randpool.cpp

来自「含有多种公开密钥算法、多种块加密、多种数据流加密、多种HASH函数、多种Chec」· C++ 代码 · 共 126 行

/*************************************************
* Randpool Source File                           *
* (C) 1999-2002 The Botan Project                *
*************************************************/

#include <botan/randpool.h>
#include <botan/lookup.h>

namespace Botan {

/*************************************************
* Generate a random byte                         *
*************************************************/
byte Randpool::random()
   {
   if(position == buffer.size())
      generate(system_clock());
   return buffer[position++];
   }

/*************************************************
* Generate a buffer of random bytes              *
*************************************************/
void Randpool::randomize(byte out[], u32bit length)
   {
   while(length >= buffer.size() - position)
      {
      xor_buf(out, buffer + position, buffer.size() - position);
      length -= (buffer.size() - position);
      out += (buffer.size() - position);
      generate(system_clock());
      }
   xor_buf(out, buffer + position, length);
   position += length;
   }

/*************************************************
* Refill the buffer                              *
*************************************************/
void Randpool::generate(u64bit input)
   {
   static const u32bit MAX_ITERATIONS = 32;
   hash->update((byte*)&input, 8);
   hash->update(pool, pool.size());
   buffer = hash->final();
   xor_buf(pool, buffer, buffer.size());
   mix_pool();
   if(++iteration == MAX_ITERATIONS)
      {
      reseed();
      iteration = 0;
      }
   position = 0;
   }

/*************************************************
* Mix up the pool                                *
*************************************************/
void Randpool::mix_pool()
   {
   for(u32bit j = 0; j != pool.size(); j += buffer.size())
      {
      xor_buf(pool + (j + buffer.size()) % pool.size(), pool + j,
              buffer.size());
      hash->update(pool + j, std::min(3 * buffer.size(), pool.size() - j));
      hash->final(pool + j);
      }
   }

/*************************************************
* Reseed the pool                                *
*************************************************/
void Randpool::reseed()
   {
   SecureVector<byte> out(pool.size() / 2);
   randomize(out, out.size());
   randomize(out, out.size());
   add_entropy(out, out.size());
   }

/*************************************************
* Add entropy to internal state                  *
*************************************************/
void Randpool::add_randomness(const byte data[], u32bit length) throw()
   {
   while(length)
      {
      u32bit added = std::min(pool.size() / 2, length);
      xor_buf(pool, data, added);
      generate(system_clock());
      length -= added;
      data += added;
      }
   generate(system_time());
   }

/*************************************************
* Clear memory of sensitive data                 *
*************************************************/
void Randpool::clear() throw()
   {
   hash->clear();
   pool.clear();
   buffer.clear();
   iteration = position = 0;
   }

/*************************************************
* Randpool Constructor                           *
*************************************************/
Randpool::Randpool()
   {
   const HashFunction* haval = retrieve_hash("HAVAL(32)");
   if(haval)
      hash = haval->clone();
   else
      hash = get_hash("SHA-1");

   buffer.create(hash->OUTPUT_LENGTH);
   pool.create(12 * hash->OUTPUT_LENGTH);
   iteration = position = 0;
   generate(system_time());
   }

}