Consider the centralized and the fully distributed approaches to dead- lock detection. Compare the two algorithms in terms of message com- plexity.

Modes of operation such as CFB and CBC require the use of an initial variable (IV), which must be known by both the sender and receiver. Discuss the pros and cons of the following suggestions for selection of IVs Randomly generate each IV; Use a counter that is incremented after each message as the IV; Use the last ciphertext block of the previous message as the IV

Problem with constructing MAC. The messages X to be authenticated consists of z independent blocks, so that: X = x1||x2|| . . . ||xz, where every xi consists of |xi| = 8 bits. The input blocks are consecutively put into the compression function  ci = h(ci−1, xi) = ci−1⊕xi At the end, the MAC value: MACk(X) = cz+k mod 28 is calculated, where k is a 64-bit long shared key. Describe how exactly the (effective part of the) key k can be calculated with only one known message X.