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Only a small amount is necessary. There is a protocol called hashcash (used by Bitcoin but generally applicable) that can be easily used with email [1]. You bas

Only a small amount is necessary. There is a protocol called hashcash (used by Bitcoin but generally applicable) that can be easily used with email [1]. You basically get a header like this: X-Hashcash: 0:030626:adam@cypherspace.org:6470e06d773e05a8 You can choose how much work you want to do and the recepient can specify thresholds for minimum work required. This header is all they have to store, and it's easily stored through existing email infrastructure. Your mail server can do it without your client's help, too. If you spent a second on a proof I'm sure grandma wouldn't notice, but it would be very difficult for spammers to do the same. [1] http://www.hashcash.org/ http://www.hashcash.org/

tscs37 9y ago
That does not sound terrible useful. For one, it'll only work if both sender and receiver use it. Which means for 99.99% of mail traffic right now, it is utterly meaningless. edit: Plus you also literally wasted everyone's time and energy. I'd rather favor some kind of mechanism like grey-lists that don't require sender opt-in otherwise it'll be a dead technology just like GPG. (You can probably count the number of GPG emails within 1000 average mails on one hand)
- Sir_Cmpwn 9y ago
  We make incremental change. Adoption starts slow, then some middle players pick it up, one big player grabs it and then it proliferates. I've been working on a mail client for some time and I have plans to write a mail server, and both will have first class, opt-out support for hashcash.
  - tscs37 9y ago
    That sounds like a lovely pipe-dream. I severely doubt any big player picks it up on grounds of it being cheaper and less energy intensive to simply greylist or blacklist.
- amelius 9y ago
  How about sending (by email) a link to a proof-of-work-website, so the hash function can be computed in javascript/wasm in a browser? Anyway, I agree on the waste of time+energy.

tscs37 9y ago

That does not sound terrible useful. For one, it'll only work if both sender and receiver use it. Which means for 99.99% of mail traffic right now, it is utterly meaningless. edit: Plus you also literally wasted everyone's time and energy. I'd rather favor some kind of mechanism like grey-lists that don't require sender opt-in otherwise it'll be a dead technology just like GPG. (You can probably count the number of GPG emails within 1000 average mails on one hand)

Sir_Cmpwn 9y ago
We make incremental change. Adoption starts slow, then some middle players pick it up, one big player grabs it and then it proliferates. I've been working on a mail client for some time and I have plans to write a mail server, and both will have first class, opt-out support for hashcash.
- tscs37 9y ago
  That sounds like a lovely pipe-dream. I severely doubt any big player picks it up on grounds of it being cheaper and less energy intensive to simply greylist or blacklist.
amelius 9y ago
How about sending (by email) a link to a proof-of-work-website, so the hash function can be computed in javascript/wasm in a browser? Anyway, I agree on the waste of time+energy.