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import ast import hashlib from fpylll import IntegerMatrix, LLL, BKZ from ecdsa import curves, ellipticcurve
RAW = r""" 0x8e0a0071e8cf437efec4233ff8444a4ff8adba2f 0xa869fce702b70799c443b450a4d41cc4f65b3eee (0x525931a9ff8ef95025939a57275ecedc2730421f, 0x5288ed7146c188ebda9b6c8909726c3d6f957891, 0x334c301c2d861fa8cceecabc542a5cb7dd7df7d9, 0x6), (0x4b21047e1112dbfee487b4f23471f2fb438e268, 0x82878368ef18996109bf10adae81e1acaeb9fa25, 0xd4d9ec1faa9534a3fa4ff0fe78488ebf175cdfec, 0x4), (0xdd2e98102508e178fdf1e289ac8342250da6408f, 0x38069b3213a57a077a38938d082a7590d0a21b95, 0xcff1f76af8f15422bb288c8af372332cc6ace970, 0x1), (0xecb8547ea2a68788665e01a7025093c47f2b45de, 0x6f7155ce9da5434227e48554a0bef7d7492cadb, 0x53f6e1a52554436620b392dea75738b5f670d2b2, 0x2), (0xefb887600edf8d279f3cca868ef641e9284ae769, 0x9caea57dd4681d1ab53029cf631a47277386bc72, 0xce7743df557c732daff4595d8430ea8485ab3aca, 0x3), (0x957ec8b7a53dea95d53a5c94d595b834c2be61ca, 0x1b24031194de7dac370a2f7c9be316dc14cbe3f2, 0xc40b5c4c674d1f4cb99891bf342f8acebca9258b, 0x5), (0x8ba1946c16b7c8d98c6e01836ae0d791ecae07d9, 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0x64ebd081e1e5be70904723e1a786d9581ad4e5a5, 0x58c16e616268863fce12b920e281ad4b1d9d2881, 0x1), (0x9bbcfa5f87bea52e4df986ecdb89dadf9fe7242b, 0x520b4e89d3e3cd032e5c8c9cfab3f706fe49ca8c, 0x198aa5c2cab8d22845c4f3ea8f710becaba98d13, 0x3), (0x42abe9b2d14ec440b51362694f93116cf4a8980d, 0x38c3965c6f9c9699476239ea669acc598bf748b6, 0xb47208202e92dbc5ed3d4319dd9e4ceeb21e9ec8, 0x5), (0x334732df257a5c08e42c56dcd31f3be5cfaa196e, 0xe6387cab10b4e3bff5c72b7a8c47bf3f73812e0c, 0x315e28210455bc5535e6f2a6dcf5a76732ad8c88, 0x3), (0x825347e82b6ecb7c40353d9282daf9804088f22b, 0xced5ac7b578c4a95a177a283f60437a70232ff0, 0xb647c743e3b4ce3ca95c586bdd14afc41d91ad09, 0x4), (0xf862df8e80ded401998ce913668155e078f5863f, 0xa73fe4db4136c28cbfc6ee73c800548a0bd463e2, 0xff0395bc6b17d90c38ba263488be5987e3b44890, 0x7), """
def parse_raw(raw: str): lines = [x.strip() for x in raw.strip().splitlines() if x.strip()] pubx = int(lines[0], 16) puby = int(lines[1], 16) sigs = [] for line in lines[2:]: line = line.rstrip(",") h, r, s, kp = ast.literal_eval(line) sigs.append({ "hash": int(h), "r": int(r), "s": int(s), "kp": int(kp), }) return pubx, puby, sigs
def inv(x: int, n: int) -> int: return int(pow(int(x), -1, int(n)))
def build_lattice_lsb(sigs, n_order: int, known_bits: int): known_bits = int(known_bits) n_order = int(n_order) m = len(sigs) kbi = int(1 << known_bits)
lat = IntegerMatrix(m + 2, m + 2)
for i in range(m): lat[i, i] = int(2 * kbi * n_order)
h = int(sigs[i]["hash"]) r = int(sigs[i]["r"]) s = int(sigs[i]["s"]) kp = int(sigs[i]["kp"])
a = (inv(kbi, n_order) * (r * inv(s, n_order))) % n_order b = (inv(kbi, n_order) * (kp - h * inv(s, n_order))) % n_order
lat[m, i] = int(2 * kbi * a) lat[m + 1, i] = int(2 * kbi * b + n_order)
lat[m, m] = 1 lat[m + 1, m + 1] = int(n_order) return lat
def test_candidate_from_matrix(lat, G, Q, n_order): n_order = int(n_order) for i in range(lat.nrows): cand = int(lat[i, lat.ncols - 2]) % n_order if cand <= 0: continue if cand * G == Q: return cand cand2 = n_order - cand if cand2 * G == Q: return cand2 return None
def recover_key(pubx, puby, sigs, known_bits=3): curve = curves.SECP160r1 G = curve.generator n_order = int(curve.order) Q = ellipticcurve.Point(curve.curve, int(pubx), int(puby), n_order)
lat = build_lattice_lsb(sigs, n_order, int(known_bits))
LLL.reduction(lat) d = test_candidate_from_matrix(lat, G, Q, n_order) if d is not None: return d
for bs in (15, 25, 35, 45, 55): BKZ.reduction(lat, BKZ.Param(block_size=min(bs, lat.nrows), auto_abort=True)) d = test_candidate_from_matrix(lat, G, Q, n_order) if d is not None: return d
return None
def main(): pubx, puby, sigs = parse_raw(RAW) d = recover_key(pubx, puby, sigs, known_bits=3) if d is None: print("[-] recover failed") return
flag = "DesCTF{" + hashlib.md5(str(d).encode()).hexdigest() + "}" print("[+] d =", hex(d)) print("[+] flag =", flag)
if __name__ == "__main__": main()
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