Answer Happy

Cipher Block Chaining
(b) With the ECB mode, if there is an error in a block of the transmitted ciphertext, only the [5%] corresponding plaintext block is affected. However, in the CBC mode, this error propagates. For example, an error in the transmitted C (Figure 3.1 below) obviously corrupts P and Pk+1- Suppose that there is a bit error in the source version of P. Through how many ciphertext blocks is this error propagated, and what is the effect at the receiver? Time - 1 P Time = 2 P₂ Time = N PH IV Encrypt KI Encrypt KI Encrypt C₁ C₂ (a) Encryption ... Decrypt Decrypt Decrypt P (b) Decryption Cipher Block Chaining (CBC) Mode Figure 3.1 ...