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From George Sassoon

The British government can never succeed in its purpose of snooping on secret
electronic communications
(17 June, p 3)
if the practice of steganography is widely adopted.

This term refers to the concealment of secret messages within a larger,
apparently innocent communication. Thus, for example, a few bytes in an image
file can be altered here and there to conceal a short text message without any
apparent degradation of the image.

A Web search using the keyword “steganography” will bring up many sites from
which suitable software for doing this may be downloaded.

There is nothing new about this technique. As a boy, I had a book in which
examples were given of spies’ messages being concealed in pencil drawings of
landscapes. One drawing showed a river scene with grass growing along one of the
banks. The long and short stems contained a message in Morse code.

Warminster, Wiltshire