Op-20-G-md
(SC)N36-1

MEMORANDUM FOR OP-20:

Subj: Equipment for Decryption of Japanese Strip Cipher.

Encl: (A) DNC Memo to CinC, U.S. Naval Computing Machine Laboratory, Dayton, Ohio, Serial 1423620.
(B) CinC, U. S. Naval Computing Machine Laboratory, Dayton, Ohio, Ltr. to Chief of BuShips, dated 16 January 1945.

1. The Japanese strip system recently introduced makes use of 48 Kana strips. Thirty of these strips are selected from a stock of 100. Certain of the strips are omitted while others are turned over. One interesting variant is the use of a transparent plastic strip board which permits hourly change from obverse to reverse side of the board. Hand methods of deciphering of this system are extremely laborious.

2. A project was initiated on 16 December 1944 to build a machine which would accomplish the complicated process of decipherment directly from a keyboard to a page copy. This equipment involves over 1,000 relays 50,000 soldered connections, stepping switches, controls, etc. Less than 30 days elapsed between the original inception of the project and the completion of the equipment which is now in operation in our Pacific section. Original rough designs were prepared by our research group. The equipment was designed, fabricated, wired, and assembled by naval personnel attached to the U.S. Naval Computing Machine Laboratory, Dayton, Ohio.

3. The personnel most intimately connected with the project put forward tremendous efforts in making the equipment quickly available. It is suggested that enclosure (A) be forwarded as a commendation to the personnel most intimately concerned. Enclosure (B) will be forwarded by the Bureau of Ships for inclusion in the service records of these personnel.

J.N. Wenger
Commander, U.S. Navy