Botan  1.11.15
src/lib/stream/ofb/ofb.cpp
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00001 /*
00002 * OFB Mode
00003 * (C) 1999-2007,2014 Jack Lloyd
00004 *
00005 * Botan is released under the Simplified BSD License (see license.txt)
00006 */
00007 
00008 #include <botan/internal/stream_utils.h>
00009 #include <botan/ofb.h>
00010 
00011 namespace Botan {
00012 
00013 BOTAN_REGISTER_NAMED_T(StreamCipher, "OFB", OFB, OFB::make);
00014 
00015 OFB* OFB::make(const Spec& spec)
00016    {
00017    if(spec.algo_name() == "OFB" && spec.arg_count() == 1)
00018       {
00019       if(BlockCipher* c = Algo_Registry<BlockCipher>::global_registry().make(spec.arg(0)))
00020          return new OFB(c);
00021       }
00022    return nullptr;
00023    }
00024 
00025 OFB::OFB(BlockCipher* cipher) :
00026    m_cipher(cipher),
00027    m_buffer(m_cipher->block_size()),
00028    m_buf_pos(0)
00029    {
00030    }
00031 
00032 void OFB::clear()
00033    {
00034    m_cipher->clear();
00035    zeroise(m_buffer);
00036    m_buf_pos = 0;
00037    }
00038 
00039 void OFB::key_schedule(const byte key[], size_t key_len)
00040    {
00041    m_cipher->set_key(key, key_len);
00042 
00043    // Set a default all-zeros IV
00044    set_iv(nullptr, 0);
00045    }
00046 
00047 std::string OFB::name() const
00048    {
00049    return "OFB(" + m_cipher->name() + ")";
00050    }
00051 
00052 void OFB::cipher(const byte in[], byte out[], size_t length)
00053    {
00054    while(length >= m_buffer.size() - m_buf_pos)
00055       {
00056       xor_buf(out, in, &m_buffer[m_buf_pos], m_buffer.size() - m_buf_pos);
00057       length -= (m_buffer.size() - m_buf_pos);
00058       in += (m_buffer.size() - m_buf_pos);
00059       out += (m_buffer.size() - m_buf_pos);
00060       m_cipher->encrypt(m_buffer);
00061       m_buf_pos = 0;
00062       }
00063    xor_buf(out, in, &m_buffer[m_buf_pos], length);
00064    m_buf_pos += length;
00065    }
00066 
00067 void OFB::set_iv(const byte iv[], size_t iv_len)
00068    {
00069    if(!valid_iv_length(iv_len))
00070       throw Invalid_IV_Length(name(), iv_len);
00071 
00072    zeroise(m_buffer);
00073    buffer_insert(m_buffer, 0, iv, iv_len);
00074 
00075    m_cipher->encrypt(m_buffer);
00076    m_buf_pos = 0;
00077    }
00078 
00079 }