To decrypt a double transposition, construct a block with the right number of rows under the keyword, blocking off the short columns. Write the cipher in by columns, and read it out by rows.

Place the Cipher Code Ring over the Decoder Ring and attach at the center with a paper brad. Note that a number is visible through the window marked INDEX.

Unlike any other numerical challenge you've seen before, Cipher Monk invites you to think differently — to decode, rotate, and arrange mysterious ancient symbols that represent numbers from 1 to ...

Here’s how it worked, as explained by John Earl Haynes and Harvey Klehr in their book Venona: Decoding ... to a cipher clerk, who uses a code book to convert the words to four-digit numbers ...