10 Incomplete columnar transposition ciphers

Having covered complete columnar transposition ciphers in the previous chapter, we now devote our attention to the more general case: columnar transposition with incompletely filled-in rectangles, also known as incomplete columnar transposition. This method works in almost the same way as the one introduced in Chapter 9, the only exception being that the line length is not a divisor of the message length.

How an incomplete columnar transposition cipher works

To explain how an incomplete columnar transposition cipher works, let’s start with the following plaintext, which is an original message encrypted ...

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