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/*
* Public Key Work Factor Functions
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/internal/workfactor.h>
#include <algorithm>
#include <cmath>
namespace Botan {
/*
* Choose the exponent size for a DL group
*/
size_t dl_work_factor(size_t bits)
{
#if 0
/*
These values were taken from RFC 3526
*/
if(bits <= 1536)
return 90;
else if(bits <= 2048)
return 110;
else if(bits <= 3072)
return 130;
else if(bits <= 4096)
return 150;
else if(bits <= 6144)
return 170;
else if(bits <= 8192)
return 190;
return 256;
#else
const size_t MIN_ESTIMATE = 64;
const double log_x = bits / 1.44;
const double strength =
2.76 * std::pow(log_x, 1.0/3.0) * std::pow(std::log(log_x), 2.0/3.0);
return std::max<size_t>(strength, MIN_ESTIMATE);
#endif
}
}
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