A hacker is analyzing a system that uses two rounds of symmetric encryption with different...

CEH covers advanced cryptanalytic attacks, including Meet-in-the-Middle (MITM) attacks, which are especially effective against multi-round symmetric encryption schemes. When an algorithm encrypts data twice using different keys, the naive brute-force method would require testing every possible combination of both keys—a time complexity of 2ⁿ × 2ⁿ. Meet-in-the-Middle dramatically reduces this complexity by splitting the problem in half. Attackers encrypt the plaintext using all potential values of the first key and store the results. They then decrypt the final ciphertext using all possible values of the second key. When an intermediate value matches one in storage, the corresponding key pair is identified. CEH highlights that this approach exploits the lack of key independence between two encryption layers, demonstrating how doubling encryption does not always double security. This attack is well-known for targeting 2DES, one of the historical examples covered in CEH. It is not related to side-channel attacks, brute-force flooding, or permutation reversal; it strictly relies on midpoint matching to reduce computational workload.