Secure Socket Layer (SSL)
Secure Socket Layer (SSL) provides security to the data that is transferred between web browser and server. SSL encrypts the link between a web server and a browser which ensures that all data passed between them remain private and free from attack.
Secure Socket Layer Protocols:
- SSL record protocol
- Handshake protocol
- Change-cipher spec protocol
- Alert protocol
SSL Protocol Stack:
SSL Record Protocol:
SSL Record provides two services to SSL connection.
- Message Integrity
In the SSL Record Protocol application data is divided into fragments. The fragment is compressed and then encrypted MAC (Message Authentication Code) generated by algorithms like SHA (Secure Hash Protocol) and MD5 (Message Digest) is appended. After that encryption of the data is done and in last SSL header is appended to the data.
Handshake Protocol is used to establish sessions. This protocol allows the client and server to authenticate each other by sending a series of messages to each other. Handshake protocol uses four phases to complete its cycle.
- Phase-1: In Phase-1 both Client and Server send hello-packets to each other. In this IP session, cipher suite and protocol version are exchanged for security purposes.
- Phase-2: Server sends his certificate and Server-key-exchange. The server end phase-2 by sending the Server-hello-end packet.
- Phase-3: In this phase Client reply to the server by sending his certificate and Client-exchange-key.
- Phase-4: In Phase-4 Change-cipher suite occurred and after this Handshake Protocol ends.
This protocol uses the SSL record protocol. Unless Handshake Protocol is completed, the SSL record Output will be in a pending state. After handshake protocol, the Pending state is converted into the current state.
Change-cipher protocol consists of a single message which is 1 byte in length and can have only one value. This protocol’s purpose is to cause the pending state to be copied into the current state.
This protocol is used to convey SSL-related alerts to the peer entity. Each message in this protocol contain 2 bytes.
The level is further classified into two parts:
This Alert has no impact on the connection between sender and receiver.
- Fatal Error:
This Alert breaks the connection between sender and receiver.
Silent Features of Secure Socket Layer:
- The advantage of this approach is that the service can be tailored to the specific needs of the given application.
- Secure Socket Layer was originated by Netscape.
- SSL is designed to make use of TCP to provide reliable end-to-end secure service.
- This is a two-layered protocol.