Export-grade

cryptohack

Task: MITM a DH cipher-suite negotiation (socket.cryptohack.org 13379) where Alice offers groups from DH1536 down to DH64, then passively observe. Solution: rewrite the negotiation so Bob accepts the weakest group DH64 (a 64-bit prime), passively capture p, g, A, B, solve the 64-bit discrete log a=dlog_g(A) with sympy discrete_log / Pohlig-Hellman, compute shared=B^a mod p, derive key=sha1(str(shared))[:16] and AES-CBC decrypt the flag — a Logjam-style downgrade.