Historically, high-assurance security used a mix of commodity and custom hardware. SCOMP had IO/MMU plus type enforcement at memory & storage level. Congress ma

Historically, high-assurance security used a mix of commodity and custom hardware. SCOMP had IO/MMU plus type enforcement at memory & storage level. Congress mandated use of commercial off-the-shelf which forced ports to insecure architectures. Aesec's GEMSOS, one of first security kernels, did some kind of custom firmware when ported to x86. Paul Karger, one of INFOSEC's founders, decided on VMM's for easier security & legacy compatibility with modifications to PALcode. Many products, like INTEGRITY-178B, targeted PowerPC to get better hardware with cross-selling to aerospace. General Dynamics with NSA modified Intel stuff with misnamed HAP (Linux + VMware aint high assurance). Others are doing custom CPU's and firmware designed for security whereas Joshua Edmison made attachment that reuses high-performing CPU's. So, there's a long history in high-assurance security of securing each layer. Mainstream security ignored it as usual until recently focusing on that stuff. Many smart folks among them are trying to secure software on backdoored CPU's while others (eg Raptor POWER, Cambridge CHERI) are trying to give us non-backdoored systems. At one point, I knew most of the latter since so few are working on that angle. Rarely fix root cause over tactical mitigations.