A history
lesson
At the start
of WWII the Kingdom
of Greece, ruled by Ioannis
Metaxas (head of the 4th of August Regime)
followed a neutral foreign policy and tried to avoid taking part in the
conflict. However constant Italian harassment and provocations (such as the sinking of the
cruiser Elli) and the transfer of Italian army units to Albania made it
clear that war could not be avoided for long.
In October
1940 Italian forces invaded Greece, in the area of Epirus, and
the Greek-Italian war
started. The Greek forces were able to contain the assault and the Greek
counterattack forced the Italians back into Albanian territory. After the
defeat of a major Italian offensive
in spring 1941 the front stabilized inside Albania.
At the time
Britain was overextended with obligations in Europe, Middle East and Asia.
However the British armed forces made a small contribution with an RAF
expeditionary corps. When more British forces started to
arrive in March 1941, their involvement gave Germany an excuse to become
involved in the conflict.
German forces
invaded Greece in
April 1941 and made rapid progress due to the fact that almost the entire
Greek Army was fighting in the Epirus area. The remaining units and the small
British forces transferred to Greece in March-April 1941 were unable to stop
them. Then in May 1941 the Germans were also able to defeat the Greek and
British forces that had retreated to the strategic island of Crete.
In the period
1941-44 Greece was split into three occupation zones, controlled by Italy,
Germany and Bulgaria. This measure
fractured the Greek economy and together with hyperinflation and loss of value
of the paper currency led to the collapse of the
economy.
Greece was a
poor agricultural country prior to WWII. The war of 1940-41, the splitting of
the country into three occupation zones and the confiscation of goods by the
occupying powers led to the impoverishment of an already poor population.
Greek
resistance groups
Under these
circumstances several
resistance groups were formed by Greek patriots in order to oppose the Axis
powers.
Small groups
operated in urban centers but the bigger ones could only survive in the
countryside where the presence of Axis troops was limited.
The main ones
were the military wing of the Greek Communist Party - ELAS (Greek
People's Liberation Army) and the liberal EDES
(National Republican Greek League).
The
resistance forces organized by the Communist Party were ostensibly created in
order to oppose the Axis rule and liberate Greece but in reality their main
goal was to eliminate their liberal rivals, unify all resistance groups under
communist control and gain power in postwar Greece (1).
During the
period 1943-44 the Communist forces showed more interest in attacking and
destroying other resistance groups than in attacking the occupiers. One of
their most infamous acts was the destruction of the EKKA (National
and Social Liberation) resistance group and the execution of its commander Dimitrios
Psarros.
The ΕΑΜ
ELAS movement grew in power during the occupation for several reasons. Compared
to the other resistance groups it had an advantage in that it was tightly
controlled by the Communist Party, an organization that knew how to operate in adverse
conditions. The main achievement of the communists was that they managed to get
British backing for their operations. British liaison officers were transported
to Greece and British money and arms supported the ΕΑΜ ELAS movement.
In addition to
British support, with the collapse of Italy in September 1943, several Italian
military units in the Balkans surrendered to the partisans and the capture of
their heavy weapons (mortars, artillery, machine guns) gave ΕΑΜ ELAS the
ability to conduct regular military operations.
Radio
communications and ciphers of the ELAS movement
According to
German sources ELAS radio communications began to be intercepted by the units
of KONA 4 (Kommandeur der Nachrichtenaufklärung - Signals Intelligence Regiment)
in early 1944.
KONA 4 was a
German Army signal intelligence unit assigned to cover radio traffic from the
Balkans and the Middle East. In
the period 1943-44 the unit was able to decode a large volume of Yugoslav
partisan traffic.
The quarterly
reports of the unit for 1944 (2) show that Greek communist radio traffic was
worked on by NAZ G (Nachrichten Nahaufklärungszug - Close Range Signal
Intelligence Platoon).
The report Ez
Bericht 1944/II says that in April 1944 radio traffic of the Greek communist
groups from the areas Volos, Lamia and Olympus was intercepted.
The messages were sent in 4-figure and 5-letter groups. The first procedure was
a letter to figure Caesar cipher and it was discontinued by the end of April.
The second procedure was double transposition with the same key used for both
cages. Both were solved and 240 messages read.
Elas-Funkverkehr
Mitte April wurde erstmalig ein
griechischer kommunistischer Bandenfunkverkehr mit Funkstellen im Raum Volos -
Lamia und im Olymp-Gebiet festgestellt. Seither sind hauptsächlich zwei Arten
von Chisprüchen der Elas (Griechisches Volksbefreiungsheer)- Verkehre
angefallen: 4Z- und 5B-Sprüche.
a) 4Z-Sprüche.
Statistische Untersuchungen des
Spruchmaterials ergaben eindeutige Hinweise auf ein mehrfach belegtes
2Z-Cäsar-Verfahren, das in seinen verschiedenen Schlüsselformen durch
4Z-Kenngruppen bezeichnet wird. Es wurden schliesslich fünf derartige
2Z-Buchstaben-Silben-Cäsaren gelöst. Bereits Ende April wurde dieses Verfahren
ausser Kraft gesetzt.
b) 5B-Sprüche.
Die in grösserem Umfange zwischen dem
Obkdo. der Elas und der Gruppe der Divisionen Makedoniens mit ihren
unterstellten Einheiten abgesetzten 5B-Sprüche wurden als
Klartext-Verwürfelungen erkannt. Untersuchungen auf einfache Verwürfelungen
waren erfolglos. Erst als zwei nahezu textgleiche Sprüche mit gleicher
4Z-Kenngruppe auftraten, von denen der eine die mit einer Spalten-vertauschung
versehene Wiederholung des anderen war, konnte die Losung erstellt und der
Spruch als Doppelwürfelverschlüsselung gelöst werden. Die folgende
Entschlüsselung aller mit dieser Losung verzifferten Sprüche ergab, dass der
Verschlüssler beim Obkdo der Elas besonders für volle Würfel eine Vorliebe hat.
Diese Annahme bestätigte sich, als festgestellt wurde, dass darüber hinaus sogar
qruadratische Würfel vorlagen, für die eine einfache Lösungsmöglichkeit
besteht. In arderen Fällen lagen der Verschlüsselung halbquadratische Würfel
zugrunde. Solche können gleichfalls gelöst werden, da in zwei Halbzeilen des
waagerecht eingetragenen Chitextes oft eine bekannte Unterschrift gefunden
werden kann. Unter Ausnutzung dieser Verschlüsselungsschwächen des Gegners
wurden bisher 20 Doppelwürfelosungen erstellt.
In der Berichtszeit wurden insgesamt
ca 240 Sprüche mitgelesen die wertvolle Aufschlüsse über den organisatorischen
Aufbau, die militärische Gliederung und die militärischen Aktionen der
kommunistischqp Banden im griechischen Raume gaben.
ELAS radio-traffic
Mid-April radio communications of
a Greek Communist gang , with radio stations in the area of Volos - Lamia and
Olympus, was detected for the first time. Since
then, mainly two kinds of cipher messages in
the ELAS traffic (Greek people's Liberation Army) have
turned: 4-figure and 5-letter messages.
a) 4-figure messages.
Statistical investigations of the
intercepted material gave clear indications of a multiply occupied 2-figure
Caesar system, which in its various cipher forms is identified by 4-figure
indicator. Finally five such 2-figure letter-syllable Caesars were solved.
Already at the end of April this procedure was cancelled.
b) 5-letter messages.
The 5-letter messages, which in larger
extent were sent between the ELAS headquarter and the group of divisions in
Macedonia with its subordinate units, were recognized as plaintext transpositions.
Studies based on simple transpositions were unsuccessful. It was not until two
nearly textually equal messages with the same 4-figure indicator group
occurred, of which one could be seen as a column swapped repetition of the
other, that an answer was found and the message solved as a double
transposition. The following decryption of all the enciphered messages with
this solution revealed that the cipher clerk at ELAS headquarter had a special
preference for complete transposition rectangles. This assumption was confirmed
when it was found that it even square transposition templates was used, for
which there exist a simple solution. In other cases, the enciphering was based
on using half-square transposition templates. Those can equally be solved because
in two half-lines of the vertically entered ciphertext one often will find a
well-known signature. So far 20 double transposition solutions have been
created using these encryption weaknesses of the enemy.
During the period under review a total
of about 240 messages were read which gave valuable insights into the
organizational structure, the military plans and the military action of the
Communist rings in the Greek area.
The report Ez
Bericht 1944/III says that double transposition continued to be used in ELAS
radio communications. Due to poor cipher practices this system could be solved.
In the reporting period about 120 keys were solved and 2.200 messages read.
Elas bewegung
Sämtliche Funkverkehre der
Elas-Bewegung im griechischen Raume verwenden nach wie vor die
Dopelwürfelverschlüsselung. Aus der bereits im letzten Bericht erwähnten
Vorliebe der gegnerischen Schlüssler für volle Würfel hat sich ein gangbarer
Weg zur Lösung dieser Doppelwürfel finden lassen. Unter Verwendung bereite
bekannter Unterschriften wurden die Würfellosungen gefunden an quadratischen,
doppelquadratischen, halb- und viertel-quadratischen Würfeln, ferner an längen-
und lösungsgleichen Würfeln und Würfeln mit Spaltenvertauschung, Dass
in einer Anzahl von bereits entzifferten Sprüchen auch Hinweise auf neue
Losungen gegeben wurden, erleichterte die Entzifferungsarbeit beträchtlich.
Mit ca. 120 Losungen konnten in der
Berichtszeit nahezu 2.200 Sprüche mitgelesen werden,
ELAS movement:
All radio traffic of the ELAs movement
in the Greek area still uses the double transposition system. From the
preference of the enemy cipher clerks for complete transposition squares, as
mentioned in the last report, a practical method of solving this double
transposition has been found. By using well-known signatures solutions were
found for square, double square, half - and quarter square transposition
templates, as well as solutions to same length and solution-equal transposition
templates and templates with column swapping.
The decipherment work was eased
considerably by the fact that a number of already decrypted messages also gave
hints about new solutions. With about 120 solutions nearly 2,200 messages could
be read during the reporting period.
The last
report Ez Bericht 1944/IV says that approximately 50% of the messages were read:
Elas Bewegung
Der griechische Bandenfunk wurde
ausschliesslich von NNA Zg G bearbeitet, der sich in der Berichtszeit 2 Monate
auf dem Rückzug befand. Im letzten Vierteljahr 1944 wurde als einziges Verfahren
der Doppelwürfel verwendet . Ungefähr 50% der angefallenen Sprüche wurden
mitgelesen. Für ca. 30 Kenngruppen wurden die Losungen erstellt.
ELAS movement
The Greek agent radio traffic was
processed exclusively by NNA Zg G who, during the reporting period, had already
been on the retreat for 2 months. In the last quarter of 1944 the only method
used was double transposition. Approximately 50% of the attacked messages were
read. Solutions were found for about 30 characteristic groups (indicators).
Dr. Otto
Karl Winkler and TICOM report I-170
Additional
information on the exploitation of ELAS communications is available from the TICOM
report I-170 ‘Report on French and Greek Systems by Oberwachtmeister Dr. Otto Karl Winkler of OKH/FNAST 4’ (dated January 1946).
The report
was written by Dr. Otto Karl Winkler, a member of KONA 4. Dr Winkler was in
charge of decoding and translating the Greek messages and in pages 4-6 he
stated about his work:
The unit
moved to BELGRADE in Autumn 1943, thence, in August 1944 to PERNITZ near WIENER
NEUSTADT, However, I received a new task in Spring 1944 with the appearance of
Greek messages sent by ELAS. In the course of our two year stay in Athens I had
been able to learn modern Greek almost perfectly, on the basis of a knowledge
of classical Greek and spurred on by love for and interest in Greece. In
addition my duties had provided me with a certain experience of cryptography
and a good translation technique. Thus I was put in charge of Greek
cryptography and was assisted in the actual cryptographic work by Uffz. Diether
STROBL from BERLIN, an English interpreter and technical student. I had held
the rank of Wachtmeister since Christmas 1943.
Regarding the
cipher systems used he also mentions the 2-figure Caesar system and the double
transposition cipher. Solution of the latter depended on the poor practices of
the ELAS cipher clerks:
Double
transpositions are regarded as a secure type of cipher and are therefore used
by many British agents. To the best of my knowledge the unit never succeeded in
breaking one and only occasional captured material has rendered it possible to
read some traffic retrospectively. For the sake of security it is essential to
avoid using complete or even square boxes, typical beginnings or endings of
messages and constantly recurring addresses and signatures, to use each key as
little as possible and as far as possible to have different keys for each box
of the pairs The Greeks overlooked all these rules right up to the end, with
the result that messages in the same setting and with the same number of groups
(Elementeanzahl) cropped up.
The solution of these messages provided valuable information about the
organization, personalities and operations of the ELAS partisan forces:
In any
case we succeeded in breaking 50 – 60% of the traffic tackled and as important
messages were always retransmitted on several links with different keys, we
were able to build up an almost complete picture of the build-up, organization
and composition of EAM and ELAS, to compile lists of their leading
personalities and officers and to inform the competent German political and
military authorities in good time about many planned military and political
actions, acts of sabotage, ambushes, dynamitings, etc. I can only remember a
few details and cannot reproduce examples systematically as the evaluation of
the material wan not my job, which consisted only of deciphering, decoding and
translating the available material.
Radio
traffic of British liaison officers in Greece
Apart from
ELAS communications the Germans were also able to read some of the messages
sent by British liaison officers assigned to the Greek partisans. The German
Army’s codebreaking agency OKH/Inspectorate 7/VI was able to decode some of
these messages in the period 1943-44 (3).
The British
authorities kept in contact with partisan groups in the Balkans through liaison
officers sent by the intelligence services SIS and SOE. These small teams
transmitted traffic by radio to their controlling stations in Cairo, Egypt and
Bari, Italy. The cryptosystems used were double transposition and the War
Office Cypher, enciphered with one time pads.
Some of the
encoded radio traffic of British officers in the Balkans was exploited by the
Germans. They were able to read messages both through captured material and by
cryptanalysis.
The reports of KONA 4 show that some cipher material was
captured in the field and messages read. For example in 1943:
Field units
had to rely on captured material in order to read British agents
transmissions but this was not necessarily true of the central department. The
reports of Inspectorate 7/VI show that this traffic (special traffic to Cairo
with indicator GESH) was first solved in June 1943 by Referats 6 and 12:
Traffic
continued to be read till November 1944 but it seems this was mostly from the
team assigned to the headquarters of General Mihailović and from the
liaison officers in Greece.
For example:
September ’43:
April ’44:
July ’44:
Conclusion
In the period
1941-44 the Greek population suffered under a triple occupation by Italian,
German and Bulgarian forces. The collapse of the Greek State, of the economy
and the falling living standards led many Greeks to take up arms against the
occupiers.
This
situation gave the Greek Communist Party an opportunity to build up a large
partisan movement in the countryside and use it to monopolize the anti Axis
resistance in Greece. With support from the British and after capturing Italian
heavy weapons in 1944 the Communists were one step away from gaining power in
the country.
During this
period the German authorities were aware of the growing strength of the
partisan movements in the Balkans but they did not have the military forces
needed to permanently destroy them. Instead their forces garrisoned strategic
areas and urban centers.
Both in
Yugoslavia and in Greece they were able to monitor the military operations and
political maneuvers of the partisan movements through signals intelligence.
In 1944 the
German Army’s signal intelligence agency was able to solve a large part of the
ELAS radio traffic. Their success was possible mainly due to the many mistakes
made by the ELAS cipher clerks. This traffic provided valuable intelligence on
the ELAS organization, personalities and planned military and political
actions.
Notes:
(1). A good summary
of the main issues surrounding the goals of the Communist party and EAM ELAS
can be found in ‘Εμφύλια πάθη: 23+2 νέες ερωτήσεις και απαντήσεις για τον Εμφύλιο’ - Στάθης Ν. Καλύβας, Νίκος Μαραντζίδης (2016)
(2). KONA 4 -
Ez Bericht 1944/II, Ez Bericht 1944/III, Ez Bericht 1944/IV (NARA - RG 457 -
Entry 9032 - box 22 - ‘German deciphering reports’)
Additional
information:
1). In TICOM
report I-170, p9 an example is given of the ELAS double transposition cipher.
The sample message reads:
OMADA MERARchIWN
MAKEDONIAS ch ch ch IMERA ch STOP SAS
PARAKALOYME NA ANAFERATE AMESWS EAN OI PENTE AXIWMATIKOI THS BRETTANIKHS
APOSTOLHS AFIchHSAN STOP STEFANOS SARAFHS YF
My
translation: ‘For Macedonian group of
divisions – Day – STOP we request that you report immediately if the five
officers of the British mission have arrived STOP Stefanos Sarafis’.
Stefanos Sarafis was
the military commander of the ELAS forces.
2). It seems
that the Greek communist military forces continued to use insecure cipher
systems even in the late 1940’s. An FBI report dated August 1950 (4) says the
AFSA (Armed Forces Security Agency) was working on the following Greek
communist crypto systems:
These were
monome-dinome substitution (enciphered with additive) and single and double
transposition, similar in concept to the systems used in 1944.
It is
reasonable to assume that the use of insecure ciphers by the communists was
exploited by the Greek Army and US agencies during the Greek Civil War.
