Basics of cryptography
How Does the Secret Key Cryptography Work?

The process of using symmetric key cryptography is as follows: User A wants to send a message to User B and wants to ensure that only User B is able to read the message. To secure the transmission, User A generates a secret key, encrypts the message with this key, and sends the message to User B. User B needs that secret key to read the encrypted message. User A can give the secret key to User B by using any means available. After User B receives the secret key, he or she can decrypt the message to retrieve the original message.

Fig. 6 – Symmetric key encryption model

The properties that a cipher algorithm must fulfill are the following:

The most widely used secret key algorithms include:

The major problem with symmetric cryptography is that the process of transferring keys to the recipient is prone to security risks. Establishment of a secure channel is not a trivial operation as sending the key via Internet in an e-mail is not secure, verbally communicating the key over a phone line runs the risk of eavesdropping. Similarly, snail mail runs the risk of possible interception.

The security risks that are involved in secret key cryptography have been overcome to a large extent by using public key cryptography. Secret key cryptography is often used to encrypt data on hard drives. The person encrypting the data holds the key privately and there is no problem with key distribution.