A Low-Overhead, High-Security NOR Flash Solution
ArmorBoot is Macronix’s mid-range, secure, serial NOR flash that supports secure boot along with other security features like on-chip authentication support (see figure). It can be used to provide security services for designs that employ microcontrollers or microprocessors that don’t have these features built in. The standard form factors mean the storage chips can be incorporated into existing designs to bring along the security features.
Secure boot is where the boot code has been verified before using it to boot a system. This is normally done by using a key to authenticate the code so that it’s known it comes from an authorized source and hasn’t been modified. Encryption of the data, provided by Macronix’s ArmorFlash, isn’t a requirement and the authentication can be done at different times depending on the desired level of security.
Most micros without built-in secure boot support will simply run off the code provided from memory. In this case it would be a serial NOR flash device. Code verification can be done when the system starts or when the data is initially stored.
Features like device recovery are tied into secure boot. In this case, a second, verified copy of a prior, working code incarnation is maintained by the NOR flash device. Switching back to this backup copy if the primary fails to boot properly prevents a device from being “bricked” (made inoperable).
Replay protection is used to authenticate data blocks. It provides rollback protection. Authentication support is used to handshake with external systems like cloud services.
ArmorBoot does a good job of delivering basic security support where features like data encryption are not necessary.
