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Editing: Salsa20.py
# -*- coding: utf-8 -*- # # Cipher/Salsa20.py : Salsa20 stream cipher (http://cr.yp.to/snuffle.html) # # Contributed by Fabrizio Tarizzo <fabrizio@fabriziotarizzo.org>. # # =================================================================== # 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. # =================================================================== from Crypto.Util.py3compat import _copy_bytes from Crypto.Util._raw_api import (load_pycryptodome_raw_lib, create_string_buffer, get_raw_buffer, VoidPointer, SmartPointer, c_size_t, c_uint8_ptr, is_writeable_buffer) from Crypto.Random import get_random_bytes _raw_salsa20_lib = load_pycryptodome_raw_lib("Crypto.Cipher._Salsa20", """ int Salsa20_stream_init(uint8_t *key, size_t keylen, uint8_t *nonce, size_t nonce_len, void **pSalsaState); int Salsa20_stream_destroy(void *salsaState); int Salsa20_stream_encrypt(void *salsaState, const uint8_t in[], uint8_t out[], size_t len); """) class Salsa20Cipher: """Salsa20 cipher object. Do not create it directly. Use :py:func:`new` instead. :var nonce: The nonce with length 8 :vartype nonce: byte string """ def __init__(self, key, nonce): """Initialize a Salsa20 cipher object See also `new()` at the module level.""" if len(key) not in key_size: raise ValueError("Incorrect key length for Salsa20 (%d bytes)" % len(key)) if len(nonce) != 8: raise ValueError("Incorrect nonce length for Salsa20 (%d bytes)" % len(nonce)) self.nonce = _copy_bytes(None, None, nonce) self._state = VoidPointer() result = _raw_salsa20_lib.Salsa20_stream_init( c_uint8_ptr(key), c_size_t(len(key)), c_uint8_ptr(nonce), c_size_t(len(nonce)), self._state.address_of()) if result: raise ValueError("Error %d instantiating a Salsa20 cipher") self._state = SmartPointer(self._state.get(), _raw_salsa20_lib.Salsa20_stream_destroy) self.block_size = 1 self.key_size = len(key) def encrypt(self, plaintext, output=None): """Encrypt a piece of data. Args: plaintext(bytes/bytearray/memoryview): The data to encrypt, of any size. Keyword Args: output(bytes/bytearray/memoryview): The location where the ciphertext is written to. If ``None``, the ciphertext is returned. Returns: 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_salsa20_lib.Salsa20_stream_encrypt( self._state.get(), c_uint8_ptr(plaintext), c_uint8_ptr(ciphertext), c_size_t(len(plaintext))) if result: raise ValueError("Error %d while encrypting with Salsa20" % result) if output is None: return get_raw_buffer(ciphertext) else: return None def decrypt(self, ciphertext, output=None): """Decrypt a piece of data. Args: ciphertext(bytes/bytearray/memoryview): The data to decrypt, of any size. Keyword Args: output(bytes/bytearray/memoryview): The location where the plaintext is written to. If ``None``, the plaintext is returned. Returns: If ``output`` is ``None``, the plaintext is returned as ``bytes``. Otherwise, ``None``. """ try: return self.encrypt(ciphertext, output=output) except ValueError as e: raise ValueError(str(e).replace("enc", "dec")) def new(key, nonce=None): """Create a new Salsa20 cipher :keyword key: The secret key to use. It must be 16 or 32 bytes long. :type key: bytes/bytearray/memoryview :keyword nonce: A value that must never be reused for any other encryption done with this key. It must be 8 bytes long. If not provided, a random byte string will be generated (you can read it back via the ``nonce`` attribute of the returned object). :type nonce: bytes/bytearray/memoryview :Return: a :class:`Crypto.Cipher.Salsa20.Salsa20Cipher` object """ if nonce is None: nonce = get_random_bytes(8) return Salsa20Cipher(key, nonce) # Size of a data block (in bytes) block_size = 1 # Size of a key (in bytes) key_size = (16, 32)
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