AT some point in the distant past our ancestors learned to communicate; at first this was presumably limited to non-verbal gestures and basic vocalisations which eventually evolved into the languages of today. In due course, it must also have become apparent that a way to disguise your communications was also critical; finding a bountiful foraging spot or locating a herd of deer for hunting was good news for your tribe, but shouting it out at the top of your lungs could also let rivals in on the discovery.

And then, as humanity went forth and multiplied in numbers but divided politically into city-states, nations and peoples, we did what humans have always done: we went to war with each other. And here the need to be able to secretly communicate with your side without letting the adversary know what you were up to began to assume critical importance.

Of all the various tricks and devices used to achieve this end, the most fascinating to me is the practice of steganography, which is simply defined as the practice of representing information within another message or physical object, in such a manner that the presence of the information is not evident to human inspection.

The earliest known example of this is as........

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