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/*
* Montgomery Exponentiation
* (C) 1999-2010,2012,2018 Jack Lloyd
* 2016 Matthias Gierlings
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/def_powm.h>
#include <botan/numthry.h>
#include <botan/monty.h>
#include <botan/internal/monty_exp.h>
#include <botan/internal/rounding.h>
namespace Botan {
void Montgomery_Exponentiator::set_exponent(const BigInt& exp)
{
m_e = exp;
}
void Montgomery_Exponentiator::set_base(const BigInt& base)
{
size_t window_bits = Power_Mod::window_bits(m_e.bits(), base.bits(), m_hints);
m_monty = monty_precompute(m_monty_params, base, window_bits);
}
BigInt Montgomery_Exponentiator::execute() const
{
/*
This leaks size of e via loop iterations, not possible to fix without
breaking this API. Round up to avoid leaking fine details.
*/
return monty_execute(*m_monty, m_e, round_up(m_e.bits(), 8));
}
Montgomery_Exponentiator::Montgomery_Exponentiator(const BigInt& mod,
Power_Mod::Usage_Hints hints) :
m_p(mod),
m_mod_p(mod),
m_monty_params(std::make_shared<Montgomery_Params>(m_p, m_mod_p)),
m_hints(hints)
{
}
}
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