FILE NO. 

.DISPOSITION· FORM TOP SECRET 

SUBJECT Lecture to be given to the ASA School at 

Carlisle. Pa •• on.Thursday. 22 June 1950 

TO FROM DATE COMMENT NO. 1 

c 

AFSA-14 AFSA-02A2 19 June 1950 

THRU: AFSA-02 F. B. Rowlett/.B,3/jmw 

0 

p 

y 

1. I propose to divide the two-hour lecture period into two 

parts as follows: 

1 Pa.rt I: (approximate tim.e--40 min.) 

Subject: Funct~ons of a modern COMINT organization with 

emphasis on cryptanalysis. 

Part II: (approximate time--1 hour) 

Subject: An actual e~ple or advanced cryptanal.ysis--The 

Japanese diplomatic cipher.machines. 

The remaining twenty minutes will be devoted to a break and question 

periods. 

2. An outline of the first part of the proposed lecture is 

appended hereto as Tab A. The classification of the subject matter 

is at most Sl!X::RET, and will depend upon the examples cited. A series 

of thirteen charts form the basis for this lecture, and they are 

explained by a running discussion. The discussion is from memory-. 

3a. The second part of the lecture deals with the historical 

cryptanalytic aspects of the Japanese Red and Purple machines up 

to the time of Pearl Harbor. No reference will be made to the post 

Pealtl. Harbor use of the Purple machine. 

b. I propose to undertake a general discussion of the actual 

cryptanalytic principles involved in the solution of these machines 

and will present either photographs or original copies of work sheets 

as appropriate. I shall disclose the cryptographic principles of the . machines and indicate the cryptanalytic attack which was actuallY' · · successful on each machine. 

c • The discussion will be from memory and I will use a blackboard to supplement the photographs and work sheets in explaining 

the ~ryptologic principles involved. 

d. An outline of Part II of the lecture is appended as Tab B. 

The material to be presented was classified secret in 1941. 

'· 

/s/ Frank B. Rowiett 

FRANK B. ROWLETT 

Technical Director @ttiR~ Qf. Operations 

. . ....;;. 

COPY 

NM E ~~1:'s;Jjifd and approved for release by NSA on 11-08-2013 pursuant to E .o. 13s2a""C11 
•' 

COPY 

Part I 

REF ID:A66748 

TAB 11A" 

OUTLINE 

A. The basic missions of AFSA are: 

l. Communication Intelligence 

2. Communication Security 

3. Communication Research and Development 

B. Definition ot Intelligence Mission of AFSA 

c. Statement of primary objectives of Communication 

Intelligence 

D. Intelligence Requirements 

1. Definition 

2. Consumers 

a. CIA 

b. ONI 

c. State Department 

d. Air Force Intelligence Division 

e. Army Intelligence Di vision 

t. Federal Bureau of Investigation 

3. Type 

a. Long range 

b. Current {monthly) 

c. Spot 

E. Intercept (touched on only in reference to cryptanalysis. 
COPY 

2 

F. Processing 

G. 

l. Traffic Analysis 

a. Objective of Traffic Analysis 

b. Elements or Traffic Analysis 

2. Cryptanalysis 

a. Objectives of cryptanalysis 

1. Determine strength and weakness of Cryptographic systems 

2. Effective exploitation and solution of 

foreign cryptographic systems 

3. Development of security precautions for 

U. S. systems 

4. Production of conununication intelligence 

b. Elements of cryptanalysis 

1. Diagnosis of internals 

2. Techniques of attack 

J. Key recovery 

_4. Production 

3. Translation 

a. Code recovery 

b. Analysis and reporting of plain text 

a. Translation of messages 

4. Ancillary Services 

a. Photographic laboratory 

b. IBM-RAM 

c. Collateral information 

Summary and Questions 
REF ID:A66748 

SUBJECT: Outline or lecture on advanced problem cryptanalysis using the Japanese Diploma.tic Communications as an example. 

Part II A 

1. Iritroductory Remarks 

2. Red Machine 

a. First appearance of Japanese cipher traffic 

noted in 1923. 

b. Discussion of external characteristics or 

messages. 

3. First serious effort of solution in October 1936 

established the following: 

a. Text definitely cipher 

b. Repi ti tions 

c. Change, nature unidentified, took place on 

1st, 11th, and 21st of each month. 

d. The basic keying element produced cycle which 

apparently was greater than the length of the longest \ 

message. 

4. First message read. 

a. Message of December 21, 1933 of approximately 

2,000 characters. 

b. Basic Vowel relation 

c. ~alysis of December 1-10 traffic 1936. 

d. Determination of the "skips." 

c 0 p y $f (l}JfPJf i 
---------------------· 

2 

l 

e. Recovery of sequence 

Part II B 

1. . Purple Ma.chine 

2. New machine mentioned in Japanese traffic. 

a. Effective date. 

b. Fi;rst m~ssage received. 

3. Preliminary examination. 

a. "Six 1 s" and "Twenty's" 

b. Recovery of 11Six1s 11 

c. Nature of substitution 

4. Attack on the 11'1\venty's" 

a. Partial decipherment of all traffic. 

b. Difficulties encountered 

5. Absence of Repetition 

a. Non-repetitive phenomena 

·b. Tentative conclusions 

6. Recovery of "TWenty's" 

a. Discussion of homologs 

b. Reduction of 2 messages to the same base. 

c. Discovery of symme~ric sequences 

d. First translations 

7. Completion of solution 

a. Indicator study. 

b. Discussion of the machine 

S. Special concluding remarks. 

COPY $~lrnE 
REF ID:A66748 

~[~fR?ElF 3 

a. Interesting examples. 

b. Cryptanalytic estimate or the problem. 
REF ID:A66748 

$~@Iffi~T 

LIST OF PHOTOGRAPHS TO BE SHOWN IN 

CONNECTION ~IITH PART II 

1. Clipping from Washington Post, 8 December 1941 

"Japanese emissaries set fire to papers in Embassy 

grounds." 

2. Clipping Washington Daily Mews, 10 December 1941 1

'llni.a.t was in Jap 1 s Trunks?" 

3. Japanese Red Ma.chine Commutator Photograph of 

actual parts of original Japanese machine. 

4. Second view of Japanese Red Machine Commutator 

(see 3 above) 

5. Third view of Japanese Red Machine Commutator 

(see 3 above) 

6. American built analog of Japanese Red Machine, 

view 1 

7. View 2 of 6 above 

8. View 3 of 6 above 

9. Selector switch (Six's) from original Japanese 

Purple Ma.chine (Picked up in Berlin) 

10. Selector seitch (Twenty's) from original Japanese Purple Machine (Berlin) 

11. Another view of switch (Twenty's) shown in 9 

above. 

12. Photograph of·Plugboard of original Purple machine. 

13. · View' of selector switch from original Purple 

machine showing wiring and index mechanism. 

14. Another view of Switches of 11 above 

I 15. American built Analog of Japanese Purple Machine 

{view 1) 

16. View 2 of 15 above. 

17. View 3 of 15 above showing details of' cryptograph 
COPY 

REF ID:A66748 

$~lm-1 2 

18. View 4 of 15 above showing wiring of selectors 

19. View 5 of 15 above showing detail or Six Is and 

Twenty's~