Crypto history expert Frode Weierud has found a number of encrypted messages in an archive. Can we help him to decipher these cryptograms?
I’m sure, many readers of Klausis Krypto Kolumne know Frode Weierud. Frode, a retired software developer from Norway, has been involved with cryptology for about 50 years. As a leading Enigma expert, he is mentioned in several books I have written (especially in Nicht zu knacken) and on this blog. Among other things, Frode has deciphered hundreds of Enigma messages from WW2. His home page is: https://cryptocellar.org.
Three unsolved consular messages
Currently, Frode is involved in some research on a number of cryptograms dating from 1938 to 1941. Unfortunately, he is unable to give any further information about the origin and specifics of these messages apart from saying that they are Japanese consular messages sent to and from the Foreign Office in Tokyo.
Frode has provided me three of these cryptograms for publication. The first message is dated January 29, 1940:
BBBTT YIXBA YIVYL OXUAB ARPBO UJTNU ASZAF UKURL YORAY MAXAD EWDKY IBEKY WITOS WIYVU MAMAN REKTI ASTCA EUKIM IVYDE UCHRE CEXLO HUNAL OXUAB ARXPU WIFOH IGAEB
The second message is dated December 23, 1939:
JAPANESE ETC BBBTT GASAN AVKOY GATVI RUNUV PYECS GARWY ADFAK ITDEX MAXAD YORAY TOVSE ATUMK IDEUW DEAGS OULYR FUWME URGBE FVSGE DEAGS
Message #3 (December 17, 1940) is:
BBBTT GEAYU EETRA UKURL AWYCZ SOGLA FUWME BYZAK NYWHI EWAYO FOIWA MUIJU DEAHT FUWME BYZAK URHAC URTWE FUWME AIRKA NYAYI DYRAP ABFYS FUWME EIYEV AWYCZ SOGLA FUWME AZSYE EHXOG KISUZ UKROL IBCAD FOISF BETVE UKURL GAXUP URGEH YORAY ARORG GAYOV COWDY KAWLE TAIFD CIZIN NEMNE ERUUL NOVZE IOSPO TAASY TAIFD NYWHI OEWFY GEAYU UJTNU IVYDE RHUYS YIAVE IBRYZ KUYAX SJYUL ITYOM IBAHZ CRIPI SYYEX IHALD POFFU HAJWU STOWU SIMAP UGZED GUNVI HGNHI CIZIN EWIHP IPDFU SEYGO ITDEX HERYD ODYLB EGNHI OTOYN ROAHW CITFE ABIGY TUXFU IBOWA UJTNU EHAOD BYBDU MAXAD AIRKA RHOKN IBAPT KULGE CEXLO EWIHP DYFLA BUYHB CYJAZ MAXAD UARKY HIPYJ ELUWU MUJRO NOENV THODO URGBE ASLAC ABWOF AIRKA JYZYM TAISP IXVLE EBMBE TRIGI NIYWR YORAY GEWBO ABKAD MAXAD IDRET IBAHZ UAKOV JYZYM CUFMY FOFUK OFGEN URHAC GYODS IBBOR JUSOS UNWYT OYCXE ROUYA OPYFT MAXAD TAISP UHUXO FEDYS UHTWO OFHYH IFSRI MAXAD EIGLI RHUSM GYJWE DEAGS OASPU OLKYW LYDAV FAWXU IYXGY AWYCZ AIRKA NOBYK DUNVY SLORI ITDEX ETZGI HADGI EKXEL UKPUH HAEHI MAXAD EGPOM ----- UGSUM BYOOJ JYZYM CUGUP MOODD UKPUH SIDFE UGLVI JUSOS UOJIR CHITO NICXO ULFTE OVCYC HADGI IVOFD EGTWE EGNHI CEWAR SVINT GHUNG NEUWR MYILN UHNAL ERKWY UHPDA FYIKT OYCXE OEWFY YPZUX SYLIC CUWDY AMZYW AIRKA TEVLA ----- EGNHI FOHZA EKBLI DEAHT ABVUZ NEMNE AMZYW EISOZ KUPKE IDBEK KIULN ITIOD TEVLA SHISY omful QUAME KGYML MGNQL PRLBZ MHJTG PRLCY MHJBN MHINN PRLSH MHJTG PRLTG MHJHT PRLYB MHITT PRUOD prpjk MHIZZ PRYAK MHJBN PRYOZ MHIXX PSAXU MHIVV MHIPP PSURU MHINN PSUXA MHIJK PSYDO MHIFG PSYKI PSYVW MHHZN PSYZY MHIDE PTAAK MHHRS PTALI MHHXY MHHJL PTATE MHHGE PTAYW MHGWY PTEKE MHGSU PTIBE POFAB MHKFG POFAC MHJDP POFAE MHJBN POFAG MHHLA MHFUX POFAZ MHHZN POGOE MHHTU NZNNZ PRUOD PTIBE BEPST POFAM CRKHZ MRHIH NQNYO LERCR ASMNR NROQT GVEXJ HXCWX AZHIB AIFQH NROQT GMEZC MRHIH GPEMR LLFMI NROQT LCSON DNCIQ GHVAT LLHNT Japanese Consul
According to Frode, there are other diplomatic messages of a similar kind, but these three cryptograms stand out as something apart from the rest, as they all carry the BBBTT starting group. Frode expects to get access to a much larger collection of these messages in the near future.
A commercial codebook?
The encryption used here is probably based on a codebook that assigns a five letter group to every frequent word of a certain language. It is known that the Japanese used dozens of codebook-based encryption methods during World War II, for example the JN-25 code.
Frode’s hunch is that in this case either a private code or a commercial codebook was used. Of course, it is an interesting question, in which language the cleartext is written. It might be Japanese, as the messages come from Tokyo. However, the last line of the third message suggests that English is an option, too.
Frode suspects that the three cryptograms he provided represent so-called raw code, which means that the code groups have been taken directly from the codebook, without further encryption. Some code groups are repeated: MAXAD, YORAY, DEAGS, OXUAB, ITDEK, URGBE, UJTNU, UKURL and IVYDE. The code group with the highest frequency is MAXAD. Also the first group BBBTT appears in all these messages and it is clearly a system indicator (for a US codebook that uses a similar indicator, see here).
Usually, a codebook-based encryption can only be deciphered if the codebook is known. This is probably the case here, too. Can a reader find a codebook, in which the code group BBBTT is used for identification? Any help is welcome.
Further reading: A German spy message from World War 2