Kl-7

KL-7

The TSEC/KL-7, code named ADONIS and POLLUX, was an off-line non-reciprocal rotor encryption machine. The KL-7 had eight rotors to encrypt the text, seven of which moved in a complex pattern, controlled by notched rings. The non-moving rotor was in fourth from the left of the stack. The encrypted or decrypted output of the machine was printed on a small paper ribbon. It was the first cipher machine to use the re-entry (re-flexing) principle, discovered by Albert W. Small, which re-introduces the encryption output back into the encryption process to re-encipher it again.