/* * OFB Mode * (C) 1999-2007,2014 Jack Lloyd * * Distributed under the terms of the Botan license */ #include #include namespace Botan { 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; } }