/*

* Two-Step KDF defined in NIST SP 800-56Cr2 (Section 5)

* (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 Two-Step KDF (Section 5)

 */

class SP800_56C_Two_Step final : public KDF {

   public:

      std::string name() const override;

      std::unique_ptr<KDF> new_object() const override;

      /**

      * @param mac MAC algorithm used for randomness extraction

      * @param exp KDF used for key expansion

      */

      SP800_56C_Two_Step(std::unique_ptr<MessageAuthenticationCode> mac, std::unique_ptr<KDF> exp) :

            m_prf(std::move(mac)), m_exp(std::move(exp)) {}

   private:

      /**

      * Derive a key using the SP800-56C Two-Step KDF.

      *

      * The implementation hard codes the context value for the

      * expansion step to the empty string.

      *

      * @param key derived keying material K_M

      * @param secret shared secret Z

      * @param salt salt s of the extraction step

      * @param label label for the expansion step

      */

      void perform_kdf(std::span<uint8_t> key,

                       std::span<const uint8_t> secret,

                       std::span<const uint8_t> salt,

                       std::span<const uint8_t> label) const override;

   private:

      std::unique_ptr<MessageAuthenticationCode> m_prf;

      std::unique_ptr<KDF> m_exp;

};

}  // namespace Botan

#endif