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/*
* OpenPGP S2K
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/pgp_s2k.h>
namespace Botan {
/*
* Derive a key using the OpenPGP S2K algorithm
*/
OctetString OpenPGP_S2K::derive_key(size_t key_len,
const std::string& passphrase,
const byte salt_buf[], size_t salt_size,
size_t iterations) const
{
SecureVector<byte> key(key_len), hash_buf;
size_t pass = 0, generated = 0,
total_size = passphrase.size() + salt_size;
size_t to_hash = std::max(iterations, total_size);
hash->clear();
while(key_len > generated)
{
for(size_t j = 0; j != pass; ++j)
hash->update(0);
size_t left = to_hash;
while(left >= total_size)
{
hash->update(salt_buf, salt_size);
hash->update(passphrase);
left -= total_size;
}
if(left <= salt_size)
hash->update(salt_buf, left);
else
{
hash->update(salt_buf, salt_size);
left -= salt_size;
hash->update(reinterpret_cast<const byte*>(passphrase.data()), left);
}
hash_buf = hash->final();
key.copy(generated, &hash_buf[0], hash->output_length());
generated += hash->output_length();
++pass;
}
return key;
}
}
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