RPOW - Reusable Proofs of Work

mitd writes "Hal Finney is inviting folks to test drive his new hashcash-based server rpow.net. " The RPOW system provides for proof of work (POW) tokens to be reused. A POW token is something that takes a relatively long time to compute but which can be checked quickly." Hal's security model paper is well worth the read and his proof of concept code is available for download. "

Comments

Umm

[Anonymous Coward]

Can someone explain the concept behind this in a little uhh easier terms. I read parts on the website, but I think I need a bit of background before I can really understand what is going on. Thanks

Re:Umm

[masoncooper]

I know you meant to be funny but in a sense, you're right. These reusable tokens can be, well, reused. So if someone were to send you an email with a token, you could use that token(or token based on the previous token) to send an email out without having to create a new token. Since spammers are primarily outbound senders they wouldn't accumulate the tokens that a normal corporation would with frequent two-way communication. In effect, this is a lot like currency.

Calibration issues

[markh1967]

I'm not sure how well this technique would work in the real world when you have a huge range of systems trying to connect to you. If you set the number of bits in the token so a fast Pentium 4 based system will take two seconds to compute it how many hours would it take a 386, palm-pilot, or Internet enabled phone? Conversely, if you set the number of bits low so that slow systems can compute them in reasonable time then someone with a much faster computer will not be slowed by any noticeable rate and the system becomes useless. If this system is taken up surely it will do more to discriminate against people without state-of-the-art hardware. Surfing is annoying enough on a very slow machine without having to wait for 30 minutes to compute the RPOW before the site will let you connct.

Let's make it do something useful

[kanweg]

Now, if this concept of having the sender do something is changed into having the sender do useful (Folding at home or another distributed computing project), it would be a nice twist.

Bert