All posts filed under “Technical protection measures

The Hacker’s Amendment


Congress shall pass no law limiting the rights of persons to manipulate, operate, or otherwise utilize as they see fit any of their possessions or effects, nor the sale or trade of tools to be used for such purposes.

From Artraze commenting on this Slashdot story about the levels of DRM in Windows 7.

I think it maybe needs some qualification about not using your things to cause harm to other people, but it’s an interesting idea. See also Mister Jalopy’s Maker’s Bill of Rights from Make magazine a couple of years ago.

Skinner and the Mousewrap

Mousewrap -, an interesting interface design experiment by Alex Frank, included this amusing idea, the Mousewrap, to ‘train’ users not to click any more “through physical pain”.

It did make me think: is the use of anti-sit spikes on window sills, ledges, and so on, or anti-climb spikes on walls, intended primarily as a Skinnerian operant conditioning method (punishment – i.e. getting spiked – leading to decrease in the behaviour), or as a perceived affordance method (we see that it looks uncomfortable to sit down, so we don’t do it)? How do deterrents like this actually work?

It might seem a subtle difference, and in practice it probably doesn’t matter; it’s probably a bit of both, in fact. Most people will be discouraged by seeing the spikes, and for the few who aren’t, they’ll learn after getting spiked.

But on what level do anti-pigeon spikes work? Do pigeons perceive the lack of ‘comfort’ affordance? Or do they try and perch and only then ‘learn’? How similar does the spike (or whatever) have to be to others the animal has seen? Do animals (and humans) only learn to perceive affordances (or the lack of them) after having been through the operant conditioning process previously – and then generalising from that experience to all spikes?

What’s the accepted psychological wisdom on this?

Some spikes in Windsor, Poundbury, Chiswick and Dalston, UK.

How to fit a normal bulb in a BC3 fitting and save £10 per bulb

BC3 and 2-pin bayonet fitting compared
Standard 2-pin bayonet cap (left) and 3-pin bayonet cap BC3 (right) fittings compared

Summary for mystified international readers: In the UK new houses/flats must, by law, have a number of light fittings which will ‘not accept incandescent filament bulbs’ (a ‘green’ idea). This has led to the development of a proprietary, arbitrary format of compact fluorescent bulb, the BC3, which costs a lot more than standard compact fluorescents, is difficult to obtain, and about which the public generally doesn’t know much (yet). If you’re so minded, it’s not hard to modify the fitting and save money.

A lot of visitors have found this blog recently via searching for information on the MEM BC3 3-pin bayonet compact fluorescent bulbs, where to get them, and why they’re so expensive. The main posts here discussing them, with background to what it’s all about, are A bright idea? and some more thoughts – and it’s readers’ comments which are the really interesting part of both posts.

There are so many stories of frustration there, of people trying to ‘do their bit’ for the environment, trying to fit better CFLs in their homes, and finding that instead of instead of the subsidised or even free standard 2-pin bayonet CFLs available all over the place in a variety of improved designs, styles and quality, they’re locked in to having to pay 10 or 15 times as much for a BC3 bulb, and order online, simply because the manufacturer has a monopoly, and does not seem to supply the bulbs to normal DIY or hardware stores.

Frankly, the system is appalling, an example of exactly how not to design for sustainable behaviour. It’s a great ‘format lock-in’ case study for my research, but a pretty pathetic attempt to ‘design out’ the ‘risk’ of the public retro-fitting incandescent bulbs in new homes. This is the heavy-handed side of the legislation-ecodesign nexus, and it’s clearly not the way forward. Trust the UK to have pushed ahead with it without any thought of user experience.
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Finestrino Bloccato

Trenitalia window lock
Trenitalia window lock

Italian railway operator Trenitalia has a simple way of locking the windows shut in some of its older carriages with (retro-fitted?) air-conditioning. This was on a train from Florence to Pisa; the sticker probably cost more than the screw. I like that.

It also allows passengers who really need some air to unscrew them – perhaps if the air-conditioning fails, or indeed otherwise – as a couple of people had done.

Design with Intent presentation from Persuasive 2008

EDIT: I’ve now added the audio! Thanks everyone for the suggestions on how best to do it; the audio is hosted on this site rather than the Internet Archive as the buffering seemed to stall a bit too much. Let me know if you have any problems.

I’ve put my presentation from Persuasive 2008 on SlideShare, – because of the visual style it really needs to be listened to, or viewed alongside the text (below, or in the comments when viewing it on the SlideShare site). Alternatively, just download it [PPT, 11.6 Mb] – it comes with the notes.

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One-way turn of the screw

One-way screw

One-way screws, such as the above (image from Designing Against Vandalism, ed. Jane Sykes, The Design Council, London, 1979) are an interesting alternative to the usual array of tamper-proof ‘security fasteners’ (which usually require a special tool to fit and remove). There’s a very interesting illustrated listing of different systems here.

A fastener requiring a special tool is effectively addressing the “Access, use or occupation based on user characteristics” target behaviour – and is functionally equivalent to a ‘what you have’ security system such as a padlock, except that anyone can look at almost any engineering catalogue and buy whatever special tools are needed to undo most security fasteners, pretty cheaply and easily, whereas it’s still a bit more difficult to obtain padlock master keys.

However, this kind of one-way clutch head screw, which can be tightened with a normal flat screwdriver, but is very difficult to undo using any tool (without destroying it) can be thought of as addressing a slightly different target behaviour: this is “No access, use or occupation, in a specific manner, by any user”. Even if the original installer wants to undo the screw, he or she can’t do it without destroying it (e.g. drilling it out). A few of the other systems illustrated on the Security Fasteners website also have this property:

Image from Securityfasteners.netImage from Securityfasteners.netImage from Securityfasteners.netImage from

I’m particularly intrigued by the Shear Nuts and No Go enclosures (last two images above) – these two types effectively self-destruct/render themselves permanent as they are fixed into place. Something about this step-change in affordance fascinates me, but I’m not sure why exactly; it’s a similar idea to a computer program deleting itself, or Claude Shannon’s ‘Beautiful Machine’ existing only to switch itself off.

A step further would be a fastener or other device which (intentionally) destroys itself if the wrong tool (by implication an unauthorised user) tries to open/undo it, but which will undo perfectly well if the correct tool is used – along the lines of the cryptex in the Da Vinci Code, just as an ATM will retain a card if the wrong PIN is entered three times: it’s both tamper-evident and limits access. What other cryptex-style measures are there designed into products and systems?