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 by a 1 or vice versa) in a ciphertext block yi that corresponds to cleartext xi.

1. Assume an error occurs, during the transmission, in the ciphertext block yi. Which cleartext blocks are affected on Bobs side when using the ECB mode? List such blocks with a comma to separate any two (e.g., xi,xi+1,xi+2)

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 an 8-bit CFB mode. Which one of the following three statements is correct? (a) Only xi will be corrupted, (b) xi and a few additional blocks will be corrupted, (c) xi and all the consecutive blocks will be corrupted. Enter a or b or c.