Andy McNab - Brute force

Brendan giggled away to himself as he handed back my passport and cracked open another packet of his beloved HobNobs. Lynn suddenly looked more animated than he had done all day. 'What's in the chip that's so worthwhile getting at?'

'Ah, there are three important files. One contains an electronic copy of the printed information on the passport's photo page. The second holds the electronic image of the holder. The third is a security device which checks that the previous two files haven't been accessed and altered.

'The government says the biometric chips are protected by what they call an advanced digital encryption technique. In other words, without the MRZ key code it is impossible to steal the passport holder's details if you do not have their travel document.

'They're talking bollocks, of course.' He laughed so hard that flecks of HobNob flew out of his mouth to join the rest of the shit on the carpet. 'The first big flaw is that someone like me can try to access the chip as many times as he likes until he cracks the MRZ code, unlike, say, putting a pin number into an ATM machine, where the security system refuses access after three wrong attempts.

'The second flaw is that there are easily identifiable recurring patterns in the MRZ key codes. Bizarrely, the ICAO suggested that the key needed to access the data on the chips should be comprised of the passport number, the holder's date of birth and the expiry date, in that order. That's about as secure as living in a bank vault but leaving the key under the mat.

'I got myself a helper, a young computer whiz-kid, and he developed a brute-force program that repeatedly tries different combinations of data to discover a password. The old programs could take months, but not any more. Those Indian fellers are smart, aren't they? Once Leena has sucked out six or seven passports from the tube I can crack the MRZ in a couple of days, four at the most.'

He chuckled away to himself. 'Brute force, now that's the way to crack a nut, eh, Nick?'

'Every time, Brendan.'

He got back into work mode. 'But remember, information cannot be added to a cloned chip, so anyone using it to make a counterfeit passport will have to use a picture that bears a reasonable resemblance to the previous owner. Sure, there are facial recognition systems in the chip – precise measurements of key points on your face and head – but they are not yet in operation. In any case, the technology throws up between 20 and 25 per cent false negatives or false positives. It won't be reliable for years to come.'

He beamed at Lynn. 'Adrian's got the same hairstyle as your good self.'

He got back to his waffle. 'So it's down to the Mark 1 human eyeball at airports and such like. People have great difficulty matching faces to pictures, even trained immigration officials. That's why photographs have never been introduced on credit cards. As long as your friend here bears a fair resemblance to the person on the chip – or grows a beard – he'll get through a border post. Or your money back.' He laughed again, but we didn't get hit by Hob Nob shrapnel this time. 'The beauty of it is that nobody knows that their passport is being cloned. Nobody's reported their passport stolen. After all, they still have it.'

He stood up and held out a hand. 'So that'll be half now and the rest tomorrow morning…'

I peeled off the dollars. 'Jesus, Brendan. Money for old rope.'

He allowed himself another giggle. 'I know, son, I know. I only wish I was thirty years younger; I'd have such fun with all this new technology. I've just got into cloning those Oyster cards everyone seems to be using – piece of piss! You fellers want a couple?'

'No, we're OK, mate. Off tomorrow, remember?'

He pocketed the down payment and started rummaging about in his desk drawer. 'It gets better. You know the ID card scheme your Gordon Brown is so keen on? It'll use the same technology. So I'll have access to around fifty pieces of information about you: your name, age, all your addresses, your national insurance number and biometric details; everything a feller could possibly need.'

He pulled out a signature tablet, the type used in US stores to check signatures electronically.

'Now, Mr Letts. If you would just sign your name…'

Where to spend the night? I wouldn't put Brendan on the spot by asking if he had a spare room. Besides, I wanted us to have a reasonable chance of surviving the night. Nor could we use a hotel, or even a B amp;B. If we'd been spotted in the area, the Firm would have the police checking every spare bed within a one-mile radius. We had a lot of walking to do through residential streets, away from the cameras' gaze, until it was time to find somewhere to hide.

The Black Cat shopping centre down the road – well, I called it that anyway – was perfect. I'd hung about there for about nine hours once while the Irishman sorted out a few documents for me. It wouldn't be the most comfortable night Lynn had ever spent away from home, but at least it meant we'd drop off the face of the earth until Brendan had done his stuff.

We could evade surveillance only for so long. If it was the Firm after us, they'd have covered all the motorways and transport hubs. Those cameras would be in overdrive.

We walked for two hours or so and landed up in Honour Oak Park. We sat on a bench like two perverts and froze. At least the rain was holding off, and by about 4.30 it was getting dark. Soon I could see the stars and clouds of my own breath. It was going to be another sub-zero night.

'Time to go.'

We made our way back to Catford. The evening commute was in full swing, which was good for us. I got Lynn his first ever doner kebab and chips and he definitely didn't like it.

'Better get them down you; it's the only shop without a camera.'

I'd bought two each.

'They're horrible when they're cold. The grease…'

We sat on a bench the other side of the shopping centre, opposite a big black plastic cat draped over the welcome sign.

Lynn picked at his kebabs, then pushed them to one side, so I got them down my neck while he turned his attention to the chips and stewed tea.

Ten minutes later we headed outside. The car park was lit, but the recycling skips that supermarkets provide to make us all feel like we're saving the planet were in deep shadow. One of them was for clothes. I leant in and pulled them out by the armload.

'Insulation. You need more between you and the ground than you do on top.'

It was so dark here I could hardly see his face, even though real life continued not more than 100 metres away. Traffic ground its way along the street and people ran for buses.

The wind had picked up and we arranged the clothes as best we could to provide some sort of mattress. I kept my arms tight against my sides and pulled up my collar to conserve as much warmth as I could. If I had to move my head I'd turn my whole body. I didn't want the slightest breath of wind down my neck.

Lynn started shivering. He hadn't spent half his life being cold, wet and hungry like I had.

I gave him a nudge. 'Duff – was he really a source?'

'Yes.' Lynn sat up. 'We turned him in the early eighties. He was arrested by the French coming back from a Hezbollah training camp with a false passport. Duff was an idealist, but he was also a realist. He was staring down the barrel of a very long prison sentence. We could spring him. All he had to do was accept a golden handshake and give us the occasional little bit of information. Nothing major. Nothing life-threatening. Just gossip, really.'

Once he had taken that first step, there would have been no way back. The handlers would have started off slow, but the die was cast. He would have taken money from the British government. They'd have made it impossible for him to get out without a PIRA bullet in his head.