A known-plaintext heuristic attack on the Fourier plane encryption algorithm

TLDR

The Fourier plane encryption algorithm, which encrypts amplitude‑encoded real‑valued images, is vulnerable to a known‑plaintext attack. A simulated‑annealing heuristic estimates the key from a known plaintext‑ciphertext pair, decrypts the ciphertext with near‑zero error, and then tests the key’s strength by decrypting a second ciphertext encrypted with the same key. The Fourier plane encryption algorithm is found to be susceptible to a known‑plaintext heuristic attack.

Abstract

The Fourier plane encryption algorithm is subjected to a known-plaintext attack. The simulated annealing heuristic algorithm is used to estimate the key, using a known plaintext-ciphertext pair, which decrypts the ciphertext with arbitrarily low error. The strength of the algorithm is tested by using this estimated key to decrypt a different ciphertext which was also encrypted using the same original key. We assume that the plaintext is amplitude-encoded real-valued image, and analyze only the mathematical algorithm rather than a real optical system that can be more secure. The Fourier plane encryption algorithm is found to be susceptible to a known-plaintext heuristic attack.