54.4.1 AES Register Endianness

In Arm processor-based products, the system bus and processors manipulate data in little-endian form. The AES interface requires little-endian format words. However, in accordance with the protocol of the FIPS 197 specification, data is collected, processed and stored by the AES algorithm in big-endian form.

The following example illustrates how to configure the AES:

If the first 64 bits of a message (according to FIPS 197, i.e., big-endian format) to be processed is 0xcafedeca_01234567, then AES_IDATAR0 and AES_IDATAR1 registers must be written with the following pattern:

• AES_IDATAR0 = 0xcadefeca
• AES_IDATAR1 = 0x67452301