/*

* Block Cipher Cascade

* (C) 2010 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/internal/cascade.h>

#include <botan/internal/fmt.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 /*length*/) {

   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 fmt("Cascade({},{})", m_cipher1->name(), m_cipher2->name()); }

bool Cascade_Cipher::has_keying_material() const {

   return m_cipher1->has_keying_material() && m_cipher2->has_keying_material();

}

std::unique_ptr<BlockCipher> Cascade_Cipher::new_object() const {

   return std::make_unique<Cascade_Cipher>(m_cipher1->new_object(), m_cipher2->new_object());

}

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;

}

}  // namespace

Cascade_Cipher::Cascade_Cipher(std::unique_ptr<BlockCipher> cipher1, std::unique_ptr<BlockCipher> cipher2) :

      m_cipher1(std::move(cipher1)),

      m_cipher2(std::move(cipher2)),

      m_block_size(block_size_for_cascade(m_cipher1->block_size(), m_cipher2->block_size())) {

   BOTAN_ASSERT(m_block_size % m_cipher1->block_size() == 0 && m_block_size % m_cipher2->block_size() == 0,

                "Combined block size is a multiple of each ciphers block");

}

}  // namespace Botan