In the world of seventeenth century cryptography, “only two English works merit attention,” according to David Kahn’s comprehensive history of secret communication, The Code-Breakers. We have both of these in the general collection.
“The first book in English on cryptology appeared anonymously in 1641, but Mercury, or the secret and swift messenger was the offspring of John Wilkins, a “lustie, strong growne . . . broad shouldered” young chaplain who later married Oliver Cromwell’s sister and became Bishop of Chester and a founder and first secretary of the Royal Society. A succinct volume, very well grounded in the classics, Mercury introduced the words cryptographia (defined by Wilkins as “secrecy in writing”) and cryptologia (“secrecy in speech”) into English. The author reserved the term cryptomeneses, or “private intimations,” for the art of secret communications in general. In addition to summing up the knowledge of the time, Wilkins depicted three kinds of geometrical cipher, a mystifying system in which a message is represented by dots, lines, or triangles. The letters of the alphabet, in normal or mixed order, were written out at known spatial intervals; this served as the key. This line of letters was held at the top of a sheet of paper, and the message was spelled out by marking a dot for each plaintext letter underneath that letter in the key alphabet, each dot lower than its predecessor. The dots could then be connected by twos to form lines, by threes to forms triangles, or all together to form what would look like a graph–or they could be left as dots. The receiver, who had an identically proportioned key, noted the positions of the dots, the ends of the lines, or the apexes of the triangles against the alphabetical scale to read the plaintext.
The second English book on the subject excelled. Cryptomenytices Patefacta was written by John Falconer, about whom nothing is known except that he was a distant relative of the Scottish philosopher David Hume, was reportedly entrusted with the private cipher of the future King James II, and died in France while following James into temporary exile there. The book came out posthumously in 1685, with its author listed only as “J.F.” It proved so popular that it was reissued in 1692 with a new title page that clearly indicates just what its 180 pages comprise: Rules for explaining and decyphering all manner of secret writing….Falconer also gave what seem to be the earliest illustration of keyed columnar transposition, a cipher that is today the primary and most widely used transposition cipher, having served (with modifications) for French military ciphers, Japanese diplomatic superencipherments, and Soviet spy ciphers.” (Kahn, 155).