49.1.1 Cryptography Subsystem Keybus

The keybus is a private bus transferring keys from hosts (TRNG, OTPC) to clients (AES, TDES, OTPC) with no possibility for processor nor software to read the keys.

The key used by the crypto IPs is provided either by the keybus internal register or by the IPs internal key register (KEYWR). To select the keybus as a source for AES and TDES, the PKRS bit must be set in the MR/EMR register.

At host level, the client destination and the key length must be defined before starting the transfer.

The device features a keybus system with two hosts and four clients, connected as shown in the following figure.