Combination Playfair Cipher Algorithm and LSB Steganography for

Data Text Protection

Apri Siswanto, Sri Wahyuni and Yudhi Arta

Department of Informatics Engineering, Universitas Islam Riau, Pekanbaru, Indonesia

Keywords:

Cryptography, Steganography, Playfair Cipher, Grayscale, Least Signiﬁcant Bit (LSB).

Abstract:

Encryption and steganography are needed to ensure the integrity and conﬁdentiality of data in the process of

sending data on the internet. In this paper, there are two stages to securing the message. The ﬁrst step is

to randomize messages to be sent with Polygram cipher substitution. The second step is to avoid messages

from third party suspicions that can be done with the steganography process. The message used in this study

is text. In the cryptographic process, the message in the form of text will be encrypted with the Playfair

Cipher method, and then the encrypted message will be carried out in the LSB steganography process on

a gray scale 8-bit digital image on a scale of 0-255. This study shows that by using Playfair Cipher and

cryptographic Steganography in insertion, encrypted messages will be difﬁcult to return to original messages

by unauthorized parties. The result of this application is that you can insert hidden messages in text form into

PNG format digital image ﬁles and can extract hidden messages from the image (stego-image).

1 INTRODUCTION

Encryption is one way to secure data, namely by en-

coding the original message (plaintext) into a secret

message (ciphertext). This security process involves

algorithms and keys. The encryption key can easily

restore the plaintext from the ciphertext. Therefore,

we need a strong encryption algorithm. With the de-

velopment of encoding, people can easily obtain en-

cryption keys in various ways (Schneier, 1996).

Therefore the development of cryptographic

methods needs to be extended to use which is not

only limited to encoding in the form of text but also

in the type of images, audio and video (Soplanit

and Bandaria, 2007). There are two techniques used

for encoding data/images i.e., classical cryptography

and modern cryptography. Encryption using classi-

cal cryptography is a method for converting original

data (plain text) to a secret message (ciphertext) us-

ing the same key. While modern cryptography used

two keys, one key called a public key that can be pub-

lished, while another key called the private key must

be kept secret (Stinson, 2005).

Playfair Cipher is one of the methods classiﬁed

in classic cryptography. The encryption process used

processing in the form of very large blocks. Play-

fair treats diagrams in the plaintext as single units and

translates these units into ciphertext diagrams. The

Playfair algorithm is based on the use of a 5x5 matrix

of letters constructed using a keyword. The rules for

ﬁlling in this 5x5 matrix are: L to R, top to bottom,

ﬁrst with keyword after duplicate letters have been re-

moved, and then with the remain letters, with I/J used

as a single letter (Desai and Rathod, ).

This method is one way to overcome the weak-

nesses of other classic cryptographic methods that are

easily guessed because there is a one-on-one corre-

spondence between plaintext and ciphertext. Like text

messages in maintaining conﬁdentiality, text mes-

sages also require encryption techniques that are as

simple as possible but difﬁcult to solve. The pro-

cess of securing messages can be done by encrypting

messages into images with certain algorithms. This

is possible considering a message can be represented

in a matrix containing integers (Rahim and Ikhwan,

2016).

Furthermore, steganography is the science and art

of hiding secret messages in a way so that no one sus-

pects the existence of the message. The aim is how

to hide the message so that the presence not detected

by third parties to avoid conspicuous suspicions (Mu-

nir, 2016). The development of computer capabili-

ties, the internet is accompanied by the development

of digital signal processing, information theory, cryp-

tography and steganography has transformed digital

media (Siswanto et al., 2018). In this realm digi-

Siswanto, A., Wahyuni, S. and Arta, Y.

Combination Playfair Cipher Algorithm and LSB Steganography for Data Text Protection.

DOI: 10.5220/0009144501250129

In Proceedings of the Second International Conference on Science, Engineering and Technology (ICoSET 2019), pages 125-129

ISBN: 978-989-758-463-3

 2020 by SCITEPRESS – Science and Technology Publications, Lda. All r ights reserved

125

tal steganography has created an atmosphere where

companies develop attractive applications, so the evo-

lution of this ﬁeld is guaranteed. One of the early

methods of discussing digital steganography was put

forward (Kurak and McHugh, 1992). They proposed

a method which breaks down and adds information at

least signiﬁcant bits (LSB). They study images at the

lower level and insert new information now known as

image-based steganography.

LSB is a technique commonly used in encryp-

tion and decryption of conﬁdential information. LSB

works by changing the redundant bits of the cover im-

age that have no signiﬁcant effect on the bits of the

secret message (Pelosi et al., 2018). Figure 1 below

shows the mechanism of the LSB method in 8-bit im-

ages by utilizing 4 bits LSB.

Figure 1: LSB Mechanism

In this paper, the Playfair Cipher method imple-

mented to encode a text message into a form of an

image to maintain secrecy with the increasingly broad

composition of cybercrime. Then the ciphertext will

be processed with LSB Steganography.

2 RELATED RESEARCH

Hatta, Ardi, and Maharani (2017) researched how

to maintain message security when sent via an SMS

(Short Message Service) network. The problem in

this study is that someone who carries a message to

the other person wants it can be read-only by the legal

person. Encryption is needed to solve this problem

to maintain message conﬁdentiality. The researcher

proposed an SMS cryptographic application on an

Android-based Smart Phone using the Playfair cipher

method. It can be sent cipher SMS messages and re-

ceive encrypted text messages then also can be de-

crypted in the receiver side. This application performs

cryptography in the form of text letters. The key used

is in the way of letters. The results of this study is

an Android-based application that can send encrypted

SMS messages using the Playfair cipher method so

that the conﬁdentiality of the message can be pro-

tected .

Then MU’MI (2017) proposed a cryptographic

application to counteract the dangers of theft and mes-

sage manipulation. The method used is hybrid Play-

fair cipher and caesar cipher method and steganogra-

phy on message insertion. The Playfair cipher method

is used in the encryption process, followed by the

Caesar cipher method. The results of encryption

from a combination of the two ways are inserted into

the image (embedding process). Insertion Simulation

The encrypted message is simulated with MATLAB

as a computing aid. The simulated image is saved in

the bitmap (.bmp) format. The results of this study

indicate that by using a combination of Playfair ci-

pher and Caesar cipher in encryption, encrypted mes-

sages are increasingly difﬁcult to return to original

messages by unauthorized parties. Inserting it into the

image makes the observer not aware of the informa-

tion embedded in the image that acts as a message.

Furthermore, Simbolon (2016) discussed how to

keep the secret of the student academic transcript.

The problem in this study is that someone who sends

a message wants the message to be secure and reaches

the right person. To solve this problem, an encryption

system is needed that can maintain the conﬁdentiality

of the message by using Playfair cipher cryptography

and LSB steganography technique. A combination

of cryptography and steganography can enhance the

message security. In this study, Playfair ciphers are

included in the Polygram Cipher. This algorithm en-

crypts the alphabet pair (bigram) in the plaintext. In

their research, they proposed the Playfair matrix table

used is a 6x6 matrix. Steganography used is a spatial

domain method with the Least Signiﬁcant Bit (LSB)

technique which consists of 2 parts, namely LSB Em-

bedding Process and LSB Extracting Process. This

research used a quantitative research method. The re-

sults obtained from this study are in the form of 8-bit

grayscale bitmap image ﬁles per pixel with a scale of

0 to 255, or with the binary format. The successful se-

cret message is fully returned to the original message

with the decryption process.

3 RESEARCH METHOD

Playfair Cipher, and LSB Steganography algorithms

are implemented using the PHP programming lan-

guage. The encryption process is done step by step

for each message that will be embedded in various

media. The ﬁrst step is the text message will be en-

crypted with the Playfair Cipher method, and then the

text cipher will be steganography on 8-bit grayscale

ICoSET 2019 - The Second International Conference on Science, Engineering and Technology

126

digital images on a scale of 0-255, with the Least Sig-

niﬁcant Bit (LSB) method. The encryption process is

as shown Figure 2.

Figure 2: Encryption and decryption process

The Playfair cipher pseudo-code algorithm is as

follows :

1. A plaintext message is split into pairs of two let-

ters (digraphs). If there is an odd number of let-

ters, a Z is added to the last letter

2. The rules of encryption are

3. If both the letters are in the same column, take the

letter below each one (going back to the top if at

the bottom)

4. If both letters are in the same row, take the letter

to the right of each one (going back to the left if

at the farthest right)

5. If neither of the preceding two rules is true, form

a rectangle with the two letters and take the letters

on the horizontal opposite corner of the rectangle

4 RESULT AND DISCUSSION

The results obtained after the coding implementation

with php like Figure 3. The ﬁrst process that is done

is the message input, key and original image.

Figure 3: Embedding process

After inputting the message and key, the system

will proceed with the encryption process. Ciphertext

encryption results later Inserted in the image. The last

step is saving the stego image in the database. The

system showed the MSE (Mean Square Error) and

PNSR (Peak Signal to Noise Ratio) normal results.

MSE valued between the original image and the ma-

nipulated image. In the case of steganography; MSE

is the mean square error value between the original

image (plain image) with the cipher image. PSNR

is usually measured in decibels (dB) (Mohsin et al.,

2018). PSNR is used to ﬁnd out the comparison of the

quality of the plain image and cipher image (Challita

and Farhat, 2011). PSNR is deﬁned as:

PSNR = 10 log



max

MSE



(1)

To determine the PSNR, the MSE (Mean Square

Error) value must ﬁrst be determined. MSE is deﬁned

as (Joshi et al., 2016):

MSE =

∑

X=1

∑

y=1

− C

)

(2)

Extraction Menu System Testing The ﬁrst step is

to select the image that was processed previously.

Then input the same key during the encryption pro-

cess. Can be seen in Figure 4.

After embedding and extraction the next step is

the result of the embedding and extraction process

contained in the data menu can be seen in table 1.

Based on the results from table 1, it shows that

there is no signiﬁcant change in the stego image from

plain image that has been inserted a secret message.

Combination Playfair Cipher Algorithm and LSB Steganography for Data Text Protection

127

Figure 4: Extraction process

Table 1: MSE and PSNR result

Message

Plain

Image

Cipher

Image

MSE PSNR

IA LA

NU TA

ﬂower1.

jpg

ﬂwcip

her1.jpg

1.02881

e-005

1.4533

e+011

SE MO

GA BE

RH AS

Flower2

.jpg

Flwcip

her2.jpg

1.7683

e-005

8.46721

e+010

PL AY

FA IR

Flower3

.jpg

Flwcip

her3.jpg

1.32681

e-005

1.12847

e+011

5 CONCLUSIONS

Based on the results of analysis and testing, a

combination of Playfair Cipher Cryptography and

Steganography with LSB for Text Data Security, sev-

eral conclusions can be drawn, i.e.:

1. Combination system Cryptography and Steganog-

raphy can help users maintain the conﬁdentiality

of a message so that it reaches the rightful person.

2. Can block attacks carried out by cryptanalysts by

using Cryptography and Steganography

3. The results of the program simulation, namely the

initial image before the message is inserted and

after the message is inserted in plain view is difﬁ-

cult to distinguish.

For future research is expected to develop this system

for mobile devices. Review further about the combi-

nation of cryptographic algorithms with methods and

data other than text, such as images, videos or audio.

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