The glossary below contains many of the terms you will find in common use throughout our website. Please refer to this list to find definitions of terms and answers to other Internet security-related questions.


A piece of information that controls the operation of a cryptography algorithm. In encryption, a key specifies the particular transformation of plain text into ciphertext or vice versa during decryption. Keys are also used in other cryptographic algorithms, such as digital signature schemes and keyed-hash functions (also known as MACs), often used for authentication.

A variable value in cryptography that is applied (using an algorithm) to a string or block of unencrypted text to produce encrypted text. A key is also a series of numbers or symbols that are used to encode or decode encrypted data.