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AMSCO Cipher

Tool to decrypt/encrypt AMSCO automatically. AMSCO is a transposition ciphering algorithm created by A.M.Scott which uses column transpositions.

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AMSCO Cipher -

Tag(s) : Transposition Cipher

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AMSCO Cipher

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AMSCO Decoder




Letters cut sequence (alternated)





Column permutation key

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AMSCO Encoder



Letters cut sequence (alternated)




Column permutation key

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Answers to Questions (FAQ)

What is AMSCO cipher? (Definition)

AMSCO is a (incomplete) columnar transposition cipher performing a permutation of an alternation of bigrams and unigrams of the plaintext.

How to encrypt using AMSCO cipher?

AMSCO Encryption consists in writing a text in a grid according to a cutting sequence then use a permutation key to switch columns.

Example: Encrypt the message DCODEAMSCO, with a cutting sequence 1,2 (alternation of 1 letter then 2 letters in the grid, both in rows and in columns)

Select a permutation key (of length L), and write the message in lines, cut over L columns.

Example: If the key is KEY (equivalent to 2,1,3) of length 3, then write the message over 3 columns:

\123
DCOD
EAMSC
O

Read the grid in columns, in the order of the key (this reading serves as permutation).

Example: Column 2 (COM) then 1 (DEAO), and the 3 (DSC). The message is COMDEAODSC.

How to decrypt AMSCO cipher?

AMSCO decryption requires knowledge of the permutation key (of length L) and the cutting sequence (usually 1,2 or 2,1).

Example: Decrypt the message COMDEAODSC (of 10-characters length) with the key KEY (equivalent to the permutation 2,1,3) of length 3, and cutting sequence 1.2.

Create a table with L columns, in which the number of characters are noted in each cell (in respect to the cutting sequence and limited by the length of the message).

Example: 1,2 for 10 characters corresponds to (1+2+1+2+1+2+1+0+0 = 10) :

\123
121
212
100

Write the message in the table in columns following the order of the columns indicated by the key.

Example: Write CO, then M in column 2, then D,EA,O in column 1, then D, DC in column 3. This leads to the grid:

\123
DCOD
EAMSC
O

The plain message is transcribed by reading the table in lines.

Example: Reading each lines gives the original plain text is DCODEAMSCO.

How to correctly split the text into the grid?

The text must alternate sizes of cuts (even if the key size is even) which then should form diagonal sets:

Example: A grid of width 3, cut by (1,2):

\123
121
212
121

Example: A grid of width 3, cut by (2,1):

\123
212
121
212

Example: A grid of width 4, cut by (1,2):

\1234
1212
2121
1212

Example: A grid of width 3, cut by (3,2,1):

\123
321
213
132

No need to fill the grid with null letters if a cell is empty or incomplete.

How to recognize AMSCO ciphertext?

The ciphered message is subjected to a single transposition, so it has an index of coincidence similar to the one of the plain text.

How to decipher AMSCO without a key?

It is possible to try to infer the key length by analyzing bigrams obtained after writing in columns.

What are the variants of the AMSCO cipher?

AMSCO is a variant of the classical transposition cipher. It adds the cut sequence that can be more complex than the usual 1,2.

When was AMSCO invented?

AMSCO dates from the 19th and bear the initials of its author A. M. Scott

Source code

dCode retains ownership of the online "AMSCO Cipher" source code. Except explicit open source licence (indicated CC / Creative Commons / free), the "AMSCO Cipher" algorithm, the applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or the "AMSCO 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, copy-paste, or API access for "AMSCO Cipher" are not public, same for offline use on PC, tablet, iPhone or Android ! Remainder : dCode is free to use.

Need Help ?

Please, check our dCode Discord community for help requests!
NB: for encrypted messages, test our automatic cipher identifier!

Questions / Comments

Thanks to your feedback and relevant comments, dCode has developed the best 'AMSCO Cipher' tool, so feel free to write! Thank you!


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