cryptomedium

Undervattensströmmar

undutmaning

Task: LCG-based XOR stream cipher with missing parameters, known file header. Solution: Known plaintext attack to recover keystream, GCD method to crack LCG parameters, decrypt and extract flag from gzip/tar archive.

$ ls tags/ techniques/
known_plaintext_attackmodular_inverselcg_parameter_recoverygcd_attack

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