hashed user IDs [was: Re: Security of the gpg private keyring?]

Jeffrey Walton noloader at gmail.com
Thu Mar 10 02:12:03 CET 2011

On Wed, Mar 9, 2011 at 8:11 AM, Ben McGinnes <ben at adversary.org> wrote:
> On 9/03/11 2:44 AM, Johan Wevers wrote:
>> MFPA schreef:
>>>>> Something that would not be necessary if the
>>>>> underlying openPGP implementations could handle hashed
>>>>> user IDs.
>>>> Isn't it much easier to use the key ID / signature for
>>>> that? You already have that.
>>> I don't understand.
>> Use the keyID / signature as the hashed user ID, since it (should)
>> uniquely identify the key. Since a hash is one way you can't derive
>> the email address from it anyway, from the keyID you also can't
>> (directly) deduce the email address.
> Ah, but the keyID can already be used to locate a key, that's not what
> MFPA is getting at.  What he wants is a function built into GPG and
> the keyservers, possibly via some kind of proxy tool, to do this:
> * User generates a key, when prompted for a name enters "Joe Citizen"
>  and when prompted for an email address enters "joe at example.net"
> * GPG or interface for it takes those strings and generates a hash
>  (let's use SHA256 for this example) so the UID for the key appears
>  to be:
>  "7b7581fe6670a6a4a29b2fd46eaf5ac34a6a86d134fe8931729e66970b707349
>  <466ffe71badce782db1808ee80bd01dabf0d95e4a3b8ccbbe5fcdc68b86c2bb9>"
> * Anyone trawling through keys on a public server or downloading
>  random keys cannot see who owns that key or what their email address
>  is, but anyone who knows Joe or his email address can search the
>  keyservers for that data because the hash can be calculated from the
>  data they do have (e.g. joe at example.net) and search for the key with
>  the matching hash.
> This would allow someone to use a single key for multiple identities
> or pseudonyms, without the information about those identities being
> learned by different groups.  Well, probably not.
> Personally, I think it's an interesting idea and I can see the value
> in it, but I'm not sure there are enough people really pushing for it
> (yet).  With things like the data retention legislation being pushed
> in Europe, Australia and other countries, that may change.
Imagine you are Tunisian or Libyan or some other nationality where
disagreeing with the regime might get you killed. Would you want your
name and email associated with another's keyring? Or would you prefer


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