The Spy Guide to Hiding

In a September 2 letter, the senator asked NSA Director Gen. Joshua Rudd to update public guidance on VPN configurations and provide unclassified answers by October 14. The target is surveillance by foreign adversaries, particularly those capable of watching internet backbone traffic. The intended beneficiaries include government personnel, journalists and human rights defenders.

This is a request for advice, not advice already issued. Nobody has won the government-approved invisibility contest.

As Dan Goodin reports in Ars Technica, Wyden wants answers more useful than “use a VPN.” Are ordinary single-hop services sufficient? Do multi-hop tools offer better protection? What difference do random delays, padding and cover traffic make? He names Apple Private Relay, Tor and Nym as systems the agency should assess, not products readers should assume are interchangeable.

The distinction underneath those questions is simple enough: hiding the contents of a communication is not the same as hiding its relationships.

A conventional consumer VPN encrypts traffic between your device and a VPN server. That can protect against observation along that stretch. It does not make the operator disappear from the trust arrangement. The Congressional Research Service memorandum attached to Wyden's letter describes the basic exchange: users shift trust from their internet service provider to the VPN operator.

The tunnel has an end. So does the promise.

There is a second problem that stronger encryption alone does not settle. As the CRS memo explains, an observer can examine traffic timing and volume to correlate activity without breaking the encryption. A system can conceal what was said while leaving clues about who was communicating with whom. Wyden is asking the agency to address that distinction rather than let the word “encrypted” carry the entire security argument.

That is a legitimate use of technical expertise. Rejecting an answer solely because it came from an intelligence agency would be the mirror image of accepting it solely because it did. Neither requires reading the answer, which is their principal convenience.

But expertise and authority are different permissions.

An intelligence agency advising people on resistance to intelligence collection occupies an obvious institutional tension. That does not prove its technical guidance false, compromised or malicious. It does mean the public needs something more inspectable than a list of approved brands. The answer should make its assumptions available to people who do not share the agency's priorities.

Against which observer? With access to which parts of the network? Under what assumptions about compromised or cooperating operators? What protection survives if those assumptions fail?

Those are not decorative caveats. They are the product.

Multi-hop designs can divide knowledge across relays; that does not establish that every implementation defeats an adversary watching multiple points. Delay and mixing aim at a different weakness from encryption alone. The letter asks for an assessment of these approaches. It supplies no independent security audit of the named services, and this article recommends none of them.

The public-interest test is whether guidance increases a person's ability to judge a claim, or merely changes whose claim they must trust. A journalist should be able to take the stated threat model to an independent researcher and ask where it breaks. A vendor should have to answer the same question. So should the government.

Wyden's demand for unclassified written answers creates an opportunity for that kind of scrutiny. Whether the response delivers it remains open.

“Use a VPN” is advice with the hard part omitted. “Use the one we recommend” could preserve the omission while adding an official seal.

The useful spy guide would tell readers where its own advice stops working.