I REF ::CD:A69850 • 

SPSIS-3 · 

7 March 1945 •. 

Cpl. Richard Br1nkvorth, 32689840, 

HQ. and HQ. Sqdn.--6th A.S.A.C., 

APO 959, % PQstmaster,, · · San Francisco,, California. 

Dear Corpora~ Br1nkvorth: 

Receipt ot your letter -ot February 21 1·s acknowledged. I regret to have to inform you that the R1v~rbank publica- tions are not available tor distribution •. Occasionally a. 

copy or two turns up in some second-band book dealer's 

establishment and you might try that source. 

. · It is possible that 7ou may be eligible for enrollment' 1n the Army Extension Courses in.Cryptography conducted by the Chief Signal Officer. A request through channels will find its way to the proper headquarters. 'Thia vould be a means of enabling you to continue your studies. 

Very truly yours,, 

vi111iam·F •. FriedDtan.t 

Director·ot Communications Research.-

I. 

@'pproved for Release by NSA on 04-04-2014 pursuantto E.O. 1352a 
• REF ID:A69850 • 

HEAQ.g,UARTERS & HEADQUARTERS SQUADRON Y.!. AIR SERVICE AREA COMMAND. 

APO 959 % POSTMASTER 

SAN FRANCISCO ,CAL IF. 

FEBRUARY 21ST 1945 

LT. COL. WILLIAM FRIEDMAN 

OFFICE OF THE CHIEF SIGNAL <:IDRPS OFFICER 

WASH l _NGTON,D.C. 

SIR: 

I AM INFORMED BY THE RIVERBANK PUBLICATIONS OF GENEVA,ILLINOIS 

THAT ALL INQUIRIES MADE OF WORKS AUTHORED BY YOU IN CRYPTOGRAPHY 

AND CRYPTOANALYSIS MUST COME FROM YOUR OFFICE. 

SIR, MY NAME IS CORPORAL RICHARD BRINKWORTH,32689840 MOS,805 

ANB FOR THE PAST TWO YEARS I HAVE BEEN.ENGAGED IN CRYPTOGRAPHIC 

WORK FOR THE AAF IN THE PACIFIC OCEAN AREAS··, SERVI NG FOR A T I ME 

TOO, UNDER THE NAVY IN THE MARSHALL ISLANDS. I AM QUITE FAMILIAR 

WITH ALL TYPES OF ARMY AND NAVY CRYPTOGRAPHIC SYSTEMS. EVER 

SINCE MY GRADUATION FROM THE AAF CRYPTOGRAPHY SCHOOL IN PAWLING, 

NEW YORK STATE (FEBRUARY 1943) I HAVE READ MANY BOOKS AND 

PUBLICATIONS ON THIS SUBJECT AND THAT OF CRYPTOANALITICS. IN 

ONE PUBLICATION'S BIBLIOGRAPHY MUCH CREDIT WAS GIVEN TO THE 

FOLLOWING PAPERS AUTHORED BY YOURSELF: 

NR.15-1917-A METHOD OF RECONSTRUCTING THE PRIMARY 

ALPHABET. 

NR.16-1918-METHODS FOR THE SOLUTION OF RUNNING KEV CIPHERS. 

NR.17·1918-AN INTRODUCTION TO METHODS FOR THE SOLUTIONS 

OF CIPHERS. 

NR.18-1918-SYNPOTIC TABLES FOR THE SOLUTION OF CIPHERS AND 

A BIBLIOGRAPHY OF Cl PHER L l.TERATURE. 

NR.19-1918-FORMULAE FOR THE SOLUTION OF GEOMETRICAL TRANSPOStTION CIPHERS BY CAPT LENOX R. LOHR WITH AN IN• 

TRODUCTION BY W.F.FRIEDMAN. 
' 

REF ID: A69850 • 

PAGE TWO 

NR. 20-1918- GENERAL MACHINE CIPHERS AND METHODS- FOR THEIR . SOLUTION. 

NR. 21-1918- METHODS FOR THE RECONSTRUCTION OF PRIMARY ALPHABETS 

NR.22-1922-· THE INDEX OF COi NCI DENCE AND l TS APPLICATIONS 

IN CRYPTOGRAPHIC ANALYSIS 

SINCE THE ABOVE PUBLICATIONS SEEM TO HAUE BEEN AVAILABLE TO THE 

OF THE WORKS I HAVE READ I WOULD LIKE TO KNOW IF THEY COULD BE AVAIL-

- ABLE.TO ME AS WELL AS ANY OTHER WORKS THAT YOU MAY SUGGEST FOR MY - - ~ -- - -

CONTINUED STUDY IN THIS FIELD. NATURALLY I HAVE PASSED ALL THE 

NECESSARY F.B.I. INVESTIGATIONS CONNECTED WITH THIS WORK. TOO, 

I AM QUITE WILLING TO DEFRAY ANY EXPENSES INVOLVED. 

MY SINCERE THANKS, SIR, FOR YOUR KIND CONSIDERATION OF THIS LETTER. 

- SINCERELY YOURS, 

CPL. RICHARD BRINKWORTH,32689~0 

HQ. AND Hq. SQDN.--6TH A.S.A.C. 

APO 959- % POSTMASTER, 

SAN FRANCISCO, CALIFORNIA.