Nonce Oracle Drift

Exploit biased nonce leakage across a custom secp curve deployment.

Challenge brief

A service signs session attestations on a custom Weierstrass curve. Nonces are derived from a hardware RNG with a documented bias window. Use the signature corpus to recover enough nonce MSB structure and forge an attestation for the target handle. Submit the forged proof as a Genesis Block flag.

Flag format: GB{...}

Puzzle artifacts

curve_params.toml

Custom curve parameters

name = "gb7-secp-custom"
p = "0xffffffffffffffffffffffffffffffff99def836146bc9b1b4d22831"
a = "-3"
b = "0x5ac635d8aa3a93e7b3ebbd55769886bc651d06b0cc53b0f63bce3c3e"
bias_msb_bits = 8

Demo artifacts — synthetic files for the interactive MVP flow

Submit proof

Demo verification is client-side for this MVP. Live contests will score server-side. Lattice Fold demo flag: GB{lattice_short_basis_recovered}