7 Transposition
This chapter covers
- Route and columnar transposition
- Random number transposition
- Key transposition
- Multiple anagramming
In chapters 5 and 6 we looked at substitution ciphers. The second major category of Secret Key encryption methods is transposition. Transposition means changing the order of elements in the message. These elements may be words, syllables, letters or the individual digits or bits that represent the letters. In this chapter we will deal primarily with letter transposition, but keep in mind you can use the same methods for other elements, such as the word transposition in section 7.2.2. This chapter will cover many different types of transposition ciphers. You can do most of these transposition ciphers using only pencil and paper.
7.1 Route Transposition
Route transposition is the simplest, and oldest, form of transposition cipher. There is no key involved. The secrecy comes from the choice of routes or paths.
Route transposition is a great way to get children interested in cryptography. It makes a great activity for classrooms, scout troops or other clubs. The main caveat is that the children must write the letters uniformly in straight columns, otherwise the message gets garbled. This can be avoided by using graph paper with wide spacing.