SSL (Secure Sockets Layer) — the protocol ensuring safety of communication. In cryptography it is today one of the most popular protocols, safety of connection in which is reached at the expense of "the multilevel environment". How does it work?
Instruction
1. The SSL protocol takes the place between two protocols: the protocol of the client program (HTTP, FTP, Telnet and so on) and the TCP/IP protocol serving for transportation of packages.
SSL is divided into two layers: Handshake Protocol Layer (connection confirmation layer) and Record Layer (record layer). At the same time the connection confirmation layer in turn breaks into three protocols: Handshake Protocol (connection confirmation), Change Cipher Spec Protocol (change of parameters of the cipher) and Alert Protocol (warning).
2. The following scheme illustrates SSL protocol levels:
Handshake Protocol Layer (connection confirmation layer)
As it was told earlier, this layer incorporates three protocols:
Handshake Protocol (protocol of confirmation of connection)
This protocol is used for coordination of data of a session between the client and the server. At the same time the following information is transferred:
1. Identification number of a session;
2. Certificates of the parties;
3. Parameters of the used cryptographic algorithm;
4. The used shrinking algorithm;
5. Information applied to creation of keys or the public key.
Change Cipher Spec Protocol (protocol of change of parameters of encryption)
This protocol is applied to change of data of the key used for data encryption between the client and the server.
Alert Protocol (protocol of the warning)
The precautionary message confirms change of the status or existence of an error. At the same time there is notification of both parties.
3. For safety, namely for authentication of participants of information exchange, in the protocol of confirmation the certificate (standard X.509) is used. The certificate in cryptography call the digital document which confirms compliance between the public key and information identifying the owner of a key. The certificate is issued certificate authority — the third party to which a priori trust the parties which are directly participating in information transfer.
4. There are two main cryptography techniques used in cryptography: symmetric and asymmetric encryption (with the public key). In the SSL protocol both methods are applied.
At application of the symmetric key by both parties the identical key for data encryption, this necessary condition is used to ensure safety of information transfer. Such type of encryption is applied to processing of large volumes of data.
Asymmetric encryption uses two keys received by means of a number of mathematical calculations. In the SSL protocol the asymmetric encryption is used in order that the server could make sure of authenticity of the client and vice versa.