Meet-in-the-middle attack

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The meet-in-the-middle attack (MITM), a known plaintext attack,^[1] is a generic space–time tradeoff cryptographic attack against encryption schemes that rely on performing multiple encryption operations in sequence. The MITM attack is the primary reason why Double DES is not used and why a Triple DES key (168-bit) can be brute-forced^{[clarification needed]} by an attacker with 2⁵⁶ space and 2¹¹² operations.^[2]