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# Lead Maintainer: Virgil Security Inc. <support@virgilsecurity.com>


from ctypes import *
from abc import *


class KeySigner(object):
    """Provide an interface for signing and verifying data digest
    with asymmetric keys."""
    __metaclass__ = ABCMeta

    @abstractmethod
    def can_sign(self, private_key):
        """Check if algorithm can sign data digest with a given key."""
        raise NotImplementedError()

    @abstractmethod
    def signature_len(self, private_key):
        """Return length in bytes required to hold signature.
        Return zero if a given private key can not produce signatures."""
        raise NotImplementedError()

    @abstractmethod
    def sign_hash(self, private_key, hash_id, digest):
        """Sign data digest with a given private key."""
        raise NotImplementedError()

    @abstractmethod
    def can_verify(self, public_key):
        """Check if algorithm can verify data digest with a given key."""
        raise NotImplementedError()

    @abstractmethod
    def verify_hash(self, public_key, hash_id, digest, signature):
        """Verify data digest with a given public key and signature."""
        raise NotImplementedError()
