This post has been updated to include the patent number.
Pomcor has been granted US patent 10,825,025 on the method of cardholder authentication that I have discussed before on this blog. The Cardholder Authentication page has links to earlier materials. Actually, the patent was granted on November 3, 2020, but I was busy working on TLS traffic visibility at the time.
3-D Secure 2 purports to reduce the friction created by 3-D Secure 1 as it redirects the cardholder browser to the card issuer’s site for authentication. But it does so by omitting cardholder authentication altogether for transactions deemed low risk, and may increase friction for other transactions.
Eliminating friction with a Service Worker
We eliminate friction instead, for all transactions, by using a Service Worker registered with the browser by the issuer to intercept the redirected request and authenticate the user by proof of possession of a private key, which is used to sign a description of the transaction and thus provide a defense against transaction repudiation to the merchant.
The private key is associated with a credit card certificate that contains the corresponding public key and a cryptographic hash of the data printed on the credit card. The card data is not included in the certificate to avoid exposing it to an attacker who uses malware or physical capture of the cardholder’s device to obtain the certificate. When the merchant’s site or native app receives the certificate along with signature, it verifies the hash against the printed card data entered by the cardholder.
Are Service Workers still usable?
People have been telling us recently that Service Workers can no longer be used because WebKit deletes Service Worker registrations, along with first-party data stored in the browser, after seven days of non-use. This is an unfortunate complication, but it does not mean that Service Workers and first-party data can no longer be used. It just means that the web app that registers the Service Worker, in this case the issuer’s web app, must be added to the home screen, as explained in this WebKit blog post.