what fields to hash with hashcash (Re: A Trial Balloon to Ban Email?)

Bill Frantz frantz at pwpconsult.com
Wed May 14 11:14:56 PDT 2003


At 7:56 AM -0700 5/14/03, Adam Back wrote:
>I was suggesting 30 days.  You could up that if you want -- the
>database won't be that big at say 32 bytes per recieved mail.
>
>The day is matched against the day in the token, as Bill said the
>tokens contain the date and the email address, in fact they look like
>this:
>
>0:030514:foo at bar.com:482d3c37d5b5c112
>
>where the first field is a version number, 2nd field is date
>(year,month,day), 3rd field is resource name (for email the
>recipient's email address) and last field is random junk to make it
>hash to trailing zeros.
>
>if you hash that with sha1:
>
>% echo -n 0:030514:foo at bar.com:482d3c37d5b5c112 | sha1
>00000bea531c1edbcee4fbb69e094026cd83ed75
>
>You can see that this one has 20 leadings 0s (in binary -- 5x4bit hex
>digits).

This approach seems like a good direction.  However, it does limit me to
email per address per day.  :-)

Cheers - Bill


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