Projects / HashCash


HashCash is an anti-spam, anti-DoS system for email. The concept centers around the sender of the mail completing a computationally expensive task (in this case, generating hash collisions) that the recipient can verify very quickly. This allows the sender to "pay" for transport in CPU cycles, creating artificial scarcity. Programs are included to add payment to messages (for the sender) and to verify message payment (for the recipient).

Operating Systems

Recent releases

  •  01 Oct 2004 09:12

    No changes have been submitted for this release.

    Recent comments

    01 Oct 2004 17:12 adamback

    spam assassin 3.0
    spam assassin 3.0 supports hashcash

    could still really use hashcash support for mozilla mail (thunderbird/mozilla mail).

    See: for the tracking bug ( info

    01 Oct 2004 02:46 samjam

    Good idea....
    and will thus require all "owned" machines to be upgraded with new spamming software than can compute these hashes. Maybe owners will wonder why their PC's are slowing down.


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