Internet Security

Encryption

Applying an algorithm or process (and normally a key) to data so that the output can no longer be understood. However this process can be reversed to return to the original data, this again may involve the use of a key.

Terms

Plain Text

The original data you want to encrypt.

Cipher

The specific algorithm or process used on the plain text.

Cipher Text

The output from running a cipher with the plain text.

Cryptography

The practice and study of techniques used in encryption.

Cryptanalysis

The art or process of deciphering coded messages without being told the key

Symmetric Encryption

Cipher text can be decrypted using an encryption algorithm and the encryption key. Symmetric means using the same key to encrypt and decrypt so it is often difficult to distribute a symmetric key without being intercepted. The key must be passed separately and obviously can’t be sent with the message. It is easy to decrypt the message with the key.

Asymmetric Encryption

Asymmetric refers to the fact that a separate encryption key and separate decryption key are used it is also called public key encryption e.g. RSA. You need a pair of keys – public and private. The private key is kept secret and secure but the encryption algorithm and public keys are freely available so:

• A message encrypted with A’s private key can only be decrypted with A’s public key
• A message encrypted with A’s public key can only be decrypted by A with it’s private key