I started a blog in 2004 which fizzled out in 2010.

It was true to the principles of sharing thoughts and processes openly online, but in my case that meant it was mostly rubbish that should never have seen the light of day, written in the morning after too much coffee as a way of putting off proper work.

There were one or two OK pieces, the best probably the one below (put here to archive it somewhere) but with hindsight the form doesn't really suit me, and I wouldn't do it again.

This piece, from 2004, is about what things a bunch of keys could learn about their owner.

I wrote it after reading a book about using data mining and network science for law enforcement.

Testicles, Spectacles, Watch, Wallet

The two things I always check for when I leave the house are door keys and mobile phone.

If I take my door keys everywhere, what can they learn about me, based on the patterns of where and when they’re used?

And in finest Smash Hits boyband interview style, the ultimate test will be do they know what my favourite colour is?

My key ring has my house and work keys, the key to the padlock on the bag I use for travelling and the front door key for my mum’s house.

(In Disney’s The Magic House, I think the keys might be the baddies, or at least the sidekicks of the baddies. Song - “You aint going nowhere without us”)

So, what do they know, in their metal hearts?

Man or Woman: Only by cheating at the moment.

If they can find out where I live, they can check the electoral register.

In the future, they’ll be able to tell in the same way they’ll know what my favourite colour is (see below).

Where I live: Yes

(I’m thinking about what they can work out from patterns of how they’re used, not that they’re imprinted with houseness. After all, my house keys are no different from my work keys except in the pattern of how I use them.)

They know that I use them at roughly the same time five days out of seven, with approximately a nine hour gap in between. They could be my work keys, but the pattern is less regular than for work keys. These keys, the most often used, with a regular-ish five day pattern, and an with a irregular two day pattern (the weekend) must be the keys to where I live.

Where I work: Yes

A very regular pattern, over five days, with almost no use on two days.

How much I earn: Yes

If they know where I live, and how long I’ve lived there, they can probably put a maximum on my earnings. (Not much, in my case.)

They might also try and estimate it from where I work, but this might be misleading because without a very detailed knowledge of the geography of my workplace they’d think I worked in a wool-spinning mill.

What my job is: Not exactly, but not far off

I use the travel bag key two or three times a year (I don’t actually bother locking it but if I did) for periods of two or three days on weekdays rather than weekends, locking it in Britain and unlocking it abroad, and the reverse a few days later.

This suggests I travel for work rather than holidays, which puts me in the category of jobs that involve foreign travel, which probably means training and qualifications.

Only one other set of keys is used to open the door where I work, so I must have a job that could be done by two people in one small room but involves travelling abroad.

If it’s manufacturing it has to be something handmade – that two people can do - and that either sells, or takes components from, abroad, or alternatively it has to be knowledge based.

So I am the owner of a small craft based manufacturing or knowledge based company that I don’t earn all that much money from.

That’s a pretty good guess.

How old am I? Yes

Based on the fact that I have my own skill or knowledge based company – which must have required a period of training, or at least development of expertise – and that I live in quite a low rent area, my keys probably think that their owner is post education but not very senior in the job, which would put me at 21 – 30.

But what about my leisure hours key pattern usage? I get up quite early at weekends and don’t often use my home keys at three in the morning, which puts me in the 30 and above band.

What social class I am: Yes

Based on job, residence, and occasional visits to another residential area in another northern English town (my mum’s house).

Am I married (or cohabiting): No (they don’t know)

Where I live there are single homeowners, couples, and shared student houses, so too much variety for my keys to make a likely guess, though the fact that I’m over 30 might give them some statistical basis for thinking I am.

Do I have children: Yes (they know I haven’t)

No regular pattern of periods away from work during school holidays.

Am I in love: No (they don’t know)

I’ve visited one foreign country for much longer than any of the others over the last two years, but that could be work.

Favourite colour (and just about everything else): It's only a matter of time

Bank account and payment details are going to be embedded in things like key rings and even mobile phone covers, rather than swipe cards, so stretching the definition of keys a bit, they’ll come to know everything.

Including that I tend to buy clothes in dark blue, which is a comforting and unobtrusive colour.

They’ll also know I’m a man, because for example I’ve read a book about the battle of Stalingrad recently, which will certainly be a 90% bloke book, and also probably puts my age mid-thirties and upwards. Added to the job and housing information which put me in the lower end of that range, and that’s pretty much bang on (36).