[Cryptography] Minimal secure boot

[Jon Callas]

> On Jun 9, 2019, at 1:57 PM, sebastien riou <matic at nimp.co.uk> wrote:
> 
> 
> Now I am wondering if I need:
>    - e larger than 3 ? if yes what is the sensible minimum ? I am inclined to set e=11 to get (digest power e) > n but I do not have really clear argument for that. 

Yes. You want something bigger than 3. Three can work, but you have to take care. It's simpler to pick something bigger.

Mathematically, 5 works just fine. Traditionally in RSA cryptography, 17 and 65537 are traditional because they're (2^n)+1. 

>    - padding the digest before the mod_exp

Knowing I don't know, why wouldn't you use OAEP or some equivalent?

	Jon