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/*
* PBKDF2
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/pbkdf2.h>
#include <botan/get_byte.h>
#include <botan/internal/xor_buf.h>
namespace Botan {
/*
* Return a PKCS #5 PBKDF2 derived key
*/
OctetString PKCS5_PBKDF2::derive_key(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");
try
{
mac->set_key(reinterpret_cast<const byte*>(passphrase.data()),
passphrase.length());
}
catch(Invalid_Key_Length)
{
throw Exception(name() + " cannot accept passphrases of length " +
to_string(passphrase.length()));
}
SecureVector<byte> key(key_len);
byte* T = key.begin();
u32bit counter = 1;
while(key_len)
{
u32bit T_size = std::min(mac->OUTPUT_LENGTH, key_len);
SecureVector<byte> U(mac->OUTPUT_LENGTH);
mac->update(salt, salt_size);
for(u32bit j = 0; j != 4; ++j)
mac->update(get_byte(j, counter));
mac->final(U);
xor_buf(T, U, T_size);
for(u32bit j = 1; j != iterations; ++j)
{
mac->update(U);
mac->final(U);
xor_buf(T, U, T_size);
}
key_len -= T_size;
T += T_size;
++counter;
}
return key;
}
}
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