#
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# A block cipher is instantiated as a combination of:
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# 1. A base cipher (such as AES)
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# 2. A mode of operation (such as CBC)
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#
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# Both items are implemented as C modules.
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#
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# The API of #1 is (replace "AES" with the name of the actual cipher):
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# - AES_start_operaion(key) --> base_cipher_state
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# - AES_encrypt(base_cipher_state, in, out, length)
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# - AES_decrypt(base_cipher_state, in, out, length)
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# - AES_stop_operation(base_cipher_state)
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#
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# Where base_cipher_state is AES_State, a struct with BlockBase (set of
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# pointers to encrypt/decrypt/stop) followed by cipher-specific data.
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#
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# The API of #2 is (replace "CBC" with the name of the actual mode):
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# - CBC_start_operation(base_cipher_state) --> mode_state
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# - CBC_encrypt(mode_state, in, out, length)
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# - CBC_decrypt(mode_state, in, out, length)
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# - CBC_stop_operation(mode_state)
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#
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# where mode_state is a a pointer to base_cipher_state plus mode-specific data.
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def _create_cipher(factory, key, mode, *args, **kwargs):
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kwargs["key"] = key
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if args:
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if mode in (8, 9, 10, 11, 12):
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if len(args) > 1:
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raise TypeError("Too many arguments for this mode")
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kwargs["nonce"] = args[0]
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elif mode in (2, 3, 5, 7):
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if len(args) > 1:
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raise TypeError("Too many arguments for this mode")
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kwargs["IV"] = args[0]
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elif mode == 6:
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if len(args) > 0:
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raise TypeError("Too many arguments for this mode")
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elif mode == 1:
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raise TypeError("IV is not meaningful for the ECB mode")
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res = None
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extra_modes = kwargs.pop("add_aes_modes", False)
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if mode == 1:
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from Crypto.Cipher._mode_ecb import _create_ecb_cipher
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res = _create_ecb_cipher(factory, **kwargs)
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elif mode == 2:
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from Crypto.Cipher._mode_cbc import _create_cbc_cipher
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res = _create_cbc_cipher(factory, **kwargs)
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elif mode == 3:
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from Crypto.Cipher._mode_cfb import _create_cfb_cipher
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res = _create_cfb_cipher(factory, **kwargs)
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elif mode == 5:
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from Crypto.Cipher._mode_ofb import _create_ofb_cipher
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res = _create_ofb_cipher(factory, **kwargs)
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elif mode == 6:
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from Crypto.Cipher._mode_ctr import _create_ctr_cipher
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res = _create_ctr_cipher(factory, **kwargs)
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elif mode == 7:
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from Crypto.Cipher._mode_openpgp import _create_openpgp_cipher
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res = _create_openpgp_cipher(factory, **kwargs)
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elif mode == 9:
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from Crypto.Cipher._mode_eax import _create_eax_cipher
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res = _create_eax_cipher(factory, **kwargs)
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elif extra_modes:
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if mode == 8:
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from Crypto.Cipher._mode_ccm import _create_ccm_cipher
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res = _create_ccm_cipher(factory, **kwargs)
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elif mode == 10:
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from Crypto.Cipher._mode_siv import _create_siv_cipher
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res = _create_siv_cipher(factory, **kwargs)
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elif mode == 11:
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from Crypto.Cipher._mode_gcm import _create_gcm_cipher
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res = _create_gcm_cipher(factory, **kwargs)
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elif mode == 12:
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from Crypto.Cipher._mode_ocb import _create_ocb_cipher
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res = _create_ocb_cipher(factory, **kwargs)
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elif mode == 13:
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from Crypto.Cipher._mode_kw import _create_kw_cipher
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res = _create_kw_cipher(factory, **kwargs)
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elif mode == 14:
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from Crypto.Cipher._mode_kwp import _create_kwp_cipher
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res = _create_kwp_cipher(factory, **kwargs)
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if res is None:
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raise ValueError("Mode not supported")
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return res
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