handshake
Use an SSL checker to examine your server's handshake behavior. It will report which TLS versions and cipher suites your server offers, and in what order. Look for any deprecated cipher suites (like RC4 or 3DES) or TLS versions (1.0, 1.1) that should be disabled.