/*
* KDF2
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#include <botan/kdf2.h>

namespace Botan {

/*
* KDF2 Key Derivation Mechanism
*/
secure_vector<byte> KDF2::derive(size_t out_len,
                                const byte secret[], size_t secret_len,
                                const byte P[], size_t P_len) const
   {
   secure_vector<byte> output;
   u32bit counter = 1;

   while(out_len && counter)
      {
      hash->update(secret, secret_len);
      hash->update_be(counter);
      hash->update(P, P_len);

      secure_vector<byte> hash_result = hash->final();

      size_t added = std::min(hash_result.size(), out_len);
      output += std::make_pair(&hash_result[0], added);
      out_len -= added;

      ++counter;
      }

   return output;
   }

}