IT has been a rough couple of months for the folks at the Tor Project. Tor — it stands for "The Onion Router" — camouflages its users' Web communications with encryption and by bouncing signals around server nodes in different parts of the world so that it's all but impossible for either governments or advertisers to track them to their origins. Its fans hail Tor as a vital tool for those who live under repressive governments.

But Tor has suffered a series of public embarrassments — embarrassments that teach important lessons about the increasingly desperate search for online privacy.

Last month, we learned that the anonymity protocols that are Tor's reason for existence had been hacked, apparently by the FBI, which was investigating an alleged purveyor of child pornography. Then, last week, we were reminded that some 60 per cent of the budget of the Tor Project comes from the federal government, including a whopping 40pc from the Department of Defence. (Tor responded in an email published in the Washington Post that these are research grants, and the US government does not control its research or software.)

Now, most unkindly of all, Technology Review is piling on. This week, the popular technology site reported a study by the same researchers at the University of Luxembourg who earlier in the year found a major security flaw at Tor. (They informed Tor of the problem, and it has been repaired.)

In their new study, the researchers have unpeeled a few layers of Tor's celebrated onion of anonymity, releasing a tabulation of the most popular among Tor's "hidden services" — that is, sites that can be accessed only via Tor itself. The news wasn't good.

For a site whose glory has long been the image of the courageous freedom fighter in, say, Syria bravely sending messages to the world, the results were depressing: "Of the top twenty most popular Tor addresses, eleven are command and control centres for botnets, including all of the top five. Of the rest, five carry adult content, one is for Bitcoin mining and one is the Silk Road marketplace. Two could not be classified." It gets even worse: "The FreedomHosting address is only the 27th most popular address," according to Technology Review.

In other words, the anonymity of Tor appeals principally to botnets, commonly used by spammers; those who peddle or seek pornography; and those who use a marketplace that has been called "Amazon.com for illegal drugs."

As for Freedom Hosting: It was, for a while, one of the glories of the Tor universe. Although not sponsored by Tor, Freedom Hosting promised free accounts to anyone. But in August, the founder of Freedom Hosting was arrested, charged by the US government with being the world's biggest purveyor of child pornography. He was also said to have turned a blind eye to other people's use of Freedom Hosting for that purpose.

So what are the lessons of Tor's long summer? Principally this: We are unlikely ever to be able to ensure our privacy through technical means alone. Ever since the days of the Polybius square, the race between encryption and decryption has been won by the decrypters.

Just this week, we learned that the National Security Agency may have developed either decryption capabilities or secret backdoors that enabled it to break most Internet encryption. (The problem may be even worse if, as some experts speculate, NSA is developing dedicated chips that will aid in cracking even the elliptical keys that not long ago were said to carry the promise of a more secure online future.)

Nor can we protect privacy online through laws and court orders. The NSA, we are now told by a federal judge, for three years "frequently and systematically" breached the limits placed on database searches by the Foreign Intelligence Surveillance Court. Think this isn't about you? The database in question includes "the phone records of nearly all Americans."

Privacy is best understood not so much as a collection of discrete constitutional rights but as a shared sense that it is possible for us to go about the business of daily life protected by a government that neither knows nor cares how we spend the bulk of our time. The minutes of our lives are entirely our own.

But in a world ruled by the Web, privacy in this traditional sense seems so … 1990s. "There's nothing you or I can do to put the genie back in the bottle," writes security analyst Neil J. Rubenking. (The title of his post: "Privacy is Dead. The NSA Killed it. Now What?") "The best we can hope for," he writes, "is to keep the government in check by electing sane, sensible candidates."

That won't be enough. The government's appetite for information isn't going to wane under either party. A voracious security bureaucracy isn't going to go on a sudden diet. The bad guys will always be drawn to the shadows. Those who chase them will always find this an adequate reason to ban darkness.

So yes, as Tor users have lately learned, privacy in the traditional sense is most certainly dead. But the killer isn't the NSA. It's the Internet itself — or, more to the point, our entire reliance on it, our naive belief that we can spend hours each day sending signals into the ether and nobody will pluck them out.

If we don't want anyone to know what we're buying, we'll have to visit brick-and-mortar stores and pay cash. If we don't want those who are sworn to protect us reading our e-mail and listening to our calls, we'll have to meet our friends in person. It's our growing unwillingness to take those time- consuming steps that's killing our privacy.

By arrangement with the Washington Post/Bloomberg News Service