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/*
* ANSI X9.31 RNG
* (C) 1999-2009,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/x931_rng.h>
#include <botan/internal/xor_buf.h>
#include <algorithm>
namespace Botan {
void ANSI_X931_RNG::randomize(byte out[], size_t length)
{
if(!is_seeded())
{
reseed(BOTAN_RNG_RESEED_POLL_BITS);
if(!is_seeded())
throw PRNG_Unseeded(name());
}
while(length)
{
if(m_R_pos == m_R.size())
update_buffer();
const size_t copied = std::min<size_t>(length, m_R.size() - m_R_pos);
copy_mem(out, &m_R[m_R_pos], copied);
out += copied;
length -= copied;
m_R_pos += copied;
}
}
/*
* Refill the internal state
*/
void ANSI_X931_RNG::update_buffer()
{
const size_t BLOCK_SIZE = m_cipher->block_size();
secure_vector<byte> DT = m_prng->random_vec(BLOCK_SIZE);
m_cipher->encrypt(DT);
xor_buf(&m_R[0], &m_V[0], &DT[0], BLOCK_SIZE);
m_cipher->encrypt(m_R);
xor_buf(&m_V[0], &m_R[0], &DT[0], BLOCK_SIZE);
m_cipher->encrypt(m_V);
m_R_pos = 0;
}
/*
* Reset V and the cipher key with new values
*/
void ANSI_X931_RNG::rekey()
{
const size_t BLOCK_SIZE = m_cipher->block_size();
if(m_prng->is_seeded())
{
m_cipher->set_key(m_prng->random_vec(m_cipher->maximum_keylength()));
if(m_V.size() != BLOCK_SIZE)
m_V.resize(BLOCK_SIZE);
m_prng->randomize(&m_V[0], m_V.size());
update_buffer();
}
}
void ANSI_X931_RNG::reseed(size_t poll_bits)
{
m_prng->reseed(poll_bits);
rekey();
}
void ANSI_X931_RNG::add_entropy(const byte input[], size_t length)
{
m_prng->add_entropy(input, length);
rekey();
}
bool ANSI_X931_RNG::is_seeded() const
{
return (m_V.size() > 0);
}
void ANSI_X931_RNG::clear()
{
m_cipher->clear();
m_prng->clear();
zeroise(m_R);
m_V.clear();
m_R_pos = 0;
}
std::string ANSI_X931_RNG::name() const
{
return "X9.31(" + m_cipher->name() + ")";
}
ANSI_X931_RNG::ANSI_X931_RNG(BlockCipher* cipher,
RandomNumberGenerator* prng) :
m_cipher(cipher),
m_prng(prng),
m_R(m_cipher->block_size()),
m_R_pos(0)
{
}
}
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