A flaw in the electronic commerce protocol SET

The Secure Electronic Transaction (SET) protocol has been developed by the major credit card companies in association with some of the top software corporations to secure e-commerce transactions. This paper recalls the basics of the SET protocol and presents a new flaw: a dishonest client may purchase goods from an honest merchant (with the help of another merchant) for which he does not pay. Fortunately, by checking his balance sheet, the merchant may trace with the help of his bank the client and his accomplice. We also propose a modification to fix the flaw.