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/*
* Blinding for public key operations
* (C) 1999-2010 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/blinding.h>
#include <botan/numthry.h>
#if defined(BOTAN_HAS_SYSTEM_RNG)
#include <botan/system_rng.h>
#else
#include <botan/auto_rng.h>
#endif
namespace Botan {
// TODO: use Montgomery
Blinder::Blinder(const BigInt& modulus,
std::function<BigInt (const BigInt&)> fwd_func,
std::function<BigInt (const BigInt&)> inv_func)
{
m_reducer = Modular_Reducer(modulus);
#if defined(BOTAN_HAS_SYSTEM_RNG)
auto& rng = system_rng();
#else
AutoSeeded_RNG rng;
#endif
const BigInt k(rng, modulus.bits() - 1);
m_e = fwd_func(k);
m_d = inv_func(k);
}
BigInt Blinder::blind(const BigInt& i) const
{
if(!m_reducer.initialized())
throw std::runtime_error("Blinder not initialized, cannot blind");
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 std::runtime_error("Blinder not initialized, cannot unblind");
return m_reducer.multiply(i, m_d);
}
}
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