Cryptography and the Coventry Problem

There's an ethical conundrum which is often posed to military strategists and philosophers alike.

In 1940, the Nazi's communications encryption had been broken by the British. Military Intelligence were able to decrypt a signal which indicated that the city of Coventry was to be bombed. The military chiefs took this information to the Prime Minister, Winston Churchill.
If he ordered the evacuation of the city, he would save hundreds of thousands of lives - but the enemy would know that their encryption was compromised.

What, gentle reader, would you do? Is it worth sacrificing lives now in the hope of saving more in the future? Is revealing your hidden knowledge a price worth paying if it means saving a city?

This utilitarianist problem was probably not actually placed in front of Winston Churchill - but it is an interesting thought experiment.

This brings us to the recent revelation that the security services of the world are tapping our communications, listening to our phone calls, and tracking our every move.

So why is there still crime?

If "Prism" (which I'll use as a shorthand for all digital surveillance) is so good and effective, why is there still any form of crime or terrorism?

There are, I think, several possibilities.

  • It doesn't work - either it can't capture the data or it's impossible to sift.
  • Criminals don't communicate via electronic means.
  • The Government don't want Prism revealed.

To go down the conspiracy theory route, is it acceptable to allow a major criminal attack in order not to reveal how intelligence is captured?

Or, to look at it through a different lens, is Prism stopping 99% of crimes, and the ones which do occur are statistical outliers?

If Prism is as amazing as claimed - and assuming revelations don't push criminals to secure crypto and unmonitored communications - why can't it be used to ticket speeding cars, foil bank robberies, or stop traders manipulating LIBOR?

Are minor and major criminal acts the price that governments are prepared to pay in order to keep Prism secret?

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2 thoughts on “Cryptography and the Coventry Problem”

  1. tim20 says:

    "or stop traders manipulating LIBOR?"

    I had to laugh there. That wouldprobably be the LAST of their concerns. With all the spying capabilities they had - did they do anything to the US bankers? Nope. Not even a prosecution. Nada.

  2. Another 'Tin Foil' possibility is that this information has been leaked in order to fortify the panopticon and no-one is in fact listening. I don't buy that. I think that it's more likely a combination of one and two. The smart crooks have ways of talking incognito and the rest of us 'innocents' are blocking the pipes with our breakfast photos.


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