/* * CTR-BE Mode Cipher * (C) 1999-2009 Jack Lloyd * * Distributed under the terms of the Botan license */ #include #include namespace Botan { /* * CTR-BE Constructor */ CTR_BE::CTR_BE(BlockCipher* ciph) : StreamCipher(ciph->MINIMUM_KEYLENGTH, ciph->MAXIMUM_KEYLENGTH, ciph->KEYLENGTH_MULTIPLE), permutation(ciph) { position = 0; counter.create(permutation->BLOCK_SIZE * BOTAN_PARALLEL_BLOCKS_CTR); buffer.create(permutation->BLOCK_SIZE * BOTAN_PARALLEL_BLOCKS_CTR); } /* * CTR_BE Destructor */ CTR_BE::~CTR_BE() { delete permutation; } /* * Zeroize */ void CTR_BE::clear() { permutation->clear(); buffer.clear(); counter.clear(); position = 0; } /* * Set the key */ void CTR_BE::key_schedule(const byte key[], u32bit 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 CTR_BE::name() const { return ("CTR-BE(" + permutation->name() + ")"); } /* * CTR-BE Encryption/Decryption */ void CTR_BE::cipher(const byte in[], byte out[], u32bit length) { while(length >= buffer.size() - position) { xor_buf(out, in, buffer.begin() + position, buffer.size() - position); length -= (buffer.size() - position); in += (buffer.size() - position); out += (buffer.size() - position); increment_counter(); } xor_buf(out, in, buffer.begin() + position, length); position += length; } /* * Set CTR-BE IV */ void CTR_BE::set_iv(const byte iv[], u32bit iv_len) { if(!valid_iv_length(iv_len)) throw Invalid_IV_Length(name(), iv_len); const u32bit BLOCK_SIZE = permutation->BLOCK_SIZE; counter.clear(); counter.copy(0, iv, iv_len); const u32bit PARALLEL_BLOCKS = counter.size() / BLOCK_SIZE; for(u32bit i = 1; i != PARALLEL_BLOCKS; ++i) { counter.copy(i*BLOCK_SIZE, counter.begin() + (i-1)*BLOCK_SIZE, BLOCK_SIZE); for(s32bit j = BLOCK_SIZE - 1; j >= 0; --j) if(++counter[i*BLOCK_SIZE+j]) break; } permutation->encrypt_n(counter, buffer, PARALLEL_BLOCKS); position = 0; } /* * Increment the counter and update the buffer */ void CTR_BE::increment_counter() { const u32bit PARALLEL_BLOCKS = counter.size() / permutation->BLOCK_SIZE; for(u32bit i = 0; i != PARALLEL_BLOCKS; ++i) { byte* this_ctr = counter + i*permutation->BLOCK_SIZE; byte last_byte = this_ctr[permutation->BLOCK_SIZE-1]; last_byte += PARALLEL_BLOCKS; if(this_ctr[permutation->BLOCK_SIZE-1] > last_byte) for(s32bit j = permutation->BLOCK_SIZE - 2; j >= 0; --j) if(++this_ctr[j]) break; this_ctr[permutation->BLOCK_SIZE-1] = last_byte; } permutation->encrypt_n(counter, buffer, PARALLEL_BLOCKS); position = 0; } }