SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
The architecture of the AES Decrypt Core is the same as that of the encrypt core described above. One difference is that the generation of round keys for decryption requires an initial conversion of the input key (always supplied by the host in the form of an encrypt key) to the corresponding decrypt key. This conversion is done by performing a dummy encrypt operation and storing the final round key as a decrypt key. The key scheduler is then “reversed” to generate the “round keys” for the decrypt operation. Consequently, for each sequence of decrypt operations under the same key, a single throughput reduction is incurred equal to the time to encrypt a single block. Once a decrypted key is generated, sequential decrypt operations with the same key uses this generated decrypt key directly.
The decrypt datapath width in this implementation equals the encrypt data path width.