Key-based Algorithms

A key-based algorithm uses an encryption key to encrypt the message. This means that the encrypted message is generated using not only the message, but also using a 'key'.

Figure 1. Key-based encryption

The receiver can then use a decryption key to decrypt the message. Again, this means that the decryption algorithm doesn't rely only on the encrypted message. It also needs a 'key':

Figure 2. Key-based decryption

Introduction to Cryptography

The term ‘Cryptography’ is derived from the Greek word ‘Kryptos’. Kryptos is used to describe anything that is hidden, obscured, veiled, secret or mysterious. In the world of data communications, cryptography can be defined as follows:

Cryptography, defined as “the science and study of secret writing concerns the ways in which communications and data can be encoded to prevent disclosure of their contents through eavesdropping or message interception, using codes, ciphers and other methods, so that only certain people can see the real message”.

Encrypting is the act of translating a ‘normal message’ to a message written with ‘secret characters’ (also known as the encrypted message). Decrypting is the act of translating a message written with ‘secret characters’ into a readable message (the unencrypted message). It is, by far, one of the most important areas in computer security, since modern encryption algorithms can ensure all three pillars of a secure conversation: privacy, integrity, and authentication.