Apparatus and method for block ciphers for real-time data transmission

A block cipher apparatus, comprising:

• a key generating unit configured to generate keys having different lengths by entering a password into a hash function and set a pattern by generating an order of the generated keys;
• a block encryption unit configured to select a key, among the generated keys, in accordance with the order of the generated keys and generate a ciphertext block by encryting a plaintext block using the selected key;
• and
• a message authentication unit configured to generate a message authentication code using a key selected at the time of encrypting a current plaintext block which is encrypted in the block encryption unit and a previous message authentication code generated by a plaintext block prior to the current plaintext block,
• wherein when the generated ciphertext block has a predetermined size or larger, the block encryption unit divides the generated ciphertext block into a header corresponding to a predetermined size and a tail corresponding to the rest, generates the header as a ciphertext block, and adds the tail with a next plaintext block to be block-encrypted.