#!/usr/bin/python3

"""

My attempt at solving the 0.025 BTC puzzle posted on Reddit:

https://www.reddit.com/r/Bitcoin/comments/8krbd3/prize_inside_25mbtc_private_key_in_puzzle/

I was too late, but it was fun!

"""

from pycoin.key import Key

from pycoin.encoding import hash160, b2a_hashed_base58, hash160, b2a_base58, a2b_base58, double_sha256

def p2sh_address(key):

return b2a_hashed_base58(b'\5' + hash160(b'\x00\x14' + hash160(key.sec(use_uncompressed=False))))

# this is the final result, but below is the brute-force algorithm that shows how it was obtained

thekey = "L5fnrCYwxHsqbFKkfBVS2if1zwK6FyXV8Xet6FnmTG4W1eYgQDFq"

# key segments (letters only) that I'm sure of

k1 = "L"

k2 = "fnrCYwxHsqbFKkfZVS"

k3 = "if1zwK"

k4 = "FyXV"

k5 = "Xet"

k6 = "FnmTG"

k7 = "W"

k8 = "eYgQDFq"

# for the numbers I was not sure for all of them, so I just brute-forced the ones I was unsure of

longest_match = 0

for i1 in '4': # sure

for i2 in '2': # sure

for i3 in '6': # sure

for i4 in '123456789': # NOT sure

for i6 in '123456789': # NOT sure

for i7 in '123456789': # NOT sure

# make candidate private key

key = k1 + i1 + k2 + i2 + k3 + i3 + k4 + i4 + k5 + i3 + k6 + i6 + k7 + i7 + k8

print('Trying {}...\t'.format(key), end='')

# the private key encoded in base58 contains also a checksum at the end to check validity

# when a candidate key is made by concatenation as above it will most likely not be valid

# so we correct the checksum and compression byte of the candidate key

data = a2b_base58(key)

data, the_hash = data[:-4], data[-4:]

data = data[:-1] + b'\01'

fixed_key = b2a_base58(data + double_sha256(data)[:4])

# calculate the P2SH SegWit address for this private key

k = Key.from_text(fixed_key)

p2sh = p2sh_address(k)

print('{}\t'.format(p2sh), end='')

# compare with the published public key

if p2sh[0:7] == '37CSnmm':

print('Bingo!')

exit(0)

else:

i = 0

stars = ''

while p2sh[i] == '37CSnmm'[i]:

stars += '*'

i += 1

if i > longest_match:

longest_match = i

print('{} {}'.format(longest_match, stars))