Please for core review to file ring_signature_factory.py

[zbohm]

Hi Fernando,
I rewrited your code to the project python-ecdsa in branch ring-signature.
zbohm/python-ecdsa@master...ring-signature

Please, would you be so kind to make me code review? Especialy file ring_signature_factory.py.

Thanks a lot.
Zdeněk

I recommend the code for easy viewing pycco:

$ git clone https://github.com/zbohm/python-ecdsa
$ cd python-ecdsa/
$ git checkout ring-signature
$ pip install --user pycco
$ pycco src/ecdsa/ring_signature_factory.py
$ firefox docs/ring_signature_factory.html

Example of usage:

$ virtualenv --python=python3 env
$ source env/bin/activate
$ pip install git+https://github.com/zbohm/python-ecdsa.git@ring-signature

$ cat > example.py

import hashlib

from ecdsa.curves import SECP256k1
from ecdsa.ecdsa import Private_key, Public_key
from ecdsa.ring_signature import signature_from_pem
from ecdsa.ring_signature_factory import (
    RingSignatureFactory,
    get_ring_signature_factory
)
from ecdsa.util import randrange

curve = SECP256k1
g = curve.generator
n = g.order()

number_participants = 10
my_private_key_position = 2

# Generate private and public keys:
private_keys, public_keys = [], []

for i in range(number_participants):
    secret = randrange(n)
    pubkey = Public_key(g, g * secret)
    privkey = Private_key(pubkey, secret)
    public_keys.append(pubkey)
    private_keys.append(privkey)

message = b"Life, the Universe and Everything."

# Make signature:
factory = RingSignatureFactory(curve, hashlib.sha3_256)
signature = factory.sign(
    message,
    private_keys[my_private_key_position],
    public_keys,
    my_private_key_position,
)

# Export to PEM:
pem = signature.to_pem()
print(pem.decode())

# Import from PEM:
sig = signature_from_pem(pem)

# Verify signature:
factory2 = get_ring_signature_factory(sig)
if factory2.verify(message, sig, public_keys):
    print("OK. Signature is valid.")
else:
    print("Error. Invalid signature.")

$ python example.py
$ deactivate