Cryptography Classification

Classification of Cryptographic Systems, Ciphers, Algorithms

1. This classification scheme has to do with the means of implementation 1.1.

Classical

  : Pre Computer Era involvements of (e.g. before 1950)

1.2.

Modern

   : Computer Era.  Usually implies  binary plaintext, key, ciphertext processing and /or encoding

2. This classification scheme has to do with the Key – Space properties 2.1.

Symmetric

,

Private Key

:  Both, Encryption and Decryption Algorithms use the same Key  

2.2. Asymmetric, usually Private – Public Key pair Algorithms : Encryption and Decryption algorithms use different keys, usually related.

3. This classification scheme has to do with the way the algorithm processes plaintext, message to be encrypted. 3.1.

Block Cipher

  : Plain text is treated as a series of fixed length sub-messages. 

3.2.

Stream Cipher

: Used as a Block Cipher with efficiently fixed small sized sub-messages to comply with real time applications. That is a consequence of the sort time interval available to process a sub-message, e.g. A5 of GSM cellular telephony.