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/*
* OFB Mode
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/ofb.h>
#include <botan/internal/xor_buf.h>
#include <algorithm>
namespace Botan {
/*
* OFB Constructor
*/
OFB::OFB(BlockCipher* ciph) :
StreamCipher(ciph->MINIMUM_KEYLENGTH,
ciph->MAXIMUM_KEYLENGTH,
ciph->KEYLENGTH_MULTIPLE),
permutation(ciph)
{
position = 0;
buffer.resize(permutation->block_size());
}
/*
* OFB Destructor
*/
OFB::~OFB()
{
delete permutation;
}
/*
* Zeroize
*/
void OFB::clear()
{
permutation->clear();
zeroise(buffer);
position = 0;
}
/*
* Set the key
*/
void OFB::key_schedule(const byte key[], size_t key_len)
{
permutation->set_key(key, key_len);
// Set a default all-zeros IV
set_iv(0, 0);
}
/*
* Return the name of this type
*/
std::string OFB::name() const
{
return ("OFB(" + permutation->name() + ")");
}
/*
* CTR-BE Encryption/Decryption
*/
void OFB::cipher(const byte in[], byte out[], size_t length)
{
while(length >= buffer.size() - position)
{
xor_buf(out, in, &buffer[position], buffer.size() - position);
length -= (buffer.size() - position);
in += (buffer.size() - position);
out += (buffer.size() - position);
permutation->encrypt(buffer);
position = 0;
}
xor_buf(out, in, &buffer[position], length);
position += length;
}
/*
* Set CTR-BE IV
*/
void OFB::set_iv(const byte iv[], size_t iv_len)
{
if(!valid_iv_length(iv_len))
throw Invalid_IV_Length(name(), iv_len);
zeroise(buffer);
buffer.copy(0, iv, iv_len);
permutation->encrypt(buffer);
position = 0;
}
}
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