Escalating The War On SPAM Through Practical POW Exchange

TL;DR

This paper proposes a practical, non-uniform proof-of-work scheme to significantly increase the cost of sending spam emails while minimally affecting legitimate email, using existing spam filters and small SMTP modifications.

Contribution

It introduces a novel non-uniform proof-of-work framework that effectively escalates spam costs without complex reputation systems, leveraging current technology and minimal protocol changes.

Findings

Spam becomes 1,000 times more expensive to send.

The approach does not significantly impact legitimate email.

It avoids the complexity of reputation-based systems.

Abstract

Proof-of-work (POW) schemes have been proposed in the past. One prominent system is HASHCASH (Back, 2002) which uses cryptographic puzzles . However, work by Laurie and Clayton (2004) has shown that for a uniform proof-of-work scheme on email to have an impact on SPAM, it would also be onerous enough to impact on senders of "legitimate" email. I suggest that a non-uniform proof-of-work scheme on email may be a solution to this problem, and describe a framework that has the potential to limit SPAM, without unduly penalising legitimate senders, and is constructed using only current SPAM filter technology, and a small change to the SMTP (Simple Mail Transfer Protocol). Specifically, I argue that it is possible to make sending SPAM 1,000 times more expensive than sending "legitimate" email (so called HAM). Also, unlike the system proposed by Debin Liu and Jean Camp (2006), it does not require the complications of maintaining a reputation system.