Monday 29 October 2012

Turing's secret papers

This year, we mark the hundredth anniversary of Alan Turing's birth. One celebration, among the less publicised but also among the most fitting, has been the release into the public domain of two of his wartime papers on mathematical aspects of cryptography. The release was announced by GCHQ, here:

It seems that the papers were not released earlier, because their contents were still considered to be sensitive. It was thought to benefit the UK to have the information while others did not have it, and (presumably) while others did not even know that the UK had information of this precise nature.

This raises an interesting general question. If a country's authorities have scientific or technical information, and feel that the country can gain a significant advantage over other countries by keeping it secret, should the information be kept secret?

An argument for release of the information would be that if the information is useful to someone, it is likely to be useful to others too, and its release might well promote economic development. It is not hard to think of examples. Encryption systems help commerce, by facilitating financial transactions where there would otherwise be a risk of diversion of funds to criminals. Knowledge of the vulnerabilities of encryption systems helps developers to make the systems more secure. Algorithms for the management and distribution of military supplies could be useful in commercial logistics, allowing goods to be stored and distributed at the lowest possible cost. If the detailed technology of radar and of jet engines, both largely developed in the run-up to war and during wartime, had been kept as military secrets, long-distance travel would not have become as convenient as it did in the 1950s and 1960s. And so on.

It is tempting to say that decisions must be made on the facts of each case, and that general principles would be very difficult to find, and of far less importance than specific facts. But we should not give up quite so quickly.

One could, for example, adopt the reasonably general principle that when the usefulness of information to others would be purely military, there would be a strong presumption in favour of keeping it secret. It may be desirable to help the world's economy, but when it comes to potential military uses, a country could be argued to be fully entitled to put its own interests first. One difficulty in applying this principle would be that it is all too easy for the military, and the security services, to see only the military uses of information, and to be unaware of commercial possibilities.

Alternatively, one could adopt a utilitarianism that gave no special weight to one's own country. Then, if the consequences of secrecy and of disclosure could be computed (which they could not be), or plausibly estimated (which might be possible), the decision on whether to disclose each piece of information could be reached by a mechanical procedure.

One could row back a little bit from this generous principle, and adopt a utilitarianism under which the interests of the citizens of one's own country were weighted more highly than the interests of others. But it would be hard to make a case for a precise difference in weighting. There would only be a plausible range. Counting each of one's own citizens as twice as important than each non-citizen might be defensible, particularly when one's own citizens formed a small minority of the world's population, so that the total weight assigned to one's own citizens was still considerably less than the total weight assigned to all non-citizens. Counting each of one's own citizens as 100 times more important as each non-citizen would not be defensible, regardless of population. One would also have to balance the potentially incommensurable economic and security interests of one's own citizens (and of non-citizens, to the extent that their security would be affected by the release of the information). And one would have to bear in mind that a boost to the world economy from an invention that new information makes possible can lead to a boost to the economies of many nations, including those that do not directly exploit the invention.

It is never going to be easy to make the right decisions, even assuming that there are right decisions to be made. One reason why this is so is that the specific facts of each case are bound to have a substantial influence on the decision, and it is in the nature of the case that those facts must be kept secret unless the decision is to publish. Only general principles can be debated publicly, and those general principles can only take us so far.