SSL

Secure Sockets Layer

A cryptographic protocol designed to provide secure communication over the internet. It has been largely replaced by its successor, TLS (Transport Layer Security), but the term SSL is still widely used to refer to both protocols. SSL provides three essential security properties:

• Confidentiality: The data exchanged between the client and server is encrypted, preventing unauthorized parties from reading it.
• Integrity: SSL uses message authentication codes to detect if the data has been altered in transit.
• Authentication: The server’s identity is verified through its SSL certificate, ensuring the client communicates with the intended server.

How SSL Works

1. Handshake: When a client (e.g., a web browser) connects to a server (e.g., a website), they initiate a handshake process. The client sends a message to the server, specifying the version of SSL it supports and a list of cryptographic algorithms it can use.
2. Server Certificate: The server responds with its SSL certificate, which contains the server’s public key and other identifying information. This certificate is typically issued by a trusted third-party Certificate Authority (CA) that verifies the server’s identity.
3. Certificate Verification: The client verifies the server’s certificate by checking if a trusted CA issues it and if the certificate’s hostname matches the server’s hostname. This step ensures that the client is communicating with the intended server and not an imposter.
4. Key Exchange: If the certificate is valid, the client generates a random session key, encrypts it using the server’s public key (obtained from the certificate), and sends it to the server. Only the server can decrypt this message using its private key, ensuring the session key remains secure.
5. Secure Communication: The client and server can communicate securely with the session key established. They use the session key to encrypt and decrypt all the data exchanged between them, preventing eavesdropping and tampering.
6. End of Session: When the communication is complete, the session is terminated, and the session key is discarded.

SSL is commonly used to secure websites (HTTPS), email communications (SMTPS, IMAPS), and other applications that require secure data transmission over the internet.

• Abbreviation: SSL