TWO MARKS

1. State Eulers theorem with example.2. Define: LFSR sequence.3. Find GCD (21,300) using Euclids algorithm.4. Write down the purpose of the S-boxes in DES?5. Distinguish between differential and linear cryptanalysis.6. What is the use of Fermats theorem?7. Define Steganography.8. Convert the given text anna university into ciphertext using rail fence technique.9. Write down the difference between the public key and private key cryptosystems.10. What are the disadvantages of double DES?20 MARKS1. Discuss about the classical cryptosystems and its types with example.2. Describe Eulers and Chinese Remainder theorem. Solve the following congruence using Chinese remainder theorem.

3. Using play fair cipher algorithm encrypt the message using the key MONARCHY and also explain the shift ciphers, transposition ciphers.4. Encrypt the message PAY using Hill cipher with the following key matrix and show the decryption to get the original plaintext.

k=

5. Explain the Key Generation, Encryption and Decryption of DES algorithm indetail.6. Describe the mathematical foundations of RSA algorithm. Perform encryption and decryption for the following.P=17, q=7, e=5, n=119.message=6.Use Extended Euclids algorithm to find the private key.

7. Explain the Key Generation, Encryption and Decryption of AES algorithm indetail._1485780370.unknown