Ars first raised the prospect of the UK government bringing in age verification for porn sites a year ago and confirmed that it would be happening in February.

In its written evidence to the House of Commons Public Bill Committee on the Digital Economy Bill, the Open Rights Group put together a good summary of the problems with the approach. These include the privacy risks of creating insecure databases of the UK's porn habits, and the fact that age verification will be easy to circumvent.

As a more recent blog post by the Open Rights Group notes, MPs have finally woken up to the fact that age verification won't in fact stop children from accessing pornographic sites, and have come up with Plan B, which is even worse than Plan A: "in order to make age verification technologies 'work,' some MPs want to block completely legal content from access by every UK citizen. It would have a massive impact on the free expression of adults across the UK. The impact for sexual minorities would be particularly severe."

Ars readers will be thoroughly familiar with all the arguments against such censorship—and against age verification—so I won't bother running through them here. Instead, I want to consider what will happen if the UK government goes ahead with its plans to bring in age verification, with or without censorship.

As the Open Rights Group noted, it will be impossible to stop at least a few young people from accessing porn sites despite age verification and Web blocks. That means they can download material and build up an offline store of it if they wish. Of course, once their friends find out about this handy source of forbidden material, they'll want a copy of everything. Thanks to the continuing collapse in storage prices, it turns out to be extremely easy to provide it.

A quick look on Amazon.co.uk today turned up a 5 terabyte portable hard drive for just over £100—readily affordable by many young people. How much porn could you fit on that? According to an answer posted on Quora last year from someone who says he works on a major porn site: "Mostly, videos are rendered with lower quality and take around 1Mbit per second if it's an HD video and even lower if it's VGA or some other, lower resolution video. So that comes out as around 3MB for 30 seconds video, give it or take."

At 6MB per minute, then, a 5TB hard drive could hold around 800,000 minutes of porn videos. Although only just starting to come through, 6TB units could hold around a million minutes.

If external hard disks are a bit too big and obvious for sharing in the playground, you could pick up a small 128GB flash drive for just over £20. That would store around 20,000 minutes. If you want something even more discreet, you can buy a micro SDXC memory card for your phone with the same capacity, for about double the price. And that's just today: next year, prices will be even lower, and capacities will be even higher—SDXC cards are designed to store up to 2 terabytes.

You only need a few people with access to online pornography and huge collections of the stuff can be created and shared using portable storage systems. And it's not just that the age verification and Web blocks become irrelevant as a result. Things would be far worse than the current situation as far as exposing young people to unsuitable material is concerned.

Rather than going online and picking out items of pornography to view, with all the context that porn sites provide, children using portable storage devices are likely to copy huge quantities—gigabytes or even terabytes—all at once. That means they can't possibly check it all before they grab it, for example to avoid disturbing or even outright illegal material.

Instead, it will all end up on their computers, smartphones, or tablets, as a completely unknown quantity. Later, it might be viewed by some unsuspecting child—possibly very young—who starts clicking randomly on things just to see what they are.

Ironically, then, by making it much harder for young people to find and view porn online, it is likely that they will be pushed to find it in far more dangerous forms—as part of huge collections swapped clandestinely, with no controls or even indications of what material is included.

In other words, the Tory government's obsession with protecting children from what's online may end up exposing them to far more, and far worse, material offline.