Hands-On Network Programming with C

Symmetric ciphers

The following diagram illustrates a symmetric cipher:

In the preceding diagram, the plaintext Hello! is encrypted using a symmetric cipher. A secret key is used with the cipher to produce a ciphertext. This ciphertext can then be transmitted over an insecure channel, and eavesdroppers cannot decipher it without knowledge of the secret key. The privileged receiver of the ciphertext uses the decryption algorithm and secret key to convert it back into plaintext.

Some symmetric ciphers in general use (not just for TLS) are the following:

• American Encryption Standard (AES), also known as Rijndael
• Camellia
• Data Encryption Standard ...