/*

* KDF1 from ISO 18033-2

* (C) 2016 Philipp Weber

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/internal/kdf1_iso18033.h>

#include <botan/exceptn.h>

namespace Botan {

void KDF1_18033::kdf(uint8_t key[], size_t key_len,

                     const uint8_t secret[], size_t secret_len,

                     const uint8_t salt[], size_t salt_len,

                     const uint8_t label[], size_t label_len) const

   {

   if(key_len == 0)

      return;

   const size_t blocks_required = key_len / m_hash->output_length();

   if(blocks_required >= 0xFFFFFFFE)

      throw Invalid_Argument("KDF1-18033 maximum output length exceeeded");

   uint32_t counter = 0;

   secure_vector<uint8_t> h;

   size_t offset = 0;

   while(offset != key_len)

      {

      m_hash->update(secret, secret_len);

      m_hash->update_be(counter++);

      m_hash->update(label, label_len);

      m_hash->update(salt, salt_len);

      m_hash->final(h);

      const size_t added = std::min(h.size(), key_len - offset);

      copy_mem(&key[offset], h.data(), added);

      offset += added;

      }

   }

}