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  1. 1. ISSN:2229-6093 A.Joseph Raphael,Dr.V Sundaram, Int. J. Comp. Tech. Appl., Vol 2 (3), 626-630 Cryptography and Steganography – A Survey A. Joseph Raphael Dr. V. Sundaram, Head & Director Research Scholar Department of Computer Applications Karpagam University Karpagam College of Engineering Coimbatore, India. Coimbatore, India. Abstract— Digital communication has become an essential private key that only the recipient of messages uses. Inpart of infrastructure nowadays, a lot of applications are Cryptography, a cipher message for instance, mightInternet-based and it is important that communication be arouse suspicion on the part of the recipient while anmade secret. As a result, the security of information passed invisible message created with steganographic methodsover an open channel has become a fundamental issue andtherefore, the confidentiality and data integrity are required to will not. In fact, steganography can be useful when theprotect against unauthorized access and use. This has use of cryptography is forbidden: where cryptographyresulted in an unstable growth in the field of information and strong encryption are outlawed, steganography canhiding. Cryptography and steganography are the two popular circumvent such policies to pass message covertly.methods available to provide security. One hides the However, steganography and cryptography differ in theexistence of the message and the other distorts the message way they are evaluated: steganography fails when theitself. Using cryptography, the data is transformed into some ”enemy” is able to access the content of the cipherother gibberish form and then the encrypted data is message, while cryptography fails when the ”enemy”transmitted. In steganography, the data is embedded in animage file and the image file is transmitted. This paper detects that there is a secret message present in thefocuses on the strength of combining cryptography and steganographic medium.stegnography methods to enhance the security ofcommunication over an open channel. The disciplines that study techniques for deciphering cipher messages and detecting hide messages are called cryptanalysis and steganalysis. The former denotes the Index Terms—Stegano object, cryptanalysis, cipher text set of methods for obtaining the meaning of encrypted information, while the latter is the art of discovering covert messages. The aim of this paper is to describe a I INTRODUCTION method for integrating together cryptography and steganography through some media such as image, Cryptography and Steganography are well known and audio, video, etc.widely used techniques that manipulate information inorder to cipher or hide their existence respectively. II HISTORYSteganography is the art and science of communicatingin a way which hides the existence of the Cryptography has followed man through many stagescommunication. Cryptography scrambles a message so it of evolution [3]. Cryptography can be found as far backcannot be understood; the Steganography hides the as 1900 B.C. in ancient Egyptian scribe using non-message so it cannot be seen. Even though both methods standard hieroglyphics in an inscription. From 500 – 600provide security, a study is made to combine both B.C. Hebrew scribes used ATBASH, a reversed alphabetcryptography and Steganography methods into one simple solution cipher. From 50 - 60 B.C. Julius Caesarsystem for better confidentiality and security. used a simple substitution with the normal alphabet in government communications. Cryptography continued Cryptography systems can be broadly classified into through history with may variations. Today cryptographysymmetric-key systems that use a single key that both the has reached a new level, quantum cryptography.sender and the receiver have, and public-key systems that Quantum cryptography combines physics anduse two keys, a public key known to everyone and a cryptography to produce a new cryptosystem that cannot 626
  2. 2. ISSN:2229-6093 A.Joseph Raphael,Dr.V Sundaram, Int. J. Comp. Tech. Appl., Vol 2 (3), 626-630be defeated without the sender and receiver having the Cryptanalysis [2] is the reverse engineering ofknowledge of the attempted and failed intrusion. cryptography—attempts to identify weaknesses ofThrough the long history of cryptography, steganography various cryptographic algorithms and theirwas developed and flourished on its own. implementations to exploit them. Any attempt at cryptanalysis is defined as an attack.Steganography comes from the Greek steganos (coveredor secret) and -graphy (writing or drawing). Cryptology encompasses both cryptography andSteganography can be defined as the hiding of cryptanalysis and looks at mathematical problems thatinformation by embedding messages within other, underlie them.seemingly harmless messages, graphics or sounds. Thefirst steganographic technique was developed in ancient Cryptosystems are computer systems used to encryptGreece around 440 B.C. The Greek ruler Histaeus data for secure transmission and storage.employed an early version of steganography whichinvolved: shaving the head of a slave, tattooing the Plaintext is message or data which are in their normal,message on the slaves scalp, waiting for the growth of readable (not crypted) form.hair to disclose the secret message, and sending the slaveon his way to deliver the message. The recipient would Encryption: Encoding the contents of the message inhave the slave’s head to uncover the message. The such a way that hides its contents from outsiders.recipient would reply in the same form of steganography.In the same time period, another early form of Cipher text results from plaintext by applying thesteganography was employed. This method involved encryption key.Demerstus, who wrote a message to the Spartans warningof eminent invasions from Xerxes. The message was Decryption: The process of retrieving the plaintext backcarved on the wood of wax tablet, and then covered witha fresh layer of wax. This seemingly blank tablet was from the cipher text.delivered with its hidden message successfully.Steganography continued development in the early 1600s Key: Encryption and decryption usually make use of aas Sir Francis Bacon used a variation in type face to carry key, and the coding method is such that decryption caneach bit of the encoding. be performed only by knowing the proper key.The microdots were complete documents, pictures, andplans reduced in size to the size of a period and attached Steganography is the method of hiding secret messagesto common paperwork. Null ciphers were also used to in an ordinary document.pass secret messages. Null ciphers are unencryptedmessages with real messages embedded in the current Steganalysis could be simply defined as the detection oftext. Hidden messages were hard to interpret within the steganography by a third party.innocent messages. An example of an innocent messagecontaining a null cipher is: Hash functions generate a digest of the message.Fishing freshwater bends and saltwater coasts rewards Substitution cipher involves replacing an alphabet withanyone feeling stressed. Resourceful anglers usually find another character of the same alphabet set.masterful leapers fun and admit swordfish rankoverwhelming any day. Mono-alphabetic system uses a single alphabetic set for substitutions.By taking the third letter in each word the followingmessage emerges: Poly-alphabetic system uses multiple alphabetic sets for Send Lawyers, Guns, and Money. substitutions. III DEFINITION & TERMINOLOGY Caesar cipher is a mono-alphabetic system in which eachCryptography defines the art and science of transforming character is replaced by the third character in succession.data into a sequence of bits that appears as random and Julius Caesar used this method of encryption.meaningless to a side observer or attacker. 627
  3. 3. ISSN:2229-6093 A.Joseph Raphael,Dr.V Sundaram, Int. J. Comp. Tech. Appl., Vol 2 (3), 626-630A digital signature is a block of data that is generated by a two-key crypto system in which two parties couldthe sender of a message using his/her secret key. engage in a secure communication over a insecure communications channel without having to share a secret IV CRYPTOGRAPHY key. Cryptography is an important element of any strategy Digital Signature: The use of digital signature came fromto address message transmission security requirements. the need of ensuring the authentication. The digitalCryptography is the study of methods of sending signature is more like stamp or signature of the sendermessages in disguised form so that only the intended which is embedded together with the data and encrypts itrecipients can remove the disguise and read the message. with the private key in order to send it to the other party. In addition, the signature assures that any change made toIt is the practical art of converting messages or data into the data that has been signed is easy to detect by thea different form, such that no-one can read them without receiver.having access to the key. The message may beconverted using a code (in which case each character or Hash Function: The hash function is a one waygroup of characters is substituted by an alternative one), encryption, the hash function is a well defined procedureor a cypher or cipher (in which case the message as a or mathematical formula that represents a small size ofwhole is converted, rather than individual bits which is generated from a large sized file, the resultcharacters).Cryptology is the science underlying of this function can be called hash code or hashes. Thecryptography. Cryptanalysis is the science of breaking generating of hash code is faster than other methodsor cracking encryption schemes, i.e. discovering the which make it more desired for authentication anddecryption key. Cryptographic systems are generically integrity. Cryptographic hash functions are much usedclassified along three independent dimensions [1]. for digital signature and cheap constructions are highly desirable. The use of cryptographic hash functions for1. Methodology for transforming plain text to cipher text. message authentication has become a standard approachAll encryption algorithms are based on two general in many applications, particularly internet securityprinciples: substitution, in which each element in the protocols. The authentication and the integrityplaintext is mapped into another element, and considered as main issues in information security, thetransposition, in which elements in the plaintext are hash code can be attached to the original file then at anyrearranged. The fundamental requirement is that no time the users are able to check the authentication andinformation be lost. integrity after sending the secure data by applying the hash function to the message again and compare the2. Methodology for number of keys used. result to the sender hash code, if it’s similar that is mean the message came from the original sender withoutThere are some standards methods[4] which is used with altering because if there is any changed has been made tocryptography such as secret key, public key, digital the data will changed the hash code at the receiver side.signature and hash function. 3. Methodology for processing plain text.Secret Key (Symmetric): With secret key cryptography, asingle key is used for both encryption and decryption. A block cipher processes the input one block of elementsThe sender uses the key to encrypt the plaintext and at a time, producing an output block for each inputsends the cipher text to the receiver. The receiver applies block. A stream cipher processes the input elementsthe same key to decrypt the message and recover the continuously, producing output one element at a time, asplaintext. Because a single key is used for both it goes along. The proposed algorithm uses a substitutionfunctions, secret key cryptography is also called as cipher method. It is a symmetric key algorithm using thesymmetric encryption. technique of stream cipher.Public Key : Public key cryptography has been said to bethe most significant new development in cryptography inthe last 300-400 years. Modern Public KeyCryptography was first described publicly by StandfordUniversity professor Martin Hellman and graduatestudent Whitfield Diffie in 1976. Their study described 628
  4. 4. ISSN:2229-6093 A.Joseph Raphael,Dr.V Sundaram, Int. J. Comp. Tech. Appl., Vol 2 (3), 626-630 V STEGANOGRAPHY According to dictionary.com: Steganography is:” Hiding a secret message within a larger one in such a way thatThe word steganography comes from the Greek others can not discern the presence or contents of theSteganos, which mean covered or secret and graphy hidden message” and Cryptography is “The process ormeans writing or drawing. Therefore, steganography skill of communicating in, or deciphering secret writingmeans, literally, covered writing. The main goal or or ciphers.” Steganography can be used to cloak hiddensteganography is to communicate securely in a messages in image, audio and even text files. It has untilcompletely undetectable manner and to avoid drawing recently been the poor cousin of cryptography. Now, it issuspicion to the transmission of a hidden data [4]. gaining new popularity with the current industryDuring the process, characteristics of these methods are demands for digital watermarking and fingerprinting ofto change in the structure and features so as not to be audio and video. Steganography must not be confusedidentifiable by human eye. Digital images, videos, sound with cryptography, where we transform the message sofiles, and other computer files that contain perceptually as to make its meaning obscure to malicious people whoirrelevant or redundant information can be used as intercept it. Therefore, the definition of breaking the“covers” or carriers to hide secret messages. After system is different. In cryptography, the system is brokenembedding a secret message into the cover-image, a so- when the attacker can read the secret message. Breakingcalled stegoimage is obtained. The basic model of a steganographic system needs the attacker to detect thatsteganography consists of Carrier, Message, Embeddingalgorithm and Stego key. The model for steganography is steganography has been used and he is able to read theshown in Figure 1. Carrier is also known as a cover- embedded message. In addition, the security of classicalobject, which embeds the message and serves to hide its steganography system relies on secrecy of the datapresence. encoding system. Once the encoding system is known, the steganography system is defeated. The distinction between cryptography and steganography is an important one, and is summarized by the following table. Fig. 1. A model of SteganographyCapacity, security and robustness are three differentaspects affecting steganography and its usefulness.Capacity refers to the amount of information that can behidden in the cover medium. Security relates to aneavesdropper’s inability to detect hidden informationand robustness is the amount of modification the stegomedium can withstand before an adversary can destroythe hidden information. VI STEGANOGRAPHY VS CRYPTOGRAPHY Basically, the purpose of cryptography andsteganography is to provide secret communication. 629
  5. 5. ISSN:2229-6093 A.Joseph Raphael,Dr.V Sundaram, Int. J. Comp. Tech. Appl., Vol 2 (3), 626-630 VII COMBINED CRYPTO-STEGANOGRAPHY The idea of this type is to encrypt the secret message or data by secret key approach and to hide the encryptedSteganography is not the same as cryptography Data data within cover carrier.hiding techniques have been widely used to transmissionof hiding secret message for long time. Ensuring data Public Key Steganography: The last type ofsecurity is a big challenge for computer users. Business steganography is to combine the public key cryptographymen, professionals, and home users all have some approach and the steganography approach. The idea ofimportant data that they want to secure from others. this type is to encrypt the secret data using the public keyEven though both methods provide security, to add approach and then hide the encrypted data within covermultiple layers of security it is always a good practice to carrier.use Cryptography and Steganography together. By REFERENCEScombining, the data encryption can be done by asoftware and then embed the cipher text in an image orany other media with the help of stego key. The [1] Neha Sharma, J.S. Bhatia and Dr. Neena Gupta, “ Ancombination of these two methods will enhance the Encrypto-Stego Technique Based secure data Transmission System”, PEC, Chandigarh.security of the data embedded. This combined chemistrywill satisfy the requirements such as capacity, security [2] I. Venkata Sai Manoj, “Cryptography and Steganography”,and robustness for secure data transmission over an open International Journal of Computer Applications (0975 –channel. 8887), Volume 1 – No.12 [3] Alan Siper, Roger Farley and Craig Lombardo, “The Rise of Steganography”, Proceedings of Student/FacultyA pictorial representation of the combined concept of Research Day, CSIS, Pace University, May 6th, 2005.cryptography and steganography is depicted in figure 2. [4] B B Zaidan, A.A Zaidan, A.K. Al-Frajat and H.A. Jalab, “On the Differences between Hiding Information and Cryptography Techniques: An Overview”, Journal of Applied Sciences 10(15): 1650-1655, 2010 [5] Domenico Bloisi and Luca Iocchi, “Image Based Steganography and Cryptography”, Sapienza University of Rome, Italy. [6] Kallam Ravindra Babu, Dr. S.Udaya Kumar, Dr. A.Vinaya Babu, “A Survey on Cryptography and Steganography Methods for Information Security”, Internaltional Journal of Computer Applications(0975-8887), Volume 12 – No. 2, November 2010. [7] Dipti Kapoor Sarmah, Neha bajpai, “ Proposed System forIn figure 2, both the methods are combined by Data Hhiding Using Cryptography and Steganography”,encrypting message using cryptography and then hiding International Journal of Computer Applications (0975 –the encrypted message using steganography. The 8887), Volume 8 – No. 9, October 2010.resulting stego-image can be transmitted without [8] Eiji Kawaguchi and Richard O. Eason, “Principlerevealing that secret information is being exchanged. and applications of BPCS-Steganography”, KyushuFurthermore, even if an attacker were to defeat the Institute of Technology, Kitakyushu, Japan,steganographic technique to detect the message from the University of Maine, Orono, Maine 04469-5708.stego-object, he would still require the cryptographic [9]Sashikala Channalli and Ajay Jadhav, “Steganographydecoding key to decipher the encrypted message. Since An Art of Hiding Data”, International Journal onthen, the steganography approaches can be divided into Computer Science and Engineering Vol.1(3), 2009,three types [4]: 137-141.Pure Steganography: This technique simply uses thesteganography approach only without combining othermethods. It is working on hiding information withincover carrier.Secret Key steganography: The secret keysteganography use the combination of the secret keycryptography technique and the steganography approach. 630