5.10. Sometimes error propagation is an issue when choosing a mode of operation in practice. In order to analyze the propagation of errors, let us assume a bit error (i.e., a substitution of a 0 bit by a 1 bit or vice versa) in a ciphertext block yi.

1. Assume an error occurs during the transmission in one block of ciphertext, lets say yi. Which cleartext blocks are affected on Bobs side when using the ECB mode?

2. Again, assume block yi contains an error introduced during transmission. Which cleartext blocks are affected on Bobs side when using the CBC mode?

3. Suppose there is an error in the cleartext xi on Alices side. Which cleartext blocks are affected on Bobs side when using the CBC mode?

4. Assume a single bit error occurs in the transmission of a ciphertext character in 8-bit CFB mode. How far does the error propagate? Describe exactly how each block is affected.

5. Prepare an overview of the effect of bit errors in a ciphertext block for the modes ECB, CBC, CFB, OFB and CTR. Differentiate between random bit errors and specific bit errors when decrypting yi.