RSA Laboratories

2.1.2 What is secret-key cryptography?

Secret-key cryptography is sometimes referred to as symmetric cryptography. It is the more traditional form of cryptography, in which a single key can be used to encrypt and decrypt a message. Secret-key cryptography not only deals with encryption, but it also deals with authentication. One such technique is called message authentication codes (MACs; see Question 2.1.7).

The main problem with secret-key cryptosystems is getting the sender and receiver to agree on the secret key without anyone else finding out. This requires a method by which the two parties can communicate without fear of eavesdropping. However, the advantage of secret-key cryptography is that it is generally faster than public-key cryptography.

The most common techniques in secret-key cryptography are block ciphers (see Question 2.1.4), stream ciphers (see Question 2.1.5), and message authentication codes.

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