No they won't. All the ones I've seen are some variant on the "build a big wall around the Internet and only let the good guys in", which will never work because the Internet doesn't contain any definable inside and outside, only 800 million Manchurian candidates waiting to activate. For example MessageLabs recently reported that *two thirds* of all the spam it blocks is from infected PCs, with much of it coming from ADSL/cable modem IP pools. Given that these "spammers" are legitimate users, no amount of crypto will solve the problem. I did a talk on this recently where I claimed that various protocols designed to enforce this (Designated Mailers Protocol, Reverse Mail Exchanger, Sender Permitted From, etc etc) will buy at most 6-12 months, and the only dissent was from an anti-virus researcher who said it'd buy weeks and not months. The alternative proof-of-resource-consumption is little better, since it's not the spammers' resources that are being consumed.
the caveat to that is many of the infected machines were originally infected by spam with spoofed origin ... somehow convincing users to click on something. authentication would help somewhat with that ... and, in fact, some of the spam being sent out by the infected machines, in turn uses spoofed origin. authentication might also help address the identity-theft oriented spam ... claiming to be your bank and needing personal information.
it doesn't help with ... click on this to get the latest, greatest game ... where there isn't any attention at all paid to the origin ... just looking for instant gratification.
the 60s/70s time-sharing systems nominally had some assurance applied to the introduction of executables into the environment. this is my comment about the desktop systems having diametrically opposing requirements ... the original design point of totally unconnected, stand alone environment where an introduced executable could take over the whole machine ... and at the same time fully wired to an increasingly hostile environment needing signficant safeguards and processes associated with assurance of introduced executables. the intermediate step was that some of these stand-alone machines acquired interconnect capability for a local, safe, isolated departmental/office network. This had hardly any restricted execution and access capability ... again not worrying about protection against a hostile and unsafe operation.
the shared environment analogy is highway traffic and rules about operating an unsafe vehicle could result in both having your license revoked and the vehicle confiscated (it doesn't require the driver to be a highly trained car mechanic ... it just holds the driver responsible).
connecting systems that were designed for fundamentally safe and isolated environment to wide-open anarchy hostile operation exposes all sorts of problems. somewhat analogous to not actually needing a helmet for riding a motorcycle ... or seat belts and airbags to drive a car.
Anne & Lynn Wheeler http://www.garlic.com/~lynn/
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