The key in a rotation cipher is composed of the block size and the rotation angle. It can be rotated to the left or to the right by 90°, 180° or 270°. If the text "KURZERTEXT" should be encoded and we have a block size of 5, then the text is assigned to blocks like this:
The box is read out line by line. Each different pattern of rotation will yield a different text as result:
Security is dependent on the block size, a very small block size is more difficult to decode than a large one. The number of possible keys however is very small, especially for short texts.