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/*
* HMAC_DRBG
* (C) 2014,2015,2016 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/hmac_drbg.h>
#include <algorithm>
namespace Botan {
HMAC_DRBG::HMAC_DRBG(const std::string& hmac_hash) :
HMAC_DRBG(hmac_hash, BOTAN_RNG_MAX_OUTPUT_BEFORE_RESEED)
{}
HMAC_DRBG::HMAC_DRBG(const std::string& hmac_hash,
size_t max_bytes_before_reseed) :
Stateful_RNG(max_bytes_before_reseed)
{
const std::string hmac = "HMAC(" + hmac_hash + ")";
m_mac = MessageAuthenticationCode::create(hmac);
if(!m_mac)
{
throw Algorithm_Not_Found(hmac);
}
m_V.resize(m_mac->output_length());
clear();
}
void HMAC_DRBG::clear()
{
for(size_t i = 0; i != m_V.size(); ++i)
m_V[i] = 0x01;
m_mac->set_key(std::vector<byte>(m_mac->output_length(), 0x00));
}
std::string HMAC_DRBG::name() const
{
return "HMAC_DRBG(" + m_mac->name() + ")";
}
void HMAC_DRBG::randomize(byte output[], size_t output_len)
{
randomize_with_input(output, output_len, nullptr, 0);
}
/*
* HMAC_DRBG generation
* See NIST SP800-90A section 10.1.2.5
*/
void HMAC_DRBG::randomize_with_input(byte output[], size_t output_len,
const byte input[], size_t input_len)
{
reseed_check(output_len);
if(input_len > 0)
{
update(input, input_len);
}
while(output_len)
{
const size_t to_copy = std::min(output_len, m_V.size());
m_mac->update(m_V.data(), m_V.size());
m_mac->final(m_V.data());
copy_mem(output, m_V.data(), to_copy);
output += to_copy;
output_len -= to_copy;
}
update(input, input_len);
}
/*
* Reset V and the mac key with new values
* See NIST SP800-90A section 10.1.2.2
*/
void HMAC_DRBG::update(const byte input[], size_t input_len)
{
m_mac->update(m_V);
m_mac->update(0x00);
m_mac->update(input, input_len);
m_mac->set_key(m_mac->final());
m_mac->update(m_V.data(), m_V.size());
m_mac->final(m_V.data());
if(input_len > 0)
{
m_mac->update(m_V);
m_mac->update(0x01);
m_mac->update(input, input_len);
m_mac->set_key(m_mac->final());
m_mac->update(m_V.data(), m_V.size());
m_mac->final(m_V.data());
}
}
void HMAC_DRBG::add_entropy(const byte input[], size_t input_len)
{
update(input, input_len);
}
}
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