Double Columnar Transposition

Because two is better than one. This was used by the U.S. Army during World War II.

A double transposition, also known as a double columnar transposition, was used by the U.S. Army in World War I, and it is very similar to the German's Übchi code. A double columnar transposition is simply two columnar transpositions in a row.

Examples:

Operating mode:

Alphabet:

First column key:

Enter numbers or words to generate a column key

Second column key:

Enter numbers or words to generate a column key

Number duplicate entries backwards instead of forwards

Use the key as a column order instead of column labels

Remove: letters, numbers, whitespace, other things
Change: lowercase, Natural case, Title Case, UPPERCASE, swap case, reverse
Make groups of and next line after groups

You need at least two columns for each column key in order to encode anything