972Unsolved Historical Ciphers
3104 4202 130 · 4152 2012 2217 2743 2137 1896 1601 801
ci tro n · sur les quatre demi pa ge blanc he
R1024 · Grand Chiffre of William V · 1782 · 1–5000

Berlin → The Hague · one-part numerical code · 4 February 1792

Van Reede to William V, 1792: a cover note for a letter in lemon juice

William V
toWilliam V

Koninklijk Huisarchief, The Hague, Prins Willem V inv. 205; DECODE R1057, one page, “partially decrypted”. Decoded in full with the Stadholder’s Grand Chiffre, the key already identified for Van Reede’s letters, and checked against a contemporary gloss over the first eight lines. The coded text is a cover note pointing to a despatch in invisible ink.

Daniel Bourdeau · posted · updated

Method: read with known key · Extent: complete

Summary. The project catalogue listed this letter (item 217) from the DECODE record: a numerical nomenclator, partially decrypted, contents unknown. DECODE’s own note already named the code as William V’s “Grand Chiffre”, and the key survives as DECODE R1024; it had just decoded two other Van Reede despatches (Van Reede 1787). A contemporary hand glossed the first eight lines between the figures, but DECODE’s transcription of that gloss is garbled (“monsieur de Raney eal avenant… blanc he de ci r cle”) and no complete decoding of the letter was found. Decoded with R1024, all 62 message groups give sense at once, with one transcription correction (4204 → 4202, tro). The letter tells M. de Larrey that there is citron, lemon juice, on the four blank half-pages of the enclosure, and asks him to warn the Prince of Orange and hand him the letter. It ends: “les chiffres suivants sont des non-valeurs”. The 21 groups after it are nulls. The enclosure, which carried the actual news, is not on the record.
The letter, rotated upright: rows of four-digit groups with a pencil gloss between the lines
The letter, with the contemporary pencil gloss over the figures (“tro n sur le(s) … demi”, “blanc he de l i n clu”). The last three rows carry no gloss: they are the nulls. Image: Koninklijk Huisarchief, The Hague, Prins Willem V inv. 205, via DECODE R1057 (rotated here).

01 The document and the key

Berlin, 4 February 1792, Van Reede to “Monsieur”, in clear except for eleven lines of figures separated by dots, signed “A. W. van Reede”. 83 groups in all. The key is the 1782 one-part French Grand Chiffre of William V (KHA A29 inv. 301, DECODE R1024, values 1–5000), the same one that decodes R1026, R1027 and the control R1028.

02 The decoded text

4519 604 886 54 3032 1131 2476 1777 3104 4202 130 4152 2012 2217 2743 2137 1896 1601 801 1496 67 4896 2664 4102 1959 4242 3192 2604 51 3608 1406 119 3430 2123 55 465 1497 488 1496 4493 315 908 2019 2222 1945 131 3194 4694 4102 1067 231 604 186 4115 3439 2659 2847 4131 2364 148 2900 64

Monsieur de Larrey est averti qu’il y a du citron sur les quatre demi-pages blanches de l’incluse. Il voudra bien en prévenir Monseigneur le Prince d’Orange et avoir la bonté de lui remettre ma lettre, que je n’adresse point pour ne pas [pas-ser?]… Les chiffres suivants sont des non-valeurs.

“M. de Larrey is warned that there is lemon juice on the four blank half-pages of the enclosure. He will kindly tell His Highness the Prince of Orange and be so good as to hand him my letter, which I do not address [to him] so as not to … The figures that follow are nulls.”

Larrey is the Prince’s secretary. Syllables are spelled out in the code’s way: ci-tro-n, pa-ge, blanc-he, l-i-n-clu-se, vou-dra, na-dre-s-se.

The tail, 3633 3160 370 1229 3645 50 3139 3650 2768 2800 3370 1681 559 57 3268 2775 1391 1268 2239 2560 57, decodes to disconnected words (je vous remercie de, Conseil d’État, la Russie, facile, Russie, reconnoître, Archiduc): political-looking bait for anyone who opened the letter, which the plaintext itself declares void.

03 Method

Decoded DECODE’s transcription (XZ, 2020) group by group with R1024 and checked every group against the image and the interlinear gloss. One misreading corrected: 4204 (trois) is 4202 (tro), as the gloss has it. No cryptanalysis was needed.

04 What remains uncertain

05 Sources

Notes, profile and ciphertext: vanreede1792/.