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/*
* OFB Mode
* (C) 1999-2007,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/ofb.h>
namespace Botan {
OFB* OFB::make(const Spec& spec)
{
if(spec.algo_name() == "OFB" && spec.arg_count() == 1)
{
if(auto c = BlockCipher::create(spec.arg(0)))
return new OFB(c.release());
}
return nullptr;
}
OFB::OFB(BlockCipher* cipher) :
m_cipher(cipher),
m_buffer(m_cipher->block_size()),
m_buf_pos(0)
{
}
void OFB::clear()
{
m_cipher->clear();
zeroise(m_buffer);
m_buf_pos = 0;
}
void OFB::key_schedule(const byte key[], size_t key_len)
{
m_cipher->set_key(key, key_len);
// Set a default all-zeros IV
set_iv(nullptr, 0);
}
std::string OFB::name() const
{
return "OFB(" + m_cipher->name() + ")";
}
void OFB::cipher(const byte in[], byte out[], size_t length)
{
while(length >= m_buffer.size() - m_buf_pos)
{
xor_buf(out, in, &m_buffer[m_buf_pos], m_buffer.size() - m_buf_pos);
length -= (m_buffer.size() - m_buf_pos);
in += (m_buffer.size() - m_buf_pos);
out += (m_buffer.size() - m_buf_pos);
m_cipher->encrypt(m_buffer);
m_buf_pos = 0;
}
xor_buf(out, in, &m_buffer[m_buf_pos], length);
m_buf_pos += length;
}
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(m_buffer);
buffer_insert(m_buffer, 0, iv, iv_len);
m_cipher->encrypt(m_buffer);
m_buf_pos = 0;
}
void OFB::seek(u64bit)
{
throw Exception("OFB does not support seeking");
}
}
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