ABSTRACT
The transition from historical to contemporary digital cryptosystems requires an understanding of binary representation. In current systems, plaintext messages first need to be converted into binary data before they are encrypted. Encryption and decryption keys are likewise binary, and so the encoding and decoding of messages involve the use of various logical operations, such as the exclusive-or (XOR). As computing power increases, security concerns have dictated that the encryption process needs to be more complex. Plaintext is therefore transformed by a series of operations that include not only substitution, but also the application of other mathematical transformations, such as permutation and matrix multiplication. Security for symmetric ciphers also involves the issue of how to transmit or share a private key, and a process for doing this is described.
