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/*
* Block Cipher Cascade
* (C) 2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/cascade.h>
namespace Botan {
void Cascade_Cipher::encrypt_n(const byte in[], byte out[],
u32bit blocks) const
{
u32bit c1_blocks = blocks * (BLOCK_SIZE / cipher1->BLOCK_SIZE);
u32bit c2_blocks = blocks * (BLOCK_SIZE / cipher2->BLOCK_SIZE);
cipher1->encrypt_n(in, out, c1_blocks);
cipher2->encrypt_n(out, out, c2_blocks);
}
void Cascade_Cipher::decrypt_n(const byte in[], byte out[],
u32bit blocks) const
{
u32bit c1_blocks = blocks * (BLOCK_SIZE / cipher1->BLOCK_SIZE);
u32bit c2_blocks = blocks * (BLOCK_SIZE / cipher2->BLOCK_SIZE);
cipher2->decrypt_n(in, out, c2_blocks);
cipher1->decrypt_n(out, out, c1_blocks);
}
void Cascade_Cipher::key_schedule(const byte key[], u32bit)
{
const byte* key2 = key + cipher1->MAXIMUM_KEYLENGTH;
cipher1->set_key(key , cipher1->MAXIMUM_KEYLENGTH);
cipher2->set_key(key2, cipher2->MAXIMUM_KEYLENGTH);
}
void Cascade_Cipher::clear()
{
cipher1->clear();
cipher2->clear();
}
std::string Cascade_Cipher::name() const
{
return "Cascade(" + cipher1->name() + "," + cipher2->name() + ")";
}
BlockCipher* Cascade_Cipher::clone() const
{
return new Cascade_Cipher(cipher1->clone(),
cipher2->clone());
}
namespace {
u32bit euclids_algorithm(u32bit a, u32bit b)
{
while(b != 0) // gcd
{
u32bit t = b;
b = a % b;
a = t;
}
return a;
}
u32bit block_size_for_cascade(u32bit bs, u32bit bs2)
{
if(bs == bs2)
return bs;
u32bit gcd = euclids_algorithm(bs, bs2);
return (bs * bs2) / gcd;
}
}
Cascade_Cipher::Cascade_Cipher(BlockCipher* c1, BlockCipher* c2) :
BlockCipher(block_size_for_cascade(c1->BLOCK_SIZE, c2->BLOCK_SIZE),
c1->MAXIMUM_KEYLENGTH + c2->MAXIMUM_KEYLENGTH),
cipher1(c1), cipher2(c2)
{
if(BLOCK_SIZE % c1->BLOCK_SIZE || BLOCK_SIZE % c2->BLOCK_SIZE)
throw Internal_Error("Failure in " + name() + " constructor");
}
Cascade_Cipher::~Cascade_Cipher()
{
delete cipher1;
delete cipher2;
}
}
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