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


from ctypes import *
from abc import *


class Kem(object):
    """Provides generic interface to the Key Encapsulation Mechanism (KEM)."""
    __metaclass__ = ABCMeta

    @abstractmethod
    def kem_shared_key_len(self, key):
        """Return length in bytes required to hold encapsulated shared key."""
        raise NotImplementedError()

    @abstractmethod
    def kem_encapsulated_key_len(self, public_key):
        """Return length in bytes required to hold encapsulated key."""
        raise NotImplementedError()

    @abstractmethod
    def kem_encapsulate(self, public_key):
        """Generate a shared key and a key encapsulated message."""
        raise NotImplementedError()

    @abstractmethod
    def kem_decapsulate(self, encapsulated_key, private_key):
        """Decapsulate the shared key."""
        raise NotImplementedError()
