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Next: 3.3.3 What is public Up: 3.3 Data Security: Cryptography Previous: 3.3.1 What is cryptography?

3.3.2 What is a key?

A key is a piece of data that can be used to encrypt or decrypt a given message.

In a common form of cryptography, secret key cryptography, the sender uses a secret key to encrypt some information. The sender must then get both the secret key and the encrypted information to the receiver securely. The problem with secret key cryptography, from the standpoint of transactions over the Internet, is that anyone who can get both the key and the encrypted information can decrypt the information. As we noted above, it is fairly easy for an unauthorized person to intercept my information on the Internet. If I send both an encrypted message and the secret key that decrypts the message over the Internet, then I risk having both intercepted and having the message decrypted by the interceptor.

Denis Arnaud