ecmfactor

#!/usr/bin/python3
#
# SPDX-License-Identifier: 0BSD
# Part of badkeys: https://badkeys.info/
#
# Simple wrapper for factoring a hex input number with gmp-ecm (Elliptic
# Curve Method) and default settings.
# Needs gmp-ecm: https://gitlab.inria.fr/zimmerma/ecm
#
# Usage example (has non-trivial, 64-bit prime factor):
#   ./ecmfactor 95050b185a7e9147cb60a84729b239e0deac19b4ba4137ff87f4ccae8c13b6ab

import argparse
import subprocess

ap = argparse.ArgumentParser()
ap.add_argument("input", nargs="+", help="Value to be factored (hex number)")
args = ap.parse_args()

for nhex in args.input:
    n = str(int(nhex, 16))

    proc = subprocess.Popen(["ecm", "-q", "1000000"], text=True,
                            stdin=subprocess.PIPE, stdout=subprocess.PIPE)

    out = proc.communicate(input=str(n))[0].strip().split(" ")
    if len(out) == 1:
        print(f"WARNING: Could not factor {nhex}")
        continue
    factor, cofactor = out
    print(factor)
    factor = int(factor)
    cofactor = int(cofactor)

    print(f"Factor:   {factor:02x}")
    print(f"Cofactor: {cofactor:02x}")