In the event of loss of capture of machines or code books, a reserve hand cipher was used, possibly Doppelkastenschlüssel. We found evidence of this from the batch of original messages from 1941 on the eastern front. Some message forms were a different cipher, possibly Doppelkastenschlüssel, unlike the Enigma we were not able to break these by computer. They were very short. Rejewski, who worked on this cipher while in England, said a minimu of 1000 characters on the same key was needed for a comfortable break.