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233 lines
8.3 KiB
Python
233 lines
8.3 KiB
Python
# Copyright (c) 2011 Sam Rushing
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"""ECC secp256k1 OpenSSL wrapper.
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WARNING: This module does not mlock() secrets; your private keys may end up on
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disk in swap! Use with caution!
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This file is modified from python-bitcoinlib.
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"""
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import ctypes
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import ctypes.util
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import hashlib
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import sys
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ssl = ctypes.cdll.LoadLibrary(ctypes.util.find_library ('ssl') or 'libeay32')
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ssl.BN_new.restype = ctypes.c_void_p
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ssl.BN_new.argtypes = []
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ssl.BN_bin2bn.restype = ctypes.c_void_p
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ssl.BN_bin2bn.argtypes = [ctypes.c_char_p, ctypes.c_int, ctypes.c_void_p]
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ssl.BN_CTX_free.restype = None
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ssl.BN_CTX_free.argtypes = [ctypes.c_void_p]
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ssl.BN_CTX_new.restype = ctypes.c_void_p
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ssl.BN_CTX_new.argtypes = []
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ssl.ECDH_compute_key.restype = ctypes.c_int
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ssl.ECDH_compute_key.argtypes = [ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p, ctypes.c_void_p]
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ssl.ECDSA_sign.restype = ctypes.c_int
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ssl.ECDSA_sign.argtypes = [ctypes.c_int, ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p]
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ssl.ECDSA_verify.restype = ctypes.c_int
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ssl.ECDSA_verify.argtypes = [ctypes.c_int, ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p]
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ssl.EC_KEY_free.restype = None
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ssl.EC_KEY_free.argtypes = [ctypes.c_void_p]
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ssl.EC_KEY_new_by_curve_name.restype = ctypes.c_void_p
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ssl.EC_KEY_new_by_curve_name.argtypes = [ctypes.c_int]
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ssl.EC_KEY_get0_group.restype = ctypes.c_void_p
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ssl.EC_KEY_get0_group.argtypes = [ctypes.c_void_p]
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ssl.EC_KEY_get0_public_key.restype = ctypes.c_void_p
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ssl.EC_KEY_get0_public_key.argtypes = [ctypes.c_void_p]
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ssl.EC_KEY_set_private_key.restype = ctypes.c_int
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ssl.EC_KEY_set_private_key.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
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ssl.EC_KEY_set_conv_form.restype = None
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ssl.EC_KEY_set_conv_form.argtypes = [ctypes.c_void_p, ctypes.c_int]
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ssl.EC_KEY_set_public_key.restype = ctypes.c_int
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ssl.EC_KEY_set_public_key.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
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ssl.i2o_ECPublicKey.restype = ctypes.c_void_p
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ssl.i2o_ECPublicKey.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
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ssl.EC_POINT_new.restype = ctypes.c_void_p
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ssl.EC_POINT_new.argtypes = [ctypes.c_void_p]
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ssl.EC_POINT_free.restype = None
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ssl.EC_POINT_free.argtypes = [ctypes.c_void_p]
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ssl.EC_POINT_mul.restype = ctypes.c_int
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ssl.EC_POINT_mul.argtypes = [ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p]
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# this specifies the curve used with ECDSA.
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NID_secp256k1 = 714 # from openssl/obj_mac.h
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SECP256K1_ORDER = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141
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SECP256K1_ORDER_HALF = SECP256K1_ORDER // 2
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# Thx to Sam Devlin for the ctypes magic 64-bit fix.
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def _check_result(val, func, args):
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if val == 0:
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raise ValueError
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else:
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return ctypes.c_void_p (val)
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ssl.EC_KEY_new_by_curve_name.restype = ctypes.c_void_p
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ssl.EC_KEY_new_by_curve_name.errcheck = _check_result
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class CECKey():
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"""Wrapper around OpenSSL's EC_KEY"""
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POINT_CONVERSION_COMPRESSED = 2
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POINT_CONVERSION_UNCOMPRESSED = 4
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def __init__(self):
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self.k = ssl.EC_KEY_new_by_curve_name(NID_secp256k1)
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def __del__(self):
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if ssl:
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ssl.EC_KEY_free(self.k)
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self.k = None
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def set_secretbytes(self, secret):
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priv_key = ssl.BN_bin2bn(secret, 32, ssl.BN_new())
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group = ssl.EC_KEY_get0_group(self.k)
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pub_key = ssl.EC_POINT_new(group)
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ctx = ssl.BN_CTX_new()
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if not ssl.EC_POINT_mul(group, pub_key, priv_key, None, None, ctx):
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raise ValueError("Could not derive public key from the supplied secret.")
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ssl.EC_POINT_mul(group, pub_key, priv_key, None, None, ctx)
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ssl.EC_KEY_set_private_key(self.k, priv_key)
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ssl.EC_KEY_set_public_key(self.k, pub_key)
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ssl.EC_POINT_free(pub_key)
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ssl.BN_CTX_free(ctx)
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return self.k
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def set_privkey(self, key):
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self.mb = ctypes.create_string_buffer(key)
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return ssl.d2i_ECPrivateKey(ctypes.byref(self.k), ctypes.byref(ctypes.pointer(self.mb)), len(key))
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def set_pubkey(self, key):
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self.mb = ctypes.create_string_buffer(key)
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return ssl.o2i_ECPublicKey(ctypes.byref(self.k), ctypes.byref(ctypes.pointer(self.mb)), len(key))
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def get_privkey(self):
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size = ssl.i2d_ECPrivateKey(self.k, 0)
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mb_pri = ctypes.create_string_buffer(size)
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ssl.i2d_ECPrivateKey(self.k, ctypes.byref(ctypes.pointer(mb_pri)))
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return mb_pri.raw
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def get_pubkey(self):
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size = ssl.i2o_ECPublicKey(self.k, 0)
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mb = ctypes.create_string_buffer(size)
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ssl.i2o_ECPublicKey(self.k, ctypes.byref(ctypes.pointer(mb)))
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return mb.raw
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def get_raw_ecdh_key(self, other_pubkey):
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ecdh_keybuffer = ctypes.create_string_buffer(32)
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r = ssl.ECDH_compute_key(ctypes.pointer(ecdh_keybuffer), 32,
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ssl.EC_KEY_get0_public_key(other_pubkey.k),
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self.k, 0)
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if r != 32:
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raise Exception('CKey.get_ecdh_key(): ECDH_compute_key() failed')
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return ecdh_keybuffer.raw
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def get_ecdh_key(self, other_pubkey, kdf=lambda k: hashlib.sha256(k).digest()):
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# FIXME: be warned it's not clear what the kdf should be as a default
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r = self.get_raw_ecdh_key(other_pubkey)
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return kdf(r)
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def sign(self, hash, low_s = True):
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# FIXME: need unit tests for below cases
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if not isinstance(hash, bytes):
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raise TypeError('Hash must be bytes instance; got %r' % hash.__class__)
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if len(hash) != 32:
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raise ValueError('Hash must be exactly 32 bytes long')
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sig_size0 = ctypes.c_uint32()
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sig_size0.value = ssl.ECDSA_size(self.k)
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mb_sig = ctypes.create_string_buffer(sig_size0.value)
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result = ssl.ECDSA_sign(0, hash, len(hash), mb_sig, ctypes.byref(sig_size0), self.k)
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assert 1 == result
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assert mb_sig.raw[0] == 0x30
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assert mb_sig.raw[1] == sig_size0.value - 2
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total_size = mb_sig.raw[1]
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assert mb_sig.raw[2] == 2
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r_size = mb_sig.raw[3]
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assert mb_sig.raw[4 + r_size] == 2
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s_size = mb_sig.raw[5 + r_size]
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s_value = int.from_bytes(mb_sig.raw[6+r_size:6+r_size+s_size], byteorder='big')
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if (not low_s) or s_value <= SECP256K1_ORDER_HALF:
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return mb_sig.raw[:sig_size0.value]
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else:
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low_s_value = SECP256K1_ORDER - s_value
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low_s_bytes = (low_s_value).to_bytes(33, byteorder='big')
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while len(low_s_bytes) > 1 and low_s_bytes[0] == 0 and low_s_bytes[1] < 0x80:
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low_s_bytes = low_s_bytes[1:]
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new_s_size = len(low_s_bytes)
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new_total_size_byte = (total_size + new_s_size - s_size).to_bytes(1,byteorder='big')
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new_s_size_byte = (new_s_size).to_bytes(1,byteorder='big')
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return b'\x30' + new_total_size_byte + mb_sig.raw[2:5+r_size] + new_s_size_byte + low_s_bytes
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def verify(self, hash, sig):
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"""Verify a DER signature"""
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return ssl.ECDSA_verify(0, hash, len(hash), sig, len(sig), self.k) == 1
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def set_compressed(self, compressed):
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if compressed:
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form = self.POINT_CONVERSION_COMPRESSED
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else:
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form = self.POINT_CONVERSION_UNCOMPRESSED
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ssl.EC_KEY_set_conv_form(self.k, form)
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class CPubKey(bytes):
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"""An encapsulated public key
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Attributes:
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is_valid - Corresponds to CPubKey.IsValid()
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is_fullyvalid - Corresponds to CPubKey.IsFullyValid()
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is_compressed - Corresponds to CPubKey.IsCompressed()
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"""
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def __new__(cls, buf, _cec_key=None):
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self = super(CPubKey, cls).__new__(cls, buf)
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if _cec_key is None:
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_cec_key = CECKey()
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self._cec_key = _cec_key
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self.is_fullyvalid = _cec_key.set_pubkey(self) != 0
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return self
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@property
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def is_valid(self):
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return len(self) > 0
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@property
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def is_compressed(self):
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return len(self) == 33
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def verify(self, hash, sig):
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return self._cec_key.verify(hash, sig)
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def __str__(self):
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return repr(self)
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def __repr__(self):
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# Always have represent as b'<secret>' so test cases don't have to
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# change for py2/3
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if sys.version > '3':
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return '%s(%s)' % (self.__class__.__name__, super(CPubKey, self).__repr__())
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else:
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return '%s(b%s)' % (self.__class__.__name__, super(CPubKey, self).__repr__())
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