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/*
* Block Cipher Cascade
* (C) 2010 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/cascade.h>
namespace Botan {
void Cascade_Cipher::encrypt_n(const uint8_t in[], uint8_t out[],
size_t blocks) const
{
size_t c1_blocks = blocks * (block_size() / m_cipher1->block_size());
size_t c2_blocks = blocks * (block_size() / m_cipher2->block_size());
m_cipher1->encrypt_n(in, out, c1_blocks);
m_cipher2->encrypt_n(out, out, c2_blocks);
}
void Cascade_Cipher::decrypt_n(const uint8_t in[], uint8_t out[],
size_t blocks) const
{
size_t c1_blocks = blocks * (block_size() / m_cipher1->block_size());
size_t c2_blocks = blocks * (block_size() / m_cipher2->block_size());
m_cipher2->decrypt_n(in, out, c2_blocks);
m_cipher1->decrypt_n(out, out, c1_blocks);
}
void Cascade_Cipher::key_schedule(const uint8_t key[], size_t)
{
const uint8_t* key2 = key + m_cipher1->maximum_keylength();
m_cipher1->set_key(key , m_cipher1->maximum_keylength());
m_cipher2->set_key(key2, m_cipher2->maximum_keylength());
}
void Cascade_Cipher::clear()
{
m_cipher1->clear();
m_cipher2->clear();
}
std::string Cascade_Cipher::name() const
{
return "Cascade(" + m_cipher1->name() + "," + m_cipher2->name() + ")";
}
BlockCipher* Cascade_Cipher::clone() const
{
return new Cascade_Cipher(m_cipher1->clone(),
m_cipher2->clone());
}
namespace {
size_t euclids_algorithm(size_t a, size_t b)
{
while(b != 0)
{
size_t t = b;
b = a % b;
a = t;
}
return a;
}
size_t block_size_for_cascade(size_t bs, size_t bs2)
{
if(bs == bs2)
return bs;
const size_t gcd = euclids_algorithm(bs, bs2);
return (bs * bs2) / gcd;
}
}
Cascade_Cipher::Cascade_Cipher(BlockCipher* c1, BlockCipher* c2) :
m_cipher1(c1), m_cipher2(c2)
{
m_block = block_size_for_cascade(c1->block_size(), c2->block_size());
BOTAN_ASSERT(m_block % c1->block_size() == 0 &&
m_block % c2->block_size() == 0,
"Combined block size is a multiple of each ciphers block");
}
}