Re: Digital postage and remailer abuse (was Re: Novel use of Usenet and remailersto mailbomb from luzskru@cpcnet.com)

[tcmay@got.net (Timothy C. May)]

At 4:47 PM 1/13/96, Alan Bostick wrote:
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>In article <v02120d02ad1ce02500bc@[192.0.2.1]>,
>shamrock@netcom.com (Lucky Green) wrote:
>
>> I am not sure that postage would solve this problem. The geeks would
>> individually pay for it. Still, nominal postage would solve a lot of the
>> problems that plague remailnet.
>
>Maybe I'm misunderstanding how using digital postage with remailers would
>work.  I was assuming that the postage stamp would be included *inside*
>the encrypted envelope, that what the remailer would do on receipt of
>mail would be: (a) decrypt the envelope; (b) validate the postage stamp;
>and (if the stamp is valid) (c) forward the message according to the
>now-decryped instructions.

The basic idea of digital postage means, as Lucky said, that individual
users and individual messages would have their own stamps. (Being just
numbers, it is certainly possible that multiple messages could have the
same exact "stamp," but then only one of them would be valid...in the model
I usually think in terms of, the first to "redeem" the stamp gets the
money, all others get nothing.)

So, each transmitter of a message would have to "pay the freight" with his
own stamp. The idea of N different messages all carrying the "same" stamp
is inconsistent with how digital postage would operate in practice.


>Using this model, if the perpetrator doesn't include a postage stamp,
>then the message is ignored.  If the perp includes a stamp, the first
>horny net geek's message is relayed but subsequent ones get bounced for
>invalid postage.

Yes.

>If the message requires external postage (remailer processing cycle is
>process postage *before* decrypting envelope), then at the very least
>the horny net geeks have to get their own postage stamps, putting a step
>in the way of instant gratification.  What's more, doing this would
>require *some* understanding of how the remailer network operates.  One
>should never underestimate the degree of cluelessness present on the
>net, but knowing how to use remailers makes it more likely that somebody
>could recognize this as a mailbomb rather than a legitimate offer.

Yes.


>The very nature of this attack makes me wonder whether it would be
>worthwhile to implement a digital postage scheme for remailers that
>doesn't happen to be backed by real money.  The remailers would continue
>to be free to use, and currency exchange hassles would be avoided, but
>many of the benefits of abuse prevention would be in place.  So would
>the infrastructure to upgrade to pay-to-play remailers at a later date.

I think someone tried this a couple of years ago, offering coupons for
remailer use.

The idea of "coupons" acting as stamps is the one most often discussed as
an alternative to having full convertability to money. A person buys a
block of numbers, each can be used once and only once. It's up to the user
not to let the numbers out of his possession (as they can be used by
whoever gets them).

So long as the numbers are in the outer encrypted envelope, packet sniffers
and sysadmins won't see them.

So long as the remailer operator is honest enough not to claim the numbers
have already been used--a reasonable assumption, at least at this
time--then this should work.

Coupons also get around laws about cash, banking, etc.

--Tim May

We got computers, we're tapping phone lines, we know that that ain't allowed.
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Timothy C. May              | Crypto Anarchy: encryption, digital money,
tcmay@got.net  408-728-0152 | anonymous networks, digital pseudonyms, zero
W.A.S.T.E.: Corralitos, CA  | knowledge, reputations, information markets,
Higher Power: 2^756839 - 1  | black markets, collapse of governments.
"National borders aren't even speed bumps on the information superhighway."