CPSC 42500 Homework 5: Secure Hashing

1. (1 point) What is the square root of 2⁴¹⁴ ?

2. (2 pts) Say there are 8 people in a room. Each person shakes every other person’s hand once, and nobody shakes the same person’s hand more than once. How many handshakes in total will take place?

3. (4 pts) Recall from class that the parity function is a very simple hash function producing a one-bit digest, which is 0 if the number of bits in the message is even and 1 if it is odd.

   Consider a communication system that uses 7 bits out of every byte to transmit data, and reserves the 8^th bit (the one on the right) to transmit the parity of the other seven bits, for purposes of error checking.

   Below is the binary representation of some bytes that were transmitted using this system. For each one, tell whether there is reason to suspect an error in transmission, giving the reason for your answer.

   10110011

         10101100

         00110011

         11101111

(3 pts) Explain why a hash function is inappropriate to use for encrypting data.

DETAILED ASSIGNMENT

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