Q21Information Security Systems
Question
Discuss the SSL/TLS protocol architecture. Detail the steps involved in the SSL Handshake Protocol.
Answer
SSL/TLS secures network communication via encrypted, authenticated transport tunnels.
Secure Sockets Layer (SSL) and its successor, Transport Layer Security (TLS), are cryptographic protocols designed to provide communications security over a computer network. The SSL/TLS architecture operates above the TCP layer and below the application layer, encapsulating application data.
The protocol is divided into two layers: the SSL Record Protocol (which handles data fragmentation, compression, MAC application, and encryption) and higher-level protocols including the SSL Handshake Protocol, Change Cipher Spec Protocol, and Alert Protocol.
The SSL Handshake Protocol involves:
1. Hello Phase: Client sends a 'ClientHello' (supported ciphers, random number). Server responds with 'ServerHello' (chosen cipher, random number).
2. Certificate Exchange: The server sends its digital certificate to prove its identity. The client verifies this certificate.
3. Key Exchange: The client generates a 'Pre-Master Secret', encrypts it with the server's public key, and sends it. Both compute the symmetric 'Master Secret' from the pre-master secret and exchanged random numbers.
4. Finished: Both parties send a 'Finished' message encrypted with the new symmetric keys. All subsequent data is encrypted.
