Encryption Algorithm Process

The cryptosystem involves a set of rules for how to encrypt the plaintext and how to decrypt the cipher text. The encryption and decryption rules, called algorithms, often use a device called a key, denoted by k, so that the resulting ciphertext depends on the original plaintext message, the algorithm, and the key value. We write this dependence as C=E(K, P). Essentially, E is a set of encryption algorithms, and the k selects one specific algorithm from the set.  Sometimes the encryption and decryption keys are the same so P= D(K, E(K,P)).

 This form is called symmetric encryption because D and E are mirror image processes. At other times, encryption and decryption keys come in pairs. Then a decryption key, Kd, inverts the encryption of key Ke, so that P=D(Kd, E(Ke,P)). Encryption algorithms of this form are called asymmetric because converting c back to p involves a series of steps and a key that are different from the steps and key of E. Both a cryptographer and a cryptanalyst attempt to translate coded material back to its original form. Finally cryptology is the research into and study of encryption and decryption.