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/*
* Blinding for public key operations
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/blinding.h>
#include <botan/numthry.h>
#include <botan/libstate.h>
#include <botan/hash.h>
#include <botan/time.h>
#include <botan/loadstor.h>
#include <memory>
namespace Botan {
/*
* Blinder Constructor
*/
Blinder::Blinder(const BigInt& e, const BigInt& d, const BigInt& n)
{
if(e < 1 || d < 1 || n < 1)
throw Invalid_Argument("Blinder: Arguments too small");
reducer = Modular_Reducer(n);
this->e = e;
this->d = d;
}
BigInt Blinder::choose_nonce(const BigInt& x, const BigInt& mod)
{
Algorithm_Factory& af = global_state().algorithm_factory();
std::auto_ptr<HashFunction> hash(af.make_hash_function("SHA-512"));
u64bit ns_clock = get_nanoseconds_clock();
for(size_t i = 0; i != sizeof(ns_clock); ++i)
hash->update(get_byte(0, ns_clock));
hash->update(BigInt::encode(x));
hash->update(BigInt::encode(mod));
u64bit timestamp = system_time();
for(size_t i = 0; i != sizeof(timestamp); ++i)
hash->update(get_byte(0, timestamp));
SecureVector<byte> r = hash->final();
return BigInt::decode(r) % mod;
}
/*
* Blind a number
*/
BigInt Blinder::blind(const BigInt& i) const
{
if(!reducer.initialized())
return i;
e = reducer.square(e);
d = reducer.square(d);
return reducer.multiply(i, e);
}
/*
* Unblind a number
*/
BigInt Blinder::unblind(const BigInt& i) const
{
if(!reducer.initialized())
return i;
return reducer.multiply(i, d);
}
}
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