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/*
* 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 BOTAN_PUBLIC_API(2,0) 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
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