def _encrypt(keyset: tink_pb2.Keyset, master_key_primitive: aead.Aead,
associated_data: bytes) -> tink_pb2.EncryptedKeyset:
"""Encrypts a Keyset and returns an EncryptedKeyset."""
encrypted_keyset = master_key_primitive.encrypt(keyset.SerializeToString(),
associated_data)
# Check if we can decrypt, to detect errors
try:
keyset2 = tink_pb2.Keyset.FromString(
master_key_primitive.decrypt(encrypted_keyset, associated_data))
if keyset != keyset2:
raise core.TinkError('cannot encrypt keyset: %s != %s' %
(keyset, keyset2))
except message.DecodeError:
raise core.TinkError('invalid keyset, corrupted key material')
return tink_pb2.EncryptedKeyset(encrypted_keyset=encrypted_keyset,
keyset_info=_keyset_info(keyset))
def _decrypt(encrypted_keyset: tink_pb2.EncryptedKeyset,
master_key_aead: aead.Aead) -> tink_pb2.Keyset:
"""Decrypts an EncryptedKeyset and returns a Keyset."""
try:
keyset = tink_pb2.Keyset.FromString(
master_key_aead.decrypt(encrypted_keyset.encrypted_keyset, b''))
# Check emptiness here too, in case the encrypted keys unwrapped to nothing?
_assert_enough_key_material(keyset)
return keyset
except message.DecodeError:
raise core.TinkError('invalid keyset, corrupted key material')