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Editing: _mode_ecb.py
# -*- coding: utf-8 -*- # # Cipher/mode_ecb.py : ECB mode # # =================================================================== # The contents of this file are dedicated to the public domain. To # the extent that dedication to the public domain is not available, # everyone is granted a worldwide, perpetual, royalty-free, # non-exclusive license to exercise all rights associated with the # contents of this file for any purpose whatsoever. # No rights are reserved. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS # BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN # ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE # SOFTWARE. # =================================================================== """ Electronic Code Book (ECB) mode. """ __all__ = [ 'EcbMode' ] from Crypto.Util._raw_api import (load_pycryptodome_raw_lib, VoidPointer, create_string_buffer, get_raw_buffer, SmartPointer, c_size_t, c_uint8_ptr, is_writeable_buffer) raw_ecb_lib = load_pycryptodome_raw_lib("Crypto.Cipher._raw_ecb", """ int ECB_start_operation(void *cipher, void **pResult); int ECB_encrypt(void *ecbState, const uint8_t *in, uint8_t *out, size_t data_len); int ECB_decrypt(void *ecbState, const uint8_t *in, uint8_t *out, size_t data_len); int ECB_stop_operation(void *state); """ ) class EcbMode(object): """*Electronic Code Book (ECB)*. This is the simplest encryption mode. Each of the plaintext blocks is directly encrypted into a ciphertext block, independently of any other block. This mode is dangerous because it exposes frequency of symbols in your plaintext. Other modes (e.g. *CBC*) should be used instead. See `NIST SP800-38A`_ , Section 6.1. .. _`NIST SP800-38A` : http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf :undocumented: __init__ """ def __init__(self, block_cipher): """Create a new block cipher, configured in ECB mode. :Parameters: block_cipher : C pointer A smart pointer to the low-level block cipher instance. """ self.block_size = block_cipher.block_size self._state = VoidPointer() result = raw_ecb_lib.ECB_start_operation(block_cipher.get(), self._state.address_of()) if result: raise ValueError("Error %d while instantiating the ECB mode" % result) # Ensure that object disposal of this Python object will (eventually) # free the memory allocated by the raw library for the cipher # mode self._state = SmartPointer(self._state.get(), raw_ecb_lib.ECB_stop_operation) # Memory allocated for the underlying block cipher is now owned # by the cipher mode block_cipher.release() def encrypt(self, plaintext, output=None): """Encrypt data with the key set at initialization. The data to encrypt can be broken up in two or more pieces and `encrypt` can be called multiple times. That is, the statement: >>> c.encrypt(a) + c.encrypt(b) is equivalent to: >>> c.encrypt(a+b) This function does not add any padding to the plaintext. :Parameters: plaintext : bytes/bytearray/memoryview The piece of data to encrypt. The length must be multiple of the cipher block length. :Keywords: output : bytearray/memoryview The location where the ciphertext must be written to. If ``None``, the ciphertext is returned. :Return: If ``output`` is ``None``, the ciphertext is returned as ``bytes``. Otherwise, ``None``. """ if output is None: ciphertext = create_string_buffer(len(plaintext)) else: ciphertext = output if not is_writeable_buffer(output): raise TypeError("output must be a bytearray or a writeable memoryview") if len(plaintext) != len(output): raise ValueError("output must have the same length as the input" " (%d bytes)" % len(plaintext)) result = raw_ecb_lib.ECB_encrypt(self._state.get(), c_uint8_ptr(plaintext), c_uint8_ptr(ciphertext), c_size_t(len(plaintext))) if result: if result == 3: raise ValueError("Data must be aligned to block boundary in ECB mode") raise ValueError("Error %d while encrypting in ECB mode" % result) if output is None: return get_raw_buffer(ciphertext) else: return None def decrypt(self, ciphertext, output=None): """Decrypt data with the key set at initialization. The data to decrypt can be broken up in two or more pieces and `decrypt` can be called multiple times. That is, the statement: >>> c.decrypt(a) + c.decrypt(b) is equivalent to: >>> c.decrypt(a+b) This function does not remove any padding from the plaintext. :Parameters: ciphertext : bytes/bytearray/memoryview The piece of data to decrypt. The length must be multiple of the cipher block length. :Keywords: output : bytearray/memoryview The location where the plaintext must be written to. If ``None``, the plaintext is returned. :Return: If ``output`` is ``None``, the plaintext is returned as ``bytes``. Otherwise, ``None``. """ if output is None: plaintext = create_string_buffer(len(ciphertext)) else: plaintext = output if not is_writeable_buffer(output): raise TypeError("output must be a bytearray or a writeable memoryview") if len(ciphertext) != len(output): raise ValueError("output must have the same length as the input" " (%d bytes)" % len(plaintext)) result = raw_ecb_lib.ECB_decrypt(self._state.get(), c_uint8_ptr(ciphertext), c_uint8_ptr(plaintext), c_size_t(len(ciphertext))) if result: if result == 3: raise ValueError("Data must be aligned to block boundary in ECB mode") raise ValueError("Error %d while decrypting in ECB mode" % result) if output is None: return get_raw_buffer(plaintext) else: return None def _create_ecb_cipher(factory, **kwargs): """Instantiate a cipher object that performs ECB encryption/decryption. :Parameters: factory : module The underlying block cipher, a module from ``Crypto.Cipher``. All keywords are passed to the underlying block cipher. See the relevant documentation for details (at least ``key`` will need to be present""" cipher_state = factory._create_base_cipher(kwargs) cipher_state.block_size = factory.block_size if kwargs: raise TypeError("Unknown parameters for ECB: %s" % str(kwargs)) return EcbMode(cipher_state)
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