The director of Europol, the European Union's law enforcement agency, has warned about the growing use of encryption for online communications. Speaking to BBC Radio, Rob Wainwright said: "It's become perhaps the biggest problem for the police and the security service authorities in dealing with the threats from terrorism." Wainwright is just the latest in a string of high-ranking government officials on both sides of the Atlantic that have made similar statements, including FBI Director James Comey, NYPD Commissioner Bill Bratton, the head of London's Metropolitan Police, Sir Bernard Hogan-Howe, and UK Prime Minister David Cameron.

Wainwright told the BBC that the use of encrypted services "changed the very nature of counter-terrorist work from one that has been traditionally reliant on having good monitoring capability of communications to one that essentially doesn't provide that anymore." What that overlooks is that the "good monitoring capability" was of very few channels, used sporadically. Today, by contrast, online users engage with many digital services—social media, messaging, e-mail, VoIP—on a constant basis, and often simultaneously. Although the percentage of traffic that can be monitored may be lower, the volume is much higher, which means that, overall, more information is available for counter-terrorism agencies.

Wainwright also claimed that terrorists were using the "dark net," "where users can go online anonymously, away from the gaze of police and security services." One of Snowden's leaks revealed that the NSA has managed to unmask anonymous users of Tor, so that ability to avoid the "gaze" of the police and security services is not absolute.

More generally, in an earlier online Q&A session hosted by The Guardian, Snowden makes an important point about the use of strong cryptography: "Encryption works. Properly implemented strong crypto systems are one of the few things that you can rely on. Unfortunately, endpoint security is so terrifically weak that NSA can frequently find ways around it." As we now know, most systems of strong encryption have been subverted in various ways. But even for those that do work as claimed, law enforcement agencies can still gain access to digital communications by attacking the endpoints.

The move to strong end-to-end encryption means that eavesdropping on communications can only be done on a targeted basis. What Wainwright is really complaining about is that the golden age of bulk surveillance when the NSA and GCHQ could "collect it all" is coming to an end. But if that forces the police and security agencies once more to target their activities more precisely, rather than simply to spy on everyone, is that really such a bad thing?