[darcs-users] Data Integrity

[Nicolas Pouillard]

Excerpts from Daniel Carrera's message of Thu Apr 09 17:09:28 +0200 2009:
> Nicolas Pouillard wrote:
> >> In fact, Darcs could sign all patches, so that tags are not "special". I 
> >> just took a look at the Darcs 2 format. It looks like it should be easy 
> >> to add an RSA signature. This is what a patch looks like:
> > 
> > Tags are kind of special. This is due to patch commutation that can change
> > their representation. But by definition a tag patch constrain all patches
> > that it depends upon to no longer change. So one can store a hash in there.
> 
> Ok. But that doesn't prevent us from signing tags, does it? I'm only 
> partially familiar with the theory of patches, but my understanding is 
> that a tag is just a patch that is artificially dependent on every 
> current patch in the repository.

Yes we can sign tags.

> The more I think about it the more I like the idea of signing tags and 
> other patches. It seems to retain the Darcs concept that "there are no 
> versions, there are only patches" and it seems to have the data 
> integrity features that some of the other SCMs have.

As said previously signing other patches does not make much sense with
commutation. Indeed since patch representation change when commuting
with another patch, then checking the hash would not work.

-- 
Nicolas Pouillard