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/*************************************************
* PBKDF2 Source File *
* (C) 1999-2007 Jack Lloyd *
*************************************************/
#include <botan/pbkdf2.h>
#include <botan/loadstor.h>
#include <botan/hmac.h>
#include <botan/lookup.h>
#include <botan/xor_buf.h>
namespace Botan {
/*************************************************
* Return a PKCS#5 PBKDF2 derived key *
*************************************************/
OctetString PKCS5_PBKDF2::derive(u32bit key_len,
const std::string& passphrase,
const byte salt[], u32bit salt_size,
u32bit iterations) const
{
if(iterations == 0)
throw Invalid_Argument("PKCS#5 PBKDF2: Invalid iteration count");
if(passphrase.length() == 0)
throw Invalid_Argument("PKCS#5 PBKDF2: Empty passphrase is invalid");
HMAC hmac(hash_name);
hmac.set_key(reinterpret_cast<const byte*>(passphrase.data()),
passphrase.length());
SecureVector<byte> key(key_len);
byte* T = key.begin();
u32bit counter = 1;
while(key_len)
{
u32bit T_size = std::min(hmac.OUTPUT_LENGTH, key_len);
SecureVector<byte> U(hmac.OUTPUT_LENGTH);
hmac.update(salt, salt_size);
for(u32bit j = 0; j != 4; ++j)
hmac.update(get_byte(j, counter));
hmac.final(U);
xor_buf(T, U, T_size);
for(u32bit j = 1; j != iterations; ++j)
{
hmac.update(U);
hmac.final(U);
xor_buf(T, U, T_size);
}
key_len -= T_size;
T += T_size;
++counter;
}
return key;
}
/*************************************************
* Return the name of this type *
*************************************************/
std::string PKCS5_PBKDF2::name() const
{
return "PBKDF2(" + hash_name + ")";
}
/*************************************************
* PKCS5_PBKDF2 Constructor *
*************************************************/
PKCS5_PBKDF2::PKCS5_PBKDF2(const std::string& h_name) : hash_name(h_name)
{
if(!have_hash(hash_name))
throw Algorithm_Not_Found(hash_name);
}
}
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