Sir Richard Forster, cipher passage of 13 May 1644

At a glanceKnown key applied · complete

The passage: A ciphered passage in French from Sir Richard Forster’s papers, dated 13 May 1644, urging prudence to preserve one’s life for service to God.
Where: Printed in Britland’s 2013 article; Tomokiyo transcribed it in 2021 and still lists it as without a known decipherment.
The cipher: A mixed homophonic alphabet of 34 symbols (18 numbers, 16 letters) over 207 tokens in 37 comma-separated words.
How it was read: Pitt’s public key stands 8.8 standard deviations above 20,000 permutations. A homophonic solver recovered the key from the ciphertext alone (202 of 207 tokens, 31 of 34 symbols) once the model spelled u for v and i for j as a 1644 hand does.
What it says: There is no ground for scruple about failing God; take the ways of prudence to preserve your life and measure whether it is better to act or to suffer.
Still open: Four single slips and two words that occur once need the manuscript.
Credit: Deciphered earlier by Lasry, independently by Biermann, and in September 2026 by Pitt. Nothing about the text is new here; this page is a verification and a result about method.

01 The passage

Britland’s 2013 article printed the ciphered passage from Forster’s papers, with two clear French passages and the date; Tomokiyo transcribed it on his blog on 21 September 2021 and Pitt’s input is token for token the same. The tracker row here had said “134 groups, 24 symbols”; the real counts:

tokens	words	distinct symbols	numbers	letters	seen once	IC
207	37	34	0 2 4 5 7 8 12 14 16 19 20 30 40 50 70 80 88 90	a b c d e f g l n p q s t u x y	8	0.047

Commonest: 30 (×24), 2 and 0 (×18 each), 20 (×13), x (×10), c and s (×9). The commas are word or word-pair boundaries, which is what makes 207 tokens tractable at all.

02 The key (Pitt; Lasry and Biermann earlier)

letters	a d · b t · c l · d i · e g · f b · g y · l r · n f · p a · q c · s o · t n · u m · x s · y p
numbers	0 e · 2 e · 4 a · 5 g · 7 d · 8 t · 12 c · 14 z · 16 i · 19 n · 20 r · 30 u · 40 s · 50 t · 70 f · 80 l · 88 q · 90 p

No shift, no block, no odd/even row: a mixed alphabet with a second symbol (for t a third) for the frequent letters e a c d f g i l n p r s t, and u single although it is the commonest letter. The family is the Richelieu type of homophonic alphabet; the regular Stuart type does not fit. The unused values presumably cover h k m o x and more homophones in the full key.

il ny a aucun subiet descrupule de manquer a dieu | ie vous en responds et mesmes dans | les reigles de perfection prenez sdulement les uoyes de prudence piur conceruer uotre uie pour en faire a dieu un plus grand sacrifiye par la multiplication des uos seruices pour le salut de uos freres | et mesurer a cela sil est meilleur d’agir, ou de soupir · 13. de may. 1644

There is no ground for scruple about failing God; I answer for it, even within the rules of perfection. Take only the ways of prudence to preserve your life, so as to make God a greater sacrifice of it by multiplying your services for the salvation of your brethren, and measure by that whether it is better to act or to suffer. Four tokens (bold) conflict with the decryption (a→d, 16→i, q→c, g→y, each against several agreeing occurrences) and are single slips of the encipherer or of the typeset transcription; four in 207 is Boswell’s rate. Britland’s correspondents give aucune voie de scrupule and preveu seulement where Pitt has aucun subiet and prenez; the tokens at issue (f, 14) occur once each and cannot be settled from the text.

03 Permutation control

The twenty plaintext-letter identities were permuted over Pitt’s homophone partition 20,000 times and the 207-letter decode scored with a French 5-gram model.

model	Pitt’s key	null mean / sd / best	z	null at least as good
letters only (6.5 M letters)	−450.3	−1327 / 117 / −960	7.5	0 / 20,000
letters + word edges, u for v, i for j	−524.9	−1768 / 142 / −1230	8.8	0 / 20,000

A homophonic solver (simulated annealing; 34 symbols to 26 letters, 150,000 steps, 8–12 restarts), first without and then with the word boundaries, on the target and on six matched controls: held-out French of 207 letters enciphered with a random key of exactly Pitt’s homophone multiplicities, adjacent words merged with probability 0.2 as in the target.

run	model	controls read (of 6)	target
1	5-gram, letters only, no word edges	0 (16–49 % right; the solver’s optimum beats the truth on 5 of 6)	gibberish, 31 % of Pitt’s key
2	5-gram with spaces, raw corpus	3 at 99.5–100 %; 3 fall into an all-i attractor from OCR Roman numerals	attractor
3	same, Roman numerals removed	5 at 99–100 %, one at 44 %	−591.6 found against −602.4 for Pitt: a wrong key outscores the truth, 14.5 % agreement
4	same, training text with v→u, j→i	6 of 6 (98–100 %)	97.6 % of Pitt’s key blind: 202 of 207 tokens

Run 1 repeats the Moray letter result at this length: 207 letters over 34 symbols with a plain letter-stream model is below the solver’s threshold even on controls, so a failure on the target would have meant nothing. Run 3 is the more useful one. The controls pass and the target fails, so the plaintext was out of the model’s distribution. The letter writes uotre, uie, uos, seruices, uoyes, subiet, ie, as every 1644 hand does; a model trained on a nineteenth-century edition with v and j scores that spelling some 200 nats worse than modern French of the same length, and gibberish wins. Normalising the training text fixes it. The recovered key differs from Pitt’s at three rare symbols only (g, 14, e), whose values n-grams cannot fix and the words do. The two 134-letter controls that were run under the same model (the tracker’s wrong length) both decrypt at 97–99 %, so the length was never the obstacle.

05 What stays open

The manuscript: Val-d’Oise 68.H.8, third bundle (the papers of the English Augustinian convent at Pontoise, where a Forster daughter was a nun, an inference from the reference). No image is online; the four slips, the two one-occurrence words, and whether this is a whole letter or an extract, depend on it.
The recipient, and whether the key recurs in other Forster or Henrietta Maria papers of 1644.
Reporting: Tomokiyo’s page still lists the passage as having no known decipherment. Lasry, Biermann and Pitt have priority and Pitt’s repository is the public record.

06 Method and files

Tokeniser, groups, Pitt’s key and literal decode (targets/forster/key.py).
Letters-only French 5-gram, permutation test, blind annealer, six matched controls (ng5fr.py, solve.py, run1.txt).
Word-edge model with u/v, i/j normalisation, same tests (solve2.py, run2–4.txt); the 134-letter repeat (control134.py, run5_134.txt).

Checked: Pitt’s input against the blog text; the key against 20,000 permutations; ciphertext-only recovery and six matched controls under four models. Not checked: the manuscript; Britland’s article itself beyond its abstract and the readings quoted by Pitt.

Full texts

The transcription and the decryption of every document on this page, so that the reading can be used and checked. Short files are shown here; all are in the repository.

Forster papers, 13 May 1644

A ciphered French passage dated 13 May 1644 in the papers of Sir Richard Forster (Val-d'Oise 68.H.8): spiritual counsel that there is no cause for scruple, and that the correspondent should take the ways of prudence to preserve his life, the better to serve God and his brethren, weighing whether it is better to act or to endure. Recipient not established.

Transcription

ciphertext.txt

d. c., t. g., p., 4. 30. q. 30. 19., x. 30. f. 16. 2. 50., a. 0. 40. 12. 20.
30. y. 30. c. 2., 7. 0., u. 4. t. 88. 30. 0. l. p., a. d. 2. 30.,
ie vous en responds et mesmes dans c. 0. x. l. 2. d. e. c.
0. 40., 7. 2., y. 0. 20. n. 2. 12. 50. 16. s. t., 90. 20. 0. t. 2. 14.
x. a. 30. c. 2. u. 0. t. b., 80. 2. x. 30. s. g. 0. x. a. 2., 90. 20.
30. a. 0. t. q. 2., 90. 16. 30. 20., 12. s. t. q. 0. l. 30. 2. 20., 30. s.
50. 20. 2., 30. d. 0., y. s. 30. 20., 2. 19. n. p. d. l. 0., 4., a. 16.
2. 30., 30. t., y. c. 30. x., 5. 20. 4. 19. 7., 40. 4. 12. l. 16. 70.
d. g. 0., 90. 4. 20. c. p., u. 30. 80. 50. 16. y. c. d. q. 4. 8.
16. s. 19., a. 2. 40., 30. s. x., 40. 0. 20. 30. d. 12. 2. x., y.
s. 30. 20., 80. 0. x. 4. c. 30. 50., 7. 0., 30. s. x., 70. 20
2. l. 0. 40. et mesurer a cela sil est meilleur d’agir, ou
de soupir 13. de may. 1644

Decryption

13may1644_decryption.md

# Forster, 13 May 1644: decryption with Pitt's key (copied from NOTES.md section 2)

Copied verbatim from NOTES.md: `key.py` applies Robert Pitt's table (`src/pitt/recovered_key.json`) literally; the
tokens in bold conflict with the other occurrences of their symbol (slips). `|` marks the clear passages. Pitt's own
literal decoder output, with the group alignment, is `src/pitt/decoder_output.txt`.

> il ny a aucun subiet descrupule de manquera dieu | ie vous en responds et mesmes dans | lesreigles de perfection
> prenez**sd**ulement lesuoyesde prudence p**i**ur con**c**eruer uotre uie pour enfaire a dieu un plus grand
> sacrifi**y**e parla multiplication des uos seruices pour lesalut de uos freres | et mesurer a cela sil est
> meilleur d'agir, ou de soupir 13. de may. 1644

"Il n'y a aucun sujet de scrupule de manquer à Dieu; je vous en réponds, et même dans les règles de perfection.
Prenez seulement les voies de prudence pour conserver votre vie, pour en faire à Dieu un plus grand sacrifice par
la multiplication de vos services pour le salut de vos frères, et mesurez à cela s'il est meilleur d'agir ou de
souffrir/subir."

Variant readings (NOTES.md): Britland's correspondents read "aucune voie de scrupule" and "preveu seulement" where
Pitt reads "aucun subiet" and "prenez"; Britland gives the clear phrase as "de soubir" where Tomokiyo has "soupir".

Decryption

decoder_output.txt

LITERAL DECODING WITH THE SUPPLIED PROPOSED KEY
207 cipher tokens; 34 distinct symbols
No editorial repairs; f -> b is a tentative lexical assignment.

il, ny, a, aucun, subiet, descrupule, de, manquera, dieu
[ALREADY PLAINTEXT] ie vous en responds et mesmes dans
lesreigles, de, perfection, prenezsdulement, lesuoyesde, prudence, piur, conceruer, uotre, uie, pour, enfaire, a, dieu, un, plus, grand, sacrifiye, parla, multiplication, des, uos, seruices, pour, lesalut, de, uos, freres
[ALREADY PLAINTEXT] et mesurer a cela sil est meilleur d’agir, ou
de soupir 13. de may. 1644

COMPLETE CIPHER GROUP ALIGNMENT
 1.   1-  2: d c -> il
 2.   3-  4: t g -> ny
 3.   5-  5: p -> a
 4.   6- 10: 4 30 q 30 19 -> aucun
 5.  11- 16: x 30 f 16 2 50 -> subiet
 6.  17- 26: a 0 40 12 20 30 y 30 c 2 -> descrupule
 7.  27- 28: 7 0 -> de
 8.  29- 36: u 4 t 88 30 0 l p -> manquera
 9.  37- 40: a d 2 30 -> dieu
[ALREADY PLAINTEXT] ie vous en responds et mesmes dans
10.  41- 50: c 0 x l 2 d e c 0 40 -> lesreigles
11.  51- 52: 7 2 -> de
12.  53- 62: y 0 20 n 2 12 50 16 s t -> perfection
13.  63- 77: 90 20 0 t 2 14 x a 30 c 2 u 0 t b -> prenezsdulement
14.  78- 87: 80 2 x 30 s g 0 x a 2 -> lesuoyesde
15.  88- 95: 90 20 30 a 0 t q 2 -> prudence
16.  96- 99: 90 16 30 20 -> piur
17. 100-108: 12 s t q 0 l 30 2 20 -> conceruer
18. 109-113: 30 s 50 20 2 -> uotre
19. 114-116: 30 d 0 -> uie
20. 117-120: y s 30 20 -> pour
21. 121-127: 2 19 n p d l 0 -> enfaire
22. 128-128: 4 -> a
23. 129-132: a 16 2 30 -> dieu
24. 133-134: 30 t -> un
25. 135-138: y c 30 x -> plus
26. 139-143: 5 20 4 19 7 -> grand
27. 144-152: 40 4 12 l 16 70 d g 0 -> sacrifiye
28. 153-157: 90 4 20 c p -> parla
29. 158-171: u 30 80 50 16 y c d q 4 8 16 s 19 -> multiplication
30. 172-174: a 2 40 -> des
31. 175-177: 30 s x -> uos
32. 178-185: 40 0 20 30 d 12 2 x -> seruices
33. 186-189: y s 30 20 -> pour
34. 190-196: 80 0 x 4 c 30 50 -> lesalut
35. 197-198: 7 0 -> de
36. 199-201: 30 s x -> uos
37. 202-207: 70 20 2 l 0 40 -> freres
[ALREADY PLAINTEXT] et mesurer a cela sil est meilleur d’agir, ou
de soupir 13. de may. 1644

Decryption

README.md

# Forster cipher — 13 May 1644

A reproducible AI-assisted reconstruction of the French passage dated
**13 May 1644** in the Richard Forster papers: ciphertext, proposed key, Python
decoder, literal output, and an edited French reading with an English translation.

**Earlier decipherments:** Karen Britland has informed Robert Pitt that George
Lasry supplied a decipherment after publication of her article, and that Norbert
Biermann independently reached the same solution. This project acknowledges their
earlier work and makes no claim to the first decipherment.

The supplied key decodes **207 encrypted tokens using 34 fixed symbol assignments**.
Four letters require editorial repair in the readable version. This repository's
specific key and editorial choices have not been verified against the handwritten
manuscript or independently reviewed.

## Update — 15 September 2026

Britland's reply identifies the earlier work by **George Lasry** and **Norbert
Biermann**. The reading she supplied agrees with the overall meaning of the
reconstruction here, with some differences in wording:

| Passage | Earlier reading supplied by Britland | This repository's edited reading |
| --- | --- | --- |
| Opening | `aucune voie de scrupule` | `aucun sujet de scrupule` (literal: `aucun subiet`) |
| Prudence clause | `preveu seulement` | `prenez seulement` (literal: `prenez sdulement`) |
| Final verb | `soupir` | `subir` (the supplied source plaintext also says `soupir`) |

The reply did not include the earlier keys, working notes, or a manuscript image.
It therefore provides evidence of prior decipherment and broad agreement in
meaning, while the differences above and the four disputed cipher-derived letters
remain unresolved. The original input, proposed key, and literal decoder output
are retained for comparison.

Source: Karen Britland's correspondence with Robert Pitt, reported by Pitt in
this update. The correspondence is not a published source or a review of this
repository's exact key.

## Files and reproduction

| File | Purpose |
| --- | --- |
| [ciphertext_source.txt](ciphertext_source.txt) | Supplied transcription, preserved unchanged, including existing plaintext and date. |
| [recovered_key.json](recovered_key.json) | Proposed token-to-letter key and uncertainty notes. |
| [decode_forster.py](decode_forster.py) | Deterministic decoder; applies the supplied key without editorial repairs. |
| [decoder_output.txt](decoder_output.txt) | Complete literal output and numbered alignment of all 37 encrypted groups. |
| [test_decoder.py](test_decoder.py) | Checks coverage, input validation, key use, and preservation of disputed letters. |

Requires Python 3.9+ and only the standard library. From the repository directory:

```sh
python3 decode_forster.py
python3 decode_forster.py --alignment
python3 -m unittest -v
```

Check that a fresh run exactly reproduces the committed output:

```sh
python3 decode_forster.py --alignment | diff -u decoder_output.txt -
```

## How the cipher and key work

The proposed key is a **homophonic substitution**: each number or letter token
maps to one plaintext letter, and several tokens can share a letter. For example,
both `0` and `2` mean `e`; `4 30 q 30 19` gives `a u c u n` → `aucun`.
Comma-separated groups can contain several words: `descrupule` is read as
`de scrupule`. Word spacing within groups is editorial.

| Plaintext letter | Cipher tokens |
| --- | --- |
| a | `4`, `p` |
| b | `f` (tentative) |
| c | `12`, `q` |
| d | `7`, `a` |
| e | `0`, `2` |
| f | `70`, `n` |
| g | `5`, `e` |
| i | `16`, `d` |
| l | `80`, `c` |
| m | `u` |
| n | `19`, `t` |
| o | `s` |
| p | `90`, `y` |
| q | `88` |
| r | `20`, `l` |
| s | `40`, `x` |
| t | `8`, `50`, `b` |
| u | `30` |
| y | `g` |
| z | `14` |

The two existing plaintext spans, beginning `ie vous en responds` and
`et mesurer a cela`, pass through unchanged. The date is already plaintext.
The decoder applies the supplied key; it does not automate recovery of the key.

## Edited reading

These are this project's readings, incorporating the editorial choices documented
below. They are not a transcription of Lasry's or Biermann's original working.

**Modernised French**

> Il n’y a aucun sujet de scrupule de manquer à Dieu ; je vous en réponds, et même
> dans les règles de perfection. Prenez seulement les voies de prudence pour
> conserver votre vie, pour en faire à Dieu un plus grand sacrifice, par la
> multiplication de vos services pour le salut de vos frères, et mesurez à cela
> s’il est meilleur d’agir ou de subir.
>
> 13 mai 1644

**English**

> There is no reason to worry that you are failing in your duty to God; I assure
> you of this, even according to the rules of spiritual perfection. Simply take
> prudent steps to preserve your life, so that you may offer it to God as a
> greater sacrifice by multiplying your services for the salvation of your
> brethren. Judge by that whether it is better to act or to endure.
>
> 13 May 1644

## Findings and uncertainties

Four literal letters conflict with the proposed reading. Positions are numbered
from 1 across encrypted tokens only, as in the output alignment.

| Token position | Cipher → literal | Editorial repair |
| --- | --- | --- |
| 70 | `a` → `d` | `sdulement` → `seulement` |
| 97 | `16` → `i` | `piur` → `pour` |
| 103 | `q` → `c` | `conceruer` → `conseruer` |
| 151 | `g` → `y` | `sacrifiye` → `sacrifice` |

These repairs are confined to the edited reading. Changing the key globally
would alter other occurrences of the same symbols. Their cause remains unresolved.

- **Tentative assignment:** `f` appears once, at token 13. Assigning `f` → `b`
  produces `subiet`, a historical spelling corresponding to `sujet`.
  [Nicot’s 1606 dictionary](https://fr.wikisource.org/wiki/Page:Thresor_de_la_langue_francoyse_-_1606_-_1_-_Nicot.djvu/217)
  attests the spelling; it does not establish this cipher assignment.
- **Additional editing:** `des uos` becomes `de vos`, omitting the `s` at token
  174. The key always gives `30` → `u`; `u/v` and `i/j` distinctions, modern
  spellings, accents, apostrophes, and sentence punctuation are editorial.
  Examples include `subiet` → `sujet`, `reigles` → `règles`, `uoyes` → `voies`,
  `ie` → `je`, `responds` → `réponds`, and `mesmes` → `même`. The existing
  plaintext `mesurer` is edited to `mesurez`.
- **Uncertain ending:** the supplied transcription ends with `soupir`.
  The [article abstract displayed by ResearchGate](https://www.researchgate.net/publication/260410273_Reading_between_the_lines_royalist_letters_and_encryption_in_the_English_civil_wars)
  gives `soubir`. The edited `subir` / “endure” follows that variant and remains
  uncertain. This word is already plaintext and supplies no evidence for the key.
- **Verification scope:** all 207 encrypted tokens are retained, every observed
  symbol is mapped, and the decoder applies no position-specific substitutions.
  Tests establish mechanical reproducibility. The archive’s 203/207 agreement
  with a proposed comparison reading measures internal consistency, not
  independently established accuracy or statistical confidence.

The interpretation is counsel to preserve one’s life for continued service to
God and one’s brethren. It does not identify the correspondent or establish a
specific political event. The published passage may be only part of a letter;
no missing text is supplied here.

## Sources and provenance

Prepared from `forster_end_to_end_evidence.zip`. Its 13 manifest checksums were
verified; the input, key, decoder, tests, and stored output retain their supplied
contents. The narrative and editorial notes are consolidated in this document.
Robert Pitt, a software engineer experimenting with modern AI, assembled this
AI-assisted reconstruction and reproducible repository. The earlier decipherments
are credited in the update above.

- Karen Britland, [“Reading between the lines: royalist letters and encryption
  in the English civil wars”](https://onlinelibrary.wiley.com/doi/10.1111/criq.12072),
  *Critical Quarterly* 55(4), 15–26 (December 2013 issue; published online
  21 January 2014), DOI: 10.1111/criq.12072. Note 1 identifies the Forster papers
  as **Archives départementales (Val-d’Oise), MS 68.H.8, troisième liasse**.
  This is the published reference; no manuscript image was available for verification.
- [Publisher’s first-page image](https://onlinelibrary.wiley.com/cms/asset/74d4d7e9-abb5-4ab0-95ba-a9a271a1d09c/criq.12072.fp.png):
  the typeset transcription identified in the supplied evidence, rather than
  a photograph of the manuscript.
- [Cryptiana, September 2021 archive](https://cryptiana.blogspot.com/2021/09/):
  the supplied evidence identifies the 21 September entry as a reproduction of
  Britland’s ciphertext, not an independent manuscript transcription.

## License

This repository’s code, key, and editorial documentation are released under the
[MIT License](LICENSE), permitting free use, modification, and redistribution,
including commercial use. The historical passage is attributed above; the license
does not extend to external publications linked as sources.

Reading

13may1644_reading.md

<!-- Reading of the 13 May 1644 cipher written 23 Oct 2026 (Claude Opus 5.5, verification 5) from the literal decode with Robert Pitt's key in texts/13may1644_decryption.md: word division, apostrophes and punctuation added, spelling as decoded (u for v, i for j). The four slips the decode marks in bold (sd, i, c, y: tokens that conflict with the other occurrences of their symbol) are read with the symbol's value elsewhere: seulement, pour, conseruer, sacrifice. Clear passages of the letter in ⟨ ⟩. Variants: Britland's correspondents read "aucune voie de scrupule" and "preveu seulement"; Britland gives "de soubir" for Tomokiyo's "soupir". -->

# Forster papers, 13 May 1644

## Reading

Il n'y a aucun subiet de scrupule de manquer a Dieu; ⟨ie vous en responds, et mesmes dans⟩ les reigles de perfection
prenez seulement les uoyes de prudence pour conseruer uotre uie, pour en faire a Dieu un plus grand sacrifice par la
multiplication des uos seruices pour le salut de uos freres; ⟨et mesurer a cela s'il est meilleur d'agir, ou de
soupir. 13. de may. 1644.⟩

Translation

13may1644_en.md

<!-- English translation of texts/13may1644_reading.md (Claude Opus 5.5, 23 Oct 2026); clear passages in ⟨ ⟩ as in the reading. -->

# Forster papers, 13 May 1644: English translation

There is no ground for scruple about failing God; ⟨I answer to you for it, and even within⟩ the rules of perfection: only
take the ways of prudence to preserve your life, so as to make of it a greater sacrifice to God by multiplying your
services for the salvation of your brethren; ⟨and to measure by this whether it is better to act or to sigh. 13 May
1644.⟩

07 Sources

K. Britland, article of 2013 on Sir Richard Forster’s papers (Val-d’Oise 68.H.8), source of the printed cipher.
S. Tomokiyo, blog post of 21 September 2021, and Unsolved Historical Ciphers (cryptiana).
R. Pitt, forster-cipher (GitHub, September 2026; Lasry and Biermann credited in the README).

Analysis scripts and the ciphertext are in the repository (targets/forster/).

Sir Richard Forster, 13 May 1644

01 The passage

02 The key (Pitt; Lasry and Biermann earlier)

03 Permutation control

04 Ciphertext-only recovery and the controls

05 What stays open

06 Method and files

Full texts

Forster papers, 13 May 1644

07 Sources