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/*************************************************
* MGF1 Source File *
* (C) 1999-2008 The Botan Project *
*************************************************/
#include <botan/mgf1.h>
#include <botan/lookup.h>
#include <botan/loadstor.h>
#include <botan/bit_ops.h>
#include <algorithm>
#include <memory>
namespace Botan {
/*************************************************
* MGF1 Mask Generation Function *
*************************************************/
void MGF1::mask(const byte in[], u32bit in_len, byte out[],
u32bit out_len) const
{
u32bit counter = 0;
std::auto_ptr<HashFunction> hash(get_hash(hash_name));
while(out_len)
{
hash->update(in, in_len);
for(u32bit j = 0; j != 4; ++j)
hash->update(get_byte(j, counter));
SecureVector<byte> buffer = hash->final();
u32bit xored = std::min(buffer.size(), out_len);
xor_buf(out, buffer.begin(), xored);
out += xored;
out_len -= xored;
++counter;
}
}
/*************************************************
* MGF1 Constructor *
*************************************************/
MGF1::MGF1(const std::string& h_name) : hash_name(h_name)
{
if(!have_hash(hash_name))
throw Algorithm_Not_Found(hash_name);
}
}
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