[Cryptech Tech] Question regarding Trusted Path Authentication

[Jakob Schlyter]

On 18 dec 2014, at 05:21, Peter Gutmann <pgut001 at cs.auckland.ac.nz> wrote:

> It's actually really, really hard to implement, hard to document, and hard to 
> use.  I use this in my book as an example of something that seems quite simple 
> (and desirable to have as a feature) until you start thinking about it, and 
> then the more you think about it the harder it gets.

There are (at least) two uses for m-of-n;

a) HSM activation (arm), performed out of band with the device before key material within can be used.
b) Key material backup/restore, splitting a wrapping key requiring m-of-n components to restore key.

IMHO, both these can be implemented by using a m-of-n secret sharing algorithm. Threshold signing would be tricker, but that is also something completely different.

Peter; could you please elaborate on the challenges to get this right? I'm most likely missing something important.


	jakob