How to sign a snap package?

Tue Jul 26 20:47:44 UTC 2016

On Tue, 26 Jul 2016 19:43:10 +0200, Oliver Grawert wrote:
>Am Dienstag, 26. Juli 2016 19:35:01 CEST schrieb Peng Liu:
>> Is there any tool we can use to sign a snap package?  
>
>i think we call that tool the store ;)

Assumed upstream builds snaps, providing them as downloads by an
upstream website, for Linux users of all distros, does it mean, that it
is required to provide a snap package, a SHA256SUMS and SHA256SUMS.gpg
or to use the Ubuntu store?