I am concerned about space, but more about usability :-)
 I'll definitely use both M and the checksum.


On Tue, Apr 22, 2014 at 10:43 AM, Matt Whitlock <bip@mattwhitlock.name> wrote:
On Tuesday, 22 April 2014, at 10:39 am, Jan Møller wrote:
> Necessary Shares = M+1, not a problem
>
> I would probably encode N-of-M in 1 byte as I don't see good use cases with
> more than 17 shares. Anyway, I am fine with it as it is.

I agree that M > 16 is probably not a viable use case for human beings, but machines would probably be able to make use of it. I, for one, welcome our new robot overlords.

Also, the byte that encodes M−1 is optional, so if you're concerned about space, you can omit it (and the checksum).