/*
* KDF defined in NIST SP 800-56c
* (C) 2016 Kai Michaelis
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_SP800_56C_H__
#define BOTAN_SP800_56C_H__

#include <botan/kdf.h>
#include <botan/mac.h>

namespace Botan {

/**
 * NIST SP 800-56C KDF
 */
class BOTAN_DLL SP800_56C : public KDF
   {
   public:
      std::string name() const override { return "SP800-56C(" + m_prf->name() + ")"; }

      KDF* clone() const override { return new SP800_56C(m_prf->clone(), m_exp->clone()); }

      /**
      * Derive a key using the SP800-56C KDF.
      *
      * The implementation hard codes the context value for the
      * expansion step to the empty string.
      *
      * @param key derived keying material K_M
      * @param key_len the desired output length in bytes
      * @param secret shared secret Z
      * @param secret_len size of Z in bytes
      * @param salt salt s of the extraction step
      * @param salt_len size of s in bytes
      * @param label label for the expansion step
      * @param label_len size of label in bytes
      *
      * @throws Invalid_Argument key_len > 2^32
      */
      size_t 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 override;

      /**
      * @param mac MAC algorithm used for randomness extraction
      * @param exp KDF used for key expansion
      */
      SP800_56C(MessageAuthenticationCode* mac, KDF* exp) : m_prf(mac), m_exp(exp) {}
   private:
      std::unique_ptr<MessageAuthenticationCode> m_prf;
      std::unique_ptr<KDF> m_exp;
   };
}

#endif