New Paper on Inertial Hardware Security Modules


World's First DIY HSM

Last week, Prof. Dr. Björn Scheuermann and I have published our first joint paper on Hardware Security Modules. In our paper, we introduce Inertial Hardware Security Modules (IHSMs), a new way of building high-security HSMs from basic components. I think the technology we demonstrate in our paper might allow some neat applications where some civil organization deploys a service that no one, not even they themselves, can snoop on. Anyone can built an IHSM without needing any fancy equipment, which makes me optimistic that maybe the ideas of the Cypherpunk movement aren't obsolete after all, despite even the word "crypto" having been co-opted by radical capitalist environmental destructionists.

An IHSM is basically an ultra-secure enclosure for something like a server or a raspberry pi that even someone with unlimited resources would have a really hard time cracking without destroying all data stored in it. The principle of an IHSM is the same as that of a normal HSM. You have a payload that contains really secret data. There's really no way to prevent an attacker with physical access to the thing from opening it given enough time and abrasive discs for their angle grinder. So what you do instead is that you make it self-destruct its secrets within microseconds of anyone tampering with it. Usually, such HSMs are used for storing credit card pins and other financial data. They're expensive as fuck, all the while being about the same processing speed as a smartphone. Traditional HSMs use printed or lithographically patterned conductive foils for their security mesh. These foils are not an off-the-shelf component and are made in a completely custom manufacturing process. To create your own, you would have to re-engineer that entire process and probably spend some serious money on production machines.

Inertial HSMs take the concept of traditional HSMs, but replace the usual tamper detection mesh with a few security mesh PCBs. These PCBs are coarser than traditional meshes by orders of magnitude, and would alone not even be close to enough to keep out even a moderately motivated attacker. IHSMs fix this issue by spinning the entire tamper detection mesh at very high speed. To tamper with the mesh, an attacker would have to stop it. This, in turn, can be easily detected by the mesh's alarm circuitry using a simple accelerometer as a rotation sensor.

In our paper, we have shown a working prototype of the core concepts one needs to build such an IHSM. To build an IHSM you only need a basic electronics lab. I built the prototype in our paper at home during one of Germany's COVID lockdowns. You can have a look at our code and CAD on my git. What is missing right now is an integration of all of these fragments into something cohesive that an interested person with the right tools could go out and build. We are planning to release this sort of documentation at some point, but right now we are focusing our effort on the next iteration of the design instead. Stay tuned for updates ;)