(a) Briefly explain the following security goals provided by cryptography: confidentiality, authentication, integrity and non-repudiation.
(b) State Kerckhoff's Principle and explain how it relates to cryptanalysis.
(c) Describe the chosen cipher text attack on encrypted messages.
(d) You have intercepted a message encrypted with a Caesar cipher. The ciphertext starts with HWDUYFSFQDXNX and you know the plaintext starts with c. Find the key and decrypt the message.
(e) Use Euclidean's algorithm to calculate gcd(763, 1729).