Interactive Learning Tool for Cryptography
Celedonio Arroyo Serrano
Computer Science
arroyonex@gmail.com
Alfredo Cruz, PhD
Associate Director for Computer Science
alfredcross@gmail.com
Polytechnic University of Puerto Rico
Abstract - Cryptography is the science of keeping the secrecy of messages. It is a
common technique used to assure data confidentiality and integrity. Using a combination
of theory and practice techniques, we can reduce the time that it takes for a student to
understand and get familiarized with the different types of ciphers that are available.
With the development of a learning tool specifically designed to provide basic
understanding and capabilities of cryptography, anyone can learn, understand and use
monoalphabetic, polyalphabetic, and polygraph ciphers. The paper will provide an inside
view of the various functionalities available for the user, and information related to the
types of cryptography used within the tool. A tutorial is provided as an in class laboratory
exercise for network security or any related course in were the student will be able to
encrypt or decrypt any plaintext or ciphertext using a key. This will also clearly show the
differences between transposition and substitution ciphers. The learning tool will lead to:
a faster understanding of cryptography; motivate and engage students to practice the
theory of the courses related to cryptography; help master encryption/decryption
concepts quickly and effectively. The tool will also provide an extra resource for the
professor incorporating the tool into the lab environment and the course.
I.
INTRODUCTION
In our society information assurance has taken an important role. Almost all the transactions that are
done over the internet are secured by different kind of algorithms in order to maintain the confidentiality,
privacy and the integrity of the information that is being shared. In order to secure this information we
rely on cryptography which is the practice and study of hiding information [1]. The terms encryption and
decryption have become more common in everyday life. In college I found that these concepts are in many
of the courses that I have taken during my academic career.
In this paper we propose the use of a visualization technique in order to understand the basic concepts of
cryptography.
The purpose of this project is to provide instructors with a tool to effectively teach the basic concepts of
cryptography. The tool will motivate the student to participate and understand the concept better by
using a tool related to classical ciphers. With this tool the user will be able to differentiate the use of
mono-alphabetic, polyalphabetic and polygraph ciphers. Even though many of these ciphers can be
solved by hand, it will engage the student into using the technique and verifying if the encrypted or
decrypted message is correct.
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II.
SUPPORTING THEORY
VISUALIZATION
In 2011, Simms and Chi [14] said that visualization is a process of taking raw data and converting it to a
form that is viewable and understandable to humans. They also said that it is becoming a basic building
block in our daily lives because of the overwhelming amount of information required to be processed by
the human brain. Visualization is a technique for creating images, diagrams, or animations to
communicate a message. Primitive drawings on buildings and monuments are an example of visualization
techniques, proving that visualization has been around since the dawn of man. Advances in technology
have made visualization a very informative and easy to practice. The use of computer models as tools for
advancing scientific knowledge is becoming a key component of current scientific research. As we can see,
the implementation of visualization in the classroom can be very productive.
In 2011 Ma, Tao, Keranen, Mayo, and Kuang [10] stated that cryptography should be a course regularly
offered at colleges and universities. Textbooks and hand-books aid in the teaching of cryptography, but
students attracted to this field may post some unique challenges to educators. In particular, Computer
Science (CS) students find that understanding the sophisticated mathematics behind the crypto-systems
is a daunting task, while math majors often get lost in the details of the complicated algorithms. Educators
need to find a way to help students understand both how and why the algorithms are used [10].
Visualization tools can be an effective way for educators to battle this challenge. While some visualization
tools have been developed, not many of them allow the user to understand both the mathematical theory
and the algorithm behind a certain crypto-system [10].
CRYPTOGRAPHY
Cryptography is the method of storing and trans-mitting data in a way that only those it is intended for
can read and process it. It is the science of protecting information by encoding it into an unreadable
format. Cryptography is an effective way of protecting sensitive information stored on media or
transmitted through a network communication path. Although the ultimate goal of cryptography, and the
mechanisms that make it up, is to hide information from unauthorized individuals, most algorithms can
be broken and the information can be revealed if the attacker has enough time, desire, and resources. So a
more realistic goal of cryptography is to make obtaining the information too work-intensive to be
attractive to the attacker [8].
If we start to look back at the history of cryptography we see in many text books that this concept can
reach back to almost 4000 years. The Egyptians used a type of substitution cipher to encipher some of
their hieroglyphic writing on monuments. It’s also a fact that ancient Hebrews enciphered certain words
in the scriptures [6]. Even 2000 years ago Julius Caesar used a simple monoalphabetic cipher to send
secret messages to his generals. In the 1200s Roger Bacon described several methods to cipher messages
[5]. In 1585 the poly-alphabetic substitution cipher was described by Blaise de Vigenere [13]. Many other
ciphers had evolved during that time, producing a clear difference between classical ciphers and modern
ciphers. In this paper the approach of classical ciphers is one of the primary concerns.
CLASSICAL CIPHER
As mentioned, the Classical cipher has been used throughout history. But now, it’s being used to learn the
basic concepts of cryptography. With the fast growth of technology many techniques such as cryptanalysis
the encryption can be broken very fast. Encrypted messages are not secure and many of them can be
solved with the use of a piece of paper and a pencil.
DEFINITION OF CONCEPTS
In order to understand better the concept involved in cryptography we need to define a couple of basic
concepts:
 Plaintext: The original intelligible message or data that is fed into the algorithm as input.
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 Ciphertext: The scrambled message produced as output.
 Encryption: The process of converting from plain-text to ciphertext.
 Decryption: The process of restoring the plaintext from the ciphertext
 Key: A value used to encrypt or decrypt a message or data.
 Cryptanalysis: The branch of cryptology dealing with the breaking of a cipher to recover information.
III.
TYPES OF CIPHERS USED IN THE TOOL
The Interactive Learning Tool is still in progress. So far, the ciphers that are available in the tool are the
Caesar cipher, Vigenere Cipher, Playfair Cipher, and the Rail Fence Cipher. In order to provide a clear
understanding it is important to understand how each of these ciphers work and to classify each of them
correctly.
MONOALPHABETIC CIPHER
Mono-alphabetic ciphers use fixed substitution over a plaintext in order to create a ciphertext. It’s
important to mention that the algorithms in this kind of cipher are based on two general principles:
substitution cipher and transposition ciphers.
Substitution cipher is a method of encoding by which units of plaintext are replaced with ciphertext,
according to a regular system, for example a pair of letters, triple letters or a mixture of letters. Using this
cipher an encrypted message can be sent and the receiver can decode the message by performing an
opposite substitution [6].
In Transposition ciphers the units of the plaintext are rearranged in a different and usually quite complex
order, but the units themselves are left unchanged. In contrast to the substitution cipher, the units of the
plain-text are retained in the same sequence in the ciphertext, but the units themselves are altered [6].
CAESAR CIPHER
The Caesar cipher is a monoalphabetic cipher. It is composed of the use of the alphabet (in our case the
English alphabet) from A to Z. It’s considered in many textbooks and other sources of information as an
early cipher method. The Caesar cipher is commonly used to teach the basic concepts of cryptography.
Other types of classical ciphers will use a key and a plain-text in order to encrypt or decrypt a message,
but this cipher uses a shift parameter. The shift parameter is responsible for the transformation of the
ciphertext or the plaintext. Based on the shift parameter, the alphabets that are aligned together will be
rotated to the left or to the right, depending on the number of shifts.
In Figure 1, we can see how the alphabet was trans-formed using a shift parameter of 3. We can see that
different lines from the top alphabet are pointing to different letters from the bottom alphabet. In this
example A was transformed into D, B was transformed into E, C was transformed into F, and so on, until
the entire alphabet is transformed. It’s important to mention that once the alphabet reaches the final
letter in the alphabet (Z) it will keep on transforming the alphabet starting from A again until the full
transformation is completed.
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Figure 1: Transformation of the Alphabet
This classical monoalphabetic cipher is very easy to break, based on the fact that it only holds 26
characters from the English alphabet. In other words, we can conclude that one of the 26 shifts will be the
correct one and once it’s found, and it can be very easy to keep doing the transformation until obtaining
the plaintext. This kind of action is known as a brute force attack.
Frequency Analysis
Another way to break this cipher is with frequency analysis. This is a technique that is very important
even in modern cryptography, as we can see in many tools that are developed to break different kinds of
ciphers. Since its part of the basic knowledge we will include more information about it.
According to Martin (2012), in monoalphabetic ciphers (like in the simple substitution ciphers),
frequency analysis can help to break the ciphertext based on the size of the ciphertext used. Since it is
looking for words that are always present in the English alphabet, it can be assumed that those letters can
be repeated almost all the time (like for example the letter T and the letter E). Martin (2012) also
explained that even though frequency analysis has a degree of trial and error before establishing what the
correct matches are, it reduces the choice with respect to the remaining letter. Frequency analysis does
have it’s limitations, but there are many tools that provide almost instant decryption of a ciphertext
generated by the simple subtitution cipher, [11].
Mathematical Description of the Caesar Cipher
The mathematical description of the Caesar cipher is one of the easiest to understand. This makes
the cipher very easy to implement using any pro-gramming language, even without the use of an
arithmetic expression. In this case, an array would be created and a series of loops can then shift the
alphabet depending on the number of shifts wanted. In the mathematical description of the cipher, we can
conclude that ciphertext will be equal to C, while the plaintext will be equal to P, and the shift parameter
will be K. Many books, articles and web pages use the same arithmetic expression of this cipher. The
arithmetic expression is as follows:
C = P + K mod 26
The alphabet will be represented from 0 to 25, in were A = 0, B = 1, C = 2…..Z = 25.
POLYALPHABETIC CIPHER
We can see a noticeable difference when we compare a polyalphabetic cipher to a mono-alphabetic
cipher. In the polyalphabetic cipher we can see how the substitution is done at different positions of the
message.
In this cipher a unit from the plaintext is mapped to one of several possibilities making this type of cipher
a little bit more secure than the regular monoalphabetic ciphers [3].
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One of the characteristic of this kind of ciphers is that multiple cipher alphabets are used. In order to
facilitate encryption, all the alphabets are usually written out in a large table that consists of a 26×26
graph, so that 26 full ciphertext alphabets are available. The method of filling the table, and of choosing
which alphabet to use next, defines the particular polyalphabetic cipher.
VIGENERE CIPHER
Considered one of the most popular, it was first published in 1585. It was considered unbreakable until
1863.
The Vigenere Cipher consists of the alphabet written out 26 times in different rows, as shown in Figure 2.
Each alphabet is shifted cyclically to the left compared to the previous alphabet, corresponding to the 26
possible Caesar ciphers [7]. In Figure 2 we can observe that the top row represents the plaintext letters.
The leftmost column of the square (that has the letters from A to Z in order from top to bottom) represent
the key letters. Now that we know that, we can use it to map that plaintext letter to the ciphertext letter on
the column. The letters on the right column represent the letter on the row that is part of the key. With
this combination we can find the ciphertext letter that we are looking for. In other words, we select the
letter from the plaintext on the top row, and then we select the letter from the right column that is part of
the key. We then trace those two and select the letter that intersects the column and the row, this letter is
then the ciphertext letter. It’s important to mention that in order to start the encryption process we need
to get the plaintext and align each letter on it with the letters of the key. If the key is too short for all the
letters, then we keep repeating the key [12]. For example, if the plaintext is SECURITY and the key is
VEGAS then the alphabet used at each point depends on repeating the key used to encode or decode,
aligning each character using the same letter on the key until all the characters in the plaintext are
covered as follows:
Plaintext:
S
E
C
U
R
I
T
Y
Key:
V
E
G
A
S
V
E
G
Figure 2: Vigenere Square
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The decryption is performed by going to the row in the table corresponding to the key, finding the position
of the ciphertext letter in this row, and then using the column's label as the plaintext, same operation as in
the encryption process but backwards.
Mathematical Description
The algebraic description of this cipher is as follows: If the letters A–Z are taken to be the numbers 0–25,
and addition is performed modulo 26, then Vigenere encryption E using the key K can be written as:
Ci = Ek ( Mi ) = ( Mi + Ki ) mod 26
For decryption we use D as decryption using the key K, for example:
Mi = Dk ( Ci ) = ( Ci – Ki ) mod 26
With these formulas, it’s very easy to create the pseudo-code that is implemented in the tool.
POLYGRAPH CIPHER
In a polygraphic substitution cipher, plaintext letters are substituted in larger groups, instead of
substituting letters individually. The first advantage is that the frequency distribution is much flatter than
that of individual letters (though not actually flat in real languages; for example, 'TH' is much more
common than 'XQ' in English). Second, the larger number of symbols requires correspondingly more
ciphertext to productively analyze letter frequencies, making this type of cipher harder to break [11].
The earliest practical digraphic cipher or pairwise substitution was the so-called Playfair cipher.
PLAYFAIR CIPHER
In this cipher, a 5 x 5 grid is filled with the letters of a mixed alphabet (two letters, usually I and J, are
combined). A digraph substitution is then simulated by taking pairs of letters as two corners of a
rectangle, and using the other two corners as the ciphertext. This was developed by Charles Weatston.
Special rules handle double letters and pairs falling in the same row or column [2].
Thanks to the way it’s implemented, the Playfair cipher is harder to break. There are almost 600 possible
digraphs rather than the 26 possible monographs, making frequency analysis harder. But with today’s
computing power and capabilities, this could take only a few seconds.
In Figure 3, we can see a 5 x 5 grid, also known as a graph. On it a key was used and the grid was
generated. Notice that I and J are together in order to fulfill the combination mentioned before.
Figure 3: Playfair Graph
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To generate the key table, one would first fill in the spaces in the table with the letters of the keyword, in
Figure 3, we used the key ANNUALCONFERENCE, (Dropping any duplicate letters) then we filled the
remaining spaces with the rest of the letters of the alphabet in order, in this version we put both "I" and
"J" in the same space, this is the classical Playfair cipher. The keyword together with the conventions for
filling in the 5 by 5 table constitutes the cipher key.
To encrypt a message, one would break the message into digraphs (groups of 2 letters) such that, for
example, "MEET ME IN LAS VEGAS" becomes "ME XE TM IN LA SV EG AS", and map them out on the
key table. If needed, append an "X" to complete the final digraph, or if two letters are the same like for
example in the word “MEET” an “X” need to be used to separate the double “EE”, for example “ME XE”.
The two letters of the digraph will be used to do the decryption or the encryption, and this is done by
using a rectangle as the reference. For example in “ME XE” we are going to start by looking “ME” on the
graph. We look for “M” and then “E” and we create a rectangle with those two, in other words we will
consider each letter as a corner of a rectangle in the key table. Depending on the type of rectangle we need
to use the following 4 rules to order each pair of letters in the plaintext in order to encrypt the plaintext:
A. If both letters are the same (or only one letter is left), add an "X" after the first letter. Encrypt the
new pair and continue.
B. If the letters appear on the same row of your table, replace them with the letters to their immediate
right respectively (wrapping around to the left side of the row if a letter in the original pair was on
the right side of the row).
C. If the letters appear on the same column of your table, replace them with the letters immediately
below respectively (wrapping around to the top side of the column if a letter in the original pair was
on the bottom side of the column).
D. If the letters are not on the same row or column, replace them with the letters on the same row
respectively but at the other pair of corners of the rectangle defined by the original pair. The order is
important – the first letter of the encrypted pair is the one that lies on the same row as the first
letter of the plaintext pair.
To decrypt, use the INVERSE (opposite) of the last four rules, and the 1st as-is (dropping any extra "X"s
that do not make sense in the final message when finished).
TRANSPOSITION CIPHER
In cryptography, a transposition cipher is a method of encryption by which the positions held by units
of plaintext (which are commonly characters or groups of characters) are shifted according to a regular
system, so that the ciphertext constitutes a permutation of the plaintext. That is, the order of the units is
changed (the plaintext is reordered). Mathematically it can be described as a bijective function in where
the characters positions to encrypt and using the inverse function to decrypt. In order to understand this
concept better we use the Rail Fence cipher [2].
RAIL FENCE CIPHER
The Rail Fence cipher gets its name from the way in which it is encoded [2]. It is one of the most basic but
always used ciphers to show the concepts of transposition ciphers. In the Rail Fence cipher, the plaintext
is written downwards on successive "rails" of an imaginary fence, then moving up when we get to the
bottom. The message is then read off in rows.
In Figure 4, we can see an example, using three "rails" and a message “INTERACTIVE*LEARNING
*TOOL*FOR CRYPTOGRAPHY”. Each space was replaced by the character ‘*’ in order to represent better
the transposition. As we can appreciate in Figure 4, we included a line that shows how the transposition
goes from the top row. First, the character “I” is placed, then we shift a column to the right in the second
row and the character “N” is placed. Then we shift another column to the right and in the third row the
character “T” is placed. All of this is done in a vertical way and once we hit the third rail (row), we do the
same but from the bottom rail to the first one. We move back to the second rail and the character “E” is
placed, then we move to the first rail and the character “R” is placed.
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Figure 4: Rail Fence example
After all the transposition of the ciphertext is done, then we can read the encrypted message. This is done
by reading the first row, from left to right and continuing to read each row as we normally do giving as a
result the encrypted message:
IRIT**PRYNEATV*OLFRCYTGAHTCEOOROP
The rail fence cipher is not very strong because the number of practical keys is small enough that a
cryptanalyst can try them all by hand. In other words, this code is very easy to break using frequency
analysis. Transposition ciphers such as the Rail Fence cipher have another major weakness: they don't
hide letter frequencies at all. What does that mean? Since this is a monoalphabetic cipher, each
substituted letter always represents the same plaintext letter; it’s easy to check for the frequency each
letter appears in the cipher. The most frequently appearing letters of the English language are E-T-A-O-IN-S-H-R-D-L-U, respectively.
IV.
INTERACTIVE LEARNING TOOL DESCRIPTION
This tool is designed to help students understand and learn the basic concepts of classical cryptography
by exposing them to a visualized representation of the algorithms used. While the instructor is giving the
lectures related to cryptography, they can find different examples in an easy to use tool that can be readily
available at the laboratory to encrypt and decrypt messages. The tool in essentially in its basic form, but
additional ciphers and information such as the source code, the algorithms and the pseudo-codes will be
available to the user.
The tool was created using JAVA, because it’s one of the most popular programming languages being
taught at Polytechnic University of Puerto Rico, and also because it uses object-oriented programming.
The IDE used to create the tool is NETBEANS 7.4, based on the fact that it’s user friendly and gets a lot
of support from different users that formerly worked with this IDE. Since it’s an open program, the
implementation of the tool can be seen by anyone that desires to see, use, and/or modify the code. Details
on the project will be available to students and faculty, as they will be able to see all the classes of ciphers
included and all the effort that is being put into the final product.
DEMO OF THE TOOL
The tools include the classes for each of the ciphers that were mentioned in this paper, Caesar, Vigenere,
Playfair and Rail Fence Cipher.
In Figure 5 we have a clear overview of the classes that are contained up to this moment under the project.
Each class is assigned a name according to the type of function it performs.
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Interactive Learning Tool for Cryptography
Figure 5: Java Classes as seen on IDE
As we can see in Figure 5, each cipher holds its own java.class where all the functionality to encrypt and
decrypt is contained.
When starting the program a menu will open as seen in Figure 6, giving the user a clear view of the
ciphers that are available.
Figure 6: Main menu of the GUI
In Figure 7 we can observe the menu that is used to select the different options that are available in the
tool. In addition, different labels were added to the menu to clearly specify each different type of cipher:
monoalphabetic, polyalphabetic and polygraph ciphers.
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In the monoalphabetic cipher we can see the substitution and transposition ciphers.
Figure 7: Menu with selections
The Caesar cipher is the first choice available in the menu. In Figure 8 the user will be able to enter a
plaintext and select the shift parameter once selected. When the plaintext “CryptographyIsEasyToLearn”
is entered the user will notice that spaces are not permitted; this is a restriction to ensure that the
encrypted message follows a standard. Then, when clicking below on the “shift” text box a combo box with
26 shift options appears to choose the shift parameter that the user wants to use in the Caesar cipher. In
Figure 8 the shift parameter used was 4. Once the user clicks on the encryption button the encrypted
message will be added to the ciphertext textbox in the screen and the ciphertext will read as follows:
“gvctxskvetlcmwiewcxspievr”; please note that upper case characters were transformed to lower case.
CAESAR CIPHER TEST
Figure 8: User input, encrypting a message
Afterwards, the user can copy the ciphertext that was generated into the decryption form on the screen,
select the shift parameter, and decrypt the message as in Figure 9, giving as a result in the decryption
textbox the plaintext used during the encryption process. As can be observed, the plaintext generated is
“cryptographyiseasytolearn”. Please note that there are no upper case words in this decryption. This
makes the user aware of changes and after reading the plaintext he can easily corroborate it with the one
entered during the encryption process.
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Interactive Learning Tool for Cryptography
Figure 9: Decryption of encrypted message
VIGENERE CIPHER TEST
If the user wishes to use a different cipher he can just click on any of the buttons in the menu as shown in
Figure 7. In Figure 10 we can observe the use of the interactive tool for the Vigenere cipher.
Figure 10: Vigenere encryption test
As we can see in Figure 10, the key entered was “VEGAS”, and the plaintext was “ANNUAL SECURITY
CONFERENCE”. Once the button to encrypt the message was selected the ciphertext was created and
added to the textbox for the user to copy it. The ciphertext generated reads: “VRTUSG YEUPVOTQ
GUNXZ VKNUZ”. In this example a restriction was added to prevent the user from entering numbers.
Furthermore, when decrypting the message, the key is copied into the decryption part automatically, as
shown in Figure 11.
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Figure 11: Decryption of Vigenere
As we can see in figure 11, the key was already provided by the encryption process. When the user adds the
ciphertext “VRTUSG YEUPVOTQ GUNX ZVKNUZ” and clicks the decrypt button the ciphertext is
decrypted. The plaintext is shown in lowercase in order for the user to see the details and become aware of
the transformation of the ciphertext into plaintext. The plaintext reads as follows: “annual security
conference”
PLAYFAIR CIPHER TEST
Users can also select the Playfair cipher. In Figure 12 we can see an example of a key entered and the
plaintext. After the user clicks the encrypt button, the ciphertext will appear. The key entered is “ANNUAL
CONFERENCE”, and the plaintext to be encrypted using the key is “NEW ORLEANS HOTEL BE
PRESENT”. The encrypted message generated reads as follows, “UF-VF-IR-OU-LP-DE-QB-CR-FQ-BRQR-CP”. It is important to mention that this was generated following the instructions for encrypting
Playfair ciphers provided in this paper. Please note that after each digraph there is a dash to make the
reading easier.
Figure 12: Encryption of Playfair
In Figure 13, the user will copy the encrypted ciphertext and with the same key provided in the
encryption, will be able to decrypt the encrypted message. The plaintext generated is also represented in
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Interactive Learning Tool for Cryptography
digraph and a dash is added after each digraph, as we can see in the plaintext that reads as follows: “newo-rl-ea-ns-ho-te-lb-ep-re-se-nt”.
Figure 13: Decryption of Playfair
It’s important to mention that in this particular cipher the user will be able to see the representation of the
5 x 5 matrix that is used in the Playfair cipher as shown in Figure 14. Please note how the key is placed in
each of the columns from left to right, in the first row and continuing into the second row in the same
pattern. In Figure 14 the key used was “ANNUAL CONFERENCE”, and since many of the letters are
repeated, only one of each will be represented, for example “ANNUAL” has 2 repeated “N’s” so only one is
added. “A N U L” represents the “ANNUAL” part of the key in the graph. For “CONFERENCE” we can see
that E is repeated 3 times, and N is already used. In this case E will be added only once and N won’t be
added. “C O F E R” represents the “CONFERENCE” part of the key in the graph. The remaining spaces on
the graph are added in ascending order using the English alphabet, without repeating the letters that are
already in the graph. “I/J” always goes together in this typical Playfair interpretation.
Figure 14: Translation Grid
In Figure 15 we can see how the Grid represented in Figure 14 is shown in the tool during the
encryption/decryption process of the Playfair cipher.
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Figure 15: Actual Representation in the Tool
V.
FUTURE WORK
Since the tool is under development additional features will be added. The source code section of the tool
and the algorithm section of the tool are still under construction. Although the webpage is available,
details are not included in the paper. Other ciphers, for example Advanced Ciphers, will be included. New
options will be added to select and change perspectives from classical ciphers to modern ciphers. This will
include ciphers to understand the concepts of block and stream ciphers.
Another section that will be included in the tool is a detailed encryption/decryption process. This process
will follow a flowchart diagram including all the processes that are done once the encryption or decryption
button in a form is selected. This idea was proposed and implemented with a modern cipher as seen in
[10].
This tool will be used by faculty and students taking courses related to cryptography. Tools and data will
be evaluated in and out of the classroom to see the impact on learning and the functionality of the
visualization tool for delivering the concepts of cryptography to others.
VI.
AKNOWLEDGEMENT
This material is based upon work supported by, or in part by, the Nuclear Regulatory Commission (NRC)
Grant Fellowship Award under contract/ award # NRC-27-10-511 and is also based upon work supported
by, or in part by, the U.S. Army Research Laboratory and the U.S. Army Research Office under
contract/grant number W911NF1110174.
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VII.
REFERENCES
[1] Ali Mayouf, M., & Shukur, Z. (2009). Using Animation in Active Learning Tool to Detect Possible
Attacks in Cryptography Protocols. 1st International Visual Informatics Conference on Visual
Informatics: Bridging Research and Practice, 510-520.
[2] Apelbaum, Y. (2007). User Authentication Principles, Theory and Practice. Fuji Technology Press.
[3] Dhull, S., Beniwal, S., & Kalra, P. (2013). Polyalphabetic Cipher Techniques Used For Encryption
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