def op_checksig(stack, z):
# check that there are at least 2 elements on the stack
if len(stack) < 2:
return False
# the top element of the stack is the SEC pubkey
sec_pubkey = stack.pop()
# the next element of the stack is the DER signature
# take off the last byte of the signature as that's the hash_type
der_signature = stack.pop()[:-1]
# parse the serialized pubkey and signature into objects
try:
point = S256Point.parse(sec_pubkey)
sig = Signature.parse(der_signature)
except (ValueError, SyntaxError) as e:
LOGGER.info(e)
return False
# verify the signature using S256Point.verify()
# push an encoded 1 or 0 depending on whether the signature verified
if point.verify(z, sig):
stack.append(encode_num(1))
else:
stack.append(encode_num(0))
return True
