Re: DEADBEEF vs SHA1

[David Shaw <[e-mail]>]

On Feb 21, 2011, at 7:35 AM, Lutz Donnerhacke wrote:

> 
> * Jon Callas wrote:
>> The bottom line is that a key id in that context is a 64-bit binary key
>> into a database. That's all that it is.
> 
> And it is *not unique*. Software has to deal with multiple keys having the
> same ID. Not importing v3, because it might generate such ambigious cases,
> is not an acceptable solution. V3 keys only enforce standard compliant
> behaviour.

I definitely agree.  Unfortunately, very widely deployed code does make the assumption that all keys have a unique ID.  A better fix for this problem is to fix that code, but that is complex and will likely not happen quickly.  A blockage of V3 keys is not the ideal fix for the problem, as V4-V4 collisions are still possible.  Given how easy it is to make a V3-V4 collision, and how hard it is to make a V4-V4 one, giving an option to block V3 goes a long way to avoid (though not eliminate) the problem, and buys time for the proper fix to be developed and released.

David