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/*************************************************
* ANSI X9.31 RNG Source File *
* (C) 1999-2008 Jack Lloyd *
*************************************************/
#include <botan/x931_rng.h>
#include <botan/lookup.h>
#include <botan/bit_ops.h>
#include <algorithm>
namespace Botan {
/*************************************************
* Generate a buffer of random bytes *
*************************************************/
void ANSI_X931_RNG::randomize(byte out[], u32bit length)
{
if(!is_seeded())
reseed();
while(length)
{
if(position == R.size())
update_buffer();
const u32bit copied = std::min(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()
{
SecureVector<byte> DT(cipher->BLOCK_SIZE);
prng->randomize(DT, DT.size());
cipher->encrypt(DT);
xor_buf(R, V, DT, cipher->BLOCK_SIZE);
cipher->encrypt(R);
xor_buf(V, R, DT, cipher->BLOCK_SIZE);
cipher->encrypt(V);
position = 0;
}
/*************************************************
* Reseed the internal state *
*************************************************/
void ANSI_X931_RNG::reseed()
{
SecureVector<byte> key(cipher->MAXIMUM_KEYLENGTH);
prng->randomize(key, key.size());
cipher->set_key(key, key.size());
if(V.size() != cipher->BLOCK_SIZE)
V.create(cipher->BLOCK_SIZE);
prng->randomize(V, V.size());
update_buffer();
}
/*************************************************
* Check if the the PRNG is seeded *
*************************************************/
bool ANSI_X931_RNG::is_seeded() const
{
return V.has_items();
}
/*************************************************
* Clear memory of sensitive data *
*************************************************/
void ANSI_X931_RNG::clear() throw()
{
cipher->clear();
prng->clear();
R.clear();
V.destroy();
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(const std::string& cipher_name,
RandomNumberGenerator* prng_ptr)
{
if(!prng_ptr)
throw Invalid_Argument("ANSI_X931_RNG constructor: NULL prng");
prng = prng_ptr;
cipher = get_block_cipher(cipher_name);
R.create(cipher->BLOCK_SIZE);
position = 0;
}
/*************************************************
* ANSI X931 RNG Destructor *
*************************************************/
ANSI_X931_RNG::~ANSI_X931_RNG()
{
delete cipher;
delete prng;
}
}
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