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Cryptanalysis Source Code in C

**********************************************************************
			       _Crypto-Basics_
			      Joseph M. Reage Jr
		   University of Maryland, Baltimore County

	The following are some basic cryptographic programs I wrote for my own 
purposes or for Dr. Stephens cryptography class with Dorothy Dennings
"Cryptography and Data Security" and Sinkov as (necessary) references.
	The documentation is sketchy, and I may improve it in time, but
most of the programs are quite small and simple and perform algorithms
that are quite well known.
	The following may be copied and modified freely provided that 
Joseph M. Reagle Jr. is acknowledged within the code as the
originator.

[e-mail]
[e-mail]

Joseph M. Reagle Jr.
3327 Hiss Ave.
Balto., Md. 21234


File Name			Purpose
------------------------------------------------------------------------
c6.c				A tool for solving transposition ciphers. 
				(Method of Sinkov)

crt.c				Solves for the inverse of a number (mod n) 
				using the Chinese Remainder Theorem.
                                                      
freq.c				Gives a frequency list of characters in
				a file.

ic.c				Give the Index of Coincidence for a
				given text file.

jac.c				Lists the probable prime numbers between
				two integer values.

knap.c				Exhaustively breaks small knapsack
				ciphers.

rprime.c			Finds the percentage of two random
				numbers happening to be relatively prime.



                                                        Page
                   Documentation for c6.c
                     By Joseph M. Reagle

Data Structures:

     The data structure is that of single dimension array which
is filled in a row order manner from left to right.
	There are two arrays, one is the original array
original_matrix, the other is the working array matrix.  The
procedures such as get_element and put_element are
interfaced as if it were a 2 dimensional matrix, they take
care of the indexing into the array.
     I also use the data structure history.  Which is an
array which keeps track of swaps done.  It's place keeper is
place.

Flow:

     My program first reads the data file (without control
characters such as line feeds), determining the
size of the cipher text.  Then it reads it into the matrix.
This allows a conservative use of system memory.
     My program, then essentially gives control to the
rather large procedure interface.  interface determines what
the user wants to do by the minimum number of keystrokes.
The user can type the whole command out (he or she can get a
listing by typing 'help'), or the a abbreviated version of
the command, that is not ambiguous.  For instance 's' is
ambiguous, since the user may want to 'save', or 'swap'.

Procedures:

     Most procedure's are self-evident in their purpose, and
I have tried to document confusing code, but a quick run-
down of the procedures follows:

is_vowel(char token): is the token a vowel?

get_size (char *argv[1], int *size) : reads the size of the
  file using the command line file name passed in through
  main.  It returns the value size by dereferencing the
  value.

get_matrix(char *argv[1], char *matrix, int size) : reads
  the file once again to read it into the array matrix, of
  size size.

get_element(char *matrix, int x, int y) : gets an element
  from matrix in a virtual, 2 dimensional format.

put_element(char *matrix, int x, int y, int element) :
  places the element into matrix in a virtual 2 dimensional
  format.

save_matrix(char *matrix, int size) : saves the matrix to
  'crypt.log' without the analysis done in print_matrix.

print_matrix(char *matrix, int size) : this procedure is
  perhaps the least cohesive procedure since it not only
  prints out the procedure, but also prints out vowel
  counts, and calculated the statistics.  I have documented
  this code pretty heavily, and the subtitles should help
  one to understand the function of each section of code.
  Such headings are Print the Header, Print and Update the
  Stat_Info, Print the Footer, and Compute Average and
  Variance Statistics.

swap (char *matrix, int first, int second) : Swaps two
  columns by first recording what columns are being swapped
  (for undo).  Then it swaps the two elements (in the
  columns first and second) in the first row, then the
  second row, down to the height of the matrix.

undo (char *matrix) : Undoes the last step, all they way
  back to the beginning if the user so desires it.  It
  looks at the last two swaps in the history array, does a
  swap using those two numbers, then decrements the pointer
  in the history array by 4.  This is because I want to
  take back the original swap that I wanted undone, and the
  swap that undid that swap!

resize (int x, int y) : changes the size of the matrix.

advise (int size) : this uses Kinkov's algorithm for finding
  possible size of a incompletely filled, rectangular
  matrix.  It creates a range from the square root of the
  size, to it's half.  Then within this range, decrements
  through it, using each number as the row.  Then with this
  row, I use Kinkov's method to provide possible columns.
  An asterisk denotes a full matrix.

interface (char* argv[], char *matrix, int size, FILE *fp) :
  a procedure that reads input from the keyboard, then
  parses the input on the first couple of significant
  characters, and performs the appropriate function.

main (int argc, char* argv[]) : main reads the size,
  initializes the two matrixes "original_matrix", and
  "matrix".  Prints the matrix out, and then runs advise.

----------------------------------------------------------------

The following is the cipher

temmaticshtra*stio*repl*ceeael*ity*wiah*rtdeaam*of*rrd*o*te*is*peiharr*opr*thisfres*o*athat*mnthsaaiecians*tremauh**strance*sgdsaociall**inyp*npeoplettoe*eo*te*oneveldst*fmathemoti*a*sc*to*tuin*sra*afrom*tye*whyipcal*wosldhr

------------------------------

The following is in the correct size matrix

temmaticshtra*
stio*repl*ceea
el*ity*wiah*rt
deaam*of*rrd*o
*te*is*peiharr
*opr*thisfres*
o*athat*mnthsa
aiecians*trema
uh**strance*sg
dsaociall**iny
p*npeoplettoe*
eo*te*onevelds
t*fmathemoti*a
*sc*to*tuin*sr
a*afrom*tye*wh
yipcal*wosldhr

--------------------------------

The following is the solution:

mathematics*tr
ies*to*replace
*reality*with*
a*dream*of*ord
er*it*is*perha
ps*for*this*re
ason*that*math
ematicians*are
*such*strange*
and*socially*i
nept*people*to
*devote*onesel
f*to*mathemati
cs*is*to*turn*
away*from*the*
physical*world
   14 x 16