Topic: how to get pubkey of signature (Read 298 times)

python3 -m secp256k1 recpub -s HxhJdJzdl0W7TeL/GWJ2bCp5gGE+kLNhRfZYKfPhQdWWcuGXkWx3W60lvCM/3bfnwdYL58ZNCcx4sgohPkCrwH4= -i 1 -m "Hello, world!"
Traceback (most recent call last):
  File "/usr/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/home/yin4/.local/lib/python3.10/site-packages/secp256k1/__main__.py", line 7, in
    main()
  File "/home/yin4/.local/lib/python3.10/site-packages/secp256k1/__init__.py", line 543, in main
    sys.exit(_main_cli(args, sys.stdout, enc))
  File "/home/yin4/.local/lib/python3.10/site-packages/secp256k1/__init__.py", line 491, in _main_cli
    sig_raw = bytes(bytearray.fromhex(args.signature))
ValueError: non-hexadecimal number found in fromhex() arg at position 0

$ python -m secp256k1 recpub \
-s 515fe95d0780b11633f3352deb064f1517d58f295a99131e9389da8bfacd64422513d0cd4e18a58d9f4873b592afe54cf63e8f294351d1e612c8a297b5255079 \
-i 1 \
-m hello

#!/usr/bin/env python3
# 2022-Dec-26 by citb0in

import hashlib
from ecdsa import SigningKey, VerifyingKey, SECP256k1
from ecdsa.util import sigencode_der, sigdecode_der

# private key in hex, 32 bytes
privateKeyHex = "2bb80d537b1da3e38bd30361aa855686bde0eacd7162fef6a25fe97bf527a25b"

# convert private key from hex to bytes
privateKeyBytes = bytes.fromhex(privateKeyHex)

# create a SigningKey object of the private key
privateKey = SigningKey.from_string(privateKeyBytes, curve=SECP256k1)

# get the associated public key
publicKey = privateKey.get_verifying_key()

# message to sign
message = "hello"

# calculate the hash of that message
messageHash = hashlib.sha256(message.encode("utf-8")).digest()

# create the signature
signature = privateKey.sign(messageHash, sigencode=sigencode_der)

# encode signatur in hex
signatureHex = signature.hex()

# show some output
print(f"privKey in hex: {privateKeyHex}")
print(f"SigningKey object: {privateKey}")
print(f"pubKey in hex: {publicKey}")
print(f"message: {message}")
print(f"messageHash: {messageHash}")
print(f"Signature: {signature}")
print(f"Signature in hex: {signatureHex}") # output is "3045022075ace5b099991073ef11947127249d0c43f16e1069762360ae1b892b13aeffb50221009792e26181f84f1882944626f669fdfc8eb0c63e80058e498ff56ee5ac1e6041" but is wrong

# the correct and expected signatureHex should be:
signatureHex = "304502210095ade2b0fd9caa90e4993e59232b774e4dc2082fdb8a30267abf21fc6a076715022016d762b4a23e30e8151f2852e88f6beebe65290266aafbbd0cbf2c1f6b3dc78c"
print(f"correct signature in hex should be: {signatureHex}")
# verify signature with pubKey
try:
    publicKey.verify(signature, message, hashlib.sha256, sigdecode=sigdecode_der)
    print("Signature is valid.")
except:
    print("Invalid signature!")