/*************************************************
* KDF1/KDF2 Source File                          *
* (C) 1999-2004 The Botan Project                *
*************************************************/

#include <botan/kdf.h>
#include <botan/lookup.h>
#include <memory>

namespace Botan {

/*************************************************
* KDF1 Key Derivation Mechanism                  *
*************************************************/
OctetString KDF1::derive(u32bit, const byte secret[], u32bit secret_len,
                         const byte P[], u32bit P_len) const
   {
   std::auto_ptr<HashFunction> hash(get_hash(hash_name));

   hash->update(secret, secret_len);
   hash->update(P, P_len);
   return hash->final();
   }

/*************************************************
* KDF1 Constructor                               *
*************************************************/
KDF1::KDF1(const std::string& h_name) : hash_name(h_name)
   {
   if(!have_hash(hash_name))
      throw Algorithm_Not_Found(hash_name);
   }

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

   std::auto_ptr<HashFunction> hash(get_hash(hash_name));
   while(out_len)
      {
      hash->update(secret, secret_len);
      for(u32bit j = 0; j != 4; j++)
         hash->update(get_byte(j, counter));
      hash->update(P, P_len);
      SecureVector<byte> hash_result = hash->final();

      u32bit added = std::min(hash_result.size(), out_len);
      output.append(hash_result, added);
      out_len -= added;

      counter++;
      }

   return output;
   }

/*************************************************
* KDF2 Constructor                               *
*************************************************/
KDF2::KDF2(const std::string& h_name) : hash_name(h_name)
   {
   if(!have_hash(hash_name))
      throw Algorithm_Not_Found(hash_name);
   }

}
