Talk:Hashcash

message: At 21:34, 2 June 2005,
someone changed
: ... a small puzzle involving the recipient's email address.
to 
: ... a small puzzle, often involving the recipient's email address.
with the comment
: "Hashcash isn't only for email (even if primarily)"
Really? Tell me more.
I reluctantly reverted it back.
If the puzzle *doesn't* include the email address, then what stops the spammer from spending an entire second calculating the hashcash header just one time, then once he has "the" hashcash header, sending identical copies of that header to millions of email address?
I would be fascinated to learn more about
* hashcash that do not involve the recipient's email address
* hashcash used for something other than email.
I see no theoretical reason why someone couldn't do either or both of these things, but I see no reason to stick them in the encyclopedia article unless someone actually does do either or both of these things.
--DavidCary 05:48, 10 November 2005 (UTC)
thread_title: comments

message: 79.117.77.137 (talk) 17:34, 19 July 2013 (UTC)
thread_title:  How does it work in case of spam (give some example)? 

message: Guys, bitcoin is NOT using hashcash. Bitcoin uses double SHA-256 with variable difficulty. The idea is superficially similar but it is NOT hashcash.
JorisVR (talk) 09:44, 15 September 2013 (UTC)
thread_title:  Bitcoin 

message: The article states that the sender will need to try 220 hashes on average until a hash value with 20 initial zeros will be found. Since the odds of any given hash being successful is 1 in 220, shouldn't 220 hashing attempts be the worst case, and therefore the average number of attempts be only half of that (i.e., 219 attempts)? — Loadmaster (talk) 20:24, 12 April 2016 (UTC)
replies: text: Agreed. I have edited it. Blooteuth (talk) 18:59, 28 August 2017 (UTC)
thread_title:  Average hashing attempts 

message: Hello fellow Wikipedians,
I have just modified 2 external links on Hashcash. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
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*Added archive https://web.archive.org/web/20051027033442/http://elliottback.com/wp/archives/2005/10/23/wordpress-hashcash-30-beta/ to http://elliottback.com/wp/archives/2005/10/23/wordpress-hashcash-30-beta/
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thread_title:  External links modified 

message: I have moved the earlier author claim to its own section, and out of the lede. Putting it in the lede gives too much WP:UNDUE WEIGHT to this content that appears to be WP:OR. But I thought I would leave the content for now. We need an WP:RS that states that Adam Back's work was based on this earlier work, not just a link to the earlier work and then the wikipedia editor does his own WP:OR to determine the connection. We just dont do that, especially as the content seems to call into question the validity of Back's invention, and is thus a WP:BLP issues. Jtbobwaysf (talk) 16:51, 15 May 2018 (UTC)
thread_title: Idea proposed in 1992

message: Have a listen to a discussion about this topic from Professor Emin Gun Sirer at Cornell .
A few important things to note:
* Adam Back's Hash Cash is not used in bitcoin, though it is cited by Satoshi. Bitcoin uses the core proof of work idea.
* The core proof of work idea came from Cynthia Dwork and Mani Noar 5 or 6 years prior to Adam Back .
* Adam Back's page says a similar system is used in bitcoin, not hash cash Adam Back
Y3sh (talk) 05:20, 1 June 2018 (UTC)
replies: text: please link to the page in google books if possible. Jtbobwaysf (talk) 12:58, 1 June 2018 (UTC)

text: updated Y3sh (talk) 18:04, 10 June 2018 (UTC)
replies: text: Cool, thanks. I thought maybe this link would say that Back's work came later. I think we need a source to tell us that Backs work was based on this, we editors can't do our own WP:OR to determine that this source came first (even it appears to me it does). Jtbobwaysf (talk) 18:44, 10 June 2018 (UTC)
thread_title:  Citations for the Hash Cash Creation Discrepancy (Give credit where credit is due) 

message: I propose the following change to the algorithm: the counter must always start at zero. Therefore it represents the number of unsuccessful attempts.
This provides two distinct benefits:
1) The recipient can maintain global stats on the number of attempts. They should converge towards half the worst-case number of tries in a nice bell. If a sender sends several outliers, they are likely cheating.
2) The recipient can elect to perform the work occasionally or in case of doubts about the sender. It can redo the exact same sequence of tries. If it finds a matching hash sooner than they said, they would have found it too, therefore the are almost surely cheating. Axelriet (talk) 05:49, 28 February 2023 (UTC)
thread_title:  Why initialize the counter to a random value?