Apparatus and method for performing authenticated encryption with associated data operation of encrypted instruction with corresponding golden tag stored in memory device in event of cache miss

An apparatus for performing an authenticated encryption with associated data (AEAD) operation of an encrypted instruction with a golden tag corresponding to the encrypted instruction stored in a memory device in an event of a cache miss, comprising:

• a bus control circuit, configured to receive a read address from a cache and obtain the encrypted instruction and the golden tag from the memory device according to the read address;
• a block buffer, coupled to the bus control circuit, configured to receive the encrypted instruction from the bus control circuit and store the encrypted instruction, wherein a size of the block buffer is preset to be N times a size of one cache line of the cache, and N is a positive integer;
• a tag buffer, coupled to the bus control circuit, configured to receive the golden tag from the bus control circuit and store the golden tag;
• and
• an AEAD circuit, coupled to the block buffer and the tag buffer, configured to receive the encrypted instruction from the block buffer and the golden tag from the tag buffer, to compute an authentication tag according to the encrypted instruction, and to compare the golden tag and the authentication tag to determine whether the encrypted instruction is tampered or not.