Hierarchical encryption/decryption device and method thereof

A hierarchical decryption method, comprising:

• receiving a ciphertext, wherein the ciphertext comprises an encrypted block and a plurality of ciphertext blocks;
• decrypting the encrypted block by a secret key with a second decryption method to generate at least one index block and a plurality of confusion blocks;
• generating a plurality of mask blocks according to the plurality of confusion blocks and the index block, wherein the number of the plurality of mask blocks is the same as that of the plurality of ciphertext blocks;
• decrypting the plurality of ciphertext blocks by the plurality of mask blocks with a first decryption method to generate a plurality of plaintext blocks, wherein the number of the plurality of plaintext blocks is the same as that of the plurality of ciphertext blocks;
• and
• outputting a plaintext, wherein the plaintext comprises the plurality of plaintext blocks.

A hierarchical encryption device, for encrypting a plaintext and outputting a ciphertext, wherein the plaintext is subdivided into a plurality of plaintext blocks according to a specific amount of data, comprising:

• at least one index block, wherein the index block has a plurality of addresses and corresponding values, and the corresponding values of the plurality of addresses of the index block are randomly generated;
• a plurality of confusion blocks, wherein the plurality of confusion blocks have a plurality of addresses and corresponding values, and the corresponding values of the plurality addresses in each confusion block are randomly generated;
• a generator, for generating a plurality of mask blocks according to the index block and the plurality of confusion blocks, wherein the number of the plurality of mask blocks is the same as that of the plurality of plaintext blocks and each mask block has the specific amount of data;
• a first encryption unit, for encrypting the plurality of plaintext blocks by the plurality of mask blocks to generate a plurality of ciphertext blocks;
• and
• a second encryption unit, for encrypting the index block and the plurality of confusion blocks by a secret key with a second encryption method to generate an encrypted block, wherein the ciphertext comprises the encrypted block and the plurality of ciphertext blocks.

A hierarchical decryption device, for decrypting a ciphertext and outputting a plaintext, wherein the ciphertext comprises an encrypted block and a plurality of ciphertext blocks, comprising:

• a second decryption unit, for decrypting the encrypted block by a secret key with a second decryption method to generate at least one index block and a plurality of confusion blocks;
• a generator, for generating a plurality of mask blocks according to the plurality of confusion blocks and the index block, wherein the number of the plurality of mask blocks is the same as that of the plurality of ciphertext blocks;
• and
• a first decryption unit, for decrypting the plurality of ciphertext blocks by the plurality of mask blocks with a first decryption method to generate a plurality of plaintext blocks, wherein the number of the plurality of plaintext blocks is the same as that of the plurality of ciphertext blocks.