class EC(object):
"""
Wrapper around python-bitcoinlib's CECKey class
"""
def __init__(self):
self.key = CECKey()
self.init = False
self.is_private = False
def load_public_key(self, key_path):
with open(key_path, 'rb') as f:
temp_key = f.read()
self.key.set_pubkey(temp_key)
self.init = True
def load_private_key(self, key_path):
with open(key_path, 'rb') as f:
temp_key = f.read()
self.key.set_privkey(temp_key)
self.init = True
self.is_private = True
def get_pubkey(self):
return self.key.get_pubkey()
def sign(self, msg):
if self.init:
if self.is_private:
sig = self.key.sign(msg)
return sig
else:
raise ValueError('Signing requires a private key')
else:
raise ValueError('No key is loaded.')
def verify(self, msg, sig):
if self.init:
return self.key.verify(msg, sig) == 1
else:
raise ValueError('No key is loaded.')
def serialize_sig(self, sig):
"""
Takes in a signature in DER format and returns a byte
string of R + S that should be 64 bytes in length
"""
sig_struct = ECDSA_SIG_st()
_ssl.d2i_ECDSA_SIG(ctypes.byref(ctypes.pointer(sig_struct)),
ctypes.byref(ctypes.c_char_p(sig)), len(sig))
r = BNToBin(sig_struct.r, 32)
s = BNToBin(sig_struct.s, 32)
return r + s
def deserialize_sig(self, serial_sig):
"""
Converts a serial signature (R + S) into DER format
Arguments:
serial_sig (bytes): A 64 byte string that represents R and S where each
is 32 bytes
Returns:
A signature in der format
Raises:
Value error if serial sig is not 64 bytes
"""
if len(serial_sig) == 64:
sig_struct = ECDSA_SIG_st()
r = BinToBN(serial_sig[:32])
s = BinToBN(serial_sig[32:])
sig_struct.r = r
sig_struct.s = s
derlen = _ssl.i2d_ECDSA_SIG(ctypes.pointer(sig_struct), 0)
if derlen == 0:
_ssl.ECDSA_SIG_free(sig_struct)
return None
der_sig = ctypes.create_string_buffer(derlen)
_ssl.i2d_ECDSA_SIG(ctypes.pointer(sig_struct),
ctypes.byref(ctypes.pointer(der_sig)))
return der_sig.raw
else:
raise ValueError('Serial sig has to be 64 bytes.')
