the slide show at http://icauce.org/proceedings.htm from http://icauce.org/proceedings/David_Harris(panel).pdf has been copied into this directory. Page 2: The Rationale: Make mail costly in some way If every spam costs something, spammers won't be able to afford to send out millions of messages. Make the cost infinitesimal. That way only spammers, who depend on sending in huge bulk, will be affected. David Nicol responds: My problem with the entire demonization of bulk advertisers paradigm, and this is a radical position I have taken, is that the demonization infringes. The Advenge server allows the recipient to set their own price, while still allowing invited new contacts to get messages through the filter without paying. Page 3: The Proposals " Two primary models have been proposed Cost as time spent in calculation Cost as a real expenditure of money " Another model, the Turing Test was suggested... In this, som e form of verification is made that proves the m essage was sent by a hum an. This proposal does not seem to have made much headw ay, although it is mentioned in M S s Penny Black research. This model may simply be too hard to implem ent. David Nicol responds: A lot of challenge/response systems use turing tests. In fact the whole c/r paradigm is an easy turing test. Page 4: "Cost as Expenditure of Time " Proposals have been around since 1999 " H ashCash, by Adam Back U ses a time-consum ing com plex one-way function to produce a hashed representation of the message. Contains provisions to deal with M oore s Law (that processor speed can be expected to double approx. every 18 months). Favours positive weighting. " Penny Black , a M icrosoft-sponsored research project Considered various ideas, som e of them very similar to HashCash. Favours negative weighting. David Nicol responds: I think "time spent in calculation" schemes are garbage, that actually exacerbate the distance between the haves and the have-nots. Mixing up messaging with computation distribution seems very odd to me. Page 5: " Cost as Expenditure of M oney " Made the headlines When U ncle Bill prom oted it at Davos late last year Microsoft s long-term position appears to be that charging for email is both inevitable and desirable. " But the idea is not as revolutionary as it seem s Ironport, Vanquish and more recently GoodM ail have begun offering bulk-mail focused paym ent-based certification. " The idea has had advocates since 1999 For an exam ple of such advocacy, see Forrester Research http://new s.com .com /2030-1028-5125275.html David Nicol responds: The idea has had advocates since before then. Sender-pays messaging has been dicsussed in the press at least since 1996, when there were news stories about people who had to pay telephone long distance charges to receive junk e-mail being annoyed. The first time I ever heard the term "cost shifting" was in such a context. the Tipjar transaction service has been a sender-pays messaging system since that year. Page 6: Cost as Expenditure of M oney " Daum O nlineStam p System Daum is a Korean ISP that charges a fee to bulk mailers for passing mail through their servers. A refund and credit system exists so recipients can issue credits for mail they find worthw hile. " The Vanquish System W orks on similar lines, with bulk mailers purchasing tokens Under this system , charges are levied as a result of recipient objection to any specific m essage. David Nicol responds: I wish "Advenge" was on that list. Under the Advenge system, recipients set their own rates and senders pay8ing in advance. No distinction is made between bulk and non-bulk senders. Recipients may whitelist individuals or mailing lists, and may also establish "magic phrases" that indicate that messages containing them may enter the recipient's mailbox for free. Page 7: Negative and Positive W eighting " Negative weighting The recipient rejects any mail that does not have a suitable proof of postage marking. Clearly only viable if uptake is considerable. " Positive weighting The recipient effectively whitelists mail with proof of postage markings, allow ing it to bypass filtering. Usable and useful even if uptake is either sm all or slow . " Microsoft appears to favour Negative W eighting David Nicol responds: Advenge does both. Page 8: Problem s with M oney-based System s " W ho collects the funds? Microsoft? The Governm ent? " How does authentication occur? A vast PKI infrastructure would be required " W ho gets the money .25c per m essage = = $11 billion per annum " How is the money collected? Microcharging? Vouchers? " W ho handles disputes? Polices abuse? David Nicol responds: A top-down approach is not desirable. Each domain may collect funds, necessuitating trust relations between sending and receiving domains. PKI is not required, SPF is sufficient for this purpose, yes it is. The recipient gets the money directly, or the operators of the domain may divide it differently. Page 9: Problem s in General " W hat about legitimate opt-in marketers? " W hat about operators of high-volum e mailing lists? " W hat about developing econom ies? The Cost as M oney model could result in considerable outflow of capital from such econom ies. David Nicol responds: The post office model of one stamp price does not map well into the sender-pays realm. With advenge, mailing list receiption is up to the recipient. That way the enforcement of "opt-in" standards is entirely decentrallized: when a recipient no longer wishes to be subscribed to a mailing list they simply delete the magic phrase associated with the mailing list, delete the list server whitelist entry associated with the mailing list server, and e-mails from that source are rejected at the server, causing the subscription to be dropped as undeliverable. Page 10: Risks " Are we throw ing out the baby with the bathw ater? Be sure that if these system s becom e entrenched, they will continue even after spam ceases to be a problem . " Do these system s compromise com m unication? Communication should be regarded as a right, not a privilege " Are we inviting a new wave of cost-plus services ? Microsoft and Yahoo have already indicated that they see this asa valuable revenue generating opportunity. David Nicol responds: As a consulting professional, i have often bemoaned the fact that I do not have a system in place for allowing a client to pay to place a priority call to me. Yes we are inviting a new wave of cost-plus services, but with Advenge the opportunity is decentralized rather than going to the big dogs.