Accountable Javascript Code Delivery

TL;DR

This paper introduces Accountable JS, a protocol and browser extension that enhances transparency and auditability of web application code delivery, addressing a critical gap in web security and accountability.

Contribution

It presents a novel protocol for accountable code delivery, formalizes its security properties, and evaluates its performance and compatibility through real-world case studies.

Findings

Accountable JS improves transparency in web code delivery.

The protocol is formally verified for security properties.

Performance impact on web applications is minimal.

Abstract

The internet is a major distribution platform for web applications, but there are no effective transparency and audit mechanisms in place for the web. Due to the ephemeral nature of web applications, a client visiting a website has no guarantee that the code it receives today is the same as yesterday, or the same as other visitors receive. Despite advances in web security, it is thus challenging to audit web applications before they are rendered in the browser. We propose Accountable JS, a browser extension and opt in protocol for accountable delivery of active content on a web page. We prototype our protocol, formally model its security properties with the Tamarin Prover, and evaluate its compatibility and performance impact with case studies including WhatsApp Web, AdSense and Nimiq. Accountability is beginning to be deployed at scale, with Meta's recent announcement of Code Verify available to all 2 billion WhatsApp users, but there has been little formal analysis of such protocols. We formally model Code Verify using the Tamarin Prover and compare its properties to our Accountable JS protocol. We also compare Code Verify's and Accountable JS extension's performance impacts on WhatsApp Web.