PyBitmessage/src/pyelliptic/cipher.py

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2013-01-16 17:52:52 +01:00
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (C) 2011 Yann GUIBET <yannguibet@gmail.com>
# See LICENSE for details.
from pyelliptic.openssl import OpenSSL
class Cipher:
"""
Symmetric encryption
import pyelliptic
iv = pyelliptic.Cipher.gen_IV('aes-256-cfb')
ctx = pyelliptic.Cipher("secretkey", iv, 1, ciphername='aes-256-cfb')
ciphertext = ctx.update('test1')
ciphertext += ctx.update('test2')
ciphertext += ctx.final()
ctx2 = pyelliptic.Cipher("secretkey", iv, 0, ciphername='aes-256-cfb')
print ctx2.ciphering(ciphertext)
"""
def __init__(self, key, iv, do, ciphername='aes-256-cbc'):
"""
do == 1 => Encrypt; do == 0 => Decrypt
"""
self.cipher = OpenSSL.get_cipher(ciphername)
self.ctx = OpenSSL.EVP_CIPHER_CTX_new()
if do == 1 or do == 0:
k = OpenSSL.malloc(key, len(key))
IV = OpenSSL.malloc(iv, len(iv))
OpenSSL.EVP_CipherInit_ex(
self.ctx, self.cipher.get_pointer(), 0, k, IV, do)
else:
raise Exception("RTFM ...")
@staticmethod
def get_all_cipher():
"""
static method, returns all ciphers available
"""
return OpenSSL.cipher_algo.keys()
@staticmethod
def get_blocksize(ciphername):
cipher = OpenSSL.get_cipher(ciphername)
return cipher.get_blocksize()
@staticmethod
def gen_IV(ciphername):
cipher = OpenSSL.get_cipher(ciphername)
return OpenSSL.rand(cipher.get_blocksize())
def update(self, input):
i = OpenSSL.c_int(0)
buffer = OpenSSL.malloc(b"", len(input) + self.cipher.get_blocksize())
inp = OpenSSL.malloc(input, len(input))
if OpenSSL.EVP_CipherUpdate(self.ctx, OpenSSL.byref(buffer),
OpenSSL.byref(i), inp, len(input)) == 0:
raise Exception("[OpenSSL] EVP_CipherUpdate FAIL ...")
return buffer.raw[0:i.value]
def final(self):
i = OpenSSL.c_int(0)
buffer = OpenSSL.malloc(b"", self.cipher.get_blocksize())
if (OpenSSL.EVP_CipherFinal_ex(self.ctx, OpenSSL.byref(buffer),
OpenSSL.byref(i))) == 0:
raise Exception("[OpenSSL] EVP_CipherFinal_ex FAIL ...")
return buffer.raw[0:i.value]
def ciphering(self, input):
"""
Do update and final in one method
"""
buff = self.update(input)
return buff + self.final()
def __del__(self):
OpenSSL.EVP_CIPHER_CTX_cleanup(self.ctx)
OpenSSL.EVP_CIPHER_CTX_free(self.ctx)