Researchers from the Massachusetts Institute of Technology’s Computer Science and Artificial Intelligence Laboratory (MIT CSAIL) and Harvard University proposed a new system that enforces privacy protections for users — without any help from their web browsers.

The system, known as Veil, allows developers to set up private browsing measures for their pages. According to the researchers’ paper, the system requires no assistance from the user’s web browser, yet can still reduce the likelihood of information leakages resulting from a browser’s privacy mode.

A Unique Approach to Private Browsing

After developers feed their HTML and CSS files through Veil’s compiler, the system searches for cleartext URLs in the data. It then applies the user’s secret key to the URLs it locates and coverts them to blinded references — encrypted URLs that are cryptographically unlinkable — so that attackers can’t trace them back to their original forms.

Blinding servers then receive items uploaded by the compiler and collaborate with the page’s JavaScript to create the blinded URLs. The program also changes the syntax of a page’s content, which alters the clientside representation of the page for each user.

Where Web Browser Protections Fail

The use of blinding servers differentiates Veil from existing private browsing modes, which commonly use the file system or SQLite database to store a session’s data. However, these tools don’t completely delete that information when the session ends.

Curious individuals can also learn about a private browsing mode session by obtaining a webpage state using random access memory (RAM) reflections after the session’s termination. Such weaknesses make it difficult to fully protect users’ privacy when they’re using a private browsing mode.

In the paper, the researchers noted that the way browsers work also contributes to security gaps. “Web browsers are complicated platforms that are continually adding new features (and thus new ways for private information to leak),” they wrote. “As a result, it is difficult to implement even seemingly straightforward approaches for strengthening a browser’s implementation of incognito modes.”

Hope for the Future

The researchers asserted that Veil can have numerous practical applications for helping developers protect users’ digital privacy when browsing the web. For example, they envision developers of a whistleblowing service using the system to prevent employers from tracking visits to the site on employees’ workstations.

Veil can’t protect users’ privacy in every scenario, however. It only works against local attackers who access a user’s computer after terminating a private browsing session. In addition, the system is currently powerless against situations in which a bad actor compromises the computer during a protected session and uses keylogging to exfiltrate sensitive information. These risks highlight the importance of users and organizations taking appropriate steps to protect themselves against phishing attacks and other digital threats.

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