In that case this should do the trick:
EDIT NUMBER 3: THIS VERSION ACTUALLY WORKS USE THIS ONE
from fastecdsa import curve
from fastecdsa.point import Point
import bit
G = curve.secp256k1.G
N = curve.secp256k1.q
def pub2point(pub_hex):
x = int(pub_hex[2:66], 16)
if len(pub_hex) < 70:
y = bit.format.x_to_y(x, int(pub_hex[:2], 16) % 2)
else:
y = int(pub_hex[66:], 16)
return Point(x, y, curve=curve.secp256k1)
# This function makes all the downscaled pubkeys obtained from subtracting
# numbers between 0 and divisor, before dividing the pubkeys by divisor.
def shiftdown(pubkey, divisor, file, convert=True):
Q = pub2point(pubkey) if convert else pubkey
print(Q, 'QQ')
# k = 1/divisor
k = pow(divisor, N - 2, N)
for i in range(divisor+1):
P = Q - (i * G)
P = k * P
if (P.y % 2 == 0):
prefix = "02"
else:
prefix = "03"
hx = hex(P.x)[2:].zfill(64)
hy = hex(P.y)[2:].zfill(64)
file.write(prefix+hx+"\n") # Writes compressed key to file
factor = 32
with open("input.txt", "r") as f, open("output.txt", "w") as outf:
line = f.readline().strip()
while line != '':
shiftdown(line, factor, outf)
line = f.readline().strip()
This is for all keys in one file, I technically *could* script the case of one set of shifted keys per file, but then it requires an argc/argv switch to toggle the one you want and implementing that will bloat the code size
EDIT: I had posted an older version of the script which people complained had a bunch of errors, admittingly I did not test this version with the file input since the base script was already "bug free" I thought these should be straightforward changes... well now I know
After some proper testing, I got rid of a bunch of artifacts from older script versions that were triggering lint errors, and the result is posted here, above.
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