cryptomedium

Chill

volgactf

Task: DSA scheme where private key x = flag, two signatures with nonces differing by at most 2^22. Solution: close nonce attack — derive linear equation in x with small unknown delta, brute-force ~4M delta values checking for VolgaCTF{} prefix.

$ ls tags/ techniques/
brute_forceprivate_key_recoverysagemathdsanonce_biasclose_nonce
dsa_close_nonce_attackmodular_arithmetic_brute_forcesignature_equation_manipulation
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