SPAM Control Using CPU Timestamps

Abstract

Email spam has reached alarming proportions 
because it costs the sender very little to send; almost all of the 
costs are paid by the recipient, carrier and the email servers. 
Email spam’s inadvertently affect the performance of email 
servers which are kept busy in processing huge number of 
emails sent by the spammers. It also affects the productivity of 
the recipients who have to skim through lots of irrelevant 
emails to find the ones that actually require their attention. We 
propose a solution to control spam at the ingress points on the 
email servers by throttling the sender’s CPU i.e., making an 
email client pay a stamp fee for every email sent. The stamp fee 
is collected in terms of resource usage, in our case CPU cycles. 
The solution is based on the use of Discrete Logarithm Problem 
(DLP), which is considered to be one of the hardest 
mathematical problems to solve and is the basis for many 
cryptosystems. DLP is used to generate CPU stamps as a proof 
of the CPU cycles expended by the sender’s system. A separate 
stamp has to be calculated for each email and for each 
recipient which restricts the total number of emails that an 
email client can send in a time interval. We further claim that a 
normal user will not notice this cost in his day to day 
operations and a spammer will not be able to get past this 
mechanism.