0

I found this python script on github.

It generates a pair of bitcoin private key and address.

I know the private key may be vulnerable if it is created insecurely.

I don't have much knowledge about Cryptology. Can you check if the script is secure?

#!/usr/bin/env python
# Joric/bitcoin-dev, june 2012, public domain

import hashlib
import ctypes
import ctypes.util
import sys

ssl = ctypes.cdll.LoadLibrary (ctypes.util.find_library ('ssl') or 'libeay32')

def check_result (val, func, args):
    if val == 0: raise ValueError 
    else: return ctypes.c_void_p (val)

ssl.EC_KEY_new_by_curve_name.restype = ctypes.c_void_p
ssl.EC_KEY_new_by_curve_name.errcheck = check_result

class KEY:
    def __init__(self):
        NID_secp256k1 = 714
        self.k = ssl.EC_KEY_new_by_curve_name(NID_secp256k1)
        self.compressed = False
        self.POINT_CONVERSION_COMPRESSED = 2
        self.POINT_CONVERSION_UNCOMPRESSED = 4

def __del__(self):
    if ssl:
        ssl.EC_KEY_free(self.k)
    self.k = None

def generate(self, secret=None):
    if secret:
        self.prikey = secret
        priv_key = ssl.BN_bin2bn(secret, 32, ssl.BN_new())
        group = ssl.EC_KEY_get0_group(self.k)
        pub_key = ssl.EC_POINT_new(group)
        ctx = ssl.BN_CTX_new()
        ssl.EC_POINT_mul(group, pub_key, priv_key, None, None, ctx)
        ssl.EC_KEY_set_private_key(self.k, priv_key)
        ssl.EC_KEY_set_public_key(self.k, pub_key)
        ssl.EC_POINT_free(pub_key)
        ssl.BN_CTX_free(ctx)
        return self.k
    else:
        return ssl.EC_KEY_generate_key(self.k)

def get_pubkey(self):
    size = ssl.i2o_ECPublicKey(self.k, 0)
    mb = ctypes.create_string_buffer(size)
    ssl.i2o_ECPublicKey(self.k, ctypes.byref(ctypes.pointer(mb)))
    return mb.raw

def get_secret(self):
    bn = ssl.EC_KEY_get0_private_key(self.k);
    bytes = (ssl.BN_num_bits(bn) + 7) / 8
    mb = ctypes.create_string_buffer(bytes)
    n = ssl.BN_bn2bin(bn, mb);
    return mb.raw.rjust(32, chr(0))

def set_compressed(self, compressed):
    self.compressed = compressed
    if compressed:
        form = self.POINT_CONVERSION_COMPRESSED
    else:
        form = self.POINT_CONVERSION_UNCOMPRESSED
    ssl.EC_KEY_set_conv_form(self.k, form)

def dhash(s):
    return hashlib.sha256(hashlib.sha256(s).digest()).digest()

def rhash(s):
    h1 = hashlib.new('ripemd160')
    h1.update(hashlib.sha256(s).digest())
    return h1.digest()

b58_digits = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'

def base58_encode(n):
    l = []
    while n > 0:
        n, r = divmod(n, 58)
        l.insert(0,(b58_digits[r]))
    return ''.join(l)

def base58_decode(s):
    n = 0
    for ch in s:
        n *= 58
        digit = b58_digits.index(ch)
        n += digit
    return n

def base58_encode_padded(s):
    res = base58_encode(int('0x' + s.encode('hex'), 16))
    pad = 0
    for c in s:
        if c == chr(0):
            pad += 1
        else:
            break
    return b58_digits[0] * pad + res

def base58_decode_padded(s):
    pad = 0
    for c in s:
        if c == b58_digits[0]:
            pad += 1
        else:
            break
    h = '%x' % base58_decode(s)
    if len(h) % 2:
        h = '0' + h
    res = h.decode('hex')
    return chr(0) * pad + res

def base58_check_encode(s, version=0):
    vs = chr(version) + s
    check = dhash(vs)[:4]
    return base58_encode_padded(vs + check)

def base58_check_decode(s, version=0):
    k = base58_decode_padded(s)
    v0, data, check0 = k[0], k[1:-4], k[-4:]
    check1 = dhash(v0 + data)[:4]
    if check0 != check1:
        raise BaseException('checksum error')
    if version != ord(v0):
        raise BaseException('version mismatch')
    return data

def gen_eckey(passphrase=None, secret=None, pkey=None, compressed=False, rounds=1, version=0):
    k = KEY()
    if passphrase:
        secret = passphrase.encode('utf8')
        for i in xrange(rounds):
            secret = hashlib.sha256(secret).digest()
    if pkey:
        secret = base58_check_decode(pkey, 128+version)
        compressed = len(secret) == 33
        secret = secret[0:32]
    k.generate(secret)
    k.set_compressed(compressed)
    return k

def get_addr(k,version=0):
    pubkey = k.get_pubkey()
    secret = k.get_secret()
    hash160 = rhash(pubkey)
    addr = base58_check_encode(hash160,version)
    payload = secret
    if k.compressed:
        payload = secret + chr(1)
    pkey = base58_check_encode(payload, 128+version)
    return addr, pkey

def reencode(pkey,version=0):
    payload = base58_check_decode(pkey,128+version)
    secret = payload[:-1]
    payload = secret + chr(1)
    pkey = base58_check_encode(payload, 128+version)
    print get_addr(gen_eckey(pkey))

def test(otherversion):
    # random compressed
    print get_addr(gen_eckey(compressed=True,version=otherversion),version=otherversion)

    # uncomment these to create addresses via a different method
    # random uncompressed
    #print get_addr(gen_eckey())
    # by secret
    #print get_addr(gen_eckey(secret=('%064x' % 0xdeadbabe).decode('hex')))
    # by passphrase
    #print get_addr(gen_eckey(passphrase='Satoshi Nakamoto'))
    # by private key
    #print get_addr(gen_eckey(pkey='5K1HkbYffstTZDuV4riUWMbAMkQh57b8798uoy9pXYUDYeUHe7F'))
    #print get_addr(gen_eckey(pkey='L3ATL5R9Exe1ubuAnHVgNgTKZEUKkDvWYAWkLUCyyvzzxRjtgyFe'))

    # uncomment this to reencode the private keys created by early versions of this script
    #reencode(sys.argv[1])

if __name__ == '__main__':
    import optparse
    parser = optparse.OptionParser(usage="%prog [options]")
    parser.add_option("--otherversion", dest="otherversion", default=0,
                    help="Generate address with different version number")
    (options, args) = parser.parse_args()

    test(int(options.otherversion))
  • 1
    crypto.stackexchange.com – MCCCS Dec 15 '17 at 8:26
  • 3
    I'm voting to close this question as off-topic because it belongs on crypto.stackexchange.com – Max Vernon Dec 15 '17 at 22:13
  • I'm not sure even crypto.SE is the place to ask for a full code review, but indeed this doesn't belong on bitcoin.SE sorry – MeshCollider Dec 18 '17 at 10:11
1

If you don't have the capabilities to review that script in detail, then you should at least research how widely use this script is.

I would recommend to not use it.

If you want the generate bitcoin private keys (and get bitcoin addresses from its corresponding public key), you should have a close look at Bitcoin Core.

If you just need keys and not access to the blockchain, you can disable the p2p interaction with -connect=0.

Bitcoin Core has a great RPC interface. You can still use python to interact with the API.

Though, don't forget, private keys highly depend on your OS entropy (random numbers). Also, if your system/OS is compromised, your funds received with the keys generated on that system are at risk.

Not the answer you're looking for? Browse other questions tagged or ask your own question.