changing the default for --keyid-format [was: Re: getting an encrypted file to show what public key was used]

David Shaw dshaw at
Tue May 29 19:47:30 CEST 2012

On May 29, 2012, at 11:51 AM, Daniel Kahn Gillmor wrote:

> On 05/29/2012 11:35 AM, Werner Koch wrote:
>> Use 
>>   gpg --keyid-format long --decrypt sensitive_file.gpg
>> to see the non-abbreviated key ID as stored in the file.  Use this to
>> find the key on a server, etc.
> i've seen a lot of these mistakes where people seem to think that 32-bit
> keyids are somehow collision-resistant.  For example:
> Perhaps GnuPG should change the default of --keyid-format from "short"
> to "long"?  certainly, the 64-bit keyID itself is not as
> collision-resistant as the full fingerprint, but it does raise the bar
> for an attacker (and discourages users from just parrotting the 32-bit
> keyid if they don't understand what they're looking at).
> I think switching the default to "long" would be on balance a Good Thing.
> What do other people think?

I think that it would bring more confusion than benefit, unfortunately.  There is a significant amount of documentation (and even code) that uses OpenPGP in terms of 32-bit key IDs, and if that if we were to change, we'd cause all sorts of problems.  Defaults should be conservative.

That doesn't mean we can't start encouraging people to use 64-bit IDs, but I don't expect it to be a quick process.

What is your concern here, though - accidental or intentional collision?


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