1. Hash functions have been called one-way encryption, i.e., there is no way to decrypt a hash. Given this property of hashes, why are they useful in cryptography?
2. An organization has 8 members. Using a symmetric cipher, it is desired that each member of the organization be able to communicate securely with any other member, without any other member being able to decrypt their messages. How many unique keys are required?
3. In terms of entropy, what is the goal of cryptography?