In 1944 a Nazi spy located in New York sent encrypted messages via Paris to Germany. These cryptograms have never been deciphered.
David Kahn (born 1930), the founder of crypto history research, is mainly known for his excellent book The Codebreakers. This 1,200 pages masterpiece, first published in 1967, marked the start of the cryptology revolution that has taken place in the last 50 years and that has brought us DES, RSA, AES and many other great developments.
Even today, The Codebreakers is still the most comprehensive crypto history source. My own book Codeknacker gegen Codeknacker has a similar scope and is sometimes compared with David’s classic (which is an honor for me, of course).
Sadly, David has now serious health problems. Since 2015, he is not active in the research community any more. The last time I met him was at the Charlotte Internation Crypto Symposium in 2014. Click here for two interviews with David Kahn (one in German, one in English).
David Kahn is not only an expert in crypto history but also in intelligence history. In 2000 he published his book Hitler’s Spies, which tells the story of the “Abwehr” and other German secret services in the Third Reich. David’s original impression was that Hitler had operated a sophisticated spy network working professionally and employing skilled people. However, during research for Hitler’s Spies, David more and more realized that intelligence work under Hitler was quite amateurish and poorly organized. Apart from the Abwehr, several other secret services were involved in espionage. The existence of several competing organisations, which didn’t cooperate, considerably weakened the German intelligence efforts. All in all, Hitler’s spies were not very successful. All this is described in Hitler’s Spies in great detail.
As David reports in his book, the Abwehr recruited a spy code-named “Köhler” in New York City. According to Hitler’s Spies, not much is known about this person. However, blog reader Max Baertl pointed out that Köhler might be identical with Nazi spy Walter Koehler, who is described in an online article published in 2016. As it seems, David was not aware of this Walter Koehler, when he wrote his book.
Are Köhler and Walter Koehler really the same person? Maybe a reader knows more.
The Köhler cryptograms
Already in 1981, David Kahn published five encrypted messages written by Köhler. Apparently, Köhler sent these messages to his contact person at the Abwehr in February 1944. These exciting crypto-puzzles have never been much appreciated in the literature. My blog post from 2013 (in German) seems to be the only publication in the last 30 years that even mentions these cryptograms. Their solution is still unknown.
David’s publication is not based on Köhler’s original messages, but on a letter quoting these kept by the British National Archive. Here it is (the numbers are indicate the length of the respective message):
Ybtat mqfvo dvbis prito kecqg kokik kyiwm zuarj
alyia qtxvi vxzya szgou skiqn rbqjq mogex ezdnf
vusda zurop ixklo cmnbl grdhz swmch kupef pzlej
hbord wkkhu vthjk sfwda jepmu izvig kzlau rdrxx
mdecs spozv eeeod dlmdz nqmia pidwg xdcyy mvkso
hmmii impwq nkipa mljvm sqsbb glevn sktlq tn.
Eekao parwo xiavy pejux lhnjh pbqdd vdvxb mdiia
gwwmn zbivm abuws dwoug djozl ylaug loaea ilihj
swjft oetad tjisn avaqn sodwb wzaxe zvoxg xpgzv
adurm shvxx xfmuq pdpvq dqwtu fryok xfvcp ydzwm
ofwfl uzfne qsslo evl.
tziqb lqqxs kinod mbvil sukms syarh mhzvp tvswm
ayddg rixyy omfzm ugfzz aznqe ljuyi ygwuo qmdbi
vcxgz rmzno pessh gpoyx qqlei xmaoj buugz czfdl
yzmkp gsmfm dteze oxmos.
dmxkb kqnvh zzeek beoop ygcca yvepv tykmt iykfl zkacv
uxiyd kruwy vnjvp xyeqp jpmfo abzpt mjtdy zvzky bjgze
vdtyd zeejw zumjp ivsna gsmzq dltxb qjqqj fnpta mqted
fpoxa tijyp qrerq znqst zasnk zarvq hhsmw vlhfg pyhqc
yuirf fsgoi twgdg sbphc fkfza bpegh jzujn wtsxp ijamg
tzdto hxzdn uivww tizoc axkye lhmdn sfzjo omrhb zpith
hklsf anvdr ynhqk syrgi ltxos wabom dzwlb byava sjomn
qqszs adddu greao alhon lxzgi iwpnf uzgui jgmya ksqfw
After my first blog article about these cryptograms in 2013 I received many comments. Some readers pointed out that it was not necessarily Köhler himself, who encrypted these messages. Instead, it might have been the sender of the letter. If so, the Abwehr Enigma might have been used for encryption. Maybe an Enigma expert can tell, whether these messages are consistent with an Enigma encryption.
If Köhler himself was the encipherer, it is unlikely that he used an Enigma (an Enigma would have been too expensive and too conspicious). Of course, the One Time Pad is an option (which is bad news, as the One Time Pad is unbeakable of used properly), but I have never heard of a German WW2 spy using this method. Instead, most Nazi spies used manual ciphers. This means that there is a good chance to break the Köhler cryptograms with modern means.