The process of protecting information as it moves from one computer to another. Passing through a complex mathematical process (an encryption algorithm), the information is encoded before it is sent and decoded with a secret key when it is received. Without this key, the information is undecipherable. Computers use a binary number, usually 40- to 128-bits in length, as the key. The larger the key, the more difficult it is to break the encryption and decipher the message in transit.
In other words, encryption is a way of making data unreadable to everyone except the receiver, and it is an increasingly common way of sending credit card numbers over the Internet when conducting e-commerce transactions.