Lightning network PTLC payment point example. Requires "pip install ECPy"

sell-example.py

import os

from ecpy.ecschnorr import ECSchnorr

from ecpy.curves     import Curve,Point
from ecpy.keys       import ECPublicKey, ECPrivateKey
from ecpy.formatters import decode_sig, encode_sig, list_formats
from ecpy            import ecrand
from ecpy.curves     import ECPyException

import hashlib


KEY_LENGTH = 32


## Step 1: Data to sell
s = "hello schnorr"

## Step 2: Generate random message
#msg = os.urandom(KEY_LENGTH)
msg = int(0x0101010101010101010101010101010101010101010101010101010101010101)
msg = msg.to_bytes(32,'big')

## Step 3: Generate key pair
#x = os.urandom(KEY_LENGTH)
cv = Curve.get_curve('secp256k1')
pu_key = ECPublicKey(Point(0x65d5b8bf9ab1801c9f168d4815994ad35f1dcb6ae6c7a1a303966b677b813b00,
                           0xe6b865e529b8ecbf71cf966e900477d49ced5846d7662dd2dd11ccd55c0aff7f,
                           cv))
pv_key = ECPrivateKey(0xfb26a4e75eec75544c0f44e937dcf5ee6355c7176600b9688c667e5c283b43c5,
                      cv)

## Step 4: Generate random nonce
#k = int.from_bytes(os.urandom(KEY_LENGTH), 'big')
k = int(0x4242424242424242424242424242424242424242424242424242424242424242)

## Step 5: Calculate signature
signer = ECSchnorr(hashlib.sha256,"LIBSECP","ITUPLE")
sig = signer.sign_k(msg,pv_key,k)

## Step 6: Verify the signature
expect_r = 0x24653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c
expect_s = 0xacd417b277ab7e7d993cc4a601dd01a71696fd0dd2e93561d9de9b69dd4dc75c
r, s = sig
print("r: {}".format(r))
print("s: {}".format(s))
r_hex = "{:64x}".format(r)
s_hex = "{:64x}".format(s)
print("r_hex: {}, len: {}".format(r_hex, len(r_hex)))
print("s_hex: {}, len: {}".format(s_hex, len(s_hex)))
assert(expect_r == r)
assert(expect_s == s)
assert(signer.verify(msg,sig,pu_key))
print("Verified signature.")

# Calculate the payment point
G = cv.generator
payment_point = s*G
print("payment_point: {}".format(payment_point))

payment_point_enc = bytes(cv.encode_point(payment_point, compressed=True))
print("payment_point_enc: {}, len: {}".format(payment_point_enc.hex(), len(payment_point_enc.hex())))