1. Electronic Code Book (ECB)

a. Sketch the flows for two successive ECB decryptions, with ciphertexts 1, 2 and plaintexts 1, 2.

b. Write the formula that links the plaintext with the ciphertext and the key : = ........................

c. If for the ciphertext blocks: , , , we have = , then what can you say about the corresponding plaintexts , ?

d. If in ECB there is a 1-bit error in the ciphertext then the decrypted plaintext is obviously corrupted. Are any blocks beyond corrupted (assuming no more bits are corrupted)?