The Camera Knows Your Walk

A younger colleague — call him REDACTED — came to me a few years back, pleased with himself, holding a cap and a scarf and a pair of glasses with clear lenses. He wanted to know if it would beat the cameras. I asked him to put it all on and walk to the end of the platform and back. Then I told him I had recognised him from forty metres before he reached the bench, and so had every modern system bolted to a wall in that station.

The cap and the scarf hide the face. By 2019 the face was the least of his problems.

What the machine actually does

A face-recognition system does not see a face the way you and I do. It detects that a face is present, it finds the landmarks — the corners of the eyes, the base of the nose, the geometry between them — and it crushes all of that down to a number. A faceprint. A mathematical template of distances. Then it matches that template against a database in the time it takes you to blink, and it hands a man at a desk a confidence score. That is the whole trick. There is no recognition in it, no memory, no instinct. It is arithmetic, run by something that never gets tired, never looks away, and is wired into every camera in the place — the transit lobby, the cash machine, the doorbell across the road, the phone in a stranger's hand.

Now. A mask defeats the faceprint. It does not defeat the rest of you, and the rest of you is plenty.

The walk, the ear, the same shoulder

Here is the part the films never caught up to. The grid does not need your face when it has your gait. The way a man walks is nearly as singular as a fingerprint, and unlike a fingerprint he cannot leave it in his pocket — he wears it down the platform, across the square, through the turnstile. Length of stride, the roll of the hips, the small hitch in the left knee from an old job that I will not describe. You can fake a limp for ten metres. You cannot fake your way out of your own skeleton for an afternoon.

Then there is the profile. The ear and the jaw read clean from the side, and the ear almost never changes and is almost never disguised — people spend an hour hiding the front of the head and present the side of it freely to every camera at shoulder height. Add your height. Your build. The coat you have not changed. The bag you keep on the same shoulder because it is comfortable, which is exactly the kind of small human truth the machine adores. Hand it any two of these and it stitches you across cameras into a single track. A line through the city with your name not yet on it but a space reserved.

And here is the trap inside the trap: the disguise that beats the algorithm summons the animal. Walk into a railway station in a balaclava and you have not gone invisible — you have triggered the oldest surveillance there is, the man in the booth who watches the screens the cameras feed. You traded an indifferent algorithm for an interested human being. That is a poor trade. Concealment that draws the eye is just a different way of being seen.

You go grey, or you go nowhere

So you do not hide. You never hid; hiding was always for amateurs and the cinema. You go grey — you look like everyone else so the system has no reason to flag you, and you give it nothing distinctive to lock onto from one camera to the next. You break the thread.

• Vary the silhouette. Change the outer layer between zones. The coat that crossed the square should not be the coat that boards the train.
• Lose the bag, or move it, or swap it. The same load on the same shoulder is a handle they grab you by.
• Where you can, vary the walk. It is the hardest of all and the most worth it, because it is the one thing you carry that you did not choose.

The aim is not to become nobody. You will be seen — in a dense, well-wired city, with the systems talking to each other, you are seen, full stop, and the man who promises you otherwise is selling something. The aim is that no single faceprint, no gait signature, no silhouette survives long enough to be assembled into a journey. You are seen in fragments that do not connect. A dozen unrelated strangers who happen to share a height. Let them try to make a line out of that.

The camera is patient and it never sleeps. So you give it nothing that repeats — because repetition is the only thing it can love.

What was lost

I came up in a world where you could be expensive to find, and being expensive was enough — make the search cost more than the answer is worth and most people stop searching. That logic held for thirty years. Facial recognition and the gait reading did not abolish it. They moved the price. The cheap, automatic seeing got very cheap indeed, and the expensive part — the part you used to be able to afford to defeat — shrank to a sliver of human attention at the end, called in only when the machine has already done the work and only wants a person to sign off.

You can still be expensive. You just have to spend the money on becoming forgettable to a thing that has no memory and infinite patience, which is a stranger discipline than fooling a man, and lonelier. I do not envy the ones starting now. They will never know the quiet pleasure of simply being a grey jacket at a tram stop and trusting that the world would forget your face by morning.

The world remembers everything now. The whole craft is making sure it remembers you in pieces.

Names moved, a job or two relocated, the limp reassigned. The lesson stands exactly where I left it.

— M.