So I have been reading up on my cryptography and I figured I should give out a brief lesson on these three amazing concepts What are they ? a) PRG (Pseudo Random Generator) You probably know the difference between stream and block cipher. One of the main differences between them is key size. Stream ciphers require the key to be of equal length of greater than the plaintext , whereas Block Ciphers take a key smaller than the PT and is then expanded. This is the PRG The PRG expands the seed Considerations: Stream Ciphers base on Perfect Secrecy whereas Block Ciphers base on Semantic Security b) PRF (Pseudo Random Function) Lets share a secret- imagine something- you want to authenticate yourself with me by proving that you know a secret that we both share. Here's a possible option i) Possible Option 1: PRNGs We both seed a PRNG with the shared secret, I pick and then send you some random number i. You then have to prove that you know the secret by respon