a simple cypher scheme

[Perry E. Metzger]

stuart johnson writes:
> a co-worker here has
> come up with a 'cypher' scheme that he would like to use to send code to our
> clients.  the scheme is this : he would take the file of code and pad all
> lines to the length of the longest line, he would then preform column swaps,
> and then row swaps, to 'mix up' the file. the person receiving the file
> would then preform the opposite functions to recover the file.  it seems so
> simple that it can't be good. i've convenced him to use pgp, but i would
> like some input if possible on why his cypher scheme is not a good one.

This is a variant on a scheme called a transposition cipher. It was
okay, but not very good, technology in the Civil War, when it was last
seriously used. It can be broken with a technique called multiple
anagramming.

Perry