After some five thousand years, the end is finally coming for cash. The replacement will not be Apple’s electronic wallet, which uses near field radio to make payments between physically close devices, such as mobile phones, or a mobile phone and a cash register. It’s very likely going to be a cruder-sounding technology, originally called Bump, that was gaining great success in North America when it was bought up by Google and withdrawn at the end of January 2014. The basic idea could hardly be simpler: to transfer a payment between two devices, you physically bang them together. In a way, it’s back to the Stone Age.
Why is that in clever? It is very easily done – which is vital. Just read a screen and bang the attached sensor with your mobile phone. But even more vital, it is intrinsically cheat-proof.
When two mobile phones are banged together, each can independently measure the timing of the impact between the stiff cases to within a microsecond or so. The location of the bump is also known by each phone independently: very accurately if it has inbuilt GPS, to a good approximation even without, using information from the masts relaying its signals.
It will be impossible for an eavesdropper to interfere for multiple reasons. First, even a sophisticated spycam observing the transaction won’t be able to work out the time of the bump with microsecond accuracy. Second, accelerometers in each device will measure the magnitude and direction of the impulse each receives. From Newton’s laws, these will be equal and opposite. For the brief time the phones are in contact, they will moreover vibrate in sync with one another. Imagine a little seismometer making an old-fashioned pen trace on a graph from each device. When compared, the two traces should match in a mathematically perfect way. It’s analogous to an old medieval method of verifying a contract: the master contract was written on a sheet of paper which was torn in half, with each contracting party keeping one half. There was no way to fabricate another piece of paper with a jagged tear of exactly the right shape, which we would nowadays describe as a fractal.
For small transactions – say, up to the value of the cash you typically keep in your wallet today – this security should be ample. Of course it can be augmented if desired. For example each phone can routinely make an independent audit trail of where and when each payment was made, including photographs of the location and persons visible there. As a precaution against phone theft, phones can be equipped with infrared microscopes, taking a real time picture not just of the fingerprint of the person holding it, but of the unique three-dimensional network of capillary blood vessels in the finger beneath, pulsating in time with the holder’s pulse. Held up to the eye, the microscope can not only verify the pattern of the iris and retina, but even deduce from the pupil’s response to changing illumination from an LED whether the eye’s owner is asleep or drugged. But these measures are only necessary for higher value payments: it is the combination of extreme convenience and good basic security that is Bump’s winning combination.
Google’s penchant for making money indirectly, or from many very small payments, should keep transaction costs down: unlike ordinary credit cards or the Apple wallet, it’s likely the cost to both the seller and purchaser will be kept minimal.
We will soon say goodbye to notes and coins, a mere temporary fad in the human race’s long history. How will this change the world, apart from the increased convenience? Ultimately, it will make most kinds of corruption and fraud impossible, because every single transfer of money will be permanently recorded in multiple places. At present money is not a conserved quantity in the electronic transfer system, because at certain points it is swapped for cash, whose subsequent fate is not known for certain. But when all money is electronic, the system becomes closed.
Purchase of high-value, easily transportable commodities like gold is still possible, but such transactions are incredibly rare compared to the enormous frequency with which cash is withdrawn and spent at present. It’s almost incidental that muggings for cash, and theft of cash from shops, security vans and banks become fundamentally obsolete crimes.
There may be downsides to this Big Brother world. But in countries where petty corruption is a way of life, which still describes the condition of most of the world’s population, the immediate benefits will be fundamental. A less corrupt economy is not just morally preferable, it provides much more efficient incentives.
This will be the first of Google’s Golden Swans.


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