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SSL/TLS protocol overview

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1.1

SSL/TLS sub-protocols

The TLS record layer and TLS handshake layer consists of four sub-protocols overall:

handshake protocol, change cipher spec protocol, alert protocol, and record protocol.

1.1.1

Handshake protocol

This sub-protocol is used to negotiate session information between the client and the server.

The session information consists of a session ID, peer certificate(s), the cipher suite, the

compression algorithm, and a shared secret that is used to generate the session key.

Figure 2 depicts the message flow for a full handshake process (see [5] in References). The

optional value indicates optional or situation-dependent messages, i.e. in the case of mutual

authentication a TLS server must send its certificate and request a certificate from the client,

while in the case of anonymous negotiation the optional messages may be skipped. The

certificate-based authentication is examined more in detail in Section 1.2.

Figure 2. SSL/TLS full handshake procedure

1.

The client sends a ClientHello message specifying the highest SSL/TLS protocol

version (SSLv3.0, TLSv1.0, 1.1 or 1.2) it supports, a random number, a list of

suggested cipher suites and compression methods.

2.

The server responds with a ServerHello message, containing the chosen protocol

version, another random number, cipher suite and compression method from the

choices offered by the client, and the session ID.

Note:

The chosen protocol version should be the highest that both client and server support.