Editing Classical cipher (section)

===Transposition ciphers===
{{Main article|Transposition cipher}}

In a transposition cipher, the letters themselves are kept unchanged, but their order within the message is scrambled according to some well-defined scheme. Many transposition ciphers are done according to a geometric design. A simple (and once again easy to crack) encryption would be to write every word backwards. For example, "Hello my name is Alice." would now be "olleH ym eman si ecilA." A [[scytale]] is a machine that aids in the transposition of methods.

In a columnar cipher, the original message is arranged in a rectangle, from left to right and top to bottom. Next, a key is chosen and used to assign a number to each column in the rectangle to determine the order of rearrangement. The number corresponding to the letters in the key is determined by their place in the alphabet, i.e. A is 1, B is 2, C is 3, etc. For example, if the key word is CAT and the message is THE SKY IS BLUE, the message would be arranged thus:

                          C A T
                          3 1 20
                          T H E
                          S K Y
                          I S B
                          L U E

Next, the letters are taken in numerical order and that is how the message is transposed. The column under A is taken first, then the column under C, then the column under T, as a result the message "The sky is blue" has become: HKSUTSILEYBE

In the Chinese cipher's method of transposing, the letters of the message are written from right to left, down and up columns to scramble the letters. Then, starting in the first row, the letters are taken in order to get the new [[ciphertext]]. For example, if the message needed to be enciphered was THE DOG RAN FAR, the Chinese cipher would look like this:

                            R R G T
                            A A O H
                            F N D E

The cipher text then reads: RRGT AAOH FNDE

Many transposition ciphers are similar to these two examples, usually involving rearranging the letters into rows or columns and then taking them in a systematic way to transpose the letters. Other examples include the Vertical Parallel and the Double Transposition Cipher.

More complex [[algorithm]]s can be formed by mixing substitution and transposition in a [[product cipher]]; modern [[block cipher]]s such as [[Data Encryption Standard|DES]] iterate through several stages of substitution and transposition.