paper_and_pencil.tex

a very popular packet of cryptography tools,it encloses the most common used algorithm and protocols

	D & s & p & o & s & i &   & S & n & i & o & - & t\\
	S & t & i & o & n & - &   & W & x & n & e & a & a\\
\hline
\end{tabular}  
\caption[Nihilist transposition]{Nihilist transposition\footnotemark}
\end{center} 
\end{table}

   Ciphertext: SPOIS EPLOM ATRNF NIOTX NEAA\\
   \footnotetext{%
   After filling the matrix with the cleartext you get the left block.
   After switching rows and columns you get the right block}

\item {\bf Cadenus} \cite{ACA2002}: Cadenus is a form of columnar 
   transposition that uses two keywords.\\
   The 1st keyword is used to swap columns.\\
   The 2nd keyword is used to define the initial letter of each column:
   this 2nd keyword is a permutation of the used alphabet. This permutation
   is written on the left of the first column.
   Afterwards, each column is moved (wrap-around) so that it begins with the
   letter, which is in the the same line as the key letter of the first 
   keyword within the second keyword.\\
   Ciphertext is read out line by line.
	
   Plaintext: cadenus is a form of columnar transposition using a keyword\\
\begin{table}[h]
\begin{center}
\begin{tabular}{|c|ccc|ccc|ccc|}
\hline 	
	  & K & {\bf E} & Y & {\bf E} & K & Y & {\bf E} & K & Y\\
\hline
	A & c & a & d & a & c & d & {\bf s} & a & a\\
	D & e & n & u & n & e & u & s & r & p\\
	X & s & i & s & i & s & s & i & f & i\\
	K & a & f & o & f & {\bf a} & o & u & l & o\\
	C & r & m & o & m & r & o & n & n & s\\
	W & f & c & o & c & f & o & k & t & g\\
	N & l & u & m & u & l & m & w & n & e\\
	S & n & a & r & a & n & r & d & o & o\\
	Y & t & r & a & r & t & {\bf a} & a & t & d\\
	{\bf E} & n & {\bf s} & p & {\bf s} & n & p & n & n & u\\
	D & o & s & i & s & o & i & i & i & s\\
	T & t & i & o & i & t & o & f & a & o\\	
	U & n & u & s & u & n & s & m & y & o\\
	B & i & n & g & n & i & g & c & r & o\\
	R & a & k & e & k & a & e & u & c & m\\
	G & y & w & o & w & y & o & a & e & r\\
	H & r & d & - & d & r & - & r & s & -\\
\hline
\end{tabular}  
\caption[Cadenus]{Cadenus\footnotemark}
\end{center} 
\end{table}%

   Ciphertext:\\
   SAASR PIFIU LONNS KTGWN EDOOA TDNNU IISFA OMYOC ROUCM AERRS\\
   \footnotetext{%
   Within the 2nd block of three chars those chars are printed bold which
   are at the top of the 3rd block after applying the 2nd key word.}

\end{itemize}


%------------------------------------------------------------------------------
\subsection{Substitution}
\index{Substitution}


%------------------------------------------------------------------------------
\subsubsection{Monoalphabetic substitution}
Monoalphabetic substitution\index{Substitution!monoalphabetic} assigns one 
character of the ciphertext alphabet to each plaintext character. This mapping
remains unchanged during the whole process of encryption.

\begin{itemize}

\item {\bf Random pairs} \cite{Singh2001}: Substitution occurs by a given
   combination of letters.

\item {\bf Atbash} \cite{Singh2001}: Replace the first letter of the 
   alphabet by the last letter of the alphabet, the second one by the last 
   but one, etc.

\item {\bf Shift cipher, for example Caesar cipher}\footnote{In CrypTool
   this method  can be find at three different places in the menu tree:\\
   - {\bf Crypt \textbackslash{} Symmetric (classic) \textbackslash{} Caesar}\\
   - {\bf Analysis \textbackslash{} Symmetric Encryption (classic)
     \textbackslash{} Ciphertext only \textbackslash{} Caesar} \\
   - {\bf Indiv. Procedures \textbackslash{} Visualization of Algorithms 
     using ANIMAL \textbackslash{} Caesar}. } 
   \cite{Singh2001}%
   : Plaintext alphabet and ciphertext alphabet are shifted against each 
   other. Using the Caesar cipher means shifting letters about three positions.

	Plaintext:	three positions to the right\\

	Ciphertext:	WKUHH SRVLWLRQV WR WKH ULJKW\\

\item {\bf Substitution with symbols} \cite{Singh2001}, for instance the so-called''freemason cipher'': Each letter is replaced with a symbol.

\item {\bf Variants}: Fill characters, intentional mistakes \cite{Singh2001}.

\item {\bf Nihilist substitution}\footnote{An animation of this Nihilist method
   can be find in CrypTool at the menu item
     {\bf Indiv. Procedures \textbackslash{} Visualization of Algorithms 
     using ANIMAL \textbackslash{} Nihilist}. }
   \cite{ACA2002}: Insert the alphabet into a 5x5-matrix and replace 
   every letter of the message with the two corresponding digits. The 
   resulting numbers are written into a grille. For this purpose, a 
   keyword is chosen and placed above the columns of the grille. Its 
   letters are substituted by numbers, too. The ciphertext results from 
   adding the numbers of the plaintext and the numbers of the keyword.
   Numbers between 100 and 110 are transformed to numbers between 00 and
   10, so that each letter is represented by a two-digit number.

	Plaintext: an example of substitution\\
\begin{table}[h]
\begin{center}
\begin{tabular}{|c|ccccc|}
\hline 	
	  & 1 & 2 & 3 & 4 & 5\\
\hline
	1 & S & U & B & T & I\\
	2 & O & N & A & C & D\\
	3 & E & F & G & H & K\\
	4 & L & M & P & Q & R\\
	5 & V & W & X & Y & Z\\
\hline
\end{tabular}  
\end{center} 
\end{table}

\begin{table}[h]
\begin{center}
\begin{tabular}{|ccc|}
\hline 	
	K & E & Y\\
	(35) & (31) & (54)\\
\hline
	a & n & e\\
	(58) & (53) & (85)\\
	x & a & m\\
	(88) & (54) & (96)\\
	p & l & e\\
	(78) & (72) & (85)\\
	o & f & s\\
	(56) & (63) & (65)\\
	u & b & s\\
	(47) & (44) & (65)\\
	t & i & t\\
	(49) & (46) & (68)\\
	u & t & i\\
	(47) & (55) & (69)\\
	o & n &  \\
	(56) & (53) &  \\
\hline
\end{tabular}  
\caption{Nihilist Substitution}
\end{center} 
\end{table}

	Ciphertext: 58 53 85 88 54~~~96 78 72 85 56~~~63 65 47 44 65~~~49 46 68 47 55~~~69 56 53\\

\item {\bf Coding} \cite{Singh2001}: In the course of time, codebooks were used again and again. A codebook assigns a codeword, a
	symbol or a number to every possible word of a message. Only if both parties hold identical codebooks and if the
	assignment of codewords to plaintext words is not revealed, a successful and secret communication can take place.

\item {\bf Nomenclature} \cite{Singh2001}: A nomenclature is an encryption system that is based upon a ciphertext alphabet. This
	alphabet is used to encrypt the bigger part of the message. Particularly frequent or top-secret words are replaced
	by a limited number of codewords existing besides the ciphertext alphabet.

\item {\bf Map cipher}: This method constitutes a combination of substitution and steganography\footnote{Instead of
	encrypting a message, pure steganography tries to conceal its existence.}. Plaintext characters are replaced by symbols
	which are arranged in a map following certain rules
	(see also: \href{http://library.thinkquest.org/27158/}{\texttt http://library.thinkquest.org/27158/}).

\item {\bf Straddling checkerboard} \cite{Goebel2003}. A 3x10-matrix is filled with the letters of the used alphabet and two
	arbitrary digits or special characters as follows: The different letters of a keyword and the remaining
	characters are written into the grille. The columns are numbered 0 to 9, the second and the third line are numbered
	1 and 2. Each plaintext character is replaced by the corresponding digit, respectively the corresponding pair of
	digits. As ''1'' and ''2'' are the first digits of the possible two-digit-numbers, they are not used as single
	digits. Besides, ''1'' and ''2'' are the most commonly used digits, but this feature is removed by the following
	technique.

	Plaintext: an example of substitution\\
\begin{table}[h]
\begin{center}
\begin{tabular}{|c|cccccccccc|}
\hline 	
	  & 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9\\
\hline
	  & K & - & - & E & Y & W & O & R & D & A\\
	1 & B & C & F & G & H & I & J & L & M & N\\
	2 & P & Q & S & T & U & V & X & Z & . & /\\
\hline
\end{tabular}  
\caption{Straddling Checkerboard with password ''Keyword''}
\end{center} 
\end{table}

	Ciphertext: 91932 69182 01736 12222 41022 23152 32423 15619

        It is ostentatious, how often the numbers 1 and 1 appear,
        but this will be fixed with the following version.

\item {\bf Straddling checkerboard, variant} \cite{Goebel2003}: This variant of the straddling checkerboard was developed by sovjet
	spies during WW2. A grille is filled with the alphabet (number of columns = length of keyword), and two digits are
	chosen to indicate the second and third line of a 3x10-matrix (see above). Now the grille is traversed
	column by column: For a faster encryption, the eight most common letters (ENIRSATO) are assigned the digits from 0
	to 9, the reserved digits are not assigned. The remaining letters are provided with combinations of digits one after
	another and are inserted into the grille.

	Plaintext: an example of substitution\\
	
\begin{table}[h]
\begin{center}
\begin{tabular}{|c|c|c|c|c|c|c|}
\hline 		
	K & {\bf E} & Y & W & {\bf O} & {\bf R} & D\\
\hline
	{\bf A} & B & C & F & G & H & {\bf I}\\
\hline
	J & L & M & {\bf N} & P & Q & {\bf S}\\
\hline
	{\bf T} & U & V & X & Z & . & /\\
\hline
\end{tabular}  
\end{center} 
\end{table}

\begin{table}[h]
\begin{center}
\begin{tabular}{|c|cccccccccc|}
\hline 	
	  & 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9\\
\hline
	  & A & T & E & - & N & O & R & - & I & S\\
	1 & K & J & B & L & U & Y & C & M & V & W\\
	2 & F & X & G & P & Z & H & Q & . & D & /\\
\hline
\end{tabular}  
\caption{Variant of the straddling checkerboard}
\end{center} 
\end{table}

	Ciphertext: 04221 01723 13252 09141 29181 14185 4
\item {\bf Tri-Digital}: A keyword with ten letters is used to create a numeric key by numbering its letters corresponding to their
	alphabetical order. This key is written above the columns of 3x10-matrix. This matrix is filled line by line
	with the alphabet as follows: The different letters of a keyword are inserted first, followed by the remaining
	letters. The last column is left out. Plaintext characters are substituted with numbers, the number of the last
	column is used to seperate words.
\item {\bf Baconian Cipher} \cite{ACA2002}: Assign a five-digit binary code to every letter and to 6 numbers or
	special characters (for example 00000 = A, 00001 = B, etc.) and replace the plaintext characters with this
	binary code. Now use a second, unsuspicious message to hide this code. This may happen by upper and lower
	case or italicized letters.
	
	message: fight\\
\begin{table}[h]
\begin{center}
\begin{tabular}{|ccccc|}
\hline
	00101 & 01000 & 00110 & 00111 & 10011 \\
	itisw & arman & thesu & nissh & ining \\
\hline \\
	itIsW & aRman & thESu & niSSH & IniNG \\
\hline
\end{tabular}  
\caption{Baconian Cipher}
\end{center} 
\end{table}
\end{itemize}


%------------------------------------------------------------------------------
\subsubsection{Homophonic substitution}

Homophonic methods\index{Substitution!homophonic} constitute a special form of monoalphabetic substitution. Each
character of the plaintext alphabet is assigned several ciphertext characters.

\begin{itemize}
\item {\bf Homophonic monoalphabetic substitution} \cite{Singh2001}: Each language has a typical frequency distribution of
	letters. To conceal this distribution, each plaintext letter is assigned several ciphertext characters. The
	number of ciphertext characters assigned depends on the frequency of the letter to be encrypted.
\item {\bf Beale cipher} \cite{Singh2001}: The Beale cipher is a book cipher that numbers the words of a keytext.
	These numbers replace the ciphertext letters corresponding to the words' initial letters.
\item {\bf Grandpr