Main Page | Namespace List | Class Hierarchy | Alphabetical List | Compound List | File List | Namespace Members | Compound Members | File Members

# modarith.h

    00001 #ifndef CRYPTOPP_MODARITH_H
    00002 #define CRYPTOPP_MODARITH_H
    00003
    00004 // implementations are in integer.cpp
    00005
    00006 #include "cryptlib.h"
    00007 #include "misc.h"
    00008 #include "integer.h"
    00009 #include "algebra.h"
    00010
    00011 NAMESPACE_BEGIN(CryptoPP)
    00012
    00013 CRYPTOPP_DLL_TEMPLATE_CLASS AbstractGroup<Integer>;
    00014 CRYPTOPP_DLL_TEMPLATE_CLASS AbstractRing<Integer>;
    00015 CRYPTOPP_DLL_TEMPLATE_CLASS AbstractEuclideanDomain<Integer>;
    00016
    00017 //! .
    00018 class CRYPTOPP_DLL ModularArithmetic : public AbstractRing<Integer>
    00019 {
    00020 public:
    00021
    00022         typedef int RandomizationParameter;
    00023         typedef Integer Element;
    00024
    00025         ModularArithmetic(const Integer &modulus = Integer::One())
    00026                 : modulus(modulus), result((word)0, modulus.reg.size()) {}
    00027
    00028         ModularArithmetic(const ModularArithmetic &ma)
    00029                 : modulus(ma.modulus), result((word)0, modulus.reg.size()) {}
    00030
    00031         ModularArithmetic(BufferedTransformation &bt);  // construct from BER encoded parameters
    00032
    00033         virtual ModularArithmetic * Clone() const {return new ModularArithmetic(*this);}
    00034
    00035         void DEREncode(BufferedTransformation &bt) const;
    00036
    00037         void DEREncodeElement(BufferedTransformation &out, const Element &a) const;
    00038         void BERDecodeElement(BufferedTransformation &in, Element &a) const;
    00039
    00040         const Integer& GetModulus() const {return modulus;}
    00041         void SetModulus(const Integer &newModulus) {modulus = newModulus; result.reg.resize(modulus.reg.size());}
    00042
    00043         virtual bool IsMontgomeryRepresentation() const {return false;}
    00044
    00045         virtual Integer ConvertIn(const Integer &a) const
    00046                 {return a%modulus;}
    00047
    00048         virtual Integer ConvertOut(const Integer &a) const
    00049                 {return a;}
    00050
    00051         const Integer& Half(const Integer &a) const;
    00052
    00053         bool Equal(const Integer &a, const Integer &b) const
    00054                 {return a==b;}
    00055
    00056         const Integer& Identity() const
    00057                 {return Integer::Zero();}
    00058
    00059         const Integer& Add(const Integer &a, const Integer &b) const;
    00060
    00061         Integer& Accumulate(Integer &a, const Integer &b) const;
    00062
    00063         const Integer& Inverse(const Integer &a) const;
    00064
    00065         const Integer& Subtract(const Integer &a, const Integer &b) const;
    00066
    00067         Integer& Reduce(Integer &a, const Integer &b) const;
    00068
    00069         const Integer& Double(const Integer &a) const
    00070                 {return Add(a, a);}
    00071
    00072         const Integer& MultiplicativeIdentity() const
    00073                 {return Integer::One();}
    00074
    00075         const Integer& Multiply(const Integer &a, const Integer &b) const
    00076                 {return result1 = a*b%modulus;}
    00077
    00078         const Integer& Square(const Integer &a) const
    00079                 {return result1 = a.Squared()%modulus;}
    00080
    00081         bool IsUnit(const Integer &a) const
    00082                 {return Integer::Gcd(a, modulus).IsUnit();}
    00083
    00084         const Integer& MultiplicativeInverse(const Integer &a) const
    00085                 {return result1 = a.InverseMod(modulus);}
    00086
    00087         const Integer& Divide(const Integer &a, const Integer &b) const
    00088                 {return Multiply(a, MultiplicativeInverse(b));}
    00089
    00090         Integer CascadeExponentiate(const Integer &x, const Integer &e1, const Integer &y, const Integer &e2) const;
    00091
    00092         void SimultaneousExponentiate(Element *results, const Element &base, const Integer *exponents, unsigned int exponentsCount) const;
    00093
    00094         unsigned int MaxElementBitLength() const
    00095                 {return (modulus-1).BitCount();}
    00096
    00097         unsigned int MaxElementByteLength() const
    00098                 {return (modulus-1).ByteCount();}
    00099
    00100         Element RandomElement( RandomNumberGenerator &rng , const RandomizationParameter &ignore_for_now = 0 ) const
    00101                 // left RandomizationParameter arg as ref in case RandomizationParameter becomes a more complicated struct
    00102         {
    00103                 return Element( rng , Integer( (long) 0) , modulus - Integer( (long) 1 )   ) ;
    00104         }
    00105
    00106         bool operator==(const ModularArithmetic &rhs) const
    00107                 {return modulus == rhs.modulus;}
    00108
    00109         static const RandomizationParameter DefaultRandomizationParameter ;
    00110
    00111 protected:
    00112         Integer modulus;
    00113         mutable Integer result, result1;
    00114
    00115 };
    00116
    00117 // const ModularArithmetic::RandomizationParameter ModularArithmetic::DefaultRandomizationParameter = 0 ;
    00118
    00119 //! do modular arithmetics in Montgomery representation for increased speed
    00120 class CRYPTOPP_DLL MontgomeryRepresentation : public ModularArithmetic
    00121 {
    00122 public:
    00123         MontgomeryRepresentation(const Integer &modulus);       // modulus must be odd
    00124
    00125         virtual ModularArithmetic * Clone() const {return new MontgomeryRepresentation(*this);}
    00126
    00127         bool IsMontgomeryRepresentation() const {return true;}
    00128
    00129         Integer ConvertIn(const Integer &a) const
    00130                 {return (a<<(WORD_BITS*modulus.reg.size()))%modulus;}
    00131
    00132         Integer ConvertOut(const Integer &a) const;
    00133
    00134         const Integer& MultiplicativeIdentity() const
    00135                 {return result1 = Integer::Power2(WORD_BITS*modulus.reg.size())%modulus;}
    00136
    00137         const Integer& Multiply(const Integer &a, const Integer &b) const;
    00138
    00139         const Integer& Square(const Integer &a) const;
    00140
    00141         const Integer& MultiplicativeInverse(const Integer &a) const;
    00142
    00143         Integer CascadeExponentiate(const Integer &x, const Integer &e1, const Integer &y, const Integer &e2) const
    00144                 {return AbstractRing<Integer>::CascadeExponentiate(x, e1, y, e2);}
    00145
    00146         void SimultaneousExponentiate(Element *results, const Element &base, const Integer *exponents, unsigned int exponentsCount) const
    00147                 {AbstractRing<Integer>::SimultaneousExponentiate(results, base, exponents, exponentsCount);}
    00148
    00149 private:
    00150         Integer u;
    00151         mutable SecAlignedWordBlock workspace;
    00152 };
    00153
    00154 NAMESPACE_END
    00155
    00156 #endif