Editing Straddling checkerboard (section)

==History==
In 1555, [[Pope Paul IV]] created the office of Cipher Secretary to the Pontiff. In the late 1580s, this position was held by members of the Argenti family, most notably [[Giovanni Batista]] and his nephew, Matteo. Matteo was the first to intentionally obscure borders between one-digit and two-digit codes, designing the first variable length cipher, although this was still a substitution cipher:<ref name=":0">{{Cite web |title=Variable-Length Symbols in Italian Numerical Ciphers |url=http://cryptiana.web.fc2.com/code/variable.htm |access-date=2024-01-30 |website=cryptiana.web.fc2.com}}</ref>
{| class="wikitable"
|a
|b
|c
|d
|e
|f
|g
|h
|i
|l
|m
|n
|o
|p
|q
|r
|s
|t
|u
|z
|et (&)
|-
|6
|84
|34
|80
|2
|43
|83
|33
|7
|03
|40
|00
|9
|48
|44
|30
|04
|08
|1
|88
|38
|}

With that cipher, ''La vigilanza di papa Clemente fu grande in ogni genere de negotii'' was enciphered as 550365178370360088658074864865534032402000824315833060080257009830075583200230258020028390875.<ref name=":0" />

The following table rearranges the same key so that the column number corresponds to the second digit and while the row correspond to the first digit or lack thereof:
{| class="wikitable"
|-
! &nbsp; || 0 || 1 || 2 || 3 || 4
! 5 || 6 || 7 || 8 || 9
|-
! &nbsp; 
| null|| u || e || colspan="2" | null 
| rowspan="5" | null || a || i || null || o
|-
! 0 
| n || rowspan="4" | null || rowspan="4" | null || l || s|| rowspan="4" | null || rowspan="4" | null || t || rowspan="4" | null
|-
! 3 
| r || h || c|| & 
|-
! 4 
| m || f || q|| p 
|-
! 8 
| d || g || b|| z 
|}

Comparing this table with a lower one, it is evident that it is not the modern straddling checkerboard, and letters encoded with one digit are not the most frequent letters of Latin (T is much more frequent than O<ref>{{Cite web |last=Trost |first=Stefan |title=Alphabet and Character Frequency: Latin (Latina) |url=https://www.sttmedia.com/characterfrequency-latin |access-date=2024-01-30 |website=www.sttmedia.com |language=en}}</ref>), but the idea exploited in the latter ciphers is present.

In its modern form described below the cipher's first documented use was in 1937 by Swedish communist {{Ill|Per Meurling|se}} during the [[Spanish Civil War]].<ref>{{Cite web |title=The straddling checkerboard cipher |url=http://www.crittologia.eu/en/critto/straddle.html |access-date=2024-01-30 |website=www.crittologia.eu}}</ref> It was later used as the basis for the message-to-digits step in the [[VIC cipher]].