1.43. Consider the affine cipher with key k (k1,k2) whose encryption and decryption functions are given by (1.1) on page 43. (a) Let p = 541 and let the key be k (34,71). Encrypt the message = 204. Decrypt the ciphertext c = 431. (b) Assuming that p is public knowledge, explain why the affine cipher is vulnerable to a known plaintext attack: (See Property on page 38.) How many plaintext/ciphertext pairs are likely to be needed in order to recover the private key? Alice and Bob decide to use the

Vigenere Cipher - The Complete Giude with Examples

21. Encrypt the message. This is an exercise using one of the following ciphers. Ignore the space between words. Decrypt the message to get the original plaintext.a. Additive cipher with key=20b. Multiplicative cipher with key=15c. Affine cipher with key=15,20