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/*
* (C) 2016 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include "fuzzers.h"
#include <botan/numthry.h>
#include <botan/reducer.h>
#include <botan/pow_mod.h>
namespace {
Botan::BigInt simple_power_mod(Botan::BigInt x,
Botan::BigInt n,
const Botan::BigInt& p,
const Botan::Modular_Reducer& mod_p)
{
if(n == 0)
{
if(p == 1)
return 0;
return 1;
}
Botan::BigInt y = 1;
while(n > 1)
{
if(n.is_odd())
{
y = mod_p.multiply(x, y);
}
x = mod_p.square(x);
n >>= 1;
}
return mod_p.multiply(x, y);
}
}
void fuzz(const uint8_t in[], size_t len)
{
static const size_t p_bits = 1024;
static const Botan::BigInt p = random_prime(fuzzer_rng(), p_bits);
static Botan::Modular_Reducer mod_p(p);
if(len == 0 || len > p_bits/8)
return;
try
{
const Botan::BigInt g = Botan::BigInt::decode(in, len / 2);
const Botan::BigInt x = Botan::BigInt::decode(in + len / 2, len / 2);
const Botan::BigInt ref = simple_power_mod(g, x, p, mod_p);
const Botan::BigInt z = Botan::power_mod(g, x, p);
if(ref != z)
{
std::cout << "G = " << g << "\n"
<< "X = " << x << "\n"
<< "P = " << p << "\n"
<< "Z = " << z << "\n"
<< "R = " << ref << "\n";
abort();
}
}
catch(Botan::Exception& e) {}
}
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