233 lines
6.9 KiB
Python
233 lines
6.9 KiB
Python
"""
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High level cryptographic functions based on `.pyelliptic` OpenSSL bindings.
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.. note::
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Upstream pyelliptic was upgraded from SHA1 to SHA256 for signing. We must
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`upgrade PyBitmessage gracefully. <https://github.com/Bitmessage/PyBitmessage/issues/953>`_
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`More discussion. <https://github.com/yann2192/pyelliptic/issues/32>`_
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"""
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import hashlib
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import os
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from binascii import hexlify
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import pyelliptic
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from pyelliptic import OpenSSL
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from pyelliptic import arithmetic as a
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from fallback import RIPEMD160Hash
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__all__ = [
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'decodeWalletImportFormat', 'deterministic_keys',
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'double_sha512', 'calculateInventoryHash', 'encodeWalletImportFormat',
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'encrypt', 'makeCryptor', 'pointMult', 'privToPub', 'randomBytes',
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'random_keys', 'sign', 'to_ripe', 'verify']
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# WIF (uses arithmetic ):
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def decodeWalletImportFormat(WIFstring):
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"""
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Convert private key from base58 that's used in the config file to
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8-bit binary string.
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"""
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fullString = a.changebase(WIFstring, 58, 256)
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privkey = fullString[:-4]
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if fullString[-4:] != \
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hashlib.sha256(hashlib.sha256(privkey).digest()).digest()[:4]:
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raise ValueError('Checksum failed')
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elif privkey[0:1] == b'\x80': # checksum passed
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return privkey[1:]
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raise ValueError('No hex 80 prefix')
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# An excellent way for us to store our keys
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# is in Wallet Import Format. Let us convert now.
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# https://en.bitcoin.it/wiki/Wallet_import_format
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def encodeWalletImportFormat(privKey):
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"""
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Convert private key from binary 8-bit string into base58check WIF string.
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"""
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privKey = b'\x80' + privKey
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checksum = hashlib.sha256(hashlib.sha256(privKey).digest()).digest()[0:4]
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return a.changebase(privKey + checksum, 256, 58)
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# Random
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def randomBytes(n):
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"""Get n random bytes"""
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try:
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return os.urandom(n)
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except NotImplementedError:
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return OpenSSL.rand(n)
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# Hashes
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def _bm160(data):
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"""RIPEME160(SHA512(data)) -> bytes"""
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return RIPEMD160Hash(hashlib.sha512(data).digest()).digest()
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def to_ripe(signing_key, encryption_key):
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"""Convert two public keys to a ripe hash"""
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return _bm160(signing_key + encryption_key)
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def double_sha512(data):
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"""Binary double SHA512 digest"""
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return hashlib.sha512(hashlib.sha512(data).digest()).digest()
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def calculateInventoryHash(data):
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"""Calculate inventory hash from object data"""
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return double_sha512(data)[:32]
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# Keys
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def random_keys():
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"""Return a pair of keys, private and public"""
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priv = randomBytes(32)
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pub = pointMult(priv)
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return priv, pub
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def deterministic_keys(passphrase, nonce):
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"""Generate keys from *passphrase* and *nonce* (encoded as varint)"""
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priv = hashlib.sha512(passphrase + nonce).digest()[:32]
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pub = pointMult(priv)
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return priv, pub
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def hexToPubkey(pubkey):
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"""Convert a pubkey from hex to binary"""
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pubkey_raw = a.changebase(pubkey[2:], 16, 256, minlen=64)
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pubkey_bin = b'\x02\xca\x00 ' + pubkey_raw[:32] + b'\x00 ' + pubkey_raw[32:]
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return pubkey_bin
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def privToPub(privkey):
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"""Converts hex private key into hex public key"""
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private_key = a.changebase(privkey, 16, 256, minlen=32)
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public_key = pointMult(private_key)
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return hexlify(public_key)
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def pointMult(secret):
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"""
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Does an EC point multiplication; turns a private key into a public key.
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Evidently, this type of error can occur very rarely:
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>>> File "highlevelcrypto.py", line 54, in pointMult
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>>> group = OpenSSL.EC_KEY_get0_group(k)
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>>> WindowsError: exception: access violation reading 0x0000000000000008
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"""
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while True:
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try:
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k = OpenSSL.EC_KEY_new_by_curve_name(
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OpenSSL.get_curve('secp256k1'))
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priv_key = OpenSSL.BN_bin2bn(secret, 32, None)
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group = OpenSSL.EC_KEY_get0_group(k)
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pub_key = OpenSSL.EC_POINT_new(group)
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OpenSSL.EC_POINT_mul(group, pub_key, priv_key, None, None, None)
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OpenSSL.EC_KEY_set_private_key(k, priv_key)
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OpenSSL.EC_KEY_set_public_key(k, pub_key)
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size = OpenSSL.i2o_ECPublicKey(k, None)
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mb = OpenSSL.create_string_buffer(size)
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OpenSSL.i2o_ECPublicKey(k, OpenSSL.byref(OpenSSL.pointer(mb)))
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return mb.raw
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except Exception:
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import traceback
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import time
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traceback.print_exc()
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time.sleep(0.2)
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finally:
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OpenSSL.EC_POINT_free(pub_key)
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OpenSSL.BN_free(priv_key)
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OpenSSL.EC_KEY_free(k)
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# Encryption
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def makeCryptor(privkey, curve='secp256k1'):
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"""Return a private `.pyelliptic.ECC` instance"""
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private_key = a.changebase(privkey, 16, 256, minlen=32)
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public_key = pointMult(private_key)
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cryptor = pyelliptic.ECC(
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pubkey_x=public_key[1:-32], pubkey_y=public_key[-32:],
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raw_privkey=private_key, curve=curve)
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return cryptor
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def makePubCryptor(pubkey):
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"""Return a public `.pyelliptic.ECC` instance"""
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pubkey_bin = hexToPubkey(pubkey)
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return pyelliptic.ECC(curve='secp256k1', pubkey=pubkey_bin)
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def encrypt(msg, hexPubkey):
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"""Encrypts message with hex public key"""
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return pyelliptic.ECC(curve='secp256k1').encrypt(
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msg, hexToPubkey(hexPubkey))
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def decrypt(msg, hexPrivkey):
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"""Decrypts message with hex private key"""
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return makeCryptor(hexPrivkey).decrypt(msg)
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def decryptFast(msg, cryptor):
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"""Decrypts message with an existing `.pyelliptic.ECC` object"""
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return cryptor.decrypt(msg)
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# Signatures
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def _choose_digest_alg(name):
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"""
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Choose openssl digest constant by name raises ValueError if not appropriate
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"""
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if name not in ("sha1", "sha256"):
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raise ValueError("Unknown digest algorithm %s" % name)
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return (
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# SHA1, this will eventually be deprecated
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OpenSSL.digest_ecdsa_sha1 if name == "sha1" else OpenSSL.EVP_sha256)
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def sign(msg, hexPrivkey, digestAlg="sha256"):
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"""
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Signs with hex private key using SHA1 or SHA256 depending on
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*digestAlg* keyword.
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"""
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return makeCryptor(hexPrivkey).sign(
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msg, digest_alg=_choose_digest_alg(digestAlg))
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def verify(msg, sig, hexPubkey, digestAlg=None):
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"""Verifies with hex public key using SHA1 or SHA256"""
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# As mentioned above, we must upgrade gracefully to use SHA256. So
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# let us check the signature using both SHA1 and SHA256 and if one
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# of them passes then we will be satisfied. Eventually this can
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# be simplified and we'll only check with SHA256.
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if digestAlg is None:
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# old SHA1 algorithm.
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sigVerifyPassed = verify(msg, sig, hexPubkey, "sha1")
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if sigVerifyPassed:
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# The signature check passed using SHA1
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return True
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# The signature check using SHA1 failed. Let us try it with SHA256.
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return verify(msg, sig, hexPubkey, "sha256")
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try:
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return makePubCryptor(hexPubkey).verify(
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sig, msg, digest_alg=_choose_digest_alg(digestAlg))
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except:
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return False
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