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/*************************************************
* OpenPGP S2K Source File *
* (C) 1999-2007 Jack Lloyd *
*************************************************/
#include <botan/pgp_s2k.h>
#include <botan/lookup.h>
#include <algorithm>
#include <memory>
namespace Botan {
/*************************************************
* Derive a key using the OpenPGP S2K algorithm *
*************************************************/
OctetString OpenPGP_S2K::derive(u32bit key_len, const std::string& passphrase,
const byte salt_buf[], u32bit salt_size,
u32bit iterations) const
{
SecureVector<byte> key(key_len), hash_buf;
u32bit pass = 0, generated = 0,
total_size = passphrase.size() + salt_size;
u32bit to_hash = std::max(iterations, total_size);
std::auto_ptr<HashFunction> hash(get_hash(hash_name));
hash->clear();
while(key_len > generated)
{
for(u32bit j = 0; j != pass; ++j)
hash->update(0);
u32bit 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, hash->OUTPUT_LENGTH);
generated += hash->OUTPUT_LENGTH;
++pass;
}
return key;
}
/*************************************************
* Return the name of this type *
*************************************************/
std::string OpenPGP_S2K::name() const
{
return "OpenPGP-S2K(" + hash_name + ")";
}
/*************************************************
* Return a clone of this object *
*************************************************/
S2K* OpenPGP_S2K::clone() const
{
return new OpenPGP_S2K(hash_name);
}
/*************************************************
* OpenPGP S2K Constructor *
*************************************************/
OpenPGP_S2K::OpenPGP_S2K(const std::string& h) : hash_name(h)
{
}
}
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