ADFGVX system
A German high-command cipher system used in World War I. Essentially, a
biliteral substitution system employing a 6 x 6 square, to which a columnar
transposition
was subsequently applied.
Alternate horizontal route transposition
Row transposition in which the route followed is alternately from left to
right and from right to left in successive rows.
Other terms with the same meaning: boustrophedon.
Alternate vertical route transposition
Columnar transposition in which the route followed is alternately up and
down
in successive columns.
Other terms with the same meaning: boustrophedon.
Anagram
Plain language reconstructed from a transposition cipher by restoring the
letters of the cipher text to their original order.
Autokey system
An aperiodic substitution system in which the key, following the application
of a previously arranged initial key, is generated from elements of the plain or cipher text
of the message.
Baconian cipher
A multiliteral cipher system invented by Sir Francis Bacon (1561-1626) in
which the cipher units are composed of arrangements of five elements, each of which may
be
chosen from one of two categories.
Beaufort system
A polyalphabetic substitution system employing a key word in connection
with a Vigenere square, but differing from the normal Vigenere method in its rules for
application of the key.
Begin spell
The plain equivalent of a code group indicating that the groups
immediately following represent elements taken from the syllabary or other special list.
Other terms with the same meaning: switch group.
Bipartite alphabet
A multiliteral alphabet in which the cipher units may be divided into two
separate parts whose functions are clearly defined, e. g., row indicators and column
indicators of a matrix.
Bipartite system
A substitution system involving the use of a bipartite alphabet.
Blocked code
A form of modified one-part code in which the code groups
and their
corresponding plaintext values are arranged in one-part order within
blocks which
themselves
are scattered in two-part order within the code.
When these reshuffled blocks are consistently of the same length as a page, the
system is called a repaginated code.
Book cipher
A cipher system, utilizing any agreed-upon book, in which the cipher
identifies a plain element present in the book.
Caesar's cipher
An ancient form of simple substitution cipher in which each plaintext
letter
was replaced by the letter three places to the right of it in the normal alphabet;
attributed to Julius Caesar.
Cipher
I. A cipher system.
II. A cryptogram produced by a cipher system (use
cryptogram instead).
Cipher alphabet
An ordered arrangement of the letters
(or other conventional signs, or both) or a written
language and of the characters which replace them in a
cryptographic process of substitution.
Cipher device
A relatively simple mechanical contrivance for encipherment and decipherment,
usually hand-operated or manipulated by the fingers, such as sliding strips or rotating
disks.
Cipher disk
A cipher device consisting of two or more concentric disks, each hearing on
its periphery one component of a cipher alphabet.
Cipher machine
A relatively complex apparatus or mechanism for encipherment and
decipherment, usually equipped with a keyboard and often requiring an external power source.
Cipher system
Any cryptosystem in which cryptographic treatment is applied to plaintext
units of regular length.
Cipher text
The text of a cryptogram which has been produced by means of a cipher system.
Of or pertaining to the encrypted text produced by a cipher system or to the elements which
comprise such text; as the ciphertext distribution.
Often shortened to cipher.
Code
l. A code system.
II. A code book.
III. A system of signals used in electrical or electronic
communication.
Code book
A book or document used in a code system, arranged in systematic form,
containing units of plain text of varying length (letters, syllables, words, phrases, or
sentences) -each accompanied
by one or more arbitrary groups of symbols used as equivalents in messages.
Code group
A group of letters or numbers, or a combination of both, assigned (in a code
system) to represent a plaintext element.
Letter / Syllable / Phrase/ Word - group: Code group that refers to letter / syllable /
phrase / word.
Code system
A cryptosystem in which arbitrary groups of symbols represent plaintext units
of varying length, usually syllables, whole words, phrases, and sentences.
Code table
A short code in tabular form.
Code text
The text of a cryptogram which has been
produced by means of a code system.
Codeword
A word which conveys an agreed upon meaning rather than its conventional
meaning. A cover name.
Columnar transposition
A method uf transposition in which the ciphertext is obtained by
inscribing
the plain text into a matrix in any way except vertically and then transcribing the
columns
of the matrix.
Cover name
An arbitrary word used, for security reasons, to indicate a specific meaning
such as a device, program, place, or unit and which specifically has no semantic connection
with its meaning.
Crib
I. Plain text assumed or known to be present
in a cryptogram.
II. Keys known or assumed to have been used in a cryptogram.
Cryptanalysis
The analysis of encrypted messages; the steps or processes involved in
converting encrypted messages into plain text without initial knowledge of the key employed
in the encryption.
Cryptanalyst
A person versed in the art of cryptanalysis.
Cryptogram
A communication in visible writing which conveys no intelligible meaning in
any known language, or which conveys some meaning other than the real meaning.
Other terms with the same meaning: encrypted message.
Cryptomaterial
All documents, devices, and machines employed in encrypting and decrypting
messages.
Cryptosystem
The associated items of cryptomaterial and the methods and rules by which
these
items are used as a unit to provide a single means of encryption and decryption. A
cryptosystem embraces
the general cryptosystem and the specific keys essential to the employment of the general
cryptosystem.
Decipher
To convert an enciphered message into its equivalent plain text by a
reversal of the cryptographic process used in the encipherment.
(This does not include solution by cryptanalysis.)
Decrypt
A decrypted, but not translated, message. To transform an encrypted
communication into
an intelligible one by a reversal of the cryptographic process used in encryption.
(This does not include solution by cryptanalysis.)
Digraphic substitution
Encipherment by substitution methods in which the plaintext units are
pairs
of characters and their cipher equivalents usually consist of two characters.
Double transposition
A cryptosystem in which the characters of a first or primary
transposition
are subjected to a second transposition.
Encipher
To convert a plaintext message into unintelligible language or signals by
means of a cipher system.
Encrypt
To convert a plaintext message into unintelligible language or signals by
means of a cryptosystem.
Encrypted text
The text produced by the application of a cryptosystem to a plaintext
message.
Equivalent key
A specific key that produces the same cryptographic results as a different
specific key.
Friedman square
A cipher square in which all the
diagonals reading in one direction contain the same sequence; in machine cipher solution,
the square represents the substitution effected by rotating a single rotor
through all possible positions.
Other terms with the same meaning: rod square.
Grille
I. A sheet of paper, cardboard, thin metal, plastic, or like material in
which perforations have been made for the uncovering of spaces in which textual units or key
may be written or read on a grid.
II. A matrix in which certain squares are blocked out or otherwise marked so as not to be
used. Also called a stencil.
Gronsfeld system
A polyalphabetic substitution system employing the first 10 alphabets of
a
direct
standard Vigenere table in conjunction with a numerical key. The cipher equivalent of a
given plaintext
letter is found by counting down the normal sequence the number of positions indicated
by
the numerical key.
Homophones
Different cipher text elements that maps to the same plain text element -
having the same meaning (by definition there are
always at least two homophones).
Initial key
The key used in starting an encipherment;
especially, the short key used to begin an autokey encipherment.
Other terms with the same meaning: preliminary key or priming key.
Inscription
I. In a transposition system, the process of writing a message into a
matrix.
II. The process of writing a series of numbers, letters, or coded meanings into a code
chart or table.
Jefferson cipher
A polyalphabetic substitution system invented by Thomas Jefferson and independently at a
later date by the French cryptographer Bazeries. It provided for encipherment by means
of a
manually operated device involving a number of revolvable disks, each bearing a mixed
alphabet on its periphery.
Key
In cryptography, a symbol or sequence of symbols applied to successive
textual elements of a message to control their encryption or decryption.
Key word
An arbitrarily selected word used as a key per se, or from which a key is
derived.
Latin square
A cipher square in which no row or column contains a repeated symbol.
Message
Any thought or idea expressed in plain or secret language, prepared in a form
suitable for transmission by any means of communication.
Mnemonic key
A key so constructed as to he easily remembered.
Monoalphabetic substitution
A type of substitution employing a single cipher alphabet by means of which each cipher
equivalent, composed of one or more elements, invariably represents one particular
plaintext
unit, wherever it occurs throughout any given message.
Multiliteral cipher alphabet
A cipher alphabet in which one plaintext letter is represented by cipher
units of two or more elements.
Multiliteral system
A substitution system involving one or more multiliteral cipher alphabets.
Multipartite alphabet
A multiliteral alphabet in
which each letter of plain text is represented by a cipher unit of two or more characters
whose functions are clearly defined.
Multiple-alphabet system
A type of substitution in
which successive lengthy portions of a message are each monoalphabetically enciphered by a
different alphabet; monoalphabetic encipherment by sections.
Nomenclator
Encryption method that contains elements of both a code and a cipher; this
usually means that frequent words, names and locations have their own code groups, while
other words are encrypted letter-wise.
Commonly used as a combination of a monoalphabetic/homophonic substitution,
digraphic/trightraphic substitution, codes and nulls;
Normal alphabet
The conventional sequence of letters which form the elements of written
language and are used to represent approximately the sounds of the spoken language. The
direct standard alphabet beginning with "A" and ending with "Z".
Null
Code group that has no meaning.
Nullifier
Code group that makes another codegroup meaningless.
Prefix nullifier / postfix nullifier / embraced nullifier / embracing
nullifier: Nullifier that makes the following / the previous / both / the embraced
code group(s) meaningless; expressions like “3-prefix nullifier”, “2-postfix nullifier”, or
“2-3-embraced nullifier” may be used if several code groups are made meaningless.
One-part code
A code in which the plaintext clements arc arranged in alphabetical, numerical, or other
systematic order accompanied by their code groups also arranged in alphabetical, numerical,
or other systematic order.
One-part
Nomenclator, in which the plaintext units and the codegroups are sorted
analogously.
One-time pad
A form of key honk used in a one-time system, so designed as to permit the destruction of
each page of key as soon as it has been used.
One-time system
A cryptosystem in which the key, normally of a random nature, is used only
once.
Open code
A system of disguised secret writing in which units of plain text are used as
the code equivalents for letters, numbers, words, phrases, or sentences.
The code equivalents themselves, usually words or phrases, can be combined to form the
intelligible text of apparently innocent messages.
Padding
Extraneous text added to a message for the purpose of concealing its length
and beginning or ending or both.
Partially-polygraphic system
Any polygraphic substitution system in which the encipherment of certain
members of the polygraphs show group relationships; small matrix systems, such as the
four-square, two-square and Playfair systems involve such group relationships and are
considered to be partially-digraphic systems.
Pattern
A plaintext or cipher sequence which contains or shows a pattern in its
construction as regards the number and positions of repeated elements.
Other terms with the same meaning: idiomorph.
Periodic substitution
Periodic polyalphabetic substitution. A method of encipherment involving the
cyclic use of two or more alphabets.
Other terms with the same meaning: repeating key method.
Periodic system
A system in which the enciphering process is repetitive in character and
which usually results in the production of cyclic phenomena in the cryptographic text.
Plain code
Unenciphered code.
Plain text
I. Normal text or language which, with no hidden or secret meaning, conveys
knowledge.
II. The intelligible text underlying a cryptogram.
Other terms with the same meaning: clear text, text in claris.
Plaintext
Of or pertaining to that which conveys an intelligible meaning in the
language in which it is written with no hidden meaning; as the plaintext equivalents.
Often shortened to plain.
Playfair system
A type of digraphic substitution using a single matrix normally of 25 cells.
Polyalphabetic substitution
A type of substitution in which the successive plaintext elements of a message, usually
single letters, are enciphered by a succession of different alphabets.
Polygraphic substitution
Encipherment by substitution methods in which the plaintext units are regular length
groupings of more than one element.
Polyphone
Cipher text element having several meanings.
Cipher text element in a polyalphabetic system.
Porta system
A forerunner of the Vigenere system of polyalphabetic substitution, this system employs 13
alphabets formed by sliding the second half of the normal alphabet against the first half.
Each alphabet may be identified by either of two key letters.
Preamble
One of the components contained in the heading of a message whose elements
include the degree of precedence, the date-time-group, and message instructions.
Probable word
A word assumed or known to be present in the underlying plain text of a
cryptogram. A crib.
Pseudo-polygraphic system
A polygraphic substitution system in which at least one of the letters in each polygraph is
enciphered monoalphabetically.
Q code and Q signal
Q code - A code adopted by the International Telecommunications Conference at Cairo, 1938.
Q signal - In joint and combined usage, a trigraph beginning with "Q" used to facilitate the
handling of traffic, to direct net operation, or to convey certain originator's instructions
in a message.
Random text
Text which appears to have been produced by chance or accident, having no
discernible patterns or limitations.
Recover
To solve; to reconstruct (e. g., cryptographic data or plain text.)
Recovered code
A codebook whose groups have been identified by cryptanalysis.
Repaginated code
A code in which the pages of the code book have been assigned a new sequence of identifying
symbols.
Revolving grille
A type of grille in which the apertures are so distributed that when the
grille is turned successively through four angles of 90 degrees and set in position on the
grid, all the cells on the grid are disclosed only once.
Other terms with the same meaning: rotating grille.
Ring
A movable metal collar bearing symbols, usually the letters of the alphabet,
on a rotor.
Rotor
A disk designed to rotate within a cipher machine and which controls the
action of some other machine component or produces a variation in some textual or keying
element.
Other terms with the same meaning: wheel.
Route transposition
A method of transposition in which the cipher-text equivalent of a message is obtained by
transcribing, according to any prearranged route, the letters inscribed in the cells of a
matrix into which the message was inscribed earlier according to some prearranged route.
Running key
In polyalphahetic ciphers, a non-periodic key arbitrarily prepared or
obtained from a book or any continuous text.
Simple substitution
Monoalphahetic uniliteral substitution.
Solution
In its cryptanalytic application, the process or result of solving a
cryptogram or cryptosystem by cryptanalysis.
Solve
To cryptanalyze. To find the plain text of encrypted communications by
cryptanalytic processes, or to recover by analysis the keys and the principles of their
application.
Stator
A stationary element in a cipher machine, (e. g., an endplate, a separator or
a rotor), that does not move during the operation of the machine.
Substitution cipher
I. A cipher system in which the elements of the plain text are replaced by
other elements.
II. A cryptogram produced by enciphering a plaintext message with a substitution
system.
Syllabary
In a code hook, a list of individual letters, combination of letters, or
syllables, accompanied by their equivalent code groups, usually provided for spelling out
words or proper names not present in the vocabulary of a code; a spelling table.
Transcription
I. In a transposition system, the process of removing the text from a matrix
or grid by a method or route different from that used in the inscription.
II. A written copy of a previously recorded radio transmission; also the process of
preparing such copy from tapes or records.
Transposition cipher
I. A transposition system.
II. A cryptogram produced by enciphering a message with a transposition system.
Transposition system
A cryptosystem in which the elements of plain text, whether individual letters, groups of
letters, syllables, words, phrases, sentences or code groups or their components undergo
some change in their relative positions without a change in their identities.
Trigraphic substitution system
A substitution system in which the plaintext units are composed of three elements.
Two-part code
A randomized code, consisting of an encoding section in which the plaintext groups are
arranged in an alphabetical or other systematic order accompanied by their code groups
arranged in a non-alphabetical or random order; and a decoding section, in which the code
groups are arranged in alphabetical or numerical order and are accompanied by their meanings
as given in the encoding section.
Two-part nomenclator
Nomenclator, in which the plaintext units and the codegroups are sorted
not analogously.
Uniliteral
Of, or pertaining only to cryptosystems, cipher alphabets and frequency
distributions which involve cipher units of single letters or characters.
Uniliteral substitution
A cryptographic process in which the individual letters or a message text are replaced by
single-letter cipher equivalents.
Weather code
A code used for the transmission of weather data.
Wheatstone cipher device
A cipher device consisting essentially of two rings mounted concentrically in a single
plane, the outer (IUld larger) ring being the plain component of the device and comprising
27 equisized divisions, the inner (and smaller) ring being the-cipher component, comprising
26 smaller divisions. The device incorporates two hands (similar to those on a clock)
pivoted at the center or the device-the larger hand serving the outer ring and the smaller
hand the inner-so geared together that for each complete revolution of the larger, the
smaller turns through one complete revolution plus one twenty-sixth.