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/*
* Rivest's Package Tranform
*
* (C) 2009 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/package.h>
#include <botan/pipe.h>
#include <botan/ctr.h>
#include <botan/loadstor.h>
#include <botan/xor_buf.h>
namespace Botan {
namespace AllOrNothingTransform {
void package(RandomNumberGenerator& rng,
BlockCipher* cipher,
const byte input[], u32bit input_len,
byte output[])
{
if(!cipher->valid_keylength(cipher->BLOCK_SIZE))
throw Invalid_Argument("AONT::package: Invalid cipher");
// The all-zero string which is used both as the CTR IV and as K0
const std::string all_zeros(cipher->BLOCK_SIZE*2, '0');
SymmetricKey package_key(rng, cipher->BLOCK_SIZE);
// takes ownership of cipher object
Keyed_Filter* ctr_mode = new CTR_BE(cipher,
package_key,
InitializationVector(all_zeros));
Pipe pipe(ctr_mode);
pipe.process_msg(input, input_len);
pipe.read(output, pipe.remaining());
// Set K0 (the all zero key)
cipher->set_key(SymmetricKey(all_zeros));
SecureVector<byte> buf(cipher->BLOCK_SIZE);
const u32bit blocks =
(input_len + cipher->BLOCK_SIZE - 1) / cipher->BLOCK_SIZE;
byte* final_block = output + input_len;
clear_mem(final_block, cipher->BLOCK_SIZE);
// XOR the hash blocks into the final block
for(u32bit i = 0; i != blocks; ++i)
{
u32bit left = std::min<u32bit>(cipher->BLOCK_SIZE,
input_len - cipher->BLOCK_SIZE * i);
buf.clear();
copy_mem(&buf[0], output + cipher->BLOCK_SIZE * i, left);
for(u32bit j = 0; j != 4; ++j)
buf[cipher->BLOCK_SIZE - 1 - j] ^= get_byte(3-j, i);
cipher->encrypt(buf);
xor_buf(final_block, buf, cipher->BLOCK_SIZE);
}
// XOR the random package key into the final block
xor_buf(final_block, package_key.begin(), cipher->BLOCK_SIZE);
}
void unpackage(BlockCipher* cipher,
const byte input[], u32bit input_len,
byte output[])
{
if(!cipher->valid_keylength(cipher->BLOCK_SIZE))
throw Invalid_Argument("AONT::unpackage: Invalid cipher");
if(input_len < cipher->BLOCK_SIZE)
throw Invalid_Argument("AONT::unpackage: Input too short");
// The all-zero string which is used both as the CTR IV and as K0
const std::string all_zeros(cipher->BLOCK_SIZE*2, '0');
cipher->set_key(SymmetricKey(all_zeros));
SecureVector<byte> package_key(cipher->BLOCK_SIZE);
SecureVector<byte> buf(cipher->BLOCK_SIZE);
// Copy the package key (masked with the block hashes)
copy_mem(&package_key[0],
input + (input_len - cipher->BLOCK_SIZE),
cipher->BLOCK_SIZE);
const u32bit blocks = ((input_len - 1) / cipher->BLOCK_SIZE);
// XOR the blocks into the package key bits
for(u32bit i = 0; i != blocks; ++i)
{
u32bit left = std::min<u32bit>(cipher->BLOCK_SIZE,
input_len - cipher->BLOCK_SIZE * (i+1));
buf.clear();
copy_mem(&buf[0], input + cipher->BLOCK_SIZE * i, left);
for(u32bit j = 0; j != 4; ++j)
buf[cipher->BLOCK_SIZE - 1 - j] ^= get_byte(3-j, i);
cipher->encrypt(buf);
xor_buf(&package_key[0], buf, cipher->BLOCK_SIZE);
}
// takes ownership of cipher object
Pipe pipe(new CTR_BE(cipher,
SymmetricKey(package_key),
InitializationVector(all_zeros)));
pipe.process_msg(input, input_len - cipher->BLOCK_SIZE);
pipe.read(output, pipe.remaining());
}
}
}
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