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/*
* ChaCha_RNG
* (C) 2017 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/chacha_rng.h>
namespace Botan {
ChaCha_RNG::ChaCha_RNG() : Stateful_RNG()
{
m_hmac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
m_chacha = StreamCipher::create_or_throw("ChaCha(20)");
clear();
}
ChaCha_RNG::ChaCha_RNG(const secure_vector<uint8_t>& seed) : Stateful_RNG()
{
m_hmac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
m_chacha = StreamCipher::create_or_throw("ChaCha(20)");
clear();
add_entropy(seed.data(), seed.size());
}
ChaCha_RNG::ChaCha_RNG(RandomNumberGenerator& underlying_rng,
size_t reseed_interval) :
Stateful_RNG(underlying_rng, reseed_interval)
{
m_hmac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
m_chacha = StreamCipher::create_or_throw("ChaCha(20)");
clear();
}
ChaCha_RNG::ChaCha_RNG(RandomNumberGenerator& underlying_rng,
Entropy_Sources& entropy_sources,
size_t reseed_interval) :
Stateful_RNG(underlying_rng, entropy_sources, reseed_interval)
{
m_hmac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
m_chacha = StreamCipher::create_or_throw("ChaCha(20)");
clear();
}
ChaCha_RNG::ChaCha_RNG(Entropy_Sources& entropy_sources,
size_t reseed_interval) :
Stateful_RNG(entropy_sources, reseed_interval)
{
m_hmac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
m_chacha = StreamCipher::create_or_throw("ChaCha(20)");
clear();
}
void ChaCha_RNG::clear()
{
Stateful_RNG::clear();
m_hmac->set_key(std::vector<uint8_t>(m_hmac->output_length(), 0x00));
m_chacha->set_key(m_hmac->final());
}
void ChaCha_RNG::randomize(uint8_t output[], size_t output_len)
{
randomize_with_input(output, output_len, nullptr, 0);
}
void ChaCha_RNG::randomize_with_input(uint8_t output[], size_t output_len,
const uint8_t input[], size_t input_len)
{
add_entropy(input, input_len);
reseed_check();
clear_mem(output, output_len);
m_chacha->cipher1(output, output_len);
}
void ChaCha_RNG::add_entropy(const uint8_t input[], size_t input_len)
{
if(input_len > 0)
{
m_hmac->update(input, input_len);
m_chacha->set_key(m_hmac->final());
secure_vector<uint8_t> mac_key(m_hmac->output_length());
m_chacha->cipher1(mac_key.data(), mac_key.size());
m_hmac->set_key(mac_key);
if(8*input_len >= security_level())
{
m_reseed_counter = 1;
}
}
}
size_t ChaCha_RNG::security_level() const
{
return 256;
}
}
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