/*

 * XMSS Signature Operation

 * (C) 2016,2017,2018 Matthias Gierlings

 *

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

 **/

#ifndef BOTAN_XMSS_SIGNATURE_OPERATION_H_

#define BOTAN_XMSS_SIGNATURE_OPERATION_H_

#include <botan/pk_ops.h>

#include <botan/xmss.h>

#include <botan/internal/xmss_address.h>

#include <botan/internal/xmss_signature.h>

#include <botan/internal/xmss_wots.h>

namespace Botan {

/**

 * Signature generation operation for Extended Hash-Based Signatures (XMSS) as

 * defined in:

 *

 * [1] XMSS: Extended Hash-Based Signatures,

 *     Request for Comments: 8391

 *     Release: May 2018.

 *     https://datatracker.ietf.org/doc/rfc8391/

 **/

class XMSS_Signature_Operation final : public virtual PK_Ops::Signature {

   public:

      XMSS_Signature_Operation(const XMSS_PrivateKey& private_key);

      /**

       * Creates an XMSS signature for the message provided through call to

       * update().

       *

       * @return serialized XMSS signature.

       **/

      std::vector<uint8_t> sign(RandomNumberGenerator&) override;

      void update(std::span<const uint8_t> input) override;

      size_t signature_length() const override;

      AlgorithmIdentifier algorithm_identifier() const override;

      std::string hash_function() const override { return m_hash.hash_function(); }

   private:

      /**

       * Algorithm 11: "treeSig"

       * Generate a WOTS+ signature on a message with corresponding auth path.

       *

       * @param msg A message.

       * @param xmss_priv_key A XMSS private key.

       * @param adrs A XMSS Address.

       **/

      XMSS_Signature::TreeSignature generate_tree_signature(const secure_vector<uint8_t>& msg,

                                                            XMSS_PrivateKey& xmss_priv_key,

                                                            XMSS_Address& adrs);

      /**

       * Algorithm 12: "XMSS_sign"

       * Generate an XMSS signature and update the XMSS secret key

       *

       * @param msg A message to sign of arbitrary length.

       * @param [out] xmss_priv_key A XMSS private key. The private key will be

       *              updated during the signing process.

       *

       * @return The signature of msg signed using xmss_priv_key.

       **/

      XMSS_Signature sign(const secure_vector<uint8_t>& msg, XMSS_PrivateKey& xmss_priv_key);

      wots_keysig_t build_auth_path(XMSS_PrivateKey& priv_key, XMSS_Address& adrs);

      void initialize();

      XMSS_PrivateKey m_priv_key;

      XMSS_Hash m_hash;

      secure_vector<uint8_t> m_randomness;

      uint32_t m_leaf_idx;

      bool m_is_initialized;

};

}  // namespace Botan

#endif