SHA1 being used despite public key preferences

smu johnson smujohnson at
Wed Oct 20 21:45:31 CEST 2010

On Wed, Oct 20, 2010 at 12:33 PM, Robert J. Hansen <rjh at>wrote:

> On 10/20/2010 3:08 PM, smu johnson wrote:
> > Sure, this is confusing, but since experts such as Bruce Schneier
> > say to quit using SHA-1...
> I like Bruce, and I think he does good work -- but appealing to
> authority here is simply a non-starter.

I think it makes perfect sense.  An expert says not to use SHA-1 and gives a
good argument.  To me, it seems like it's okay in this case.

> In real-world systems you can't simply stop using an algorithm cold and
> start using something new.  The overwhelming majority of times you have
> to establish a migration path to allow the system to continue operating
> as new capabilities are added to it and old capabilities removed.
That may be true for a lot of systems but as we've seen from responses it
seems like an easy change in GnuPG's case.

> Why should your preferences affect what algorithms they elect to use for
> their signatures?  That would be like telling me, "Rob, I like
> WHIRLPOOL.  Therefore, use WHIRLPOOL when signing data."  To heck
> with that: I'm going to use SHA256, or whatever algorithm I like.

I didn't say there is a problem with that.  In fact, the solution I agreed
on still lets you do that.  I'm talking about the people who simply don't
care and install GnuPG with the default settings, and use it from that point
on without changing anything.  In that case, which I believe is a huge
majority, the prefs you picked in your public key will be used by default
instead of SHA-1.  If you want to do use something else, the freedom is
still there, and I haven't once said on this thread that we should disallow

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