Completion of Programs

The Goals We Have Met

The listings of the 'programs.p' should be used in conjunction with this index of all programs, their input/output requirements and their authors.

These programs are released under the GNU General Public Licence and may be used in other projects under the terms of the GPL.
Mono-alphabetic Substitutions

Definition of substitution

Where each letter of plaintext is mapped to a unique letter in the ciphertext. This takes the form of either:

Cæsar cipher (ie "Shift by 3" rule)
"Random" mapping of each letter to another

Programs to attack a substitution

Cæsar cipher program to translate given the most frequent letter of the cipher

ShiftFreq.p by Brett Avery
Input:

standard input(redirected <) of the most frequent letter

infile - containing the text to be translated
Output:

standard output(screen or redirected >) of prompts
outfile - contains translated text

Progresses through each of the 26 Cæsar cipher keys or until the user selects one as being the correct cipher

caesar_n.p by Stuart Prescott
Input:

standard input(keyboard) key
infile - containing text to be translated
Output:

standard output(screen) translated text
outfile - contains text which has been translated

A monoalphabetic substitution program which applies a given substitution table to the given text. The user is given the option not to encrypt HTML tags (ie text between < and >)

substHTML.p by Stuart Prescott
Input:

standard input(keyboard) of menu
infile - containing text to be translated
substtable - containing the substitution table. Comments may be made in substtable using braces ({comment}). Unknown letters may be signified using a question mark ('?'). Such unknowns will be arbitrary allocated an unused letter. This is denoted in the text by a capital letter.
Output:

standard output(screen) of menu and messaging
outfile - contains text which has been translated

Performs a letter frequency analysis of the given text. This program is combined with a comparison to 'standard' English frequencies and formulates a possible substitution table based on this comparison.

freq.p by Stuart Prescott
Input:

standard input(redirected <) - menu prompts
engfreq - standard English frequencies
infile - the file to be analysed
Output:

standard output(screen) of letters sorted by frequency giving the absolute frequency, the percentage frequency and the possible plaintext equivalents.
substtable - possible substitution table sorted by letter frequency

A program which finds all the 2 lettered words in a piece of text. This assists in formulating a substitution table.

2letter.p by Stuart Prescott
Input:

infile - the file to be analysed
Output:

nletterwords - contains each 2 lettered word in the text and (if it occurs more than once) its frequency

A program to find all digrams (2-letter combinations) or trigrams etc in a piece of text. This prog may also be used to find all n-lettered-words in a piece of text.

string.p by Michael Shuter
Input:

standard input(redirected <) user info
infile - the file to be analysed
Output:

standard output(screen or redirected >) of user info
outfile - analysis details

A program to find all digrams (2-letter combinations) or trigrams etc in a piece of text.

stringDist.p by Jack Dermody
Input:

infile - the length of the analysis string and the file to be analysed
Output:

standard output(screen or redirected >) of digrams and frequencies.

The Vigenére Cipher

Definition of the Vigenére Cipher

Provided with a keyword of length n, the algorithm uses n different Cæsar ciphers for each of the letter positions 1...n. This is illustrated below using the key hello:

Plain-text:	`the quick brown fox jumped`
Keystream:	`hel lohel lohel loh ellohe`
Cipher-text:	`bmq chqhw ngwbz rdf ogyemi`

Programs to attack a Vigenére cipher

Encryption using Vigenére keys of any length

encipvig.p by David Grogan
Input:

standard output(screen) of the user info.
infile - the text to be encrypted

Output:

standard output(screen) of the user info
outfile - the encrypted text

Decryption using Vigenére keys of any length

vigdecip.p by David Grogan
Input:

standard output(screen) of the user info.
infile - the text to be decrypted

Output:

standard output(screen or redirected >) of the user info
outfile - the decrypted text

Find the length n of the Vigenére key using The Index of Coincidence.

vig.p by David Grogan
Input:

infile - the text to be analysed

Output:

standard output(screen or redirected >) of the indices of coincidence.

Performs a letter frequency analysis of every nth letter (for n = 1...26) . This will find the length of the Vigenére key. This program is combined with a comparison to 'standard' English frequencies.

freq_var_n.p by Stuart Prescott
Input:

standard input(redirected <) - menu prompts
engfreq - standard English frequencies
infile - of the file to be analysed
Output:

standard output(screen) of letters sorted by frequency giving the actual freq, the %freq and the possible plaintext equivalents
substtable - substitution table(s) sorted by letter freq
summary - a summary of each of the nth letter analyses and their rating

Performs a letter frequency analysis of every nth letter for a given n and starting position in the text. This will find the length of the Vigenére key. This program is combined with a comparison to 'standard' English frequencies.

freq_n.p by Stuart Prescott
Input:

standard input(redirected <) - menu prompts
engfreq - standard English frequencies
infile - of the file to be analysed
Output:

standard output(screen) of letters sorted by frequency giving the absolute frequency, the percentage frequency and the possible plaintext equivalents
substtable - substitution table sorted by letter freq

Performs a letter frequency analysis of every nth letter for a given n and each starting position 1...n in the text. This information is then used to find the Vigenére key.

freq_const_n.p by Stuart Prescott
Input:

standard input(redirected <) - menu prompts
infile - of the file to be analysed
Output:

standard output(screen) of Vigenére Key.

A script to link all these packages for cracking Vigenére encryption

vigenere by Stuart Prescott
Input:

standard input(keyboard or redirected <) of menu responses
whatever file(s) are to be analysed
Output:

standard output(screen or redirected >) of menus.
whatever file is the product of the cracking

Rotations

Definition of the Rotation: Provided with a Rotation function ( R(x), where x is the position of the letter within the document), the algorithm uses a number (dependent on R(x) ) of different Cæsar ciphers in the same manner as the Vigenére cipher.

The rotation (in its simplest form) is R(x) = x. This is effectively a Vigenére cipher with a keystream of abcdefg...xyz.

In more complex forms the Rotation function may be a polynomial or a Fibonacci relation. The general form of a Fibonacci relation is:

R(x) = a(R(x - m)) + b(R(x - n))

where:
x is the position of the letter within the document
a, b, m, n are constants
Programs to attack a Rotation

Encryption/Decryption using a Linear Rotation function
R(x) = ax
(Use a to encode, -a to decode)

rotation.p by Chris Boshuizen
Input:

standard input(screen or redirected <) of the Rotation coefficient
infile - the text to be translated

Output:

standard output(screen or redirected >) of prompts
outfile - the translated text

Encryption/Decryption using a Fibonacci Rotation function
R(x) = a(R(x - 1) + R(x - 2))
where: R(1) = R(2) = 1.
(Use a to encode, -a to decode)

fibonacci.p by Chris Boshuizen
Input:

standard input(keyboard) of the rotation coefficient
infile - the file to be translated
Output:

standard output(screen) of prompts
outfile - the translated text.

A script to link all these packages for Rotations

rotations.men by Chris Boshuizen and Jack Dermody
Input:

standard input(keyboard or redirected <) of menu responses
whatever file(s) are to be analysed
Output:

standard output(screen or redirected >) of menus.
whatever file is the product of the cracking

AutoKey Encryption

Definition of AutoKey Encryption: The AuotKey method of encryption uses a key (of length n) for the first n letters of the cipher. After that the actual cipher-text itself is used as the key (hence the terminology auto-key. The Key is applied in the same manner as the Vigené key.
Programs to implement an AutoKey cipher

Encryption/Decryption using an AutoKey cipher
AutoKey.p by Brett Avery
Input:

standard input (keyboard or redirected <) of the Key.
infile - the text to be encrypted

Output:

standard output(screen or redirected >) of the user info
outfile - the encrypted text

SkyTail Cipher

Definition of the SkyTail cipher: The text is translated from columns of characters to rows of characters and then broken up into words.
Programs to implement a SkyTail cipher

Encryption using the SkyTail cipher

encipsky.p by David Grogan
Input:

infile - the text to be encrypted

Output:

standard output(screen or redirected >) of the user info
outfile - the encrypted text

Decryption using the SkyTail cipher

decipsky.p by David Grogan
Input:

infile - the text to be decrypted

Output:

standard output(screen or redirected >) of the user info
outfile - the decrypted text

A script to link all these packages for SkyTail ciphers

skytail by Jack Dermody
Input:

standard input(keyboard or redirected <) of menu responses
whatever file(s) are to be translated
Output:

standard output(screen or redirected >) of menus.
whatever file is the product of the translation

Enigma Encryption

Definition of the Enigma Variations (not Elgar's . . .): The Enigma encryption methods were developed during the 19th century. The German implementation of this system in WWII consisted of an electro-mechanical machine which allowed the user to type in the message on a keyboard and the translated text was then written out.

The machine used 3 rotors which had the numbers 1..26 on them. These wheels turned the same way the wheels on an odometer turn (ie each time the first wheel completes a revolution, the next wheels moves round one place . . .)

A monoalphabetic substitution was also placed over the text.

This variation allows the user to set up 4 wheels (the last one is only useful on very long documents) where the numbers on the wheels are in any order and may be repeated.
Programs to crack the Enigma encryption

Encryption/Decryption using the Enigma Variations (without the substitution - see Monoalphabetic Substitutions)
Allowing the user to choose whether or not to operate on HTML tags.

enigma.p by Stuart Prescott
Input:

standard input(keyboard or redirected <) of menu
infile - the text to be encrypted

enigmawheels - four rows of 26 numbers for the wheels
Output:

standard output(screen or redirected >) of prompts
outfile - the encrypted text

Encryption/Decryption using a different Enigma Variations (without the substitution - see Monoalphabetic Substitutions)
Allowing the user to choose whether or not to operate on HTML tags.

enigvar.p by Michael Shuter
Input:

standard input(keyboard or redirected <) of menu
infile - the text to be encrypted

wheeldata - up to 400 numbers for the wheels
Output:

standard output(screen or redirected >) of prompts
outfile - the encrypted text

Decrypting/Encrypting/Solving the unsubstituted Enigma.

solenig.p by Michael Shuter
Input:

standard input (keyboard) of wheel refinements.
infile - the text to be decrypted
wheeldata - contains the information on the contents of the wheels
Output:

standard output(screen or redirected >) of the user info
outfile - the (partially)decrypted text

A script to implement a full Enigma Encryption (ie Substitution, Enigma, Substitution)

SES by Stuart Prescott
Input:

standard input(keyboard or redirected <) of menu responses
enigmawheels - four rows of 26 numbers for the wheels
substtable1 - 1st letter substitution table
subattable2 - 2nd letter substitution table
whatever file(s) are to be translated
Output:

standard output(screen or redirected >) of menus.
whatever file is the product of the translation
enigmasummary - summary log of the process

Plain-Text Attacks

Definition of the Plain-Text Attack: A plain text attack on a piece of cipher-text consists of looking for parts of the text which may be assumed. Such parts are often names, headings, equations, salutaions or dates.
Programs to implement a plain-text attack

Finds the numerical difference between guessed and encrypted text.

diffe.p by Michael Shuter
Input:

standard input (keyboard or redirected <) of menu
infile1 - the text to be compared

infile2 - the text to be compared

Output:

outfile - the letter differences

Written by Stuart Prescott for and on behalf of the group of
Brett Avery
Christopher Boshuizen
Jack Dermody
David Grogan
Stuart Prescott
Michael Shuter

Copyright © MCMXCVI Stuart Prescott

Last edited: Friday June 25, 2004

Completion of Programs

The Goals We Have Met

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