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/*************************************************
* Modular Reducer Source File *
* (C) 1999-2005 The Botan Project *
*************************************************/
#include <botan/reducer.h>
#include <botan/bit_ops.h>
namespace Botan {
/*************************************************
* Construct a ModularReducer *
*************************************************/
ModularReducer::ModularReducer(const BigInt& n) : modulus(n)
{
if(modulus <= 0)
throw Invalid_Argument("ModularReducer: modulus must be positive");
if(modulus.size() > 8 && !power_of_2(modulus.size()))
modulus.grow_reg((1 << high_bit(modulus.size())) - modulus.size());
}
/*************************************************
* Convert to the modular form *
*************************************************/
BigInt ModularReducer::convert_in(const BigInt& i) const
{
return i;
}
/*************************************************
* Convert from the modular form *
*************************************************/
BigInt ModularReducer::convert_out(const BigInt& i) const
{
return i;
}
/*************************************************
* Modular Multiplication *
*************************************************/
BigInt ModularReducer::multiply(const BigInt& x, const BigInt& y) const
{
return reduce(x * y);
}
/*************************************************
* Modular Squaring *
*************************************************/
BigInt ModularReducer::square(const BigInt& x) const
{
return multiply(x, x);
}
}
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