Zendian Problem
Encyclopedia
The Zendian Problem was an exercise in communication intelligence operations (mainly traffic analysis
and cryptanalysis
) devised by Lambros D. Callimahos
as part of an advanced course, CA-400, that Callimahos taught to National Security Agency
cryptanalysts.
contingent of a United Nations
force landed on the fictional island of Zendia in the Pacific Ocean
.
A typical intercept looks like this:
For each message, the first line is provided by the intercept
operator, giving call sign
s, frequency
, time, and reference number. The rest of the message is a transcript of the Morse code
transmission.
Initially, the meaning of the numeric header
is not known; the meanings of various components of this header (such as a serial number
assigned by the transmitting organization's message center) can be worked out through traffic analysis.
The rest of the message consists of "indicators" and ciphertext
; the first group is evidently a "discriminant" indicating the cryptosystem used, and (depending on the cryptosystem) some or all of the second group may contain a message-specific keying
element such as initial rotor
settings. The first two groups are repeated at the end of the message, which allows correction of garble
d indicators. The remaining characters are encrypted text. Since the transmissions always use complete groups, "nulls" may have been used to pad out the text.
Cryptosystems employed include transposition
, dinome, and rotor
-based cipher
s and a one-part code
. While these can be successfully tackled without use of a computer, solution is not easy. The practical exercise reinforces many basic principles, including ways to exploit having a collection of message traffic.
A certain amount of cleartext inter-operator "chatter" is also provided, and may help with the analysis.
Headers and discriminants are also given for intercepts from the next three days; these may be used for traffic analysis and in determining daily operating procedures.
and is available either as part of Military Cryptanalytics
or as a book in itself. Both are published by Aegean Park Press
, Walnut Creek, CA, USA.
. This society was founded by Lambros D. Callimahos and was so named after the empty Dundee marmalade jar on his desk, as he couldn't disclose the society's real purpose.
, which is run by NSA.
Traffic analysis
Traffic analysis is the process of intercepting and examining messages in order to deduce information from patterns in communication. It can be performed even when the messages are encrypted and cannot be decrypted. In general, the greater the number of messages observed, or even intercepted and...
and cryptanalysis
Cryptanalysis
Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...
) devised by Lambros D. Callimahos
Lambros D. Callimahos
Lambros Demetrios Callimahos was a US Army cryptologist. Born in Alexandria of Greek parents, the family emigrated to the United States when he was four...
as part of an advanced course, CA-400, that Callimahos taught to National Security Agency
National Security Agency
The National Security Agency/Central Security Service is a cryptologic intelligence agency of the United States Department of Defense responsible for the collection and analysis of foreign communications and foreign signals intelligence, as well as protecting U.S...
cryptanalysts.
Content
The scenario involves 375 radio messages said to have been intercepted on December 23 by the US ArmyUnited States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
contingent of a United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...
force landed on the fictional island of Zendia in the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
.
A typical intercept looks like this:
XYR DE OWN 4235KCS 230620T USM-99/00091
9516 8123 0605 7932 8423 5095 8444 6831
JAAAJ EUEBD OETDN GXAWR SUTEU EIWEN YUENN ODEUH RROMM EELGE
AEGID TESRR RASEB ENORS RNOMM EAYTU NEONT ESFRS NTCRO QCEET
OCORE IITLP OHSRG SSELY TCCSV SOTIU GNTIV EVOMN TMPAA CIRCS
ENREN OTSOI ENREI EKEIO PFRNT CDOGE NYFPE TESNI EACEA ISTEM
SOFEA TROSE EQOAO OSCER HTTAA LUOUY LSAIE TSERR ESEPA PHVDN
HNNTI IARTX LASLD URATT OPPLO AITMW OTIAS TNHIR DCOUT NMFCA
SREEE USSDS DHOAH REEXI PROUT NTTHD JAAAJ EUEBD
For each message, the first line is provided by the intercept
SIGINT
Signals intelligence is intelligence-gathering by interception of signals, whether between people , whether involving electronic signals not directly used in communication , or combinations of the two...
operator, giving call sign
Call sign
In broadcasting and radio communications, a call sign is a unique designation for a transmitting station. In North America they are used as names for broadcasting stations...
s, frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
, time, and reference number. The rest of the message is a transcript of the Morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
transmission.
Initially, the meaning of the numeric header
Header (information technology)
In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header are sometimes called the payload or body....
is not known; the meanings of various components of this header (such as a serial number
Serial number
A serial number is a unique number assigned for identification which varies from its successor or predecessor by a fixed discrete integer value...
assigned by the transmitting organization's message center) can be worked out through traffic analysis.
The rest of the message consists of "indicators" and ciphertext
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
; the first group is evidently a "discriminant" indicating the cryptosystem used, and (depending on the cryptosystem) some or all of the second group may contain a message-specific keying
Key (cryptography)
In cryptography, a key is a piece of information that determines the functional output of a cryptographic algorithm or cipher. Without a key, the algorithm would produce no useful result. In encryption, a key specifies the particular transformation of plaintext into ciphertext, or vice versa...
element such as initial rotor
Rotor machine
In cryptography, a rotor machine is an electro-mechanical device used for encrypting and decrypting secret messages. Rotor machines were the cryptographic state-of-the-art for a prominent period of history; they were in widespread use in the 1920s–1970s...
settings. The first two groups are repeated at the end of the message, which allows correction of garble
Garble
Garble is a blogging system based on the Jasper web programming framework. It also supports Facebook integration via the About Face theme.- External links :* * for the word garble, see wikt:garble...
d indicators. The remaining characters are encrypted text. Since the transmissions always use complete groups, "nulls" may have been used to pad out the text.
Cryptosystems employed include transposition
Transposition cipher
In cryptography, a transposition cipher is a method of encryption by which the positions held by units of plaintext are shifted according to a regular system, so that the ciphertext constitutes a permutation of the plaintext. That is, the order of the units is changed...
, dinome, and rotor
Rotor machine
In cryptography, a rotor machine is an electro-mechanical device used for encrypting and decrypting secret messages. Rotor machines were the cryptographic state-of-the-art for a prominent period of history; they were in widespread use in the 1920s–1970s...
-based cipher
Cipher
In cryptography, a cipher is an algorithm for performing encryption or decryption — a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. In non-technical usage, a “cipher” is the same thing as a “code”; however, the concepts...
s and a one-part code
Code (cryptography)
In cryptography, a code is a method used to transform a message into an obscured form, preventing those who do not possess special information, or key, required to apply the transform from understanding what is actually transmitted. The usual method is to use a codebook with a list of common...
. While these can be successfully tackled without use of a computer, solution is not easy. The practical exercise reinforces many basic principles, including ways to exploit having a collection of message traffic.
A certain amount of cleartext inter-operator "chatter" is also provided, and may help with the analysis.
Headers and discriminants are also given for intercepts from the next three days; these may be used for traffic analysis and in determining daily operating procedures.
Availability
The Zendian Problem has been declassifiedClassified information
Classified information is sensitive information to which access is restricted by law or regulation to particular groups of persons. A formal security clearance is required to handle classified documents or access classified data. The clearance process requires a satisfactory background investigation...
and is available either as part of Military Cryptanalytics
Military Cryptanalytics
Military Cryptanalytics is a revision by Lambros D. Callimahos of the series of books written by William F. Friedman under the title Military Cryptanalysis. It also contains contributions by other cryptanalysts. It was a training manual for National Security Agency and military cryptanalysts...
or as a book in itself. Both are published by Aegean Park Press
Aegean Park Press
Aegean Park Press is a publisher based in Walnut Creek, California, specializing in cryptology, military intelligence and Mayan languages. The company's books on cryptology are "mostly reprints of fairly advanced texts," Including at least 16 books by World War II cryptologists William F. Friedman,...
, Walnut Creek, CA, USA.
The Dundee Society
Cryptanalists who successfully finished CA-400 became members of the Dundee SocietyDundee Society
The Dundee Society was a society of graduates of CA-400, a National Security Agency course in cryptology devised by Lambros D. Callimahos, which included the Zendian Problem . The class was held once a year, and new members were inducted into the Society upon completion of the class...
. This society was founded by Lambros D. Callimahos and was so named after the empty Dundee marmalade jar on his desk, as he couldn't disclose the society's real purpose.
Map of Zendia
A print showing the fictional nation of Zendia hangs on the wall of the library at the National Cryptologic MuseumNational Cryptologic Museum
The National Cryptologic Museum is an American museum of cryptologic history that is affiliated with the National Security Agency . The first public museum in the U.S. Intelligence Community, NCM is located in the former Colony Seven Motel, just two blocks from the NSA headquarters at Fort...
, which is run by NSA.
External links
- Aegean Park Press — Reprints books containing the Zendian Problem, and other training material.
- Partial solutions for the Zendian Problem. Anyone intending to learn from working on this exercise should not look at these solutions.