Ciphers of Coleman's Correspondence Discovered in the Popish Plot

The Popish Plot (1678-1681), as falsely alleged by Titus Oates, caused an anti-Catholic hysteria, which led to execution of many innocent people. However, Oates' bluff happened to reveal secret correspondence of one of his targets: Edward Coleman, secretary to the Duchess of York (the wife of the Catholic royal brother, future James II). The discovery, along with the mysterious murder of the magistrate Edmund Godfrey, gave undue plausibility to Oates' tales, which had not been taken up seriously at first (Wikipedia).

Nearly 200 letters of Coleman's correspondence are preserved. In particular, his dealings with Father de la Chaise (Wikipedia), Jesuit confessor of Louis XIV, were the most serious evidence against him (Pollock, p.34).

Letters to and from Coleman were published in Collection of letters and other writings, relating to the horrid Popish plot: printed from the originals in the hands of George Treby, chairman of the committee of secrecy of the house of commons (1681). In most of these letters, key terms and names were written in cipher but could be deciphered by the keys found with the letters. But there were some that could not be deciphered.

Code in a Letter from St Germain to Coleman

A letter of Father St Germain, as is commonly known Dr. Burnet, a Jesuit in the household of the Duchess of York (Pollock, p.16), uses code numbers such as 39 (the Duke), 93 (the Dutchess), 163 (the King of France), 488 (his Confessor), 300 (the Catholicks), 26 (a Pension), 80 (Money), etc. (Davys p.56)

Codenames in Letters from Earl of Berkshire to Coleman

Letters of Rice, pseudonym of the Earl of Berkshire (Wikipedia), use codenames. Conjectures made by the Committee of the Lords include: Brother or Aunt or Lady (the Duke of York), Lady's Sister (the King [i.e., the Duke's brother]), Lady's Niece (the Duke of Monmouth [i.e., the Duke's nephew]), Lady's House (Romish Religion), Plenipotentiary (Lord Treasurer). (Davys p.57)

Undecoded Letter from Albani to Coleman

Letter dated Rome, Jan. 12, 1675 of Albani, a papal nuncio in Brussels (State Trials, p.1221; Pollock p.33, 39; Davys p.57) could not be deciphered and was printed with code numbers, with intervening plaintext portions translated from French to English. John Davys (see another article) deciphered it and pointed out some errors of the printed text but did not publish the solution. The deciphering is printed in Hay (1944).

The following is the coded letter printed in Hay, in which errors in the plaintext including those pointed out by Davys have been corrected.

.... What you propose touching 51666279669961 which is, 667177576661676676 cannot be put in execution 566662516756665667 but with the 777699916699616797669961 of all 5167917766629664996719 and only 667191776691 comprising 9666999151679194715 1416791 you may then consider if in the terms wherein at present are 5167916654566646267919680204 it would be for the interest of the Duke to produce unto light an affair of this nature. That which I can with truth assure you, and whereof the Duke may be persuaded is that 669977669165645191676276646171996476716251679766649 1616267963204 will employ 6681272 and 5108126 and 516777626796646 for 51669191649161676266626791616694 5164645166516681266679981204 seeing that Rome and the Emperor have a most particular zeal and affection for all which regard it. ...
PS The cypher which I left with 300 and which you may have from him, will serve to open what you here find.

This is deciphered as follows. As it turned out, the long sequences of figures are the result of concatenation of two-figure code numbers representing letters. Two-figure numbers including "8" (81, 80, 08) appear to indicate three-figure code numbers for names and words.


What you propose touching 51〈l〉 66〈a〉 62〈r〉 79〈g〉 66[should be 67]〈e〉 99〈n〉 61〈t〉 which is, 66〈a〉 71〈u〉 / 77〈c〉 57〈h〉 66〈a〉 61〈t〉 67〈e〉 66〈a〉 76[should be 71]〈u〉 cannot be put in execution 56〈p〉 66〈a〉 62〈r〉 / 51〈l〉 67〈e〉 / 56〈p〉 66〈a〉 56〈p〉 67〈e〉 but with the 77〈c〉 76〈o〉 99〈n〉 91〈s〉 66〈a〉 99〈n〉 61〈t〉 67〈e〉 97〈m〉 66〈a〉 99〈n〉 61〈t〉 of all 51〈l〉 67〈e〉 91〈s〉 77〈c〉 66〈a〉 62〈r〉 96〈d〉 64〈i〉 99〈n〉 67[should be 66]〈a〉 19[no contradiction but maybe 71]〈u〉 [x] and only 66〈a〉 71〈u〉 91〈s〉 / 77〈c〉 66〈a〉 91〈s〉 comprising 96〈d〉 66〈a〉 99〈n〉 91〈s〉 / 51〈l〉 67〈e〉 91〈s〉 / 94〈b〉 71〈u〉 51〈l〉 41[no contradiction but maybe 51]〈l〉 67〈e〉 91〈s〉 / you may then consider if in the terms wherein at present are 51〈l〉 67〈e〉 91〈s〉 / 66〈a〉 54〈f〉 56[should be 54]〈f〉 66〈a〉 [6]4〈i〉 62〈r〉 67〈e〉 91〈s〉 / 96〈d〉 80〈[indicator]〉 204〈Angleterre〉it would be for the interest of the Duke to produce unto light an affair of this nature. That which I can with truth assure you, and whereof the Duke may be persuaded is that 66[should be 67]〈e〉 99〈n〉 / 77〈c〉 66〈a〉 91〈s〉 / 65〈q〉 64〈i〉 51〈l〉 / 91〈s〉 67〈e〉 62〈r〉 76〈o〉 64〈i〉 61〈t〉 / 71〈u〉 99〈n〉 / 64〈j〉 76〈o〉 71〈u〉 62〈r〉 51〈l〉 67〈e〉 / 97〈m〉 66〈a〉 64〈i〉 91〈s〉 61〈t〉 62〈r〉 67〈e〉 / 96〈d'〉 3〈[this must be an error for an indicator, e.g., 8 or 81]〉204〈Angleterre〉 will employ 66〈a〉 81〈[indicator]〉 272〈Rome(?)〉 and 51〈l'〉 08〈[indicator]〉 126〈argent(?)〉 and 51〈l〉 67〈e〉 / 77〈c〉 62〈r〉 67〈e〉 96〈d〉 64〈i〉 6 t for 51〈l'〉 66〈a〉 91〈s〉 91〈s〉 64〈i〉 91〈s〉 61〈t〉 67〈e〉 62〈r〉 / 66〈a〉 / 62〈r〉 67〈e〉 91〈s〉 61〈t〉 66〈a〉 94〈b〉 51〈l〉 64〈i〉 64[should be 62]〈r〉 / 51〈l〉 66〈a〉 51〈l〉 66〈a〉 [*inadvertent repetition of "la"] 81〈[indicator]〉 266〈religion Catholique〉 67〈e〉 99〈n〉 81〈[indicator]〉 204〈Angleterre〉 seeing that Rome and ....

The corrections of figures in the above account for some errors pointed out by Davys but not all. For example, Davys also points out "1" is left out in two places but such errors could not be found. So there remains a possibility Davys' reading was different from the above.

Cipher Sent by Coleman to Father de la Chaise

Shortly after 29 September 1675, Coleman sent a cipher to Father de la Chaise and also proposed use of secret ink.

I SENT your Reverence a tedious long Letter on our Nine-and-twentieth of September, to inform you of the Progress of our Affairs for these Two or Three last Years. Having now again the Opportunity of a very sure Hand to convey this by, I have sent you a Cypher; because our Parliament now drawing on, I may possibly have Occasion to send you something, which you may be willing enough to know, and may be necessary for us that you should, when I may want the Convenience of a Messenger. When any thing occurs of more Concern than ordinary, which may not be fit to be trusted even to a Cypher alone, I will (to make such a thing more secure) write it in Lemon, between the Lines of a Letter, which shall have nothing in it visible, but what I care not who sees; but dried by a warm Fire, shall discover what is written: So that, if the Letter comes to your Hands, and, upon drying it, any thing appears, more than did before, you may be sure nobody has seen it by the Way. I will not trouble you with that Way of Writing, but upon special Occasions; and then I will give you a Hint, to direct you to look for it, by concluding my visible Letter with something of Fire or Burning: By which Mark you may please to know, that there is something underneath; and how my Letter is to be used to find it out.
(House of Commons Journal Volume 9: 31 October 1678, pp. 524-530, (British History Online); Mr. Coleman's two letters to monsieur l'Chaise (1678) p.20 (Google))

References

Collection of letters and other writings, relating to the horrid Popish plot: printed from the originals in the hands of George Treby, chairman of the committee of secrecy of the house of commons (1681) (quoted by Davys and others)

John Davys, An Essay on the Art of Decyphering (1737)

Malcolm V. Hay, Jesuits and the Popish Plot (1934, 2003) (Google)

John Pollock, The Popish Plot (1944, 2015) (Google)

State Trials, vol.7 (Google)



©2015 S.Tomokiyo
First posted on 25 July 2015. Last modified on 25 July 2015.
Articles on Historical Cryptography
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