Charles I and Nicholas to Boswell, 2 November 1643

At a glanceKnown key applied · complete

The letters: Two cipher letters of 2 November 1643: Charles I to the Duke of Courland’s envoy, and Sir Edward Nicholas to Sir William Boswell, the King’s resident at The Hague.
Where: The National Archives, SP 84/157/96 (f. 217) and SP 84/157/97 (f. 219). No images are online; the only text is S. Tomokiyo’s 2021 transcription.
The cipher: A 24-letter row repeated four times over the figures 20–115, supplementary homophones at 116–159, nulls below 20 and four word codes. 455 numeric groups, 171 distinct.
How it was read: Robert Pitt published the alphabet on 14 September 2026 and it was applied here. A permutation control puts his row 9.6 standard deviations above 20,000 random rows. The four graphic signs are word signs, which Pitt’s notes left unexplained.
What it says: The King answers and re-credentials the Duke’s envoy, sent through Boswell in Boswell’s own cipher. Simpson’s 1893 print of the parallel letter to the Duke confirms this and gives 291 = Duke.
Still open: About a dozen word codes that occur once, and some transcription slips; both need the folios, which are not online.
Credit: The alphabet is Robert Pitt’s; the transcription is S. Tomokiyo’s.

01 The documents

TNA Discovery has the items at folio level: SP 84/157/96, f. 217, “Charles I to Boswell — in cipher” and SP 84/157/97, f. 219, “Nicholas to Boswell — in cipher”, both 2 November 1643. No images exist online. Tomokiyo’s transcription (blog, 17 September 2021), with asterisks where he was unsure, is the only text; Pitt’s inputs are line for line the same. Sir William Boswell was the King’s resident at The Hague; Sir Edward Nicholas was Secretary of State at Oxford.

Across both letters: 455 numeric groups, 171 distinct, 69 seen once. The bands separate cleanly by usage:

band	occurrences	distinct	seen once	what it is
0–19	45	17	4	nulls (no reading anywhere needs one)
20–115	276	80	17	the alphabet: 24 letters × 4 homophones (96 predicted, 80 seen; q z unused)
116–159	61	31	14	supplementary homophones for a d e i m n o r s t u y, in alphabetical blocks
160–399	25	22	19	word codes, plus a null block 361–386
400–999	48	21	15	word codes continued: 800 to ×14, 588 of ×7, 873 you ×6

02 The key (Pitt’s alphabet)

plain   a  b  c  d  e  f  g  h  i  k  l  m  n  o  p  q  r  s  t  u  w  x  y  z
1st     20 32 21 33 22 34 23 35 24 36 25 37 26 38 27 39 28 40 29 41 30 42 31 43
2nd     44 56 45 57 46 58 47 59 48 60 49 61 50 62 51 63 52 64 53 65 54 66 55 67
3rd     68 80 69 81 70 82 71 83 72 84 73 85 74 86 75 87 76 88 77 89 78 90 79 91
4th     92 104 93 105 94 106 95 107 96 108 97 109 98 110 99 111 100 112 101 113 102 114 103 115

That is letter = row[(n − 20) mod 24] with the row a c e g i l n p r t w y b d f h k m o q s u x z — the odd positions of the 24-letter alphabet (no j, no v) and then the even ones. Each letter’s four values are 24 apart. It is the same type as the regular Stuart keys Tomokiyo describes for Scudamore (1636), Cave (1638) and Ormonde–Clanricarde (1643), and as the Maltravers–Ormonde key. The supplementary block 116–159 is five alphabetical runs (a d e · m n o r s t y, a d e · n o · t u, …), so even its unseen values are constrained; 142 = s is added here from Nicholas’s opening “[His Majesty] comands”.

03 Verification

The 21 maximal runs of four or more alphabet groups (106 letters) were scored with a 4-gram model built from 2.7 million characters of seventeenth- to nineteenth-century English. The null hypothesis permutes the 24 letter identities over the same periodic structure.

	score
Pitt’s row	−217.5
20,000 random rows: mean / sd / best	−333.7 / 12.1 / −271.1
z; rows scoring at least as well	9.6; 0 of 20,000

A free period scan (annealing a 24-letter row for periods 20–32) is not decisive and is recorded as such: at 106 letters the annealer over-fits, and periods 27–32 reach higher scores than the true key. The argument for period 24 is structural (the odd/even construction, the 24-apart homophones, the alphabetical supplementary blocks), and the decryptions that match the cleartext (“A C · · knowledge”, “[835] D E R stand”, “Y O U R E [C] R E D E N T I A L S” beside Simpson’s “Our Re-credentials”) are the confirmation.

04 The four signs

Tomokiyo renders four graphic signs: △, 中, □ and +. Each occurs once inside a spelled word and afterwards on its own, and the stand-alone occurrences come in exactly the combination the embedded ones predict.

sign	embedded occurrence	stand-alone	value
△	`47 86 △ 110 33` = GO△OD	“back to OUR △ 中 873 □”	good
中	`93 122 中 41 112` = CO中US-in	“Our 中 873 □ S affeccons”, “our said 中 873 □”, “our △ 中 873 □”	Cousin
□	`61 116 88 □ 77 70 28` = MAS□TER	the same three places	Master
+	`158 + 150` = U+S (“inuiting us”)	“acceptable to +”, “preiudiced +”, “to + to the port of”, “addres by 213 to +”	us

So △ 中 873 □ is “good Cousin your Master”. The clerk wrote the sign beside the word where he spelled it out (compare “for whom 270 thus hereafter” in the Ormonde letter, where a code is introduced inline), and the transcription placed the sign in the middle of the word. This is the explanation Pitt’s notes said was missing, and with it 873 = you / your fits all six occurrences.

05 Decryption

Codes in brackets, proposed transcription corrections in braces, spelling as the cipher gives it.

Charles I to the Duke of Courland’s envoy, Oxford, 2 November 1643 (f. 217):

Sir, Wee have received your ciuill {&} welcom letter of the {6th} of 8ber 1643. But never heard of any [514] letter of Our good Cousin the Duke of Curland’s, your Master, saue those inuiting us to send to the Funerals of the Late [303] Dukes his Father & Unkle [376] deceased of happy memory; to [which] we made an answer, but know not whether the same arriued [289] safe. The Difficulty of passage {we} feare {hath} preiudiced us. Our Cousin your Master’s affeccons & offers are soe reall & acceptable to us, specially in this coniuncture of our Affaires, as we acknowledge [our] [selves] there[by] highly obliged. We [pray] you therefore to present our princely thanks [177] on this behalf, to [assure] our said Cousin your Master, & to lett him understand that we shall most [wel]comly receiue his [assistance] with in [755] [188] [musket]s, match & [powder], in {what} [pro]por[tion] it shall please him to transmit the same to us, to the [port] of Weymouth, Dartmouth, Exeter, Falmouth or [228]. Not doubting but God will shortly enable Us to recompence soe free & soe [gener]ous a c[591] & es[126]. Doe assure your self also of our fauour particular, & doe take your addres by [213] to us in very good part, as also that you haue taken care to avoyde the dangerousnes of the passage hither. And soe wishing you a safe returne back to our good Cousin your Master, to whom w[e] herewith [send] your re-credentials, Wee commit you to the Protection of the Almighty. Given at our court at Oxford the second day of Nouember in the Nineteenth yeare of Our Reigne 1643.

Nicholas to Boswell, 2 November 1643 (f. 219):

Sir, [His Majesty] comands [me] to signify his pleasure to you, that you use all possible diligence & industry by your meanes of the [170] & otherwise [secret]ly to hinder the coming ouer of the [181]s from the [726], for it is here apprehended that they [will] doe more hurt then good, for that they [are] understood here not to affect Monarchy. His Majesty’s two letters herewith sent with flying Seales are put into your character, because most safe & ready; you are to decifer & interpret them. Monsieur F I R X S S appeares not here. …

Word codes with a value: 800 to, 588 of, 873 you/your, 291 Duke (from Simpson’s printed cipher line 291 588 C U R L A N D on the letter to the Duke), 516 letter, 835 un-, 749 selves, 750 send, 205 assure, 223 by, 629 pray, 640 port, 636 pro-, 406 gener-, 484 His Majesty, 746 secret-. Sorted, the readable codes run alphabetically (a 170–228 … d 291 … o 588–591 … s 726–755, t 800, u 835, y 873), so the nomenclator was probably an alphabetical list; a second letter in the key would test that.

06 What the letters are

The King’s letter is addressed to the envoy. It answers the envoy’s letter of 6 October, calls the Duke “your Master” three times, sends “your re-credentials”, and wishes him a safe return to his master. Simpson’s Civil War Papers (Scottish History Society Miscellany I, 1893) prints the King’s letter to Duke James of Courland of the same day, calling itself “these Our Re-credentials”, and the envoy’s later memorial: the passage was unsafe and “the ministers of their Majesties at the Hague” dissuaded him from crossing and took his letters. Nicholas tells Boswell that the King’s two letters are “put into your character” and that Boswell is to “decifer & interpret them”. Hence the catalogue’s “Charles I to Boswell”.
“Monsieur F I R X S S appeares not here.” Simpson names Major Georg von Firks as the Duke’s agent. A man expected at Oxford who has not come is the envoy’s own account of himself.
The arms. Muskets, match and powder to Weymouth, Dartmouth, Exeter, Falmouth or a fifth port: the Duke’s memorial says he was told their Majesties needed munitions rather than men, and Nicholas wrote to Roe in December 1643 that “arms and powder are arrived at Dartmouth for his Majesty” (CSPD).
The funerals of Duke Friedrich (d. 1642) and his brother Wilhelm (d. 1640), held together in February 1643: “the Late Dukes his Father & Unkle”.
Nicholas’s instruction to hinder “the coming ouer of the [181]s from the [726]”, people “understood here not to affect Monarchy”, fits the States General’s embassy of mediation resolved on in late 1643 and received at Oxford early in 1644, which the King did not want: 181+S = Ambassadors, 726 = States. These two values rest on the history; the cipher alone does not fix them.

07 Method, credit and files

Pitt’s repository robertpitt/charles-i-boswell-cipher (MIT; commit 609ebf4, 14 September 2026) had the alphabet, the supplementary homophones, most nulls and four word codes before this session. Cite it for the alphabet.
Band statistics and the decoder (targets/boswell/key.py); 4-gram model (lm4.py); permutation control (permtest.py); period scan (periodscan.py).
Simpson 1893 and CSPD 1641–43 from Internet Archive OCR; TNA references from the Discovery API.

Checked: Pitt’s inputs against the blog text; the alphabet against 20,000 permuted rows; every decryption against the tokens; Simpson’s letter and memorial; the TNA and CSPD references. Not checked: the manuscripts (no images online); the Latvian archive descriptions Pitt cites. The identity of the envoy as Firks, the alphabetical-order hypothesis and the proposed transcription slips are inferences to verify before repeating.

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.

Charles I, Oxford, 2 Nov 1643, TNA SP 84/157 f. 217

Not a letter to Boswell but to the Duke of Courland's envoy at The Hague: Charles I thanks the Duke for his offers, asks for his assistance with arms, muskets, match and powder shipped to Weymouth, Dartmouth, Exeter, Falmouth or another port, and sends the envoy his re-credentials. The transcription is Tomokiyo's provisional one (no images online).

Transcription

charles.txt

Sir, Wee have received 873 69 72 65 361 ill 26 102 92 97 45 86
85 17 516 588 134 be* 6_ 132 106 8_ 32 46 100 1643. But never
heard of any 514 516 588 Our 47 86 △ 110 33 17 93 122 中 41 112 m.y^w
291 588 362 21 41 52 49 and 40 15 873 61 116 88 □ 77 70 28
saue* 134 35 86 112 70 in 41 24 53 in 71 374 158 ＋ 150 to 14
64 end 800 y^w Funerals of the Lave*≪→Late?≫ 303 291 40 his 34 44 29 hir &
65 50 60 25 22 16 376 deceased of happy memory 800 851 102 154
made an 1 4 40 30 69 28 3 but 18 10 5 36 now not 78 59 it.
380 he 149 364 29 he same ar 76 24 135 33 289 safe The Difficul
ty of passage in* 34 22 are hash* preiudiced + look*. Our 中 873
□ 40 20 34 58 22 21 45 38 26 40 & 588 82 70 123 124 are
soe 149 146 362 all & 153 93 69 46 27 29 381 able 800 + spe-
cially in this coniuncture of our Affaires, as w*[with?] 20 21 18 10 knowledge
591 749 there 223 high 25 79 4 62 80 49 48 71 70 81 w* 629
you therefore 800 27 28 70 15 sent 62 89 100 prince 97 159 16 2
77 107 an* 84 88 177 on this behalf 800 205 148 151 123
said 中 873 □ & to lett him 835 33 22 100 stand that w 64
83 15 all most 854e 45 62 120 ly 123 138 69 94 96 89 118 his
185 w[with?] in 755 188 539 40 16 61 at 45 83 & 639 in rebat* w 636por
it 5 124 107 all 99 97 1 5 lease* 35 24 61 16 800 134 123 an
112 120 it the 150 14 am 70 6 800 + 800 y^w 640 588 30 70 31 61
110 77 107 10 33 20 28 & 61 62 u 101 107 18 90^ 46 29 70 52
386 106 all 85 110 41 53 107 or 228 Not doubting but God
will shortly enable Us to recompence soe 8 82 100 46 154 & soe
406ous 20 69 591 & 70 88 126 ^w doe as 40 89 100 118 17 103
(verso)
Our self also of our 58 68 113 our particular & doe take your
addres by 213 800 + in very good part, as also that you haue taken
care to avoyde the dangerousnes of the passage hither. And soe
wishing you a safe returne back 800 62 89 100 △ 中 873 □
to whom w herewith 750 79 122 135 28 70 6* 76 118 105 94
121 53 72 92 49 64
Wee commit you to the Protection of the
Almighty. Given at our court at Oxford the second day of Nobember
in y^w e [N]ineteenth yeare of Our Reigne 1643.

Decryption

charles_f217_decryption.md

Copied verbatim from NOTES.md section 4 ("Reading") on 22 Oct 2026. The mechanical output of key.py over the whole letter is decoded.txt.

Codes in [brackets], graphic signs and clear words as read, proposed transcription corrections in {braces} (§6).
Spelling as the cipher gives it.

**Charles I to [the Duke of Courland's envoy], Oxford, 2 November 1643 (SP 84/157 f. 217):**

> Sir, Wee have received your ciuill {&?} welcom letter of the {6th} of 8ber [= October] 1643. But never heard of
> any [514] letter of Our good△ Cousin中 the Duke of Curland's, your Master□, saue those inuiting us+ to send to
> the Funerals of the Late [303] Dukes his Father & Unkle [376] deceased of happy memory; to [which] we made an
> answer, but know not whether the same arriued [289] safe. The Difficulty of passage {we} feare {hath} preiudiced
> us [look*]. Our Cousin your Master's affeccons & offers are soe reall & acceptable to us, specially in this
> coniuncture of our Affaires, as we acknowledge [our] [selves] there[by] highly obliged. We [pray] you therefore
> to present our princely thanks [177] on this behalf, to [assure] our said Cousin your Master, & to lett him
> understand that we shall most [854]e-comly receiue his [assistance] with in [755] [188] [musket]s, match &
> [639], in {what} [pro]por[tion] it shall please him to transmit the same to us, to the [port] of Weymouth,
> Dartmouth, Exeter, Falmouth or [228]. Not doubting but God will shortly enable Us to recompence soe free & soe
> [gener]ous a c[591] & es[126]. Doe assure your self also of our fauour particular, & doe take your addres by
> [213] to us in very good part, as also that you haue taken care to avoyde the dangerousnes of the passage hither.
> And soe wishing you a safe returne back to our good Cousin your Master, to whom w[e] herewith [send] your
> re-credentials, Wee commit you to the Protection of the Almighty. Given at our court at Oxford the second day of
> Nouember in the Nineteenth yeare of Our Reigne 1643.

Decryption

decoded.txt

Mechanical output of key.py over Tomokiyo's transcription. Capitals = alphabet letters; {word} = word code or sign; · = null; [n] = unresolved.
The clear-text tails of each letter (after 'Wee commit you' / 'His Ma^ys two letters') are printed as transcribed; the digits there are dates, not cipher.

===== charles.txt
Sir , Wee have received {your} C I U · ill N W A L C O
M · {letter} {of} T be* 6_ O F 8_ B E R [1643] . But never
heard of any [514] {letter} {of} Our G O {good} O D · C O {Cousin} U S m.y^w
{Duke} {of} · C U R L and S · {your} M A S {Master} T E R
saue* T H O S E in U I T in G · U {us} S to ·
S end {to} y^w Funerals of the Lave*≪→Late?≫ {two} {Duke} S his F A T hir &
U N K L E · · deceased of happy memory {to} {which} W E
made an · · S W C R · but · · · K now not W H it.
· he R · T he same ar R I U D [289] safe The Difficul
ty of passage in* F E are hash* preiudiced {us} look*. Our {Cousin} {your}
{Master} S A F F E C C O N S & {of} F E R S are
soe R E · all & A C C E P T · able {to} {us} spe
cially in this coniuncture of our Affaires , as w*[with?] A C · · knowledge
{our} {selves} there {by} high L Y · O B L I G E D w* {pray}
you therefore {to} P R E · sent O U R prince L Y · ·
T H an* K S [177] on this behalf {to} {assure} O U R
said {Cousin} {your} {Master} & to lett him {un} D E R stand that w S
H · all most {will} e C O M ly R E C E I U E his
{assistance} w[with?] in {store} {armes} {musket} S · M at C H & {powder} in rebat* w {pro} por
it · S H all P L · · lease* H I M · {to} T R an
S M it the S · am E · {to} {us} {to} y^w {port} {of} W E Y M
O T H · D A R & M O u T H · X ^ E T E R
· F all M O U T H or {Bristol} Not doubting but God
will shortly enable Us to recompence soe · F R E E & soe
{gener} ous A C {our} & E S Y ^w doe as S U R E · Y
( verso )
Our self also of our F A U our particular & doe take your
addres by [213] {to} {us} in very good part , as also that you haue taken
care to avoyde the dangerousnes of the passage hither. And soe
wishing you a safe returne back {to} O U R {good} {Cousin} {your} {Master}
to whom w herewith {send} Y O U R E · * R E D E
N T I A L S
Wee commit you to the Protection of the
Almighty. Given at our court at Oxford the second day of Nobember
in y^w e [N]ineteenth yeare of Our Reigne 1643.
===== nicholas.txt
Sir , {his Majesty} C O M A N D S {to}
S I G n I A Y · H I S pleasure {to}
{your} r T H at Y O U · U S E all
P · S S I B L [b?] E [y?] diligence & industry
B [ ?] Y [of?] y^w[your?] M E A N E S {of} the {Ambassadors} &
other W I S E {secret} L Y {to} H I
N D E R the C O M G O U E R
{of} y^w [181] S · from y^w [726] F O R ·
it I S H E R E · A P P R
E H E N D E D that T he Y
· {will} D O more H U R T · P
he N · G O O D for that T · · he
Y {are} understood H E R E · N O T
{to} A F F E N * T · M O N
A R C Y
His Ma^ys two letters herewith sent with
flying Seales are put into yo^r character, because
most safe & ready, your are to decifer & interpret
them. Monsieur 82 48 52 42 40 64 appeares
not here.
(Page 2)
I must entreat yo^r care over the enclosed in
this & another pacqt going herewith, and having
acknowledged the receipt of yo^rs of the 8th 22/12
& 29/19 of October with many thanks, I must
remit you to the not* for more account upon
them, & ever remains

Nicholas to Boswell, 2 Nov 1643, TNA SP 84/157 f. 219

Secretary Nicholas tells Boswell to hinder secretly the coming over of [ambassadors?] from the [States?], thought not to affect monarchy, and that the King's two letters are put into Boswell's cipher for him to decipher and interpret for the envoy; 'Monsieur F I R X S S' (probably Firks, the Duke's agent) has not appeared.

Transcription

nicholas.txt

Sir, 484 21 86 85 127 131 128 142 800
40 24 23 n 48 44 31 2 35 24 64 pleasure 800
873r 29 59 at 55 38 41 6 65 88 118 all
27 0 88 112 72 56 49[b?] 70[y?] diligence & industry
80[-?] 79[of?] y^w[your?] 37 94 20 26 118 112 588 the 170 &
other 54 96 112 22 746 25 103 800 59 72
98 105 118 123 the 21 62 61 47 110 113 70 52
588 y^w 181 40 15 from y^w 726 82 122 141 18
it 147 150 107 94 123 118 12 153 27 51 100
129 83 138 121 33 22 81 that 125 he 126
374 854 117 62 more 107 41 76 101 14 27
he 50 2 95 62 86 117 for that 53 14 17 he
79 190 understood 35 70 52 129 11 50 62 29
800 145 106 82 94 98* 53 377 109 122 131
44 100 69 79
His Ma^ys two letters herewith sent with
flying Seales are put into yo^r character, because
most safe & ready, your are to decifer & interpret
them. Monsieur 82 48 52 42 40 64 appeares
not here.
(Page 2)
I must entreat yo^r care over the enclosed in
this & another pacqt going herewith, and having
acknowledged the receipt of yo^rs of the 8th 22/12
& 29/19 of October with many thanks, I must
remit you to the not* for more account upon
them, & ever remains

Decryption

nicholas_f219_decryption.md

Copied verbatim from NOTES.md section 4 ("Reading") on 22 Oct 2026. The connected reading stops at the ellipsis; the mechanical output of key.py over the whole letter, including its clear-text tail, is decoded.txt.

Codes in [brackets], graphic signs and clear words as read, proposed transcription corrections in {braces} (§6).
Spelling as the cipher gives it.


**Nicholas to Boswell, 2 November 1643 (SP 84/157 f. 219):**

> Sir, [His Majesty] comands [me] to signify his pleasure to you, that you use all possible diligence & industry
> by your meanes of the [170] & otherwise [secret]ly to hinder the coming ouer of the [181]s from the [726], for it
> is here apprehended that they [will] doe more hurt then good, for that they [are] understood here not to affect
> Monarchy. His Majesty's two letters herewith sent with flying Seales are put into your character, because most
> safe & ready; you are to decifer & interpret them. Monsieur F I R X S S appeares not here. …

Decryption

decoded.txt

Mechanical output of key.py over Tomokiyo's transcription. Capitals = alphabet letters; {word} = word code or sign; · = null; [n] = unresolved.
The clear-text tails of each letter (after 'Wee commit you' / 'His Ma^ys two letters') are printed as transcribed; the digits there are dates, not cipher.

===== charles.txt
Sir , Wee have received {your} C I U · ill N W A L C O
M · {letter} {of} T be* 6_ O F 8_ B E R [1643] . But never
heard of any [514] {letter} {of} Our G O {good} O D · C O {Cousin} U S m.y^w
{Duke} {of} · C U R L and S · {your} M A S {Master} T E R
saue* T H O S E in U I T in G · U {us} S to ·
S end {to} y^w Funerals of the Lave*≪→Late?≫ {two} {Duke} S his F A T hir &
U N K L E · · deceased of happy memory {to} {which} W E
made an · · S W C R · but · · · K now not W H it.
· he R · T he same ar R I U D [289] safe The Difficul
ty of passage in* F E are hash* preiudiced {us} look*. Our {Cousin} {your}
{Master} S A F F E C C O N S & {of} F E R S are
soe R E · all & A C C E P T · able {to} {us} spe
cially in this coniuncture of our Affaires , as w*[with?] A C · · knowledge
{our} {selves} there {by} high L Y · O B L I G E D w* {pray}
you therefore {to} P R E · sent O U R prince L Y · ·
T H an* K S [177] on this behalf {to} {assure} O U R
said {Cousin} {your} {Master} & to lett him {un} D E R stand that w S
H · all most {will} e C O M ly R E C E I U E his
{assistance} w[with?] in {store} {armes} {musket} S · M at C H & {powder} in rebat* w {pro} por
it · S H all P L · · lease* H I M · {to} T R an
S M it the S · am E · {to} {us} {to} y^w {port} {of} W E Y M
O T H · D A R & M O u T H · X ^ E T E R
· F all M O U T H or {Bristol} Not doubting but God
will shortly enable Us to recompence soe · F R E E & soe
{gener} ous A C {our} & E S Y ^w doe as S U R E · Y
( verso )
Our self also of our F A U our particular & doe take your
addres by [213] {to} {us} in very good part , as also that you haue taken
care to avoyde the dangerousnes of the passage hither. And soe
wishing you a safe returne back {to} O U R {good} {Cousin} {your} {Master}
to whom w herewith {send} Y O U R E · * R E D E
N T I A L S
Wee commit you to the Protection of the
Almighty. Given at our court at Oxford the second day of Nobember
in y^w e [N]ineteenth yeare of Our Reigne 1643.
===== nicholas.txt
Sir , {his Majesty} C O M A N D S {to}
S I G n I A Y · H I S pleasure {to}
{your} r T H at Y O U · U S E all
P · S S I B L [b?] E [y?] diligence & industry
B [ ?] Y [of?] y^w[your?] M E A N E S {of} the {Ambassadors} &
other W I S E {secret} L Y {to} H I
N D E R the C O M G O U E R
{of} y^w [181] S · from y^w [726] F O R ·
it I S H E R E · A P P R
E H E N D E D that T he Y
· {will} D O more H U R T · P
he N · G O O D for that T · · he
Y {are} understood H E R E · N O T
{to} A F F E N * T · M O N
A R C Y
His Ma^ys two letters herewith sent with
flying Seales are put into yo^r character, because
most safe & ready, your are to decifer & interpret
them. Monsieur 82 48 52 42 40 64 appeares
not here.
(Page 2)
I must entreat yo^r care over the enclosed in
this & another pacqt going herewith, and having
acknowledged the receipt of yo^rs of the 8th 22/12
& 29/19 of October with many thanks, I must
remit you to the not* for more account upon
them, & ever remains

Key: key.py

08 Sources

S. Tomokiyo, “Charles I–Boswell Cipher (1643)”, blog post of 17 September 2021, and Unsolved Historical Ciphers (cryptiana).
R. Pitt, charles-i-boswell-cipher (GitHub, September 2026).
TNA Discovery, SP 84/157/96–97.
H. F. Morland Simpson (ed.), “Civil War Papers”, Miscellany of the Scottish History Society I (1893), pp. 143–170 (Internet Archive miscellanyofscot01scot).
Calendar of State Papers Domestic 1641–43 (1887), Nicholas to Roe, December 1643.

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