cryptomedium

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Task: Break a Diffie-Hellman key exchange to decrypt an AES-encrypted flag. Solution: Exploit a small subgroup attack where the generator order q is only 42 bits, compute the discrete logarithm using Baby-step Giant-step algorithm in O(sqrt(q)) time, recover the shared secret, and decrypt the flag with AES-ECB.

$ ls tags/ techniques/
aesdiscrete_logdiffie-hellmansmall_subgrouppohlig-hellmanbsgs
small_subgroup_attackbaby_step_giant_steppohlig_hellman
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