3.1. The SSL protocol

Secure Socket Layer v3 (SSL) and Transport Layer Security v1 (TLS) are widely used crypto protocols guaranteeing data integrity and confidentiality in many PKI and e-commerce systems. They allow both the client and the server to authenticate each other. SSL/TLS use reliable TCP connection for data transmission and cooperate with any application level protocol. SSL/TLS guarantee that:

  • Communication in the channel is private, only the other communicating party can decrypt the messages.

  • The channel is authenticated, so the client can make sure that it communicates with the right server. Optionally, the server can also authenticate the client. Authentication is performed via certificates issued by a Certificate Authority (CA). Certificates identify the owner of an encryption keypair used in encrypted communication.

  • The channel is reliable, which is ensured by message integrity verification using MAC.

SSL/TLS is almost never used in itself: it is used as a secure channel to transfer other, less secure protocols. The protocols most commonly embedded into SSL/TLS are HTTP and POP3 (i.e. these are the HTTPS and POP3S protocols).

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