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/*
* ANSI X9.31 RNG
* (C) 1999-2009 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/x931_rng.h>
#include <botan/internal/xor_buf.h>
#include <algorithm>
namespace Botan {
/*
* Generate a buffer of random bytes
*/
void ANSI_X931_RNG::randomize(byte out[], size_t length)
{
if(!is_seeded())
throw PRNG_Unseeded(name());
while(length)
{
if(position == R.size())
update_buffer();
const size_t copied = std::min<size_t>(length, R.size() - position);
copy_mem(out, &R[position], copied);
out += copied;
length -= copied;
position += copied;
}
}
/*
* Refill the internal state
*/
void ANSI_X931_RNG::update_buffer()
{
const size_t BLOCK_SIZE = cipher->block_size();
secure_vector<byte> DT = prng->random_vec(BLOCK_SIZE);
cipher->encrypt(DT);
xor_buf(&R[0], &V[0], &DT[0], BLOCK_SIZE);
cipher->encrypt(R);
xor_buf(&V[0], &R[0], &DT[0], BLOCK_SIZE);
cipher->encrypt(V);
position = 0;
}
/*
* Reset V and the cipher key with new values
*/
void ANSI_X931_RNG::rekey()
{
const size_t BLOCK_SIZE = cipher->block_size();
if(prng->is_seeded())
{
cipher->set_key(prng->random_vec(cipher->maximum_keylength()));
if(V.size() != BLOCK_SIZE)
V.resize(BLOCK_SIZE);
prng->randomize(&V[0], V.size());
update_buffer();
}
}
/*
* Reseed the internal state
*/
void ANSI_X931_RNG::reseed(size_t poll_bits)
{
prng->reseed(poll_bits);
rekey();
}
/*
* Add some entropy to the underlying PRNG
*/
void ANSI_X931_RNG::add_entropy(const byte input[], size_t length)
{
prng->add_entropy(input, length);
rekey();
}
/*
* Check if the the PRNG is seeded
*/
bool ANSI_X931_RNG::is_seeded() const
{
return (V.size() > 0);
}
/*
* Clear memory of sensitive data
*/
void ANSI_X931_RNG::clear()
{
cipher->clear();
prng->clear();
zeroise(R);
V.clear();
position = 0;
}
/*
* Return the name of this type
*/
std::string ANSI_X931_RNG::name() const
{
return "X9.31(" + cipher->name() + ")";
}
/*
* ANSI X931 RNG Constructor
*/
ANSI_X931_RNG::ANSI_X931_RNG(BlockCipher* cipher_in,
RandomNumberGenerator* prng_in)
{
if(!prng_in || !cipher_in)
throw Invalid_Argument("ANSI_X931_RNG constructor: NULL arguments");
cipher = cipher_in;
prng = prng_in;
R.resize(cipher->block_size());
position = 0;
}
/*
* ANSI X931 RNG Destructor
*/
ANSI_X931_RNG::~ANSI_X931_RNG()
{
delete cipher;
delete prng;
}
}
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