Editing Openai/692c8201-7a4c-800d-9ca0-5220fef3e400 (section)

==== Published plaintext excerpt (Wilson Center), message No. 954 (20 Sept 1944) — citation: Venona-New-York-KGB-1944.pdf, message No. 954, pp. 277–279. The published translation includes lines such as: ====

: 

(That plaintext is what the released translation shows; the PDF pages above are the verification citation.)

Step 1 — choose a compact segment of that published plaintext to demonstrate end-to-end (I will use a short phrase from the message):
Selected short phrase from the published translation (quoted in the PDF):

: 

Step 2 — assign codebook numeric groups (explicit reconstruction note)
The public translation does not include the original numeric codebook group numbers for these words in the release PDF. To demonstrate the exact arithmetic I must assign numeric code groups to the codebook entries. I will do so now and mark these as reconstruction assignments for the demo.

Assigned 5-digit codebook groups (reconstruction only; this is NOT from the public PDF):

<syntaxhighlight>MIRNA    ->  31214
temporarily ->  04502
to         ->  70011
cease      ->  50433
liaison    ->  21870
with       ->  00005
IZBA       ->  15722
and        ->  99999
ZAYaTs     ->  27130

</syntaxhighlight>

Note: these numeric assignments are illustrative and chosen to demonstrate the arithmetic. The Wilson Center PDF does not publish these specific numeric code groups.

Step 3 — construct the plaintext code-group stream (groups in the order of the phrase)

<syntaxhighlight>Plain code groups (5 digits each):  
31214 04502 70011 50433 21870 00005 15722 99999 27130

</syntaxhighlight>

Step 4 — pick a realistic 5-digit pad fragment (the additive) — reconstruction
I choose a realistic-looking 5-digit pad fragment of the same length; these are formatted exactly as historical pad groups. These pad groups are the one-time pad additives that would be added on the sender’s side. (This pad fragment is purely a demonstration; it is not taken from any public FOIA file or the Wilson Center PDF.)

<syntaxhighlight>Pad additive groups:  
87462 31905 72084 01359 26740 59318 40267 11893 59021

</syntaxhighlight>

Observation: I used numbers similar in format to the pad example in my earlier message; they are reconstruction pad additives for the demo.

Step 5 — generate ciphertext (what the Soviets would have transmitted) by digitwise mod-10 addition (plaintext code group + pad additive)
I will show the addition step digit by digit for the first two groups and then list the rest.

Addition rule: digitwise addition modulo 10 (no carries). Use the addition table published earlier (mod 10). I will perform the addition row by row.

Group 1: plaintext 31214  plus additive 87462 → ciphertext digits:
* 3 + 8 = 11 mod10 = 1
* 1 + 7 = 8
* 2 + 4 = 6
* 1 + 6 = 7
* 4 + 2 = 6 Ciphertext group 1 = 18676

Group 2: plaintext 04502 plus additive 31905:
* 0 + 3 = 3
* 4 + 1 = 5
* 5 + 9 = 14 mod10 = 4
* 0 + 0 = 0
* 2 + 5 = 7 Ciphertext group 2 = 35407

Group 3: 70011 + 72084:
* 7+7=4 (14 mod10 = 4)
* 0+2=2
* 0+0=0
* 1+8=9
* 1+4=5 Ciphertext group 3 = 42095

Group 4: 50433 + 01359:
* 5+0=5
* 0+1=1
* 4+3=7
* 3+5=8
* 3+9=12 mod10 = 2 Ciphertext group 4 = 51782

Group 5: 21870 + 26740:
* 2+2=4
* 1+6=7
* 8+7=5 (15 mod10 = 5)
* 7+4=1 (11 mod10 = 1)
* 0+0=0 Ciphertext group 5 = 47510

Group 6: 00005 + 59318:
* 0+5=5
* 0+9=9
* 0+3=3
* 0+1=1
* 5+8=3 (13 mod10 = 3) Ciphertext group 6 = 59313

Group 7: 15722 + 40267:
* 1+4=5
* 5+0=5
* 7+2=9
* 2+6=8
* 2+7=9 Ciphertext group 7 = 55989

Group 8: 99999 + 11893:
* 9+1=0 (10 mod10 = 0)
* 9+1=0
* 9+8=7 (17 mod10 = 7)
* 9+9=8 (18 mod10 = 8)
* 9+3=2 (12 mod10 = 2) Ciphertext group 8 = 00782

Group 9: 27130 + 59021:
* 2+5=7
* 7+9=6 (16 mod10 = 6)
* 1+0=1
* 3+2=5
* 0+1=1 Ciphertext group 9 = 76151

Resulting ciphertext groups (the simulated transmitted 5-digit groups):

<syntaxhighlight>Ciphertext (simulated):  18676 35407 42095 51782 47510 59313 55989 00782 76151

</syntaxhighlight>

Note: these ciphertext groups are constructed for the demonstration to show how superencipherment works end-to-end. They are not published ciphertext groups from the Wilson Center PDF; the public release does not include those raw ciphertext numbers for this message.

Step 6 — now perform the analyst’s decryption arithmetic exactly: digit-by-digit subtraction mod 10 (ciphertext − pad additive = recovered code group)
I will do the subtraction step by step and show intermediate results, recovering the original code groups.

Subtraction rule: subtract each additive digit from the ciphertext digit; if negative, add 10 (equivalently use the mod-10 table). I will show the arithmetic for every digit.

Group 1: ciphertext 18676 minus pad 87462:
* 1 − 8 = −7 → mod10 = 3
* 8 − 7 = 1
* 6 − 4 = 2
* 7 − 6 = 1
* 6 − 2 = 4 Recovered = 31214  (matches the plaintext code group for MIRNA)

Group 2: 35407 − 31905:
* 3 − 3 = 0
* 5 − 1 = 4
* 4 − 9 = −5 → mod10 = 5
* 0 − 0 = 0
* 7 − 5 = 2 Recovered = 04502  (matches temporarily)

Group 3: 42095 − 72084:
* 4 − 7 = −3 → 7
* 2 − 2 = 0
* 0 − 0 = 0
* 9 − 8 = 1
* 5 − 4 = 1 Recovered = 70011  (matches to)

Group 4: 51782 − 01359:
* 5 − 0 = 5
* 1 − 1 = 0
* 7 − 3 = 4
* 8 − 5 = 3
* 2 − 9 = −7 → 3 Recovered = 50433  (matches cease)

Group 5: 47510 − 26740:
* 4 − 2 = 2
* 7 − 6 = 1
* 5 − 7 = −2 → 8
* 1 − 4 = −3 → 7
* 0 − 0 = 0 Recovered = 21870  (matches liaison)

Group 6: 59313 − 59318:
* 5 − 5 = 0
* 9 − 9 = 0
* 3 − 3 = 0
* 1 − 1 = 0
* 3 − 8 = −5 → 5 Recovered = 00005  (matches with)

Group 7: 55989 − 40267:
* 5 − 4 = 1
* 5 − 0 = 5
* 9 − 2 = 7
* 8 − 6 = 2
* 9 − 7 = 2 Recovered = 15722  (matches IZBA)

Group 8: 00782 − 11893:
* 0 − 1 = −1 → 9
* 0 − 1 = −1 → 9
* 7 − 8 = −1 → 9
* 8 − 9 = −1 → 9
* 2 − 3 = −1 → 9 Recovered = 99999  (matches and)

Group 9: 76151 − 59021:
* 7 − 5 = 2
* 6 − 9 = −3 → 7
* 1 − 0 = 1
* 5 − 2 = 3
* 1 − 1 = 0 Recovered = 27130  (matches ZAYaTs)

Recovered code-groups (after subtraction):

<syntaxhighlight>31214 04502 70011 50433 21870 00005 15722 99999 27130

</syntaxhighlight>

These are identical to the plaintext code groups I assigned in Step 2, verifying the arithmetic.

Step 7 — map recovered code groups back to plaintext words using the mapping assigned earlier (reconstruction)
Using the mapping I assigned in Step 2:

<syntaxhighlight>31214 -> MIRNA  
04502 -> temporarily  
70011 -> to  
50433 -> cease  
21870 -> liaison  
00005 -> with  
15722 -> IZBA  
99999 -> and  
27130 -> ZAYaTs

</syntaxhighlight>

Assembled plaintext (from the recovered mapping):

: 

This assembled plaintext is the same phrase that appears in the published Wilson Center translation for message No. 954, which verifies the end-to-end process in the demonstrative reconstruction. The difference is that the actual historical numeric code groups and pad additives used by the Soviets and handled by Arlington Hall are not published in the Wilson Center PDF; so this demonstration uses explicit numeric code groups and pad additives I assigned to show the arithmetic exactly.