RakNet/DependentExtensions/cat/math/BigMontgomery.hpp

/*
	Copyright (c) 2009-2010 Christopher A. Taylor.  All rights reserved.

	Redistribution and use in source and binary forms, with or without
	modification, are permitted provided that the following conditions are met:

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	  this list of conditions and the following disclaimer.
	* Redistributions in binary form must reproduce the above copyright notice,
	  this list of conditions and the following disclaimer in the documentation
	  and/or other materials provided with the distribution.
	* Neither the name of LibCat nor the names of its contributors may be used
	  to endorse or promote products derived from this software without
	  specific prior written permission.

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	AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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	ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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*/

/*
    Several algorithms based on ideas from the "Handbook of Applied Cryptography"
    http://www.cacr.math.uwaterloo.ca/hac/
*/

#ifndef CAT_BIG_MONTGOMERY_HPP
#define CAT_BIG_MONTGOMERY_HPP

#include <cat/math/BigRTL.hpp>
#include <cat/rand/IRandom.hpp>

namespace cat {


// Performs fast modular arithmetic in the Montgomery Residue Number System
class BigMontgomery : public BigRTL
{
    static const int MON_OVERHEAD = 3 + 4;
    int mon_regs;

protected:
	Leg *TempProduct;
	Leg *TempProductHi;
    Leg *CachedModulus;
	Leg mod_inv;

public:
    BigMontgomery(int regs, int bits);

	// Must call SetModulus() before using this object
	void SetModulus(const Leg *mod);

public:
    const Leg *GetModulus() { return CachedModulus; }
    void CopyModulus(Leg *out);

public:
	// Convert value in register into RNS, stored in out
	void MonInput(const Leg *in, Leg *out);

	// Convert value in register from RNS, stored in out
	void MonOutput(const Leg *in, Leg *out);

	// Note: This will clobber the input product!
	// Reduce a double-register product to a single register in the RNS
	void MonReduceProduct(Leg *inout_product, Leg *out);

public:
	// Inputs and outputs must be in the Montgomery RNS
    void MonAdd(const Leg *in_a, const Leg *in_b, Leg *out);
    void MonSubtract(const Leg *in_a, const Leg *in_b, Leg *out);
    void MonNegate(const Leg *in, Leg *out);
    void MonDouble(const Leg *in, Leg *out);

public:
	// Inputs and outputs must be in the Montgomery RNS
    void MonMultiply(const Leg *in_a, const Leg *in_b, Leg *out);
    void MonSquare(const Leg *in, Leg *out);

public:
	// Base must be in the Montgomery RNS.  in_base != out
	void MonExpMod(const Leg *in_base, const Leg *in_exp, Leg *out);

public:
	// Input is NOT in the RNS (don't call MonInput)
	// Probably a prime, certainty = 4^-trials.  20: %99.9999999999 certainty
	bool IsRabinMillerPrime(IRandom *prng, const Leg *n, int trials = 20);
};


} // namespace cat

#endif // CAT_BIG_MONTGOMERY_HPP