In the textbook the four basic modes of operations of block ciphers (ECB, CBC, OFB, CFB) are analyzed with respect to error propagation in encryption. That is, the consequences on ciphertext blocks by changing a single plaintext block are discussed.
Explain how only the knowledge of two dierent ciphertext sequences C = C1C2 Cn and C0 = C01 C02 C0n, obtained by applying the same secret key, can compromise the security of the system.