TCS Daily

Mail Me the Money!

By David Friedman - August 8, 2002 12:00 AM

My email contains much of interest. It also contains READY FOR A SMOOTH WAY OUT OF DEBT?, A Personal Invitation from make_real_money@BIGFOOT.COM, You've Been Selected..... from, and a variety of similar messages, of which my favorite offers "the answer to all your questions." The internet has brought many things of value, but for most of us unsolicited commercial email, better known as spam, is not one of them.

There is a simple solution to this problem-so simple that I am surprised nobody has yet implemented it. The solution is to put a price on your mailbox. Give your email program a list of the people you wish to receive mail from. Any mail from someone not on the list is returned, with a note explaining that you charge five cents to read mail from strangers. Five cents is a trivial cost to anyone with something to say that you are likely to want to read-but five cents times ten million recipients is quite a substantial cost to someone sending out bulk email on the chance that one recipient in ten thousand may respond.

In order for this to work, we need an easy way of making such payments-a widely available form of digital cash. From a technical point of view, this is a solved problem, thanks to the work of David Chaum, a Dutch cryptographer. Some years back he came up with a workable system for the online equivalent of cash and got an American bank to implement one version of it on an experimental basis.

You are a firm interested in selling a solution to the spam problem. The first step is to write and distribute plug-ins for the leading email programs, allowing the user to set a price-whatever price he likes-for receiving mail from strangers and to attach ecash payments-digital stamps-to mail he sends to strangers. The second is to create digital stamps and sell them from an online stamp machine.

Some potential customers may be concerned that the use of your stamps will compromise their privacy, allowing you to collect information about who is corresponding with whom. You therefore explain that your stamps implement the fully anonymous version of Chaumian ecash. You are no more capable of tracing their path from one user to another than the Treasury is of reconstructing the path followed by a particular quarter.

Your digital stamps differ from the stamps provided by the post office in one important respect-yours are reusable. From the standpoint of the ordinary email user, digital stamps cost, on average, nothing, since he receives about as many as he sends. They may even cost less than nothing; if he sets a low enough price on his mailbox, some spam will make it through, giving him a positive balance of stamps received over stamps sent. Your online stamp machine will buy as well as sell, allowing such users to convert that balance into a small income. Spam is no longer a problem for those who do not want to receive it, and it is now a positive, if small, benefit for those who do.

The author is a professor in the Santa Clara University Law School and Economics Department and author of (most recently) Law's Order: What Economics Has to Do With Law and Why It Matters.



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