Cameron's problem with instant-messaging services such as WhatsApp is that all use encryption that prevent security services from keeping tabs on us and our conversations. Also see: Security Advisor
He said: "In our country, do we want to allow a means of communication between people which, even in extremis, with a signed warrant from the home secretary personally, that we cannot read Now, up until now, governments of this country have said no, we must not have such a means of communication. That is why, in extremis, it has been possible to read someone's letter; that is why, in extremis, it has been possible to listen in to someone's telephone call; that is why the same applies with mobile communications.
"Let me stress again: this cannot happen unless the home secretary personally signs a warrant. We have a better system for safeguarding this very intrusive power than probably any other country I can think of.
"But the question remains: are we going to allow a means of communication where it simply isn't possible to do that And my answer to that question is no we must not. The first duty of any government is to keep our people and our country safe."
London Mayor Boris Johnson also commented: "I'm not interested in this civil liverties stuff. If they're a threat, I want their emails and calls listened to." Also see: Facebook Messenger isn't evil and it isn't about to spy on you
WhatsApp ban: What does it mean for you
Under Cameron's plans, there are only two viable options - and neither sound good. Either these instant messaging services will be taken offline and people will be forced to use less-secure, unencrypted services, or backdoors will be opened within the apps that make it possible to decrypt messages, which may present new opportunities to hackers and allow the messages of ordinary people to be checked on by the government. In other words, in Cameron's attempts to improve national security from terrorism he will reduce personal privacy and security.
WhatsApp ban: Should you be worried What can you do about it
Don't worry too much just yet. It's incredibly unlikely that Cameron will get his wicked way.
His remarks were a knee-jerk reaction in response to the Charlie Hebdo Paris shootings, and if anything show just how little the government understands technology - if terrorists want to collude in private then they will continue to do so, and spying on the normal person on the street won't solve the problem. As an example, last week we wrote about the Dark Web, which proves just how much of the internet is beyond the government's remit. What about VPNs, too
Plus, not only do the Conservatives have to win the next election (and there are other parties that would love your vote), but Cameron faces a great deal of opposition to his desire to decrypt IM - and not just from WhatsApp's 500,000,000 users.
Peter Sommer, professor of cybersecurity and digital evidence at de Montford and the Open Universities, told The Guardian: "You can pass laws in Westminster until you're blue in the face, but you can't enforce them."
And while the government wants the power to read our private messages, WhatsApp and other instant-messaging services have our privacy at their hearts.
Commenting previously on its stance on privacy in its blog, WhatsApp said: "Respect for your privacy is coded into our DNA, and we built WhatsApp around the goal of knowing as little about you as possible: You don't have to give us your name and we don't ask for your email address. We don't know your birthday. We don't know your home address. We don't know where you work. We don't know your likes, what you search for on the internet or collect your GPS location. None of that data has ever been collected and stored by WhatsApp, and we really have no plans to change that."
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