Spam Control by Source Throttling Using Integer Factorization

Abstract

Existing solutions for spam control that are limited to spam filtering at the receiver side underestimate the fact that the network bandwidth and processing time of the recipient email servers are wasted. To cut down these costs spam should be controlled before it reaches the receiving email server. In this paper, we propose a solution to control spam at the senders email server by throttling the client’s CPU using integer factorization problem. Integer factorization is used to generate stamps as a proof of CPU cycles expended by the senders system for each email recipient. Cost of generating stamps is negligible when the client is sending emails to only a few recipients. However, as the number of recipients increases, the cost of generating stamps also increases which adversely affects the processing speed of the client. The server requires minimal processing time to verify stamps generated by the client.