
It's simple. In any system capable of fraud, having multiple ID checks makes it /much/ tighter than if you simply have just one ID check - even if that single check is very, very secure. Still sceptical? A quick probability lesson, then.
Let's suppose you have two systems of checking someone's identity:
1) Here you use just one one ID card. Let's say there's a 1/1000,000,000th chance (one in a billion) of a fraudster being able to successfully use it undetected. Sounds pretty secure, doesn't it?
2) Let's suppose you have another system of checking you are, that requires you to have:
- a bank statement with your address on it
- your driver's license
- national insurance card
- passport
Now let's assume that each one of those is much less secure, individually, than the ID card; Just for argument's sake, let's say that there's a 1/1000th chance of each one of those checks being successfully bypassed. Sounds like system 1 is looking pretty good, isn't it?
Well, no. Basic probabilty theory states that the probability of events A, B, C, D all happening together is - ie. a successful fraud -
P(fraud)= P(A) x P(B) x P(C) x P(D)
Which for system 2 works out at 1 in 1000,000,000,000. That's a *thousand* times more secure than system 1. Moreover, because all these ID checks are essentially seperate, you're not likely to get a flood of successful frauds in a 'dam burst' scenario, because ID fraud of system 2 requires you to negotiate all these ID system checks, rather than just one.
Where does this lead me? ID cards would be fine for lower-level services, but I wouldn't trust them as far as I could shove them up the immigration minister's arse (that's with rubber gloves on, too). It would be foolish to let them through the door, as false sense of securities are inevitable.
We've not even got to data protection issues yet - hang the big brother conspiracy theories; what would happen if the proverbial fly fell into the printer, wreaking bureaucratic havoc?
Or am I the only one that's watched Brazil?