Bootgen can encrypt the boot image partitions based on the user-provided encryption commands and attributes in the BIF file. AES is a symmetric key encryption technique; it uses the same key for encryption and decryption. The key used to encrypt a boot image should be available on the device for the decryption process while the device is booting with that boot image. Generally, the key is stored either in eFUSE or BBRAM, and the source of the key can be selected during boot image creation through BIF attributes, as shown in the following figure.
Figure 1. Encryption Process Diagram