Volume 13, Issue 02, March 2013_Anika Review Paper

7/28/2019 Volume 13, Issue 02, March 2013_Anika Review Paper

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IJCSMS International Journal of Computer Science & Management Studies, Vol. 13, Issue 02, March 2013

ISSN (Online): 2231 5268

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Review of Cryptography and SteganographyReview of Cryptography and SteganographyReview of Cryptography and SteganographyReview of Cryptography and Steganography

TechniquesTechniquesTechniquesTechniques

Anika Anand1, Deepak Gupta2

1M.Tech Student, Vaish College of Engineering, Rohtak, Haryana (India)[email protected]

2Associate Professor, Vaish College of Engineering, Rohtak, Haryana (India)

[email protected]

Abstract

Information security is of utmost importance in todays fastdeveloping era. Information or messages are beingexchanged over various types of networks. A large part of

this information is confidential or private which increasesthe demand for a more robust method of data transfer.Steganography and Cryptography are two widely used

techniques that manipulate information in order to cipher or

hide their existence. Steganography is an art and science ofhiding the message in such a way that no one other than theintended recipient knows about the existence of message.

Steganography can be applied on many objects like audio,

video, text etc. Cryptography is the study of methods ofsending messages in the disguised form to the intendedrecipients. Steganography and cryptography bothtechniques share the common goals and services of

protecting the confidentiality, integrity and availability ofinformation from unauthorized access. In this paper various

steganography and cryptography with their techniques arestudied: Spectrum, Phase coding, RSA (Ron Rivest, AdiShamir and Len Adlemen), DES (Data Encryption

Standard).

Keywords: Steganography, Cryptography, LSB

coding, Parity coding, spread.

1. IntroductionCommunication through internet and digital media

has become an essential part of infrastructure now a

days and it is important that communication be madesecret. As a result, the security of information passed

over an open channel has become a fundamental

issue and therefore, the confidentiality and data

integrity are required to protect against unauthorized

access and use. This has resulted in an unstable

growth in the field of information hiding.

Steganography and cryptography and are the two

popular methods available to provide security [1].

Steganography is the art and science of

communicating in a way which hides the existence of

the communication. Cryptography scrambles amessage so it cannot be understood by the unintended

recipient. Cryptography and Steganography achieve

the same goal using different means [1]. The power

of steganography is in hiding the secret message by

obscurity, hiding its existence in a non-secret file. In

that sense, steganography is different from

cryptography, which involves making the content of

the secret message unreadable while not preventing

non-intended observers from learning about its

existence. Steganography can be applied in various

objects as images, videos, audios etc. Steganography

conceals a message such that it would not draw any

attention and therefore would not raise suspicionsthat a secret communication is taking place[12]. For

this reason, steganography is often regarded as a

stealthy method for transmitting sensitive data into

total secrecy across public channels in such a way

that no one, apart for the communicating parties

namely the original sender and the intended receiver,

can know about the existence of the communication.According to [4] cryptography is not sufficient for

secure communication. Even though both methods

provide security, a study is made to combine both

Cryptography and Steganography methods into one

system for better confidentiality and security.

Combining these two methods together for the

purpose of developing a system, that will improve the

confidentiality and security of the message.

2. Related workProf. Samir Kumar Bandyopadhyay and BarnaliGupta Banik (2012) proposed a new method of

audio steganography using layering approach named

multi-level steganography. In multi-level

setganography two traditional method of

setganography i.e lsb encoding and parity encoding


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were blended in a level based approach to reach the

goal. Multi-Level Steganography has advantage of

difficult decoding and sending two secret messagethrough a single cover object.S.S. Divya, M. Ram

Mohan Reddy (2012) proposed two novel

approaches of substitution technique of audio

steganography that improves the capacity of cover

audio for embedding additional data. Using these

methods, message bits are embedded into multiple

and variable LSBs. These methods utilize upto 7

LSBs for embedding data.Results show that boththese methods improve capacity of data hiding of

cover audio by 35% to 70% as compared to the

standerd LSB algorithm with 4 LSBs used for data

embedding and using RSA as encryption and

decryption techniques for performing cryptography.

R SRIDEVI, DR. A DAMODARAM, DR.SVL.NARASIMHAM( 2009 ) proposed Enhanced

Audio Steganography (EAS) system which is based

on audio Steganography and cryptography that

ensures secure data transfer between the source and

destination. EAS uses most powerful encryption

algorithm in the first level of security, which is very

complex to break. In the second level it uses a more

powerful modified LSB (Least Significant Bit)

Algorithm to encode the message into audio. It

performs bit level manipulation to encode the

message. This proposed system is a good and

efficient method for hiding the data from hackers and

sent to the destination in a safe manner. In thissystem the size of the file is not changed even after

encoding and also suitable for any type of audio file

format. Abikoye Oluwakemi C. Adewole Kayode

S. Oladipupo Ayotunde J. (2012) proposed a data

hiding system based on audio steganography and

cryptography which is proposed to secure data

transfer between the source and destination. Audio

medium is used for the steganography and a LSB

(Least Significant Bit) algorithm is employed to

encode the message inside the audio file.Padmashree G, Venugopala P S (2012) proposes

that steganography works by replacing bits of

useless or unused data in regular computer files (suchas graphics, sound, text, HTML, or even floppy disks

) with bits of different, invisible information. This

hidden information can be plain text, cipher text, or

even images. Audio steganography is a young branch

of this discipline. An encoding mechanism is used for

embedding the message into the audio file. He used

the 4th Bit LSB method to do it. The quality of the

audio file after encoding remains unaffected. A

public key cryptographic algorithm, RSA was also

used to ensure greater security.

3. SteganographySteganography is derived from the Greek wordstegnos (meaning covered/secret) and graphein

(meaning to write/draw). It is the study of means of

concealing the information in order to prevent

hackers from detecting the presence of the secret

information.. Steganography is the form of convert

communication in which a secret message is

camouflaged with a carrier data. Steganography

masks the very presence of communication, making

the true message not discernable to the observer [8].

The main goal or steganography is to communicate

securely in a completely undetectable manner and to

avoid drawing suspicion to the transmission of a

hidden data. The characteristics of these methods areto change in the structure and features of object so as

not to be identifiable by human eye. Digital images,

videos, sound files, and other computer files that

contain perceptually irrelevant or redundant

information can be used as covers or carriers to

hide secret messages. After embedding a secret

message into the cover-image, a so-called stegoimage

is obtained. The basic model of steganography

consists of Carrier, Message, Embedding algorithm

and Stego key. The model for steganography is

shown in Figure 1. Carrier is also known as a cover-

object, which embeds the message and serves to hide

its presences [6]

Fig.1 A model of Steganography

Capacity, security and robustness are three mainaspects of steganography from which its usefulness

and effect can be measured. Capacity refers to the

amount of information that can be hidden in the cover

medium. Security relates to an eavesdroppers


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inability to detect hidden information and robustness

is the amount of modification the stego medium can

withstand before an adversary can destroy the hiddeninformation.[6].

To embed data secretly onto digital audio file there

are few techniques introduced earlier. The lists of

methods are:

LSB Coding Phase Coding Parity Coding Spread Spectrum

3.1 LSB coding

Least significant bit (LSB) coding is the simplest way

to embed information in a digital audio file. In this

technique, LSB of binary equivalent of each sample

of digitized audio file is replaced with a binary

equivalent secret message [2]. By substituting the

least significant bit of each sampling point with a

binary message, LSB coding allows for a large

amount of data to be encoded. In LSB coding, the

ideal data transmission rate is 1 kbps per kHz. Figure

2 illustrates how the message 'HEY' is encoded in a

16-bit CD quality sample using the LSB method.

Fig. 2 Message 'HEY' is encoded in a 16-bit CD

quality sample using the LSB method

To extract a secret message from an LSB encoded

sound file, the receiver needs access to the sequence

of sample indices used in the embedding process.Normally, the length of the secret message to be

encoded is smaller than the total number of samples

in a sound file. One must decide then on how to

choose the subset of samples that will contain the

secret message and communicate that decision to the

receiver[5]. One trivial technique is to start at the

beginning of the sound file and perform LSB coding

until the message has been completely embedded,leaving the remaining samples unchanged. This

creates a security problem, however in that the first

part of the sound file will have different statistical

properties than the second part of the sound file that

was not modified. One solution to this problem is to

pad the secret message with random bits so that the

length of the message is equal to the total number of

samples.

3.2 Phase coding

In phase encoding scheme the phase of carrier file is

replaced with reference phase which represents

hidden data. The basic idea is to split the original

audio stream or cover file(C) into blocks and embed

the whole message data sequence into the phase

spectrum of the first block. One drawback of the

phase coding method is a considerably low payloadbecause only the first block is used for secret

message (M) embedding. In addition, the M is not

distributed over C that means it is localized data

and thus can be removed easily by the cropping

attack. [2]

3.3 Parity coding

Instead of breaking a signal down into individual

samples, the parity coding method breaks a signal

down into separate regions of samples and encodes

each bit from the secret message in a sample region's

parity bit. If the parity bit of a selected region doesnot match the secret bit to be encoded, the process

flips the LSB of one of the samples in the region [1].

3.4 Spread Spectrum

In spread spectrum method secret information is

spread over the audio signal's frequency spectrum as

much as possible. Basically this method calculates

the frequency masking threshold using psycho

acoustic model, data signal is spread by a M-


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sequence code, and the spread signal is embedded in

audio below the frequency masking threshold. M-

sequence codes have good autocorrelation propertieswhere the autocorrelation function has peaks equal to

1 at 0, N, 2N (approximately 1/N elsewhere).

Because of these periodic peaks, the M-sequence

code is self-clocking, so the receiver can easily

synchronize the data frame and retrieve the

embedded data by de-spreading with the same M-

sequence code [9].

4. CryptographyCryptography is the study of methods of sending

messages in disguised form so that only the intended

recipients can remove the disguise and read themessage. It is the practical art of converting messages

or data into a different form, such that no-one can

read them without having access to the 'key'. The

message may be converted using a code or a 'cipher'

or 'cipher' .Cryptology is the science underlying

cryptography [6]. It is a means of converting

information from its normal comprehensible form

into an incomprehensible format, rendering it

unreadable without the secret knowledge. The

process of converting information (plain text) by

transforming it into unreadable format (cipher text) is

known as encryption. Encryption techniques can be

sometimes broken by cryptanalysis, also called ascode breaking, although modern cryptographictechniques are virtually unbreakable[8].

Cryptography encrypts the actual message that is

being sent. This mechanism employs mathematical

schemes and algorithms to scramble data into

unreadable text. It can only be decoded or decrypted

by the party that possesses the associated

key.

There are two main types of cryptography:

Secret key cryptography Public key cryptography

In cryptographic systems, the term key refers to a

numerical value used by an algorithm to alter

information, making that information secure and

visible only to individuals who have the

corresponding key to recover the information.

4.1 Secret key cryptography

This is also known as symmetric key cryptography.With this type of cryptography, both the sender and

the receiver know the same secret code, called the

key. Messages are encrypted by the sender using the

key and decrypted by the receiver using the same

key. This method works well if you are

communicating with only a limited number of

people, but it becomes impractical to exchange secret

keys with large numbers of people. In addition, there

is also the problem of how you communicate the

secret key securely. It includes DES, AES, 3DES,

IDEA, Blowfish algorithms.

4.1.1 DES

It uses block cipher. In this same algorithm and key is

used for encryption and decryption. It encrypts the

data in block size of 64 bits each 8 bits (one octet) of

which are used for parity checks (to verify the key's

integrity). Each of the key's parity bits (1 every 8

bits) is used to check one of the key's octets by odd

parity, that is, each of the parity bits is adjusted to

have an odd number of '1's in the octet it belongs to.

The key therefore has a "useful" length of 56 bits,

which means that only 56 bits are actually used in the

algorithm.

The algorithm involves carrying out

combinations, substitutions and permutations

between the text to be encrypted and the key, while

making sure the operations can be performed in both

directions (for decryption). The combination of

substitutions and permutations is called a product

cipher [10]. This Substitution and Permutation is

done in 16 rounds. In each round key and data bits

are shifted, permuted, XORed and sent through, 8 s-box. In the first round 64 bit plaintext is handed to

initial permutation(IP).Then IP generates two half

left plaintext(LPT)and right plaintext(RPT).Each

LPT and RPT goes through 16 rounds. At the lastLPT and RPT are rejoined. Decryption is same

process perform rounds in reverse order.

4.2 Public key cryptography

It also called asymmetric encryption uses a pair of

keys for encryption and decryption. With public key

cryptography, keys work in pairs of matched public

and private keys. The public key can be freely


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distributed without compromising the private key,

which must be kept secret by its owner. Because

these keys work only as a pair, encryption initiatedwith the public key can be decrypted only with the

corresponding private key. It includes RSA, Digital

Signature and Message Digest algorithms.

4.2.1 RSA

This is public key encryption algorithm developed by

Ron Rivest, Adi Shamir and Len Adlemen in 1977. It

is most popular and asymmetric key cryptographic

algorithm. It may used to provide both secrecy and

digital signature. It uses the prime no. to generate the

public and private key based on mathematical fact

and multiplying large numbers together. It uses theblock size data in which plaintext and cipher text are

integers between 0and n1 for some n values. Size of n

is considered 1024bits or 309 decimal digits. In this

two different keys are used for encryption and

decryption purpose. As sender knows encryption key

and receiver knows decryption key [4].

The arithmetic calculations of the algorithm:

1. Choose one number and divide it to twoprime numbers.

2. Select p and q.3. Calculate n=p*q.4. Calculate Z=(p-1)(q-1)5. Select integer e which is relatively prime

to 2. (Z=(n))

6. Calculate e*d=1 Mod((n)) and determined.

7. Public key = {e, n} and private key={d, n}8. For Data Encryption:

c=M^e Mod n.

9. For Data Decryption :M=c^d Mod n.

5. ConclusionsSteganography and Cryptography with their

techniques are studied for information security.

Steganography is the method of data hiding whereas

cryptography is an encryption technique. In

comparison to other steganographic techniques LSB

modification algorithm is simple and effective. RSAand DES techniques of cryptography are studied in

detail and it studies shows that DES is better than

RSA. Both steganography and cryptography are

information security techniques and when they are

combined together security can be enhanced many

times. As a future work an algorithm combining both

techniques can be proposed for data security.

References

[1] Prof. Samir Kumar Bandyopadhyay, BarnaliGupta Banik, Multi-Level Steganographic

Algorithm for Audio Steganography using LSB

Modification and Parity Encoding Technique.

International Journal of Emerging Trends &

Technology in Computer Science (IJETTCS)

2012.

[2] S.S. Divya, M. Ram Mohan Reddy, HidingText in Audio Using Multiple Lsb

Steganography and Provide Security Using

Cryptography. International Journal Of

Scientific & Technology Research Volume 1,

Issue 6, July 2012

[3] R Sridevi, Dr. A Damodaram, Dr.Svl.Narasimham, Efficient Method of Audio

Steganography by Modified Lsb Algorithm And

Strong Encryption Key With Enhanced

Security. Journal of Theoretical and Applied

Information Technology.

[4] Abikoye Oluwakemi C. Adewole Kayode S.Oladipupo Ayotunde J. Efficient Data Hiding

System using Cryptography and

Steganography. International Journal of AppliedInformation Systems (IJAIS) 2012

[5] Padmashree G, Venugopala P S, AudioStegnography and Cryptography: Using LSB

algorithm at 4th and 5th LSB layers.

International Journal of Engineering and

Innovative Technology (IJEIT) 2012

[6] A. Joseph Raphael Dr. V. Sundaram,Cryptography and Steganography A Survey.

A. Joseph Raphael, Dr.V Sundaram, Int. J.

Comp. Tech. Appl., Vol 2 (3), 626-630


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[7] B. Santhi, G. Radhika and S. Ruthra Reka,Information Security using Audio

Steganography -A Survey. Research Journal ofApplied Sciences, Engineering and Technology

4(14): 2255-2258, 2012.

[8] Manoj Kumar Sharma, Dr. Amit Upadhyaya,Shalini Agarwal, Adaptive Steganographic

Algorithm using Cryptographic Encryption RSA

Algorithms. Journal of Engineering, Computers

& Applied Sciences (JEC&AS) ISSN No: 2319-

5606 Volume 2, No.1, January 2013[9] Md. Shafakhatullah Khan, V.Vijaya Bhasker, V.

Shiva Nagaraju, V. Shiva Nagaraju, An

Optimized Method for Concealing Data using

Audio Steganography. International Journal of

Computer Applications (0975 8887) Volume

33 No.4, November 2011

[10]Internet source:http://en.kioskea.net/contents/134-introduction-

to-encryption-with-des

[11]Youssef Bassil, A Two Intermediates AudioSteganography Technique. Journal of Emerging

Trends in Computing and Information Sciences

VOL. 3, NO.11 Nov, 2012

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Volume 13, Issue 02, March 2013_Anika Review Paper