I'm not sure how you could use the birthday paradox to brute force a block cipher. You have a message you want to decrypt, and you don't know the key. A brute

I'm not sure how you could use the birthday paradox to brute force a block cipher. You have a message you want to decrypt, and you don't know the key. A brute force attack is trying all the possible keys (2^128 for AES-128) and on average you will find the right one with 2^127 guesses.