Lesson 20:
Codes
CLASSICAL CRYPTOGRAPHY COURSE
BY LANAKI
28 NOVEMBER 1996
Revision 0
COPYRIGHT 1996
ALL RIGHTS RESERVED
LECTURE 20
CODES
SUMMARY
Lecture 20 covers historical use of codes and code
systems. We will trace their development and look at
some examples of famous code systems. We will develop
our subject with the help of several expert references.
[FR8 ], [OAKL], [KAHN], [DEVO], [WEBE], [DEV3], [ELLI],
[ACME], [LINC] [SIG2], [DAGA], [TRIT], [MACB], [COLE],
[NICH], [MANS], [MAN1], [WEBE]
CODE SYSTEMS
A code system is a highly specialized form of substit-
bution. The basic principle underling code systems is
the replacement of entire words, long phrases, or
complete sentences constituting the plain text of a
message by arbitrarily selected equivalents having
little or no relation to the elements they replace;
these equivalents may be other words, groups of letters,
groups of figures, or combinations thereof. [FR8 ]
This replacement process is rarely applied to elements
smaller than whole words and when this is done the
elements are single letters, groups of letters, or
syllables. In a codebook, the words, phrases, and
sentences are listed in a systematic manner and
accompanied by their code equivalents; correspondents
must possess identical copies of the document in order
to be able to communicate with each other. An ordinary
dictionary may serve the purpose of code communication,
so far as single words are concerned, but as a rule a
specially prepared document containing the words,
phrases, and sentences suited to particular types of
correspondence is used. In the U.S. they are called
codebooks or codes. Other names come from different
locations: repertories, word books, and cipher
dictionaries.
TRITHEIM CODE BOOK
One of the earliest code books was developed by the
Benedictine Abbot, John Tritheim. He collected many of
the ciphers used in the European courts. He was familiar
with the occult and proposed a code based on cabalistic
words wherein he tried to hide the real meaning under
cover of a mysterious language. The courts burned his
book "Polygraphia" in great pomp and ceremony. John was
lucky that he didn't go with the fire. The first edition
was published in Latin in 1518, a French translation in
1541, followed by a German translation.
Part one of Polygraphia consisted of a number of code
words for each letter of the alphabet, but arranged in
such a manner that if each letter of the message was
replaced by a code word, the result was a complete
sentence having an innocent meaning. (Something akin to
the three column management techno-babble matrix that
was popular in the 80's - pick a word from columns A, B
and C, put them together and you have a clever sounding
and totally bogus phrase like "computer redundancy
equivalents'.) Table 20-1 shows the fourteen coded
alphabets illustrating the way they were meant to be
used:
Table 20-1
TRITHEIM'S CODE ALPHABETS
1st 2nd 3rd 4th
A Jesus Immortal Producing Angels
B God Omnipotent Saving Archangels
C Saviour Compassionate Illuminating Saints
D King Ineffable Conferring Spheres
E Pastor Universal Moderating Heavens
F Author Almighty Expressing Sea
G Redempter Magnificent Governing Earth
H Prince Puissant Disposing(of) World
IJ Maker Just Dominating Men
K Conservator Sempiterneal Creating Sun
L Governor Celestial Cognising Moon
M Emperor Divine Guiding All
N Moderator Excellent Blessing Hierarchies
O Rector Triumphant Constituting Bodies
P Judge Clement Confirming Spirits
Q Illustrator Peaceful Conducting Souls
R Illuminator Pacific Sanctifying Times
S Consolator Invisible Honouring Humanity
T Sire Eternal Ministrating Ages
UVW Dominator Invincible Exorcising Eternity
X Creator Benign Elevating Firmaments
Y Psalmist Pitiable Sustaining Stars
Z Sovereign Incomprehensible Vilifying Air
& Protector Excellent Ordering Cosmos
5th 6th 7th 8th
A Gives (Tothe) Christians Eternal Life
B Delivers Requiring (needy) Perpetual Joy
C Attributes Faithful Infinite Joyousness
D Increases Attendants Angelic Glory
E Presents Righteous Immortal Consolation
F Renders Penitents Enduring Felicity
G Remits Good Incomprehensible Beatitude
H Renders Supplicants Incorruptible Jubilation
IJ Envoys Hopeful Durable Tranquility
K Transmits Patient Permanent Amenity
L Administers Afflicted Ineffable Recreation
M Permits All Celestial Clarity
N Inspires Tormented Divine Union
O Retributes Perturbed Interminable Peace
P Orders Desolated Perfect Light
Q Contributes Mortals Sincere Glorification
R Frees Humans Pure Benediction
S Confers Languishing Glorious Security
T Manifests Repentant Supernatural Favours
UVW Reveals Catholics Indicible Fruition
X Maintains In the World Peaceful Happiness
Y Admits Sinners Happy Light
Z Agitates Charitables Excellent Exultation
& Develops Virtuous Uplifting Pleasures
9th 10th 11th 12th
A (Together with in Heavens Majesty Incomprehen-
his Saints) sible
B Servants Ever and Ever Goodness God
C Loved Without end Kindliness Creator
D Saved In one Infinity Sapience Favour
E Beatified Perpetuity Charity Jesus
F Elected Sempiternity Power Transformator
G Confessors Enduring Infinity Dominator
H Apostles Incessantly Sublimity Preservator
IJ Evangelists Irreversible Benignity Immortal
K Martyrs Eternally Commiseration Supreme
L Angels In Glory Excellence Mighty
M Archangels In the Light Pity Omnipotent
N Dominions In Paradise Clemency Ineffable
O Proselytes Always Mercy Redemtor
P Disciples In divinity Divinity Sempiternal
Q Deified In Deity Deity Governor
R Ministers In felicity Omnipotence Rector
S Sanctified In his reign Virtue Sovereign
T Predestined in His Kingdom Love Invincible
UVW Preferred in beatitude Perfection Puissant
X Prophets in his vision Force Merciful
Y Patriarches in his magnif- Magnificence All Powerful
cence
Z Cherubs to the Throne Grandeur Magnificent
& Professors in all Eternity Favour Sanctified
13th 14th
A Sincerely Preached
B Really Announced
C Saintly Published
D Evangelically Revealed
E Devotedly Denounced
F Intelligibly Acclaimed
G Evidently Exalted
H Publicly Sermoned
IJ Faithfully Interpreted
K Ardently Reported
L Constantly Narrated
M Sagely Served
N Carefully Praised
O Virtuously Recited
P Catholically Pronounced
Q Cordially Repeated
R Reverently Treated
S Theologically Speculated
T Justly Collated
UVW Divinely Spread
X Learnedly Cognitized
Y Entirely Recognized
Z Studiously Contemplated
& Spiritually Produced
Amen
Example:
Plain text: 'Do not use bearer.'
D O N O T U S E B E A R E R
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Cipher text:
(The) King Triumphant Blessing (the) Bodies Manifests
(to the) Catholics Pure Consolation (together with)
His Servants (in) Perpetuity The Majesty (of the)
Rector Devotedly Treated. Amen.
Look under D in the first alphabet = King, 'O' under the
2nd alphabet = Triumphant, etc.
Note the interesting and rich language in the above 14
alphabets. The unfortunate thing about Tritheim's codes
was that coded messages required as many words as there
were letters in the plain text, which made for a long
cryptogram. Note also that some of the words were
duplicated which might have caused some confusion.
FROM LLOYD TO MARCONI
In 1688 Edward Lloyd ran a coffee-house in Tower Street,
London. An enterprising man, he found that several
brokers used to discuss their business over coffee. To
sell more coffee, he decided he must make things easier
for them. He instituted a blackboard, and then a weekly
bulletin of shipping information. More independent
brokers came and consumed his coffee while doing their
business. He later moved his coffee house to Lombard
street, in the very center of the old city of London
frequented by merchants of the highest class. It was
not until 1774, with the rapid increase of marine
insurance business, a committee was set up and a
constitution formed which has remained practically
unaltered to the present day. There is no longer a
Lloyds' coffee-house, yet the name is preserved, and
Lloyds'is known all over the world as the center of the
Marine Insurance business.
Lloyds devised a method of signalling between sea and
shore, so that advance news of ships and cargoes might
be received. A primitive projector was set up and a
system of light signals based on the Polybius' system
was started. It was this that gave rise later on to the
use of codes for commercial purposes; and apart from the
Venetian merchants in the eighteenth century, Lloyds
signals were the first to come into general use.
In 1794 in Europe, a system of rapid communications
known as ' aerial telegraphy', employing semaphores on
high towers visible at considerable distances, was
instituted. Whole phrases or sentences could be
expressed by one group of signals.
In 1825 codes employing figure groups were in common
use. In 1845 the Telegraphic Vocabulary Code was used
between Liverpool and Holyhead for the semaphore
telegraph. In this code there appear words, phrases,
long sentences, each represented by groups of one to
four digits.
In England the earliest practical trial of electric
telegraphy was made in 1837 on the London and North
Western Railway, and the first public line, under
Wheatstone and Coke Patents, was laid from Paddington to
Slough on the Great Western railway in 1843. [DAGA]
In New York, in 1860, Brewell published his Mercantile
Cipher for condensing telegrams, in which English
dictionary words were employed, and in which we find a
fairly complete vocabulary, arranged under captions.
The ABC code, also based on dictionary words, first
appeared in 1874. (Refer to Table 20-2.) Up to 1872 the
telegraph companies, by international agreement, charged
pronounceable code language words as plain text; the
higher tariff applied only to cipher or numeral
language. These were charged for at a rate of five
characters per word; and in 1875, at St. Petersburg, the
maximum length was fixed for either plain text or code
words at seven syllables. This led to abuse, such as
words as Chinesiskslutningsdon - 21 letters, but only 6
syllables - were used by coders. [DAGA]
The rule was changed to apply to European or Latin words
but not artificial words. In 1903, code words of ten
characters were allowed. They had to be pronounceable to
be authorized for transmission at the cost of plain text
words.
ABC CODE
Table 20-2
Example of ABC Code Page
Code No. Half Code Meaning
Word
00000 ABAAA 'ABC' CODE
00001 ABADE Please use 'ABC' Code 6th
edition
00002 ABAEF Please use 'ABC' Code 6th
edition and Code ---- (s)
00003 ABAFG Please Use 'ABC' Code 6th
edition and private Code
00004 ABAGH Using 'ABC' Code 6th edition
00005 ABAHI Using 'ABC' Code 6th edition
and Code -----------
00006 ABAIJ Abandon
00007 ABAJK Abandon altogether
00008 ABAKL Abandon for the present
00009 ABALM Abandon or (---)
00010 ABAMN Abandon the action
In 1904 Whitelaw's Telegraph Ciphers appeared with 400
million pronounceable words. Not really a code book, it
was a list of 'artificials' used for private codes.
These code words were composed of five letter only, for
example FORAB, LUFFA, LOZOJ, etc. as are all words used
in commercial codes today. Twenty-thousand words of five
letters each were given, and since each was pronoun-
ceable, and any two of these words could be joined
together to form a chargeable according to telegraph
regulations as one word, so 20,000 **2 gave the total of
potential words as 400 million.
In 1906 Bentley's code appeared, a compact phrase book
based on five-letter groups, applicable to business
affairs in general. It cut the cost of international
transmissions by half.
MORSE CODE
Samuel Finley Breese Morse was born in 1791 in
Charlestown, Mass. His invention of the electrical
telegraphy was second only to the famous 'Morse Code'.
He based his Morse Code on the frequencies of letters
calculated on quantities of type found in the printing
office. Since his frequency tables are an enormous help
in deciphering every code, lets compare here the
original calculation made by Morse with the Normal
Frequency and the Telegraph Frequency. (See Table 20-3)
For the letters which were most frequent he used the
simplest combination of dots and dashes, which an
automatic contrivance of the electric current
alternately transmitted and suspended during longer or
shorter intervals and reproduced at the other end of the
wire on strips of paper. The experienced operator knew
the 'fist' of the sender as well as the differences
between the dots and the dashes.
Table 20-3
Comparative Table of Order Of Morse's Count with
Telegraph Frequencies
Actual number of Order of
letters found by Normal
Morse at his printers Frequency
[NICH]
E 1st 12,000 1st
T 2nd 9,000 2nd
A 3rd 8,000 3rd
I 3rd 8,000 6th
N 3rd 8,000 5th
O 3rd 8,000 4th
S 3rd 8,000 8th
H 4th 6,400 9th
R 5th 6,200 7th
D 6th 4,400 11th
L 7th 4,000 10th
U 8th 3,400 13th
C 9th 3,000 12th
M 9th 3,000 16th
F 10th 2,500 15th
W 11th 2,000 17th
Y 11th 2,000 18th
G 12th 1,700 20th
P 12th 1,700 14th
B 13th 1,600 19th
V 14th 1,200 21st
K 15th 800 22th
Q 16th 500 23rd
J 17th 400 25th
X 17th 400 24th
Z 18th 200 26th
Comparative Table of Order of Morse's Count with
Telegraph Frequencies
Order 1 2 3 3 3 3 3 4 5 6 7 8 9 9
Morse: E, T, A,I,N,O,S, H,R,D,L,U, C,M
Telegraph: E, O, A, N, I, R, S, T, D, H, L, U
Order 10 11 12 13 14 15 16 17 18
Morse: F, W,Y, G,P, B, V, K, Q, J,X, Z
Telegraph: C, M, P, Y, F, G, W, B, V, K, X, J, Q, Z
This comparison is remarkable. The normal frequency
order corresponds to LANAKI's data presented in Lecture
1. [NICH]
The Morse code was not only used in telegraphy but also
in signalling by flags, by flashes of lights, by long
and short blasts from a whistle, and for some of us
knocks on the wooden cages to fellow prisoners in Viet
Nam.
The Army used to allow 10 days for recruit signalmen to
learn Morse code. Morse presents a simple method that
he invented in Table 20-4. This table presents a short
list of words, one for each letter of the alphabet, the
long and short syllables indicating dashes and dots.
Table 20-4
Learning Morse Code
(Invented by Morse)
Morse Phonetic
A Ag-ainst . - dit dah
B Bar-ba-ri-an -... dah dit dit dit
C Cont-in-ent-al -.-. dah dit dah dit
D Dah-li-a -.. dah dit dit
E (short) . dit
F Fu-ri-ous-ly ..-. dit dit dah dit
G Gal-lant-ly --. dah dah dit
H Hu-mi-li-ty .... dit dit dit dit
I I-vy .. dit dit
J Ju-ris-dic-tion .--- dit dah dah dah
K Kan-ga-roo -.- dah dit dah
L Le-gis-la-tor .-.. dit dah dit dit
M Moun-tain -- dah dah
N Nob-le -. dah dit
O Off-ens-ive --- dah dah dah
P Pho-tog-rapher-er .--. dit dah dah dit
Q Queen Kath-er-ine --.- dah dah dit dah
R Re-bec-ca .-. dah dit dah
S Sev-er-al ... dit dit dit
T Tea - dah
U Un-i-form ..- dit dit dah
V Ve-ry Var-ied ...- dit dit dit dah
W Wa-ter-loo .-- dit dah dah
X Ex-hi-bi-tion -..- dah dit dit dah
Y Youth-ful and Fair -.-- dah dit dah dah
Z (two long,
two short) --.. dah dah dit dit
The famous message SOS = SAVE OUR SHIP = ... --- ... =
dit dit dit dah dah dah dit dit dit.
Observe that each of these words contains as many
syllables as there are dots and dashes in the
corresponding Morse alphabet; but owing to the
difficulty of finding suitable words, it was assumed
that vowels followed by two or more consonants are long
and those by single ones short. In the words Katherine
and offensive, for instance, the final syllable must be
considered long. Morse put together the following
memorization aid:
GALLANTLY and FURIOUSLY he fought AGAINST the foe at
WATERLOO.
IVY creeping along the ground suggests HUMILITY.
The JURISDICTION of the NOBLE LEGISLATOR was OFFENSIVE
to the BARBARIAN.
A PHOTOGRAPHER saw SEVERAL KANGAROOS on the MOUNTAIN.
U. S. COAST GUARD DISCONTINUES MORSE CODE
Cipher history takes strange turns. It was with some
sadness that I read the 31 March 1995 announcement by
the USCG that Morse code equipment would shut down after
more than 83 years of monitoring telegraph distress
calls such as the 1912 Titanic collision with an
iceberg. Switchoff occurred at USCG communication
centers in Boston, Honolulu, Hawaii, Miami, New Orleans,
San Francisco, and Kodiak, Alaska. Even private
listening posts will cease service.
Samuel Morse invented the code to carry messages on the
telegraph machine he patented in 1840. Morse cipher
systems followed soon after that. USCG operators were
a breed apart because they could send and receive
international language at 20-35 wpm or more. Radio hams
know the meaning of "personal touch" as keyed dots and
dashes bounce off the atmosphere. WWII vets know that
the radioman's "fist" was more identifiable than
passwords.
I took my radio training via USCGA SAR. I know the
feeling of listening to 11 radios concurrently.
Sometimes a May Day could be heard only once and action
had to be decisive. Morse has been replaced by automatic
equipment to link with Global Maritime Distress and
Safety Systems via satellite relayed signals with
location fixes.
The ending of the Chesapeake USCG Atlantic COM Center
for Morse at 1919 hours EST is the ending of a great
era.
I went to my closet today. My USCG web belt still fits.
I couldn't bring myself to pull out my old uniform. I
just don't look like Arnold Schwartznegger anymore.
COMMERCIAL CODES
Historically, commercial codes were used not so much
used for secrecy as for saving money on long telegrams.
Authorized, pronounceable words of maximum length of ten
letters being used to cover several sentences. The code
words used were entirely fictitious, and followed each
other in alphabetical order, being made up of five
letters each, so that two codewords can be sent by
telegraph for the price of a half word. [Note that
modern day E-mail on the Net has completely made this a
non-issue. In any one day, I may write to classmates in
England, Germany, Italy, Japan and Spain and in less
than 30 minutes have answers, with attachments, and be
charged a flat rate for the service on this end!] Other
codes constructed on these principles were Bentley's and
Webster's. They allow two words, or even short
sentences, to be formed into one telegraph word of ten
letters. There are commercial codes today with
equivalent translations into every European language, so
that English, German, or Italian business men, without
knowing each other's languages, can exchange telegrams
(or FAXS).
MARCONI CODE
Senator Guglielmo Marconi was devoted to an idea - the
sending and receiving of wireless signals through space.
His wireless inventions are legendary. Marconi also
invented and perfected the Marconi Codes. The complete
Marconi code consists of four volumes comprising
English, Spanish, Japanese, Russian, Italian,
Portuguese, German and Dutch equivalents. The English
text is alphabetical, and every other language has a
complete index of all the words. The code is divided
into two parts - one containing general phrases and the
other a numerical system.
Again, the chief aim of standard code was to save cost
of cable charges and the cost of time required to code
the messages. Upwards of 17,050 combinations could be
obtained by the Marconi code. A checking system was used
to ensure accuracy.
The code words were composed of five letters each,
corresponding to a word or sentence used in trade or
business. The codewords could be combined to for a
telegraph word of ten letters by the International
Telegraph regulations.
There were some differences with codes such as the ABC
code. Each code word has a two-letter difference from
each other code word. This two-letter difference ensured
that no two words would have the same four letters in
the same position. A code word like BOPEZ would
eliminate codewords like COPEZ, DOPEZ and also such
forms as BAPEZ and BEPEZ. (see below)
The Marconi Numerical System was arranged so that a
range of figures in combination with some of the most
commonly used qualifying phrases, together with an
efficiency check, could be transmitted in one complete
pronounceable word of ten letters. The first syllable in
this section consisted of two consonants, thereby
distinguishing it from a phrase section in which none of
the code words began win two consonants. As the code
words in the numerical section were only two letters
long, five words or phrases could be included in one
telegraph word of ten letters.
The Marconi arrangement was as follows (Refer to Table
20-5):
1st Syllable provided for a variety of phrases which
were employed in combination with the figures or phrases
in the following syllables, describing as 'qualifying
phrases'; e.g. 'TH' = remit by cable, 'TW' = ship
immediately.
2nd Syllable provides for an extensive variety of
phrases descriptive of the following weights and
measures; i.e. 'OM' =pounds, 'WG' = tons.
3rd Syllable provides for figures from factions to 100.
4th Syllable provides for more figures to be used in
conjunction with the third syllable. If unnecessary a
blank must be used here, or short phrase to qualify,
such as 'ZA' = per month.
5th Syllable provides for a further series of phrases to
be used in conjunction with the foregoing; e.g. 'AL' =
for immediate shipment. It also supplies a check for the
whole coded word.
The checking system is very simple. The check numbers
given in brackets on each code syllable are added
together for the four syllables used; tens are dis-
regarded, and for the fifth syllable the letters are
chosen from the column bearing the same number as the
total arrived at from the addition of the first four
syllables.
Compare the ABC code Table 20-2 with the Marconi code in
Table 20-5.
Table 20-5
The First part of the Marconi Code. General
Phrases Code words, five letters
Numerical System. Code word of two letters.
No. Code English French Spanish
Word
00000 ABABA A or an un, une un,uno,una
00001 ABAHB A1 at Lloyds A1 chez A1 en el
Lloyds registro de
Lloyd
00002 ABALC Abandon(s) Abandonn(r) Abandona(r)
(z) (u)
00003 ABAND Abandon all Abandonne Abandona
claims toutes rec- todas las
lamations reclamaciones
00004 ABAPE Abandon neg- Abandonne Abandona las
otiations les negocia- negociaciones
tions
00003 ABARF Abandon pro- Abandonne Abandona
ceedings les demar- los proced-
ches imientes
1st Syllable.
Check Code English French Spanish
No in Syll-
Red able
(0) BL Blank or At Blanc ou A Blanco o A
(5) BR Bid (they) Ils offrent ofrecen
(8) CH Bid (we) Nous offrons ofrencemos
(1) CL Bought (we Nous avons Hemos comp-
have) achete rado
(6) CR Breadth (or Largeur (ou Anchura (o
thickness) epaisseur) espesura)
2nd Syllable.
(5) AB Blank Blanc Blanco
(6) AC Acre(s) Acre(s) Acre(s)
(7) AD Ampere(s) Ampere(s) Amperio(s)
(8) AF Anna(s) Anna(s) Anna(s)
(9) AG Ante Mere- Matin, avant Antes de
dian (A.M.) midi mediodia
(A.M.)
3rd Syllable.
(5) AB Blank Blanc Blanco
(6) AC 0 0 0
(7) AD 1/16 1/16 1/16
(8) BI 1 1 1
(7) BO 1/14 1/14 1/14
4th Syllable.
(9) YA 000 000 000
(0) YB 100 100 100
(1) YC 200 200 200
(1) YM per annum par an por ano
(2) YN per cent- par cent- por cent-
imeter metre metro
5th Syllable. Control of check.
0 1 2 3 4 5 6 7 8 9
Blanc AR EN BU HI JA NA OY TO VA YG
Anout AC EP BY HO JE NE OZ TU YE YH
Average AD ER CA HU JI NI PA TY VI YI
C.I.F. AF ES CE HY JO NO PE WB VO YJ
(Cost
Insurance
Freight)
each AG ET CI IB JU NU PI UC VU YK
NON-SECRET CODES
Various codes are suited to particular types of
correspondence. Many large commercial firms have their
own private codes. For example, an early commercial
codebook was made by ACME Commercial Code Company in the
1930's. (See Tables 20-2a&b) Most industries have highly
specialized technical language (part of the defense of
mystique in every industry or profession -Latin for
doctors and lawyers, female terms and mathematics for
engineers, ISO 9000 terms for quality managers, snake
oil terms for computer types, plus a whole bevy of terms
for cryptographers, etc). The purposes of many these
codebooks are brevity and compression not secrecy. The
military and diplomatic applications call for security,
and speed of communications, especially for front-line
communications.
The PKZIP program, which is used so widely on the net,
is a compression 'codebook'. It provides economy of
transmission and minimal crypto-security. The power of
the program lies in the ability to delineate and hold
entire directories and then to create an indexed tree
of the coagulated sum of files. PKZIP is an example of a
non-secret code. Compression is more valuable than
secrecy. The condensing power of a code is dependent on
its vocabulary. When we add the goal of secrecy to
economy, we then have a secret code. Actually, code
transmissions save money because of the lowers number of
characters to be transmitted over the channel.
ACME SEVEN DIGIT CODEBOOK
In 1934, the ACME Code Company, with offices in London,
New York and San Francisco, developed a codebook for
condensation 7 figures into 5 figure groups for
international business cables. The transoceanic
standard for code language was issued 1 January 1934,
and superseded the category 'B' regulation (CDE) five
letter code words without vowel restrictions. Category B
service was cheaper on short coded messages that the
category cable A intercontinental transmissions.
I have codebook number 6015. It is laid out in three
tables on each page. Table 1 is for 1st and 2nd Figures,
First and Second Letters; Table 2 is for 3rd, 4th and
5th Figures, Third and Fourth letters; Table 3 is for
6th and 7th Figures, fifth letters. The conversion
(condensation) of 7 Figures into a five letter code
word and visa versa is accomplished on one page, in a
single operation. Numbers 0000000 to 9999999 are
included in the codebook. The condenser is used for :
14 Figure codes (2 Five Letter code words)
21 Figure codes (3 Five Letter code words)
28 Figure codes (4 Five Letter code words)
etc.
It can be used in conjunction with any numbered code,
catalogue, parts list, steamer list, etc.
Encoding
To encode the figures 4732651 into a five
letter code word, we divide the 7 figures into three
groups:
47 - 326 - 51
The 3rd, 4th, and 5th figures determine the page from
which we apply the condensation codes. 326 is found on
page 3 of the codebook. (Table 20-6a&b reproduces part
of the pages.)
Alongside the figures 326 are the two letter groups YM,
YN, YO, YP, which gives us the 3rd and 4th letters of
the codeword we will form.
To determine the group to use, we look at the 6th and
7th figures table and find the fifth letter. The figures
51 are in the same column as YP and the letter alongside
of 51 is M. Thus we have the 3rd, 4th, and 5th letters
of our codeword YPM.
To get the 1st and 2nd letters of the codeword, we refer
to the table covering the 1st and 2nd figures, on the
same page and is found that for 47 are FR. The entire
codeword is then FRYPM.
Table 20-6a
page 3
3rd, 4th, and 5th Figures
Third and Fourth Letters
326 YM YN YO YP
327 YQ YR YS YT
328 YU YV YW YX
329 YY YZ ZA ZB
330 ZC ZD ZE ZF
. . . .
39 J
6th and 43 K
7th 47 L
Figures 51 M
Fifth 55 N
Letter 59 O
. . . . .
.. ..
45 FP
46 FQ
47 FR 1st and 2nd
48 FS Figures
49 FT First and
50 FU Second Letters
.. ..
The codeword then is FRYPM.
Decoding
To decode the codeword STROW we break it down:
ST - RO - W
The first and second letters determine the page from
which you will decode your full seven figures. In this
instance the First and Second letters ST, they will be
found on page 6, alongside of which we find the 1st and
2nd figures "87".
You then look on the same page for RO, in the table
covering the third and fourth letters. It is found that
RO means "782," thus giving you the 3rd, 4th and 5th
figures.
W being the final letter, we refer to the table for 6th
and 7th figures. In the same column as RO appear and on
the same line that the letter W is found, we find the
6th and 7th figures 84. Our final product is
87-782-84. STROW = 8778284.
Table 20-6b
page 6
3rd, 4th, and 5th Figures
Third and Fourth Letters
782 RO RP RQ RR
783 RS RT RU RV
784 RW RX RY RZ
785 SA SB SC SD
786 SE SF SG SH
. . . .
6th and 84 85 86 87 W
7th 88 89 90 91 X
Figures 92 93 94 95 Y
Fifth 96 97 98 99 Z
Letter .. .. .. .. .
.. ..
85 SR
86 SS
87 ST 1st and 2nd
88 SU Figures
89 SV First and
90 SW Second Letters
.. ..
ACME also produced a Commodity and Phrase Code
Supplement which was just as much fun? [ACME]
BREVITY CODES
In military cryptography, the greatest degree of
condensation is afforded by 'prearranged-message codes,'
or 'brevity codes.' A prearranged-message code is a
tactical code adapted to the use of units requiring
special or technical vocabularies; it is comprised
almost exclusively of groups representing complete or
nearly complete messages and is intended for shortening
messages and concealing their content. The police '10'
codes fall into this category. A brevity code has as its
sole purpose the shortening of messages. A field code
is a small tactical code which contains a large number
of code groups representing words and a few common short
phrases, from which sentences can be composed; a
syllabary, which is a list of code groups representing
individual letters, combinations of letters, or
syllables, is used for spelling out proper names and .
numerical tables, or list of code groups representing
numbers, dates, and jargon. The Army Special Forces
Codes fall into this category. A jargon code is a very
short code in which bona fide dictionary words,
baptismal names, rivers, lakes, etc are used as code
groups. Lincoln's war time codes fall into this
category. [LINC] A voice code or recognition code
is used for transmission by small radio-telephone sets
used in combat. Other names are combat code or operat-
ions code. [TEC] The Navy has a special brand of codes
used for protection of marine traffic. An example of
this code system is the International Code of Signals
(1969 edition, revised 1981 INTERCO ) [SIG2]
INTERNATIONAL CODE OF SIGNALS FOR VISUAL, SOUND AND
RADIO COMMUNICATIONS (INTERCO)
The Defense Mapping Agency, Hydrographic/Topographic
Center issued in 1969 and again in 1981, their
Publication No. 102, "International Code of Signals
For Visual, Sound, and Radio Communications," United
States Edition. This code was adopted by the Fourth
Assembly of the intergovernmental Maritime Consultative
Organization in 1965. The document was prepared in nine
languages: English, French, Italian, German, Japanese,
Spanish, Norwegian, Russian and Greek.
This is very good example of the brevity and non-secret
codes that had wide distribution for ocean going
vessels. Modern day vessels use uplinks to satellites in
geo-synchronous orbits to navigate and communicate.
The INTERCO was designed to communicate for situations
relating to the safety of navigation and persons,
especially when language difficulties arise. It is
suitable for transmission by all means of communication
including radiotelephony and radiotelegraphy. The
INTERCO embodies the principle that each signal has a
complete and distinct meaning.
The INTERCO is broken into four parts: 1) Signal
Instructions, 2) General Signal Code, 3) Medical Signal
Code, and Distress and Lifesaving Signals and Radio
Procedures. The appendix includes a National Identity
Signals for Ships and Aircraft, plus US/USSR
Supplementary Signals for Naval Vessels.
General Signal Code includes sections on: Distress,
Emergency, Casualties, Damages, Aids to Navigation,
Hydrography, Maneuvers, Cargo, ballast, Meteorology,
Communications and Sanitary Regulations. [SIG2] See
Table 20-7 for sample entries. In Table 20-7, capital-
ized headings represent major topics, predominantly
lower case headings represent subtopics. You can see
from the small sample in Table 20-7, that the INTERCO
deals with serious situations. I was assigned to a U.S.
Coast Guard Radio Room and I can tell you that listening
to 11 radios at the same time can be very intense. A
MAYDAY maybe heard only once and rarely in calm voice.
Sending the cutter is serious business. The USCG does
their job exceptionally well.
Table 20-7
Sample Entries from INTERCO Codebook
Distress - Emergency
Code Meaning
ABANDON
AD I am abandoning my vessel which has suffered
a nuclear accident and is a possible source of
radiation danger.
Accident
SB I am proceeding to the position of the
accident.
GC 2 I have searched area of accident but have
found no trace of derelict or survivors.
Doctor
AM Have you a doctor on board?
AP I have ... (number) casualties.
ASSISTANCE
Required
CB I require immediate assistance.
CB 1 I require immediate assistance; I have a
dangerous list.
CB 6 I require immediate assistance; I am on fire.
Given-Not Given
CN 1 You should give immediate assistance to pick
up survivors
CO 1 I cannot give the assistance required (or
vessel/aircraft indicated)
DISABLED-DRIFTING-SINKING
DS I have sighted disabled aircraft in lat ...
long ... at time indicated.
DX I am sinking.
SEARCH AND RESCUE
Proceeding To Assistance
FE I am proceeding to the position of the
accident at full speed. Expect to arrive at
time indicated.
Position of Distress or Accident
FF I have intercepted SOS/MAYDAY from vessel
(name or identity signal or aircraft) in pos
lat ... long ... at time indicated.
Results of Search
GJ 1 Wreckage is reported in lat .. long ... No
survivors appear to be in vicinity.
ICEBREAKER
WC 1 Icebreaker is being sent to your assistance.
SEA
WY The state of the sea is ... (Complements 0-9
corresponding to following table):
Height
In Meters In Feet
0 Calm (glassy) 0 0
1 Calm (rippled) 0 - 0.1 0 - 1/3
2 Smooth (wavelets) 0.1 - 0.5 1/3 - 1 2/3
3 Slight 0.5 - 1.25 1 2/3 - 4
4 Moderate 1.25 - 2.5 4 - 8
5 Rough 2.5 - 4 8 - 13
6 Very Rough 4 - 6 13 - 20
7 High 6 - 9 20 - 30
8 Very High 9 - 14 30 - 45
9 Phenomenal over 14 over 45
MEDICAL
Diseases of Respiratory System
MIF Patient is coughing up blood.
MIM Patient has blueness of face.
Special Treatment
MRW Give frequent gargles one teaspoon
of salt in a tumblerful of water.
RECEPTION OF SAFETY MESSAGES
MAYDAY Indicates that the ship, aircraft,
or(Distress) other vehicle is
threatened by grave and imminent
danger and requests immediate
assistance.
PAN Indicates the calling station has a
(Urgency) very urgent message to transmit
concerning the safety of a ship,
aircraft or other vehicle, or the
safety of a person.
SECURITE Indicates that the station is about
(Safety) to transmit a message concerning the
safety of navigation or giving
important meteorological warnings.
To indicate DISTRESS:
1. If possible transmit ALARM SIGNAL (i.e. two tone
signal) for 30 seconds to one minute, but do not
delay the message if there is insufficient time in
which to transmit the Alarm Signal.
2. Send the following DISTRESS CALL:
MAYDAY MAYDAY MAYDAY. This is ...(name or call sign
of ship spoken three times).
3. Then send the DISTRESS MESSAGE composed of:
MAYDAY followed by the name or call sign of the
ship;
Position of ship;
Nature of distress;
And if necessary, transmit nature of the aid
required and any other information which will help
the rescue.
USE PLAIN LANGUAGE WHENEVER POSSIBLE or send the word
INTERCO to indicate that the message will be in the
International Code of Signals.
example:
MAYDAY MAYDAY MAYDAY ... ( name of ship spoken three
times, or call sign of ship spelled using Phonetic
Alphabet in Table 20-8); MAYDAY ... (name or call sign
of ship) Position 54 25 North 016 33 West I am on Fire
and require immediate assistance.
Table 20-8
Phonetic Alphabet used with INTERCO
Letter/ Word Pronounced
Number
A Alfa AL FAH
B Bravo BRAH VOH
C Charlie CHAR LEE or SHAR LEE
D Delta DELL TAH
E Echo ECK OH
F Foxtrot FOKS TROT
G Golf GOLF
H Hotel HOH TELL
I India IN DEE AH
J Juliett JEW LEE ETT
K Kilo KEY LOH
L Lima LEE MAH
M Mike MIKE
N November NO VEM BER
O Oscar OSS CAR
P Papa PAH PAH
Q Quebec KEH BECK
R Romeo ROW ME OH
S Sierra SEE AIR RAH
T Tango TANG GO
U Uniform YOU NEE FORM or OO NEE FORM
V Victor VIK TAH
W Whiskey WISS KEY
X Xray ECKS RAY
Y Yankee YANG KEE
Z Zulu ZOO LOO
0 NADAZERO NAH-DAH-ZAY-ROH
1 UNAONE OO-NAH-WUN
2 BISSOTWO BEES-SO-TOO
3 TERRATHREE TAY-REE-TREE
4 KARTEFOUR KAR-TAY-FOWER
5 PANTAFIVE PAN-TAH-FIVE
6 SOXISIX SOK-SEE-SIX
7 SETTESEVEN SAY-TAH-SEVEN
8 OKTOEIGHT OH-TAY-AIT
9 NOVENINE NO-VAY-NINER
. DECIMAL DAY-SEE-MAL
BASICS OF CODE CONSTRUCTION
The encoding and reverse procedure of decoding is
accomplished by replacing various words, phrases,
sentences, and numbers by their code equivalents. The
code text is built up from code units each representing
the longest possible plaintext unit the code book
affords. Encoding the phrase "enemy force estimated at
one battalion," and the codebook has phrases "enemy
force," and "estimated at," as well as the individual
words, we would write down the phrase equivalents.
The elements of which code groups are composed may be
one or more of the following:
1. Bona fida words - real words from Dutch, English,
French, German, Italian, Latin, Portuguese and
Spanish.
2. Artificial words - groups of letters without
meaning with vowels and consonants arranged to
appear like real words.
3. Random groups of letters.
4. Groups of Arabic figures.
5. Intermix groups, ie. call signs for stations K2KAA,
or W5AZZ.
6. All the above.
PARALLEL SETS
A code may contain two or more parallel sets of code
groups of different types. In many commercial codes and
some military codes, there is one series of code groups
of the bona fide type or artificial word type and
another series of the figure-group type, both applying
to the same series of words phrases, and sentences of
the code. In parts of the world where English letters
are used for writing, letters possess greater advantages
in accuracy of reading than figures - especially for
telegraph or radio transmissions. For communications to
China and Russia or obscure ports, Arabic figures are
well accepted and code groups composed of figures are
used. The main reason for this is assurance of the
correct transmission and reception of messages in all
parts of the world. Another reason is that certain
methods of enciphering code messages for the sake of
greater secrecy, figure groups often form the basis for
encipherment more readily than do letter groups.
The greatest advantage possessed by letter groups over
figure groups lies in the availability of a far greater
number of permutations, or interchanges, of letter
groups, because there are 26 letters which may be
permuted to form letter groups compared to 10 digits for
figure groups (assumes base 10 historical use). If code
groups of five letters are used, then there are 26 ** 5
or 11,881,376 groups of five letters versus 10 ** 5, or
100,000 groups of five figures. Letter code groups are
usually constructed to reduce error in transmission.
The length of code groups used, whether the groups
consist of two, three, four, or five elements, depends
upon the size of the code. This applies almost
exclusively to field military or naval codes, where
transmission is through a governmental agency; in
commercial messages or governmental communications
transmitted over privately operated lines, five-letter
or five letter groups are the standard. [FR8]
Code groups of modern codes are constructed by the use
of tables which permit more-or less automatic and
systematic construction in the form desired. These are
called permutation tables. Because they may be used to
correct most errors made in transmission or writing,
such tables are usually included in the code book and
are called mutilation tables, garble tables, error
detector charts, etc.
TWO-LETTER DIFFERENTIAL
The average telegraph or radio operator did not work
without error. One letter different code groups like
ABABA and ABABE were easy to mistake and the message
could be made unintelligible by only a few transmission
errors. If however, every code group in the code book
is distinguished from all other code groups in the same
code by a difference of at least two letters, then
there would have to be two errors in a single group and
these two errors would have to produce a code group
actually present in the code before a wrong meaning
would be conveyed. The principle of making code groups
differ by a minimum of two letters is called the two-
letter differential. The two-letter differential
reduces the possibilities for constructing letter code-
groups from 26 ** 5 to 26 ** 4 (456,976) but considering
the advantages, the sacrifice was worthwhile.
Permutation tables for construction of figure-code
groups are similar in nature and purpose to tables for
construction of letter-coded groups. Because of a more
limited number of characters available for permutations,
the maximum number of 2-figure difference groups
possible in a 5-figure code is 10 ** 4, or 10,000. (This
does not account for ASCII code derivations.)
TYPES
In their construction or arrangement, codes are
generally of two types:
(1) One-part, or alphabetical codes. The plaintext
groups are arranged in alphabetical order
accompanied by their code groups in alphabetical
or numerical order. Such a code serves for decoding
as well as encoding.
(2) Two-part or randomized codes. The plaintext groups
are arranged in alphabetical order accompanied by
their code groups in a non-systematic order. The
code groups are assigned to the plaintext groups at
random by drawing the code groups out of a box in
which they have been thoroughly mixed. Such a list
serves for encoding. For decoding, another list must
be provided in which the code groups are arranged in
alphabetical or numerical order and are accompanied
by their meanings as given in the encoding section.
Another name for the two-part code is cross-
reference codes. Here are extracts from typical one-
part and two-part codes.
(Tables 20-9 and 20-10.)
Table 20-9
One-part code
ABABD A
ABACF Abaft
ABAHK Abandon
ABAJL .....it
ABALN Abandoned
ABAMP .....by
ABAWZ Abandoning
ABBAD Abandonment
......................
......................
ZYZYZ Zero
Table 20-10
Two-part code
Encoding Section Decoding Section
GAJVY A ABABD Obstructed
TOGTY Abaft ABACF Term
FEHIL Abandon ABAHK Zero
BAYLT .....it ABAJL If it has not
ZYZYZ Abandoned ABALN To be sent by
NYSYZ .....by ABAMP Acceding
IFWUZ Abandoning ABAWZ Building
RUMGO Abandonment ABBAD Do not attempt
...................... ......................
...................... ......................
ABAHK Zero ZYZYZ Abandoned
Between the two extremes are codes which have features
of both; that is complete sections may be arranged in
random sequence, but within each section the contents
are arranged in some logical order.
When a strict alphabetic arrangement is used in the
sequence of the phrases, the code is said to be a
strictly alphabetical code. When the phrases are
listed under separate headings based upon the principal
word or idea in the whole expression, the code is called
a caption code. (Tables 20-11 and 20-12)
Table 20-11
Caption code
Assistance
Give assistance
Require assistance
No assistance
Assistance has been sent
Assistance for
Assistance from
Assistance to
Assistant
Assisted
Table 20-12
Strictly-alphabetical
Assistance
Assistance for
Assistance from
Assistance has been sent
Assistance to
Assistant
Assisted
.........................
Give
Give assistance
.........................
No
No assistance required
.........................
Require
Require assistance
More precise and economical coding is possible with a
caption code than with an alphabetical code. With a
caption code it is easier to assemble an extended
variety of expressions and shades of meaning under
specific headings than with alphabetical code. On the
other hand, the use of a caption code involves more time
and labor in encoding.
Two-part codes are used by many governments for their
secret diplomatic, military and naval communications
because of the advantages they offer over one part
codes. Some disadvantages include twice as large in
context, printing and distribution costs, compilation is
four times greater because of the requirement of
accurate cross references. The advantages of two-part
codes are greater security and greater accuracy.
In some commercial code messages there is sometimes
encountered the practice of mixing plaintext and code
text. In governmental and naval communications such
intermixtures are rare and present an abysmal ignorance
of the fundamental rules of cryptographic security.
Because the plaintext words give definite clues to the
meaning of the adjacent code groups, even though the
former convey no meaning in themselves (such words as
and, but, by, comma, for, in, period, stop, that, the,
etc) constitutes a fatal danger to the message security.
ENCIPHERED CODE SYSTEMS
Sometimes the code groups of a code message undergo a
further process of encipherment; the resulting crypto-
gram constitutes an enciphered code message. Both
transposition and substitution may be used to encipher
the code. Enciphered code is used under the following
circumstances:
(1) When the code has a wide distribution and may fall
into enemy hands,
(2) to improve the security of commercial codes and non-
secret codes, and
(3) when increased security is necessary for highly
classified communications.
Transposition methods are generally used within code
groups, such as rearranging or shifting about the
letters or figures composing them. A common method is
keyed columnar transposition with special matrices with
nulls. All the substitution methods previously studied
may be used for "super-encipherment" of the code. The
most effective methods of enciphering code are
arithmetical methods.
If the code groups are numerical, the addition (usually
mod 10) of an arbitrarily selected number (called the
additive ) to each code group message constitutes a
simple form of encipherment. The additive may be fixed.
Additive methods may actually be weak cryptographically
if the basic code book and code groups embody
limitations in construction. Instead of adding a fixed
number in encipherment, the latter is subtracted, in
which case , in decipherment, the fixed number must be
added to the enciphered code groups as received. Such a
group (called subtractive or subtractor ) in decipher-
ment the group becomes an additive. A third method used
commonly is the minuend method. It involves the
subtraction of the plain code group from the key to
yield the enciphered code group in encipherment, and the
subtraction of the enciphered code group in from the key
in decipherment. Addition and subtraction of a fixed
numerical group may be alternated within the same
message such as +200, +100 +400 as a cycle or +200, -
100, +400, -200 etc. Instead of a fixed additive, it is
possible to employ a repeating large key.
When special tables are employed as the source of the
additives or subtractors for enciphered code, a much
more secure system is provide. These tables are called a
key book or an additive book or a subtractor book. by
applying identifying symbols called indicators to the
pages, as well as to the rows and columns on each page
of the key book, it is possible to provide for secure
encipherment of a large volume of traffic. All
corespondents must have the same key books. In
employing the key book, the indicators tell the
recipient of the message what key groups were used and
where to begin the decipherment of the enciphered code.
In actual practice, indicators are often disguised or
encrypted by a special key or set of keys; this
procedure may add considerably to the security of the
system.
Table 20-13 shows a page from a typical key book. It
contains two sets of 100 4-digit key groups, disposed in
numbered blocks each containing 10 rows and 10 columns
of groups. To designate a group as the initial one to be
employed in encipherment or decipherment, we give the
block number, the row and column numbers of the group.
For example, 0116 is the indicator for the group 8790.
It is usual to take the successive groups in the normal
order of reading. Some keys books consist of 50 + pages
containing 200 + groups making 10,000 in all. The
digits in each block are random numbers. [FR8 ]
If the key book is used once and only once, security of
the system approaches the one-time pad. The messages are
one time system secure even if the enemy has basic code
book. Friedman discusses indicators in much more detail
in [FR8 ].
Table 20-13
Indicators and Key Blocks
Block 00
1 2 3 4 5 6 7 8 9 0
1 0378 9197 3260 3607 2699 9053 9733 1844 6622 4213
2 7185 0135 6091 2387 4957 3113 7284 0750 3501 1945
3 5037 3365 1294 8261 2149 0718 3678 2510 7238 5268
4 8004 5199 3859 1293 5311 3550 9915 0512 1518 3776
5 9282 6893 4229 9736 0927 1418 1930 9864 0090 8974
6 7259 9399 0769 3144 9801 1378 4732 5134 1435 5282
7 2878 9963 7943 4519 3404 9810 1090 4467 7069 5348
8 1620 5879 0218 1064 9560 5732 6661 0883 1883 2619
9 3868 1905 2500 6654 0824 3710 3875 6332 1503 7259
0 4319 3298 7819 8721 1549 6630 6301 5701 3586 1907
Block 01
1 2 3 4 5 6 7 8 9 0
1 9328 1135 3871 1549 0839 8790 1771 8251 3274 1173
2 2297 9550 5033 0102 6817 5579 0847 4038 1200 2949
3 3640 3984 3299 1181 3811 8844 2500 4557 4133 0487
4 1256 9614 5520 8372 1941 2417 1098 4039 3943 8282
5 1751 4254 8479 8647 2684 5511 8680 4660 2315 4857
6 4587 5968 2568 1254 0258 1254 3568 2548 4521 8795
7 1258 6241 0125 2458 4587 5632 2589 1548 1235 1458
8 1254 2548 0004 4561 2565 2437 7849 1245 3265 4879
9 4582 1546 2589 2145 7854 7895 4589 6369 3698 1254
0 1255 1544 7850 2569 9989 8754 2548 1220 0387 0589
DICTIONARY CODES
Dictionary codes are highly specialized forms of
substitution systems. Code books (modified dict-
ionaries) used by the Department of State and military
represent a greater condensation of words than comm-
ercial systems - a single code group may represent a
long phrase. The average condensation of a diplomatic
code is 1:5 while a commercial code is only 1:3. [DAGA]
By way of comparison, modern PKZIP compression is 1:3 -
1:4 on normal text. I recently experimented with PKZIP
on the TEA program library for eight words and up and
found an average compression of 1:2.5. These groups
are all pronounceable artificial words. For example, we
might have ABACA in commercial code, EXA in diplomatic
code and occasionally syllables as BA in Marconi code.
It is difficult to safeguard against the loss of
codebooks which have to be printed in fair numbers.
Macbeth reports on an interesting story about Ottoman
Field-Marshal Osman Pasha during the Russo-Turkish war
in 1877. Pasha entrusted one of his generals, Selim
Pasha with a confidential mission. Selim was the officer
in charge of ciphers and codes and always kept the code
book on his person. Selim departed so promptly on his
mission that he forgot to leave the volume with his
chief. And the latter, during the whole time of the
Adjutant's absence, saw a pile of ciphered messages from
Constantinople accumulate on the table without being
able to read or reply to them. [DAGA]
Codes used in conjuction with ciphers (superencipher-
ment) can be very difficult to break; but the work and
time involved in making this combination can be
significant (if done by hand in the field.) Computers
reduce the legwork significantly.
The typical dictionary code protocol is as follows:
1) Agree with the recipient on the exact edition of the
diction to be used, i.e. Concise Oxford Dictionary,
current edition, by Fowler and Le Mesurier.
2) Use the number of the page, and the number of the
word down the page to encipher:
Given Plain: " Reunion Berlin Tomorrow"
Code:
1006 (page no.), 12(word no) = Reunion
0104 (pages with fewer than four numbers would have a 0
added in front to keep to the uniformity), 17 (word no.)
= Berlin
1291 - 08 (on the same principles) = To-morrow
Ciphertext:
100612 010417 129108
These figures, if greater secrecy is required, could
again be enciphered and thus converted into letters by
means of an agreed upon cipher.
3) Prepare for superencipherment by dividing the figures
into pairs and then convert them into letters by
means of a table such as Table 20-14.
Table 20-14
Digraphic Equivalents for Superencipherment
1 3 5 2 4 9 7 8 6 0
9 AN DA HN JT MB KC GF ES BZ ZA
2 CK AO DB HO JS GE ER BY FR YB
7 IR CJ AP DC GD EQ BT FQ LH VA
4 MC IY CI AR DD BS FP LI NL VB
8 MA KB GC CG AS DF HP JU OB VC
1 KA GB EP BR CE AT DG HQ JQ TZ
5 GA EO BP FO IX CC AX DH HR TY
3 EN BO FN LJ NK IZ CB AY DJ SB
6 BN FM LK NJ OA OC IV CB AZ QA
0 XY YA BY YB XC XE YD YE YX QC
Nulls: WA WE W, to end message in groups of fove
letters.
The numbers enciphered into letters:
TZYXBR XYXCDG BRANYE
and the cryptogram for transmission:
TZYXB RXYXC DGBRA NYEWA
The suggested cipher can easily be arranged to make
pronounceable words suitable for telegraph or
radiotelegraph transmission.
Certain dictionaries have been issued which give two
columns on each page with words directly opposite to
each other. Then it is possible to give the word
opposite the one we really mean, or a word which is 5 or
3 or 10 places either above or below the one we want to
encode. Codes of this kind can be solved readily.
CRYPTANALYSIS OF A SIMPLE DICTIONARY CODE
An Australian criminologist named Mansfield presented
some interesting principles for solving dictionary
codes. He calculated dictionary progressive lists,
giving numbers of words beginning with any two letters
in dictionaries of 10,000 - 100,000 words. [DAGA]
Given:
55381 42872 35284 44381 45174 56037 55381 46882
23171 44234 55366 55381 00723 12050 61571 36173
55381 56442
We rearrange the list from lowest numbers to highest.
00723 42872 55381 (5 times)
12050 44234 56037
23171 45174 56442
35284 46882 61571
36173 55366
Words beginning with XYZ are seldom used, so we can take
it that the highest number indicates a word beginning
with a W or a T. [ Mansfield made big assumptions about
nulls and standardization of the dictionary. Lectures 2
and 3 showed how we can rip this assumption to shreds.]
But the list of bigram frequencies (from Lecture 1)
gives us the commonest initial group as TH or THE, and
if we fix any repetition of such nature, then we may
have the T in that dictionary. Naturally, we start with
55381 occurring five times and assume it is THE.
The highest number after that is 61571, so that it could
indicate a word beginning with a W. This gives us a
clue to the probable number of words in the dictionary
used for the code. It cannot be over 65,000 words as XYZ
words are very few, seldom more than 3,000. [This part
of Manfield's analysis is an extraordinary jump of faith
-what is more extraordinary is that it will work more
than 60% of the time on simpler dictionary codes.]
According to Mansfield's Progressive Dictionary Lists,
we attempt to fix the probable first two letters of each
word in the code. For instance the 2nd group 12050 will
be between 11646 (terminating words beginning with DA)
and 12850 (terminating words beginning with DE), so that
it is probable to be a word beginning with DE. [DAGA]
[MANS], [MAN1]
Using Mansfield's lists we obtain:
THE RE--- OF THE RO--- TO- THE SE- -HA - RE- TH- THE
RE- DE- - WA- OV- THE TO-
We locate in the dictionary the word THE (55381) and
count back twenty words for 55366 (th). This gives us
an area covering words THANE, THANK, THAT, THATCH. We
try the most likely THAT. We note the two words
starting with letters TO- 56037 and 56442. Words
beginning with TO start at 56037 and stop at 56466, so
that it is reasonable guess to assume the first is TO
and the second (56442), we count twenty words back to
find the word TOWN.
The R group is: -RE- (42872) and RE- (44234) and RO-
(45174). RE stands 300 words from the end of the RA's
which stop at 42573, according to Mansfield's tables.
This gives us the following words to select from:
RECLINE, RECOMMEND, RECOMPOSE, RECONNAISSANCE, RECOUP,
and RECOVER. We choose RECONNAISSANCE. The next look at
our cipher is:
THE RECONNAISSANCE OF- THE ROUTE TO THE SE- HAS-
REVEALED THAT THE AE- DE- WA- OV- THE TOWN.
We apply the same process to the AE- 00723 and get
airplane, while the DE- 12050 occurring one-quarter of
the way from the end of the DA to the end of the DE
brings us to DEF, limited by DEFACE and DEFY, where only
DEFEAT, DEFENSE, DEFEND, and DEFENSIVE are probable. We
select airplane defensive us near the mark.
SE- should be sea 46882 and OVER for OV- 36173. The of-
is in fact OF, and the HA- is has, and the WA- is was.
The complete message reads:
THE RECONNAISSANCE OF THE ROUTE TO THE SEA HAS
REVEALED THAT THE AIRPLANE DEFENSIVE WAS OVER THE
TOWN.
[MANS] tells us that the real message was off by two
words. Instead of AIRPLANE DEFENSIVE, it was AIR
DEFENSES, but the meaning was essentially the same.
What Mansfield did show us in 1936 was that the laws of
probability work with dictionary codes. The search in
the area of possible words will give us the root of the
plain text so that we may deduce the whole meaning of
the code.
DIPLOMATIC CODES
One of the best references on historical codes (1775-
1938) in the United States was written by Professor
Ralph Weber. [WEBE] He describes one interesting code
used in 1867 by the State Department known as WE029.
(Refer to Table 20-15) It used a simple substitution
masking procedure, eliminated the use of the letter W
because it was not used in European or Latin nations,
focused on 24 letters of the alphabet and assigned them
to the 24 most common parts of speech such as articles
and other words (s= plural; a = THE; e = AND, etc.)
Other ordinary words were assigned to the approximately
600 combinations of 2 of the letters. Three letters were
used for the remainder of the vocabulary required for
common diplomatic usage; a fourth letter was added for
plurals, participles and genitives. When encoding the
plural, genitive, or participle of a 2-letter word, the
third letter would be placed apart in order to avoid
confusion. Code symbols were prepared for principal
countries and cities in the world, for states, major
cities, and territories of the United States, and for
proper names of men in English. A cipher table was to be
used for those words not on the list. The first 74
pages of the code was the encode section, and contained
the words in alphabetical order together with the code
symbols; for example the very first word was Aaron with
the symbol ABA, the last word of the first page was
Acknowledge with a symbol of EA. The decode section (3-
letter symbols) was not published in one sequential
alphabet and was time consuming. Transmission of the
code by cable was awkward because number of characters
was not standard. It was not until 1876 that the 5 digit
form became standard in the American ciphers. This code
became the secret communication mask for American
ministers in foreign legations in the years to 1876.
Table 20-16 is a chart of the number of encoded lines
sent from American ministers in seven major nations
using this code.
Table 20-15
1/3 Sample page WE029
ekf Lamentation
elf Language
emf Languid
enf Languidly
eof Languish
epf Languishing
eqr Lapse
erf Large
esf Largely
etf Lasting
euf Lastly
evf Late
exf Latent
eyf Latently
ezf Latin
faf Latitude
fbf Later
fcf Laugh
fdf Launch
fef Lavish
fff Lavishly
fgf Lawyer
fhf Lawful
fif Lawfully
fjf Lawfulness
fkf Lawless
flf Lawlessly
fmf Lawlessness
fnf Lax
fof Laxity
fpf Laxly
fqf Laxness
frf Lay
fsf Laziness
ftf Lazy
fuf Leader
fvf League
fxf Leak
fzf Lean
gaf Leap
gbf Learning
gcf Leave
gdf Lecture
gef Lecturer
gff Left
ggf Legal
ghf Legally
gif Legibility
Table 20-16
Russia Netherlands Great Britain Mexico
1866 11
1867
1868 38
1869 122
1870 6 184
1871 259 61
1872 3 189
1873 1
1874 17
1875 20
1876
Total 305 606
France Spain Germany
1866 33
1867
1868 7
1869 26
1870 27 52 11
1871 5 40
1872 31 10
1873 1 34 6
1874 20 2
1875 25 46
1876 13
Total 71 170 115
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