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/******************************************************
* Modulus and related data for a specific *
* implementation of GF(p) (header file) *
* *
* (C) 2008 Martin Döring *
* doering@cdc.informatik.tu-darmstadt.de *
* Christoph Ludwig *
* ludwig@fh-worms.de *
* Falko Strenzke *
* strenzke@flexsecure.de *
******************************************************/
#ifndef BOTAN_MATH_GF_GFP_MODULUS_H_GUARD_
#define BOTAN_MATH_GF_GFP_MODULUS_H_GUARD_
#include <botan/bigint.h>
namespace Botan
{
class GFpElement;
/**
* This class represents a GFpElement modulus including the modulus related
* values necessary for the montgomery multiplication.
*/
class GFpModulus
{
friend class GFpElement;
private:
BigInt m_p; // the modulus itself
mutable BigInt m_p_dash;
mutable BigInt m_r;
mutable BigInt m_r_inv;
public:
/**
* Construct a GF(P)-Modulus from a BigInt
*/
GFpModulus(BigInt p)
: m_p(p),
m_p_dash(),
m_r(),
m_r_inv()
{}
/**
* Tells whether the precomputations necessary for the use of the montgomery
* multiplication have yet been established.
* @result true if the precomputated value are already available.
*/
inline bool has_precomputations() const
{
return(!m_p_dash.is_zero() && !m_r.is_zero() && !m_r_inv.is_zero());
}
/**
* Swaps this with another GFpModulus, does not throw.
* @param other the GFpModulus to swap *this with.
*/
inline void swap(GFpModulus& other)
{
m_p.swap(other.m_p);
m_p_dash.swap(other.m_p_dash);
m_r.swap(other.m_r);
m_r_inv.swap(other.m_r_inv);
}
/**
* Tells whether the modulus of *this is equal to the argument.
* @param mod the modulus to compare this with
* @result true if the modulus of *this and the argument are equal.
*/
inline bool p_equal_to(const BigInt& mod) const
{
return (m_p == mod);
}
/**
* Return the modulus of this GFpModulus.
* @result the modulus of *this.
*/
inline const BigInt get_p() const
{
return m_p;
}
/**
* returns the montgomery multiplication related value r.
* Warning: will be zero if precomputations have not yet been
* performed!
* @result r
*/
inline const BigInt get_r() const
{
return m_r;
}
/**
* returns the montgomery multiplication related value r^{-1}.
* Warning: will be zero if precomputations have not yet been
* performed!
* @result r^{-1}
*/
inline const BigInt get_r_inv() const
{
return m_r_inv;
}
/**
* returns the montgomery multiplication related value p'.
* Warning: will be zero if precomputations have not yet been
* performed!
* @result p'
*/
inline const BigInt get_p_dash() const
{
return m_p_dash;
}
// default cp-ctor, op= are fine
};
}
#endif
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