Shalala Cipher, a New Implementation of Vigenere Cipher for

Wireless Sensor Node Security

Muhammad Shaiful Azrin Md Alimon

, L.M. Kamarudin

1,2

, Azizi Harun

, Ammar Zakaria

and Shaufikah Shukri

Center of Excellence in Advanced Sensor Technology, University Malaysia Perlis, Malaysia

School of Computer & Communication Engineering, University Malaysia Perlis, Malaysia

Keywords: 8-bit Cipher, Cryptography, WSN Security, Vigenere Cipher, Shalala.

Abstract:

Cryptography is a science that deals on the method of converting plaintext into cipher text, usually with the

help of encryption keys and encryption algorithm. Current standard implementation of cryptography is

proved to require high resource in memory which is not suitable to be implemented in low memory

embedded system, thus a lightweight cryptography are required. Vigenere cipher is one of the encryption

algorithms that was easy to implement and comprehand, which can be used to provide confidentiality from

the third party. Vigenere cipher is a polyalphabetic Ceaser cipher, which means it shifting the character in

plaintext to become character of mod of its key character. Even thou Vigenere cipher are a classical cipher

that doing its cipher using character compared to modern cipher that doing its cipher using bits and byte, it

still can be implemented in modern computer by representing its character based on ASCII Table.

Furthermore, because of this, its character can be extended to contain all alphabet and special character in

the ASCII Table, thus allowing it to encrypt every character that can be represented using ASCII Table.

Originally the resilience of Vigenere cipher is based on two factors: (1) the length of its key, and (2) the

randomness of character in its key. Even though increasing the length and the used random character

provide a great resilience, it takes away the fun of using dictionary word to encrypt the plaintext. To

overcome that, this paper, proposing a method of implementing a Pseudorandom Path that change the flow

of mod use by the Vigenere Cipher to encrypt and decrypt either positive mod or negative mod. Usually

Vigenere Cipher use positive mode to encrypt, while negative mod to decrypt, however this paper propose a

method to combine both mod during encryption or decryption with the supervision from the Pseudorandom

Path. This method of implementation and its result were discussed in this paper and named as Shalala

Cryptography. The results were compared between using original resilience and a Shalala Cryptography

method. The resource requirement to implement this algorithm using C++ language is also shown, which

shows a lightweight cryptography scheme in term of RAM consumption and fast processed time, which are

suitable to be used in WSN or IoT environment.

1 INTRODUCTION

Cryptography, a Greek word for secret writing, it’s

an art of applied mathematics and science used to

hide plaintext to become cipher text. Cryptography

provides confidentiality between two parties,

provided that both parties use the same method and

know the key, while securing the message during

massage delivery from getting known by the third

party. Thus making cryptography is one of the

essential ingredients in secure network

communication (William Stalling, 2004).

There are two types of encryption key:-

1. Symmetric encryption – both parties use the

same key for encryption and decryption, and

2. Asymmetric encryption – where both parties

used private key and public key for encryption

and decryption respectively.

In this paper, Vigenere cipher is used as the

cryptographic algorithm, which is a symmetric

encryption that used the same key for both parties. It

is considered as le chiffre indéchiffrable (French for

'the indecipherable cipher'), because for 300 years it

Alimon, M., Kamarudin, L., Harun, A., Zakaria, A. and Shukri, S.

Shalala Cipher, a New Implementation of Vigenere Cipher for Wireless Sensor Node Security.

DOI: 10.5220/0006358403630369

In Proceedings of the 2nd International Conference on Internet of Things, Big Data and Security (IoTBDS 2017), pages 363-369

ISBN: 978-989-758-245-5

363

cannot be cracked, not until it is cracked by

Friedrich Kasiski during 1863 using a frequency

analysis. Even though by increasing the length of its

key as long as the plaintext and using a random

character as its key can create an uncrack able

cipher, it takes away the fun of using Vigenere

cipher, which was to use dictionary words as its

keyword. Nowadays, this cracking process is much

easier to implement, by writing a small call that

automatically brute forcing the cipher text using all

the words in dictionary and this kind of attack were

known as “Dictionary Attack”.

To enhance this Vigenere cipher, while

maintaining the fun, this paper proposes Shalala

Cryptography, a method that combines both positive

mod and negative mod of character shifting with a

supervision of Pseudorandom Path as shown in

section 2, and the result of its implementation can be

seen in section 3, followed with section 4 that shows

the resilience test, comparing the original Vigenere

Cipher with the Shalala Cipher. Last, is section 5,

shows the resource requirement and the example of

its application.

2 PROPOSED METHOD

Figure 1: Original Vigenere Cipher Algorithm, Left for

Encryption and Right for Decryption.

It is good to note that Vigenere Cipher used in this

paper is using an extended Vigenere Cipher that

contain every character that can be represented by

ASCII Table, thus creating a mod96 instead of

mod26 as in Original Vigenere Cipher. Diagram 1

shows the implementation diagram of the original

Vigenere Cipher Algorithm using mod96 during

encryption and decryption while Diagram 2 shows

the algorithm of a Shalala Cryptography method

using the same mod.

Diagram 2: Proposed Method Algorithm to Enhance

Vigenere Cipher Resilience.

Diagram 2 shows the algorithm of a Shalala

Cryptography method which is consist of two block

diagram, each for encryption and decryption. Top

block is used for encryption, it works by:

Algorithm 1: Encryption Algorithm

Take Character at Nth position of the

plaintext and key

Take Character at 1th position of the key

and take the 1

bit Then Masking

with 1

bit of Masking Character

If result of Masking Block is ‘1’

Forward the Nth position of the

plaintext using Positive Mod

Encrypt using Positive Mod

Forward result as Nth position

encrypted

Else If result of Masking Block is ‘0’

Forward the Nth position of the

plaintext using Negative Mod

Encrypt using Negative Mod

Forward result as Nth position

encrypted

IoTBDS 2017 - 2nd International Conference on Internet of Things, Big Data and Security

364

Increment

increasing the Masking bit and N

character key’s bit followed with

next character

If the entire bit of Nth position of

the key were used

Take the next position of

the key and take the

bit Then

Masking with 1

bit

of Masking

Character

While [Ciphertext.length() <

Plaintext.length()]

Repeat at number 3

Meanwhile the bottom block is used for

decryption, it works by:

Algorithm 2: Decryption Algorithm

Take Character at Nth position of the cipher

text and key

Take Character at 1th position of the key

and take the 1

bit Then Masking with

bit of Masking Character

If result of Masking Block is ‘1’

Forward the Nth position of the

cipher text using Negative Mod

Decrypt using Negative Mod

Forward result as Nth position

decrypted

Else If result of Masking Block is ‘0’

Forward the Nth position of the

plaintext using Positive Mod

Decrypt using Positive Mod

Forward result as Nth position

decrypted

Increment

increasing the Masking bit and N

character key’s bit followed with

next character

If the entire bit of Nth position of

the key were used

Take the next position of

the key and take the

bit Then Masking

with 1

bit of

Masking Character

While [Plaintext.length() <

Ciphertext.length()]

Repeat at number 3

This implementation can also be represented in

algebraic form shown in equ.1 and equ.2 for original

Vigenere using mod96 and equ.3 and equ.4 for the

Shalala Cryptography method using the same mod.

By representing each character used in mod96 with

ASCII Table, those characters can be represented as

number from number 32 to 126. Taken E as

encryption and K as key, the algorithm can be

written as follow (S. Garg, 2016).

Ci = EK(Pi) = ( Pi + Ki ) mod96

(equ.1)

And decryption D using the key K

Pi = DK( Ci ) = ( Ci - Ki ) mod96

(equ.2)

Where

P = P0…Pn is the message,

C = C0….Cn is the ciphertext and

K= K0.....Km is the used key.

Representing the proposed method in

algebraic form require an if-else conditional

statement. Take:

P = P0…Pn is the message,

C = C0….Cn is the ciphertext and

K= K0.....Km is the used key.

Kbit[n] = K0….Km in 8 bit arrays of its

byte representational as in ASCII Table and n is the

position of bit

Mask = 8 bit array, predetermined by the

user

M() = Masking function that masking

Kbit[n] with Mask[n] using X-OR logic

The encryption algebraic is like follow:











































,



1

























,



0

(equ.3)

And decryption D







































,1





















,0

(equ.4)

Shalala Cipher, a New Implementation of Vigenere Cipher for Wireless Sensor Node Security

365

3 EXAMPLE AND RESULT OF

IMPLEMENTATION

Let’s take an example to understand the Shalala

Cryptography algorithm in a better way where its

result can be analyzed. This are the parameter used

for this example for encryption:

Plaintext: - 2016BatmanvsOni#@

Keyword: - Bat

Masking key: - 10010011

4 ANALYSIS AGAINST THE

ADVISARY

It is good to note that the analysis method used in

this paper is to compare the cipher text generated

between the original Vigenere Cipher and the

proposed method against Frequency Analysis and

Dictionary Attack.

Table 1: Encryption using Shalala Cryptography Method.

Plaintext 2 0 1 6 B a t m a n v s O n i # @

ASCII

Plaintext

Keywor

B a t B a t B a t B a t B a t B a

ASCII

Keywor

66 97

Kbit

B = dec66 or B = hex42 a = dec97 or a = hex97

hex7

0 1 0 0 0 0 1 1 0 1 0 1 0 1 1 1 0

Masking 1 0 0 1 0 0 1 1 1 0 0 1 0 0 1 1 1

X-OR 0 0 1 0 1 1 1 1 0 0 1 1 1 0 1 1 0

Result T N < s $ 1 7 O l 1 5 ~ q P ^ E “

Table 2: Decryption using Shalala Cryptography Method.

Cipher

Text

T N < s $ 1 7 O l 1 5 ~ q P ^ E “

ASCII

84 78 60 115 36 49 55 79 108 49 53 126 113 80 94 69 34

Keyword B a t B a t B a t B a t B a t B a

ASCII

Keyword

66 97 116 66 97 116 66 97 116 66 97 116 66 97 116 66 97

Kbit

B = dec66 or B = hex42 a = dec97 or a = hex97 74

0 1 0 0 0 0 1 1 0 1 0 1 0 1 1 1 0

Masking 1 0 0 1 0 0 1 1 1 0 0 1 0 0 1 1 1

X-OR 0 0 1 0 1 1 1 1 0 0 1 1 1 0 1 1 0

Result 2 0 1 6 B a t m a n v s O n i # @

Table 3: Encryption using Original Vigenere Cipher.

Plaintext 2 0 1 6 B a t m a n v s O n i # @

ASCII

Plaintext

50 48 49 54 66 48 116 109 97 110 118 115 79 110 105 35 64

Keyword B a t B a t B a t B a t B a t B a

ASCII

Keyword

66 97 116 66 97 116 66 97 116 66 97 116 66 97 116 66 97

Result T q & X $ V 7 O V 1 X h q P ^ E “

IoTBDS 2017 - 2nd International Conference on Internet of Things, Big Data and Security

366

Table 4: Decryption using Original Vigenere Cipher.

Plaintext T q & X $ V 7 O V 1 X h q P ^ E “

ASCII

Plaintext

84 113 38 88 36 86 55 79 86 49 88 104 113 80 94 69 34

Keyword B a t B a t B a t B a t B a t B a

ASCII

Keyword

66 97 116 66 97 116 66 97 116 66 97 116 66 97 116 66 97

Result 2 0 1 6 B a t m a n v s O n i # @

4.1 Frequency Analysis

It is a part of descriptive statistic that measure the

frequency of event to occur, in term cryptanalysis

however is the study of the frequency of letters or

groups of letters to be happen in a cipher text.

Based on the example shown in section 3. The

process is repeated using much longer sentence as

described as follow:

“Batman Batman Batman Batman Batman Batman

Batman Batman Batman Batman Batman Batman

Batman”

There are total of 25 repeated “Batman”, hence it

is expected to reveal some pattern if using original

Vigenere cipher. The result of the process between

original and Shalala Cryptography can be

compared using the distribution diagram produced

using both result and were shown in Diagram 4

and 5. Diagram 3 shows the original plaintext

character distribution.

Good cryptography is a cryptography that

can hide the plaintext character to become more

distributed across the character. Diagram 5 have

shown that the Shalala Cryptography provide a

more distributed character compare to the original.

Diagram 3: Plaintext Character Distribution (6 character).

Diagram 4: Original Vigenere Cipher Character Distribution (16 character).

Diagram 5: Proposed Method Character Distribution (32 character).

100

anBmt

017$VCc idPtbOBa

]

‐

Space

Shalala Cipher, a New Implementation of Vigenere Cipher for Wireless Sensor Node Security

367

4.2 Charles Babbage Analyses

Vigenere cipher is a combination of a series of

Ceaser cipher, if the key used were “Bat” it means

that the cipher text is divided into 3 subtexts and

each subtexts is cipher using separate Ceaser shift,

which were in this case it use modB, moda, and

modt. According to Charles Babbage, Vigenere

cipher can be cracked by:

 Identify the repeated sequence

 Determine the spacing, thus knowing the length

of its key

 Either implement frequency analysis or start

guessing systematically

Diagram 6 shows the result of cipher text of

original Vigenere cipher implementation, the

highlighted region shows the repeated sequence and

strikethrough shows the spacing.

dCi0CcB$V7OV1a7$Vb$PtdCi0CcB$V7OV1a

7$Vb$PtdCi0CcB$V7OV1a7$Vb$PtdCi0CcB

$V7OV1a7$Vb$PtdCi0CcB$V7OV1a7$Vb$Pt

dCi0CcB$V7OV1a7$Vb$PtdCi0CcB$V7OV1a

7$Vb$PtdCi0CcB$V7OV1a7$Vb$PtdCi0Cc

Diagram 6

dKCyB$l7,l1a7$Vb$‐

+dCi0Cy]$lROVL>M$3b$‐t

i0CcB$VR,V1a7$3x$‐+dCK

c]$VROlLa7$Vb$P+

Ci0Cc]`VR,V1>M?Vx$P+d

0CcB$V7,l1a7$Vx?P+CiK

yB`V7,VL>7$Vb$Pt

i0CcB`l7,l1aM?3b?PtCKCc

Diagram 7

Meanwhile diagram 7 shows the result of cipher

text of proposed method, the highlighted region

shows the repeated sequence and strikethrough

shows the spacing. Places where repeating sequence

happened in original Vegenere were not happened in

Shalala method, thus proving that the proposed

method to be frequency-analysis-proof.

4.3 Dictionary Attack

It is a method to systematically guessing the

keyword to beat the decryption algorithm to decrypt

the cypher text, such keywords can be every words

in dictionary. Based on the Diagram 6, it shows that

the length of its keyword were 3 characters because

of 3 set of repeating sequence, and according to

here[5] there were only 1015 of English words that

can be found in dictionary.

The process to implement dictionary attack

is to guess a single word from the expected

plaintext, let say it is “Batman”. Then a small code

can be written that feed those dictionary word and

cipher text into the decryption algorithm, upon

completed, a quick search on “Batman” is conducted

at the resultant plaintext. If the word “Batman” is

found the process end, if not it is repeated until all

the dictionary word were used. Again if it still fail,

change “Batman” to another word, and repeat the

process.

Because of Charles Babbage analysis on

the Shalala method doesn’t show any sequence, and

it is concluded to be frequency-analysis-proof, thus

it also concluded that the proposed method have

successfully enhance the Vigenere Cipher against

Dictionary Attack.

5 RESOURCE REQUIREMENT

AND EXAMPLE OF ITS

APPLICATION

The Shalala Cryptography has been tested using

Arduino Board. It is very lightweight and proved to

be high cryptography resilience. Table 1 shows the

resource requirement of the algorithm written using

C++, and because of this it is very suitable to be

implemented in Internet of Things application to

provide resilience during communication.

Table 5: Hardware Requirement.

Study Proposed

Method

ROM Consumption (kB) 4,850

RAM Consumption (kB) 883

Processing Time (ms) 8

6 CONCLUSION

Vigenere Cipher is a lightweight cryptography

implementation that was easy to comprehend and

implement. Depending on its implementation it can

be uncrack able cipher by making the keyword as

long as plaintext and in random sequence, however

by doing so, it takes out the fun of using dictionary

word to encrypt the plaintext. In this paper, a new

implementation using Vigenere as its core

cryptography with the idea of maintaining the fun of

IoTBDS 2017 - 2nd International Conference on Internet of Things, Big Data and Security

368

using the dictionary word has been proposed, the

idea is to encrypt or decrypt the text using a

combination of positive mod and negative mod of

Vigenere character supervised by the Pseudorandom

Path. Pseudorandom Path give output ‘0’ or ‘1’

based on the byte represented by the keyword. To

further increase the resilience, a Masking Block is

implemented on top of the Pseudorandom Path, that

X-OR the bit from Pseudorandom Path with the bit

from the Masking Block. Example of this

implementation can be seen in section 3, and the

implementation technique with its diagram is shown

in section 2. Depending on the number that were

produce by Pseudorandom Path after Masking, the

plaintext will follow a different encryption path, 0 is

for positive mod and 1 is for negative mod, which

were vice versa during decryption process. As a

conclusion compared with the original

implementation of Vigenere Cipher, this proposed

method were frequency proofed and cannot be

dictionary attacked even thou it used a dictionary

word as it encryption key. Furthermore, because of

this algorithm is lightweight, it is very suitable to be

implement in motes used in the Internet of Things

environment. The good things about it is by

changing the masking key, it will change the entire

cipher text output, thus if it implement on 8bit

devices, it will create a unique 255 difference

output, for each sentence.

REFERENCES

Stallings, William. Network Security Essentials. 1st ed.

Pearson Education. Print.

S. Garg, et al, “Extended Vigenere Cipher with Stream

Cipher”. International Journal of Engineering Science

and Computing, (2016) 5176-5180

Beutelspacher, Albrecht. Cryptology. 1st ed. Washington:

The Mathematical association of America, 1994. Print.

Analysis, Frequency et al. "Frequency Analysis Tool -

Letter Counter - Online Software Tool

★

". Dcode.fr.

N.p., 2017. Web. 15 Feb. 2017.

"Decrypting Text". Richkni.co.uk. N.p., 2017. Web. 15

Mar. 2017.

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