Double DES

This is a meet in the middle attack on DES. The program allows us to encrypt arbitrary data in which it returns the encrypted data after double DES encryption.

Intuition

The intuition here is that we know the key size is not that large since the key is only 6 characters long we could simply try every possible key on the input as well as the output. Anything that matches means that this pair of keys is the correct one.

Method

Initially, I though that we would need many input interactions to narrow it down to a reasonable dictionary size but after only 1 character A there were only around 64 valid key pairs left. I just brute forced the flag and it seems like all 64 pairs work to decrypt the ciphertext given.