Product Specification - 1.1 English

Advanced Encryption Standard (AES) Engine LogiCORE IP Product Guide (PG383)

Document ID
Release Date
1.1 English

The functional block diagram of the core is shown in the following figure.

Figure 1. Core Block Diagram

The core instantiates several AES engines internally based on the AXI4-Stream data width selected by you. It consists of a scalable tweak-calculation that generates several tweak values in a single clock-cycle so that all the engines can process data simultaneously without getting stalled. The key expansion module generates the round keys independently and provides them to all the engines.

When high-throughput mode is selected, the engines use a pipelined design that enables the core to provide data every cycle at the output. The high-throughput core also supports prefetch which enables you to provide the key and IV for the next packet while the current packet is being driven to the core. This enables the core to mask the latency that is introduced due to the generation of tweak or other metadata that must by ready before the engine can start accepting data. Thus, the design allows you to send in packets back-to-back without having to wait for the metadata to be ready for successive packets. This is useful in block-storage applications where the keys for all the blocks are pre-generated and stored in some memory within the system.

Prefetch is achieved by having a handshake mechanism for the key and IV. You are expected to drive the key_valid signal while sending valid key and IV. The core asserts the key_fetch signal to indicate that it is ready to take the next set of key and IV. The key and IV are latched only when both the key_valid and key_fetch are asserted during a particular clock cycle. The controller within the core ensures that the keys are managed properly so that they do not get overwritten when you feed the key and IV for the next packet. It also ensures that the keys are provided to the pipeline based on the state of movement of data through it.