Classical Encryption Techniques.
1. Cryptography Study of Secure data communication is called cryptography. Fig. 1 explains the entire working of cryptography. Plaintext : Human Readable Data Encryption Algorithm : Which converts plaintext into ciphertext. Secret Key : It is an input which is used for encryption and decryption algorithm. Ciphertext : It may be human readable or may be non readable but always contains a logic. Decryption Algorithm : Which converts ciphertext into plaintext. Mathematical Background : Assume Plaintext (P) : {p1,p2,p3,p4,....pm} Key (K) : {k1,k2,k3,...,km} Ciphertext (C) : {c1,c2,c3,.....,cm} Now after Encryption - C = E(K,P) Now after Decryption - P = D(K,C) Now opponent observing 'C' but having no access to 'K' and 'P' will try to find out the 'K', or 'P', or both. so to recover the message the opponent generate a plaintext estimate 'Px' and if interested in Key so gener...