mbruton/keybridge-models

Decryption models for historical substitution ciphers

Each model in this collection has been trained for one known historical cipher key. It reads transcribed ciphertexts written with that key and produces a draft decryption for expert review. Testing a ciphertext against all models (a scan) suggests which known key, if any, it was written with; the drafts of the best-ranked models are then read to decide. The models do not recover unknown keys.

Use the models with the notebooks or command-line tool at https://github.com/mbruton0426/keybridge. You do not need to download anything from here by hand.

Contents

File	Purpose
index.json	Lists every model with its symbols, transcription format, language and source. The tools read this file first.
<model id>/<model id>_model.pt	The trained model.
<model id>/<model id>_key.tsv	The key it was trained on.
<model id>/<model id>_training_report.txt	Training settings and accuracy on synthetic text.
<model id>/README.md	Description, source of the key, test results and contributor.
submissions/	Models contributed by others, waiting for review.

Models

The 35 models of the paper, one for each key built from the DECODE database (records are DECODE record numbers). Digits: digit keys, whose ciphertexts may be written as running digits (keybridge finds the codes). All other transcriptions are written as symbols separated by spaces, exactly as in the key.

ID	Cipher	Language	Period	Transcription	DECODE records
copiale_5000_english	Copiale cipher, manuscript of a secret society	German	1734-1736	named symbols	2
maximilian_II_5000_english	Maximilian II to his ambassadors in Poland and Lithuania	German	1575	single characters	1407, 1412, 1471
maximilian_1472_5000_english	Johan Chodkiewicz to Maximilian II	German, Latin	1574-1575	named symbols	1472, 1473
borg_A_5000_english	Borg cipher (BAV Borg.lat. 898), Latin medical manuscript	Latin	not dated	symbols	210
ramanacoil_A_5000_english	Rijcklof van Goens at Ramanacoil, Ceylon, to the VOC (Heeren XVII)	Dutch	1674	named symbols	1564
ucl_A_5000_english	English letter, Brougham Archive, UCL Special Collections	English	1724	number codes separated by spaces	6317
kew_E_5000_english	Letters in TNA SP 106 (Dr Stephen Goffe and others)	English	1645-1646	codes separated by spaces (e.g. n3)	928, 929
bnf_C_5000_english	Philip II to Juan de Vargas Mexía (BnF Espagnol 132)	Spanish	1575-1580	symbols (key incomplete: codes with marks not included)	1964-2025 (48 records)
tna_CK_5000_english	Italian key, TNA SP 106/10	Italian	not dated	whole codes (e.g. z19 m23), separated by spaces	723
na_B_5000_english	Codebook of S. E. Croiset for Dirk van Hogendorp; letters from Saint Petersburg	Dutch	1803 (key); 1808-1810 (letters)	digits with end marks	1033, 1035
kha_A_5000_english	Comte d'Avaux, The Hague, to Louis XIV	French	1684	digits	1055
kew_A_5000_english	Henrietta Maria to Charles I (TNA SP 106)	English, French	1645	digits	752, 754, 785, 788, 790, 923
kew_B_5000_english	Henrietta Maria to Charles I (TNA SP 106)	English, French	1645	digits	787, 788
kew_C_5000_english	Lord Digby to Charles I (TNA SP 106)	English	1645	digits	789
kew_D_5000_english	Henrietta Maria to Charles I (TNA SP 106)	English, French	1646	digits	924, 925
kew_F_5000_english	Unknown writer to Lord Goring (TNA SP 106)	English	1645	digits	932
vatican_A_5000_english	Papal correspondence, ASV Francia 4	Italian	1587	digits	5
vatican_B_5000_english	Papal correspondence, ASV Francia 3	Italian	1552-1554	digits	6-10
vatican_C_5000_english	Papal correspondence, ASV Francia 6	Italian	1573-1574	digits	11, 12
vatican_D_5000_english	Papal correspondence, ASV Francia 17	Italian	1583-1585	digits	13, 14
vatican_E_5000_english	Papal correspondence, ASV Francia 18	Italian	1585-1587	digits	15, 16
vatican_F_5000_english	Papal correspondence, ASV Francia 22	Italian	1585-1589	digits	17-58 (35 records)
vatican_G_5000_english	Papal correspondence, ASV C15	Italian	1721	digits	24
vatican_H_5000_english	Papal correspondence, ASV P117	Italian	1757-1761	digits	25, 195-201 (7 records)
vatican_I_5000_english	Papal correspondence, ASV S423	Italian	1736	digits	26, 179-188
vatican_J_5000_english	Papal correspondence, ASV Francia 22b	Italian	1588-1589	digits	53, 54
vatican_K_5000_english	Papal correspondence, ASV Francia 64	Italian	1624-1625	digits	59-71 (13 records)
vatican_L_5000_english	Papal correspondence, ASV Francia 283	Italian	1580	digits	72, 73
vatican_M_5000_english	Papal correspondence, ASV Francia 346	Italian	1632-1634	digits	74-84
vatican_N_5000_english	Papal correspondence, ASV S304	Italian	1767	digits	120, 121
vatican_O_5000_english	Papal correspondence, ASV S364 (Secretariat to the nuncio in Spain)	Italian	1717-1720	digits	122-177
vatican_P_5000_english	Papal correspondence, not given	Italian	1535-1536	digits	189
vatican_Q_5000_english	Papal correspondence, ASV P8	Italian	1579-1581	digits	190-194
vatican_R_5000_english	Papal correspondence, ASV C13	Italian	1656-1657	digits	208, 209
vatican_S_5000_english	Papal correspondence, BAV Barb.lat. 6956 and 6960 (Pallotto)	Italian	1628-1629	digits	215-225 (10 records)

All 35 were trained with keybridge's released defaults: 5,000 synthetic examples from the built-in English HistCiph plaintext, rare-unit insertion 0.02 (see each model's training report). Where a model has test letters, its README gives the results against the key reference (the transcription read through the key) and, for digit keys, against the transcribers' readings. The Maximilian and Copiale models uploaded in October 2026 have been replaced by these.

Contributing a model

Train a model for your key with notebook ① and tick Share my model. Your contribution will be reviewed and added to index.json.

Licence and citation

All models and keys are released under CC BY 4.0: you may use and adapt them for any purpose, provided you give appropriate credit. Please cite:

[citation to be added]

When you use a specific model, please also credit the original source of its key, given in that model's README.