/*

* Blinding for public key operations

* (C) 1999-2010,2015 Jack Lloyd

*

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

*/

#include <botan/blinding.h>

namespace Botan {

Blinder::Blinder(const BigInt& modulus,

                 RandomNumberGenerator& rng,

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

                 std::function<BigInt (const BigInt&)> inv) :

      m_reducer(modulus),

      m_rng(rng),

      m_fwd_fn(fwd),

      m_inv_fn(inv),

      m_modulus_bits(modulus.bits()),

      m_e{},

      m_d{},

      m_counter{}

   {

   const BigInt k = blinding_nonce();

   m_e = m_fwd_fn(k);

   m_d = m_inv_fn(k);

   }

BigInt Blinder::blinding_nonce() const

   {

   return BigInt(m_rng, m_modulus_bits - 1);

   }

BigInt Blinder::blind(const BigInt& i) const

   {

   if(!m_reducer.initialized())

      throw Invalid_State("Blinder not initialized, cannot blind");

   ++m_counter;

   if((BOTAN_BLINDING_REINIT_INTERVAL > 0) && (m_counter > BOTAN_BLINDING_REINIT_INTERVAL))

      {

      const BigInt k = blinding_nonce();

      m_e = m_fwd_fn(k);

      m_d = m_inv_fn(k);

      m_counter = 0;

      }

   else

      {

      m_e = m_reducer.square(m_e);

      m_d = m_reducer.square(m_d);

      }

   return m_reducer.multiply(i, m_e);

   }

BigInt Blinder::unblind(const BigInt& i) const

   {

   if(!m_reducer.initialized())

      throw Invalid_State("Blinder not initialized, cannot unblind");

   return m_reducer.multiply(i, m_d);

   }

}