Q1. A) How many different Vigenere keys of length 4 are there for coding the English alphabet? The last string must be of size 2 to get to 26. Please show what this cipher table with the last string of size 2 would look like.

B) Say you have an n block of bits message. You split it to 8 bits each (assume that 8 divides n). For each of the 8 bit we choose a permutation of the bits. How many different codes could come out of this? Why?

C)

For any two bits xi,yi, define xiXORyi=xi+yimod2. For two vectors, v,u, define vXORu to be the vector whose i-th bit is uiXORvi. Say that the plaintext has x bits. For the cyphertext we randomly select a random number r with x bits, (this means that all of the 2x vectors with x bits, have probability 1/2x to be selected). For a vector u, our code message is xXORr In a known plaintext attack how would you discover the key r