/*

* Blinding for public key operations

* (C) 1999-2010,2015 Jack Lloyd

*

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

*/

#ifndef BOTAN_BLINDER_H_

#define BOTAN_BLINDER_H_

#include <botan/bigint.h>

#include <botan/reducer.h>

#include <functional>

namespace Botan {

class RandomNumberGenerator;

/**

* Blinding Function Object.

*/

class Blinder final

   {

   public:

      /**

      * Blind a value.

      * The blinding nonce k is freshly generated after

      * BOTAN_BLINDING_REINIT_INTERVAL calls to blind().

      * BOTAN_BLINDING_REINIT_INTERVAL = 0 means a fresh

      * nonce is only generated once. On every other call,

      * an updated nonce is used for blinding: k' = k*k mod n.

      * @param x value to blind

      * @return blinded value

      */

      BigInt blind(const BigInt& x) const;

      /**

      * Unblind a value.

      * @param x value to unblind

      * @return unblinded value

      */

      BigInt unblind(const BigInt& x) const;

      /**

      * @param modulus the modulus

      * @param rng the RNG to use for generating the nonce

      * @param fwd_func a function that calculates the modular

      * exponentiation of the public exponent and the given value (the nonce)

      * @param inv_func a function that calculates the modular inverse

      * of the given value (the nonce)

      */

      Blinder(const BigInt& modulus,

              RandomNumberGenerator& rng,

              std::function<BigInt (const BigInt&)> fwd_func,

              std::function<BigInt (const BigInt&)> inv_func);

      Blinder(const Blinder&) = delete;

      Blinder& operator=(const Blinder&) = delete;

      RandomNumberGenerator& rng() const { return m_rng; }

   private:

      BigInt blinding_nonce() const;

      Modular_Reducer m_reducer;

      RandomNumberGenerator& m_rng;

      std::function<BigInt (const BigInt&)> m_fwd_fn;

      std::function<BigInt (const BigInt&)> m_inv_fn;

      size_t m_modulus_bits = 0;

      mutable BigInt m_e, m_d;

      mutable size_t m_counter = 0;

   };

}

#endif