The Spartan scytale

The scytale is one of the oldest known ciphers. A strip of leather was wound around a rod and the message written along the rod. Unwound, the letters looked scrambled; only someone with a rod of the same thickness could read it. It is a simple transposition: the letters stay the same but change places.

The key is how many letters fit around the rod. Leave "Try all rod sizes" on and CacheCrack decodes with every size and puts the most English-looking result first.

Example

IRYYATBHMVAEHEDLURLP with 4 letters around the rod decodes to IAMHURTVERYBADLYHELP.