Key to the Visconti Italian cipher, 1727 (Add MS 32270 f. 42)

Summary. The catalogue (item 73) listed DECODE R7931 as “Count Visconti to Visconti, 1727”, a partly decrypted homophonic nomenclator letter of one page. DECODE had typed it as a ciphertext. Add MS 32270, however, is a volume of keys: of its 130-odd DECODE records from ff. 2–295, all but four are typed as keys. The images of f. 42 show a ruled table numbered 1 to 300, with a letter, a syllable or a word against 193 of the numbers. The dorse is endorsed Count Visconti at Bruxelles with Marq.s Visconti here, 1727, Italian Cypher. The next leaf (R7932, ff. 43–44) is the branch’s working draft of the same table, with tally dots. R7933 (ff. 45–46) is a second key between the same two men, in French. Nothing on the leaf is enciphered, so there is nothing to decipher. The entry is closed as not a cipher, the key is transcribed, and a correction is queued for DECODE.

The head of the key table on f. 42: numbers 1 to 30 and beyond in three columns with their values — Add MS 32270 f. 42, the head of the table: 1 Walpole, 3 Maestà, 21 Vienna, 22 Sinzendorff, 101–144 syllables, 201 Parlamento, 203 Trattato. Image: British Library, Add MS 32270 f. 42, via DECODE R7931.

01 What the record is

From the 1720s the Deciphering Branch in London broke the ciphers of intercepted foreign letters. It kept each key it rebuilt, and many of those keys are now bound in the British Library’s Additional Manuscripts. Add MS 32270 holds the keys for the German courts and for the Empire: Palm, Kinsky and Wasner for Vienna, then Bavaria, Brunswick, Hesse-Kassel and the Palatinate. Folio 42 sits among the imperial keys. The endorsement dates it to 1727 and names the parties. “Here” is London, where the branch worked. The table is headed by the ministers whose names a Brussels–London correspondence needed in 1727: Walpole, Townshend, Sinzendorff (the imperial chancellor), Staremberg, Richelieu. The places it names are Ostenda, Ollanda, Annover and Parigi. The words include Commercio, Trattato, Congresso and Pace. Together they point to the dispute over the Ostend Company and the congress that followed it.

The table is the branch’s reconstruction of the key. About a hundred of the 300 places are empty; 262–300 are blank. Some values have a dotted underline, which marks a doubtful value (Governo, Rialso, progetto, Camara bassa, Arciduchessa). Three places are guesses, written “p.n. of a country”, “p.n. of a place (Londra)” and “p.n. of a Place (Amsterdam)”. At 172 Imperadore is struck out because it was already at 218. These marks show a key recovered from intercepted letters.

02 The key

Numbers 1–144 and 160–168 carry the alphabet with homophones: e = 2, 13, 126; a = 4, 37; i = 11, 131; u = 78, 94, 114. They also carry doubled letters (mm 8, ff 10, nn 39, rr 77, tt 104, ss 113, ll 128, pp 129) and consonant–vowel syllables. The syllables run mostly in blocks by vowel: 42–57 be, fe, le, pe, se, ze, da, ha, na, ra … te; 58–72 bu to uu; 105–110 bi to zi; 115–120 bo to zo; 161–168 co to no. The words fill most of 145–261:

No.	Value	No.	Value	No.	Value
1	Walpole	152	Inghilterra	207	Regno
3	Maestà	158	Marchese	208	Commercio
21	Vienna	159	Principe	212	Ministro
22	Sinzendorff	170	Townshend	218	Imperadore
24	Francia	171	Ollanda	220	Parigi
26	Ambasciadore	173	dispaccio	224	Madrid
145	Maestà Imperiale – Altezza	177	Richelieu	228	Corriere
146	Ostenda	184	Londra	243	America
148	Monsieur	189	Annover	247	Pace
151	Conte	197	Congresso	254	Staremberg

All 193 filled places are in visconti1727/key_f42.tsv.

03 What remains open

No letter written in this cipher is bound in Add MS 32270. Where the branch’s decipherments of the Visconti letters are now filed was not searched. Someone who finds them could test this key against them.
The two Viscontis are not identified beyond the endorsement.
Two readings are uncertain (grade C): 33 “Rialso”, which is also written that way in the draft, and the word written beside the struck-out 172 (“Reggenza”?). The other 191 places are H.
R7933, the French Visconti key of 1727/8, was only looked at for its endorsement.

04 Sources

British Library, Add MS 32270 f. 42: DECODE R7931 (images 1–2); ff. 43–44: DECODE R7932; ff. 45–46: DECODE R7933. DECODE images require login.

Notes, key transcription and profile: visconti1727/ in the repository.