Tool to decrypt / encrypt with 4 squares cipher. The four-square encryption uses 4 5-by-5 grids combined 2 to 2 to extract letters.
Four Square Cipher - dCode
Tag(s) : Polygrammic Cipher
dCode is free and its tools are a valuable help in games, maths, geocaching, puzzles and problems to solve every day!
A suggestion ? a feedback ? a bug ? an idea ? Write to dCode!
Four Square Cipher
Four Squares Decoder
Four Squares Encoder
Answers to Questions (FAQ)
How to encrypt using Four Squares cipher?
The 4-squares encryption is made, as its name suggests, with four square grids (possibly generated from a keyword) themselves positioned in a square:
| Grid 1 | Grid 2 |
| Grid 3 | Grid 4 |
Example: 4 grids formed from the first names JOHN, GEORGE, PAUL and RINGO (the letter Z is omitted)
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
The first step is to split the plain message into pairs of two letters (completed with a neutral letter if necessary).
Example: The plain message BEATLES is decomposed into 'BE, AT, LE, SX'
For each pair (bigram), locate the first letter in grid 1 and the second letter in grid 4. Intersect the rows and columns of the letters found in the two adjacent grids and write down these 2 new letters.
Example: Bigramme BE: B is positioned (row 2, column 1) in grid 1 E is positioned (row 2, column 5) in grid 4
The extension of their rows and Columns in grids 2 and 3 leads to 2 intersections: H, positioned (row 2, column 5) in grid 2 and C, positioned (row 2, column 1) in grid 3
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
The encrypted text consists of the letters found at the intersections: first the letter in the grid 2 and then the letter in the grid 3.
Example: The final encrypted message is HCASMFSX
How to decrypt Four Squares cipher?
4 Squares decryption is almost identical to the encryption. The difference is that it is necessary to position the letters of the encrypted bigram in grids 2 and 3, then read the light letters in grids 1 and 4.
Example: (See above) the bigramme HC is positioned in grids 2 and 3 and deciphers BE in grids 1 and 4.
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
The message HCASMFSX is decrypted BEATLESX
How to recognize a 4 Squares ciphertext?
Four Squares is a polygrammic encryption, so it is advisable to perform an analysis of the bigrams if the text is long enough.
Also, the presence of 4 keywords that can generate the grids is a clue.
Grids with 25 letters, there is normally at least one missing letter from Latin alphabet in the encrypted text.
The company foursquare has a name that can be linked with this cipher.
What are the variants of the 4-Squares cipher?
Source code
dCode retains ownership of the "Four Square Cipher" source code. Except explicit open source licence (indicated Creative Commons / free), the "Four Square Cipher" algorithm, the applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, breaker, translator), or the "Four Square Cipher" functions (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) and all data download, script, or API access for "Four Square Cipher" are not public, same for offline use on PC, mobile, tablet, iPhone or Android app!
Reminder : dCode is free to use.
Cite dCode
The copy-paste of the page "Four Square Cipher" or any of its results, is allowed (even for commercial purposes) as long as you credit dCode!
Exporting results as a .csv or .txt file is free by clicking on the export icon
Cite as source (bibliography):
Four Square Cipher on dCode.fr [online website], retrieved on 2024-12-21,
