Securing User Content In The Javascriptable Web

My latest blog post appeared on O’Reilly Media’s programming blog.

Recent work by a W3 Working Group plans to expose many powerful cryptographic operations for web applications. Although the planned API adds much needed functionality to JavaScript, it doesn’t address the JavaScript runtime’s terrible security properties. For instance, any script running in the web application has the power to hijack the web app’s content and UX. Just last February a mistake in Facebook’s "like" button brought down millions of web sites. Further, if you are an online service provider wanting to support higher privacy use cases like encrypted chat or web-based PGP email, the trust model is fundamentally broken since you can’t serve cryptographic JavaScript code without making the server a potential attack point.

The security challenges faced by JavaScript are mitigated by Privly, also labeled “the Web Privacy Stack,” by addressing two issues: (1) scoping code to the data, and (2) pre-distributing the code to the clients when possible.