Re: exporting signatures only/CAPI (was Re: Why not PGP?)

[azur@netcom.com (Steve Schear)]

>Steve Shear <azur@netcom.com> writes:
>> >The problem however, is finding a non-US site to hold the hot potato
>> >once it has been exported.  For example 128 bit Netscape beta was
>> >exported a while ago.  I don't see it on any non-US sites.  This is
>> >due to Netscape's licensing requirements, you need a license to be a
>> >netscape distribution site, the license doesn't include the right to
>> >mirror non-exportable versions on non-US sites.
>>
>> That's one good application for remailers, and .warez newsgroups. at.
>
>I don't know of any advertised files by email services using nym
>servers, where the file request, and the files are both sent via
>remailers.
>
>The problem with this is currently is that the nym servers couldn't
>stand up to the scrutiny if SPA or whoever got interested.  The
>message flood attack on the nym would reveal the services host.
>
>The BlackNet architecture solves this problem by posting requests
>encrypted with the services key to a newsgroup, but USENET newsgroup
>disitribution time is slow (*), and people are spoilt these days with
>WWW, and expect results now, not days later.

Has anyone tried this to see whether the LOS would or wouldn't be acceptable?

>
>The requested file can be posted via mixmaster.  You would want to use
>a different, random chain of remailers each time.  A reverse message
>flood could reveal the host also, as you can request lots of copies,
>and the service will blindly serve the files.  (If someone wants to
>discover the service host, they send 1000s of requests, then sit back
>and watch which user sends most data into the remailer net.)

On a related note:

I've been charged with developing an Internet service which needs to assure
its clients of anonymity.  However, we fear some clients may abuse the
service and we wish to prevent the abusers from re-enrollment if
terminated for misbehavior. (In your example, it would be the person(s)
trying to discover the service host via flood).

My thought was to base enrollment on some sort of 'blinding' of their
certified signature (e.g., from Verisign) which produces a unique result
for each signature but prevents the service from reconstructing the
signature itself (and thereby reveal the client's identity).  I'm calling
this negative authentication.

Have you come across anyone who has considered this problem or
another one which is mathematically very similar?

>
>To combat this the service could impose a limit on the number of
>copies it would serve per day.  This allows a denial of service
>attack, if someone wants to stop anyone else getting a copy, they just
>saturate the service.  Still an improvement over no limit.

If the service could negatively authenticate users it would need such
limits and might not be subject to such attack.

>
>Of course Ross Anderson's `eternity service' provides the general case
>solution for distribution of such data.  It is complex to implement
>well though.

I've never heard of the eternity service.  Where can I get more information?

BTW, would Eric Hughes' Universal Piracy System also solve such a
situation, by distributing or parking snippets of encrypted file data
across many 'cooperating' ftp (or whatever access/storage mechanism) sites.
Perhaps the negative authentication approach would help here too by
preventing flood/denial of service attacks against the 'key' sites.  If
only snippets of encrypted data are stored on any one host it might make
the SPA's goal even more elusive legally.



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