Abstract: A variable-length block encryption circuit having a simplified structure and that reduces the load on a host computer. A plaintext memory and an encryption/decryption circuit for encrypting or decrypting original data in blocks. The original data is transferred to the plaintext memory from the exterior. The transferred original data is supplied to the encryption/decryption circuit and is subjected to encryption or decryption in blocks. The result data is substituted for the original data in the plaintext memory. When all transferred original data is substituted, the result data is externally output.

Abstract: A block cipher method eliminates the overhead associated with key scheduling, decreases the required time for encryption or decryption, and increases the total throughput. A key scheduling circuit (12) for generating round key data from key data for the encryption or the decryption and a bank memory (13) for storing the round key data generated by the key scheduling circuit (12) at a predetermined bank of the bank memory are provided. An encrypting/decrypting circuit (11) is provided for encrypting plaintext data or decrypting ciphertext data upon receipt of the round key data stored in the bank and a block of the plaintext data or the ciphertext data one by one. The output of the encryption or the decryption is retrieved from the encrypting/decrypting circuit (11).

Abstract: A block cipher method eliminates the overhead associated with key scheduling, decreases the required time for encryption or decryption, and increases the total throughput. A key scheduling circuit (12) for generating round key data from key data for the encryption or the decryption and a bank memory (13) for storing the round key data generated by the key scheduling circuit (12) at a predetermined bank of the bank memory are provided. An encrypting/decrypting circuit (11) is provided for encrypting plaintext data or decrypting ciphertext data upon receipt of the round key data stored in the bank and a block of the plaintext data or the ciphertext data one by one. The output of the encryption or the decryption is retrieved from the encrypting/decrypting circuit (11).

Abstract: The present invention includes a plaintext memory 11 and an encryption/decryption circuit 13 for encrypting or decrypting original data in blocks. The original data is transferred to the plaintext memory 11 from the exterior. The transferred original data is supplied to the encryption/decryption circuit 13 and is subjected to encryption or decryption in blocks. The result data is substituted for the original data in the plaintext memory 11. When all transferred original data is substituted, the result data is externally output. Therefore, a variable-length block encryption circuit having a simplified structure and reducing the load on a host computer is achieved.