Ciphers
Columnar transposition
Also found as keyed columnar · incomplete columnar · columnar transposition cipher
How it works
The number of Key entries gives the grid width. Write the text across rows, then read the columns from the lowest Key rank to the highest. Decipher stores one unique rank for each physical column. If a keyword contains repeated letters, rank equal letters from left to right.Friedman, Codes and CiphersACA Incomplete Columnar
- Input
UNFILLEDBLOCK- Rows
UNF / ILL / EDB / LOC / K- Read ranks
column 2, then 3, then 1- Ciphertext
NLDOFLBCUIELK
Incomplete final rows
No padding is added. When the last row is short, the leftmost physical columns have one extra character. To decrypt, work out which ciphertext segments fill the long and short columns, put them back, then read across the rows.ACA Incomplete Columnar
What to look for
The letter counts stay unchanged, so the frequencies can look normal even when words and common letter pairs are broken. Test likely widths, column lengths, orders, reversals, and read directions as explicit grid arrangements. Judge each guess by the adjacencies it restores.Military Cryptanalysis, Part IVGaines, Cryptanalysis
How Decipher handles it
Decipher removes whitespace before transposition. Everything else, including punctuation, digits, emoji, and accented letters, is moved as a user-perceived character. Spaces added when displaying the ciphertext are not part of the Key.