4.) Hex Five
San Jose's Hex Five is the creator of MultiZone Security, what it calls the first trusted execution environment for RISC-V. MultiZone requires no additional hardware, dedicated cores, or programming models, and allows for policy-based, hardware-enforced separation for an unlimited number of security domains, with full control over data, code, interrupts, and peripherals. And since it's open source, like RISC-V, engineers can also implement open course libraries, third-party binaries, and even old legacy code into MultiZone as well. Hex Five also maintains an open source repository for MultiZone on GitHub.
In February 2019, as part of a partnership with cryptography company wolfSSL, Hex Five released an industry-first secure Internet of Things (IoT) stack for RISC-V. The stack is designed to be implemented with FreeRTOS and to handle the security risks inherent in the embedded operating system.
MultiZone allows engineers to isolate the firmware into an unlimited number of separate zones, essentially walling them off from one another in terms of security. According to Hex Five, the result of this is preventing shared memory attacks and other exploits from spreading throughout the system. Any exploit is confined into the zone in which it happens.
(Image source: Hex Five)