Cryptography: An Art of Data Hiding

ISSN: 2312-7694 Prabhsimran et al, / International Journal of Computer and Communication System Engineering (IJCCSE), Vol. 2 (1), 2015, 117-120

Cryptography: An Art of Data Hiding Prabhsimran Singh Department of Computer Science & Engineering Guru Nanak Dev University Amritsar, India [email protected]

Sukhmanjit Kaur Department of Computer Science & Engineering Guru Nanak Dev University Amritsar, India [email protected]

Sabia Singh University Business School Guru Nanak Dev University Amritsar, India [email protected]

Abstract—Cryptography is being used by mankind in order to successfully transmit secret message without being caught by the enemies. From the ancient times to this modern world Cryptography has evolved rapidly. This paper discusses the various cryptographic techniques being used in the modern world along with its applications. Index Terms—Data Hiding, Encryption, Cryptography, Hashing

I. INTRODUCTION Cryptography is branch of computer science which deals with transforming the simple plain text into an unreadable form. Technically, Cryptography is the study of mathematical formulas and techniques that are concerned with security of information like confidentiality, authentication, data integrity etc [1].

C. Plain Text: The message or data which need to be secured for various reasons is called plain text. D. Cipher Text: The unreadable form of data which is produced at the end of Encryption process is called Cipher Text. E. Key: It is a parameter that determines what will be the final output of a cryptographic process. The key length plays a significant role in encryption process. The figure 1 shows the diagrammatical representation of the encryption process, while Figure 2 shows the diagrammatical representation of the decryption process.

Cryptography comes from Greek words “kryptos” meaning “Secret” and “graphein” meaning “Writing”, so cryptography is defined as the art/science of secret writing [2]. The history of Cryptography goes back to 1900 B.C. in Egypt, where the Egyptians used to write secret message on the stones [3].

Fig 1. Encryption Process

II. IMPORTANT TERMINOLOGIES The modern day terminologies:

Cryptography

uses

the

following

A. Encryption: The process of encoding the message with help of key is called encryption. In this the simple text is converted into unreadable text. B. Decryption: The process of decoding the encoded message with the help of key are called Decryption. It is the reverse of encryption process.

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Fig 2. Decryption Process

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ISSN: 2312-7694 Prabhsimran et al, / International Journal of Computer and Communication System Engineering (IJCCSE), Vol. 2 (1), 2015, 117-120

III. CRYPTOGRAPHIC GOALS The various goals of Cryptography are [1]: A. Confidentiality: To ensure that no one other than the receiver is able to read the message. This is also known as privacy or secrecy. B. Data integrity: Making assure that the message received by the receiver is not manipulated i.e. is not altered and is in its original form. C. Authentication: It is process related to user’s identification. It is really important that the two parties (i.e. sender and receiver) engaged in communication should identify each other. D. Non-repudiation: It is a mechanism to check/prove that the message received by the receiver is really send by the sender itself. IV. TYPE OF CRYPTOGRAPHY

b. Self-synchronous Stream Ciphers: In this technique the decryption is automatically synchronized with randomly generated binary digits. The most commonly used stream cipher algorithms are Scream, SEAL, SNOW, Turing etc.

ii.

Block Cipher: In this a group of bits called block get encrypted at a time using the key. It is generally used for encryption of large amount of data. The most commonly used block cipher algorithms are DES, RC5, AES, Blowfish etc.

B. Public-Key Cryptography: It is also called Asymmetric Cryptography. In this technique two keys are used i.e. public key and private key. The public used to perform the encryption operation, while the private key is used to perform the decryption operation. The diagrammatic representation is shown in figure 4.

Most Authors and Researchers divide cryptography in 3 major categories: [1, 4, 5] A. Secret-Key Cryptography: It is also known as Symmetric or Secret Key Cryptography. The basic idea behind this technique is the use of single key for both encryption and decryption, i.e. the key is used to transform plain text to cipher text is the same that is used to transform the cipher text back to the plain text. Figure 3 shows the diagrammatic representation of secret key cryptography.

Fig. 4, Public-Key Cryptography

Stanford University Professor Martin Hellman and graduation student Whitefield were the first to publish a modern paper on Public-Key Cryptography in 1976 [4]. The most commonly used RSA, Digital Signature Algorithm (DSA), Elliptic Curve Cryptography (ECC) etc.

Fig 3. Secret-Key Cryptography

The Secret-Key Cryptography is further divided into 2 major categories: [4] i.

Stream Cipher: It is also called state cipher. In this each plaintext digit is encrypted with the key one at a time, i.e. bit by bit or character by character. The Stream Cipher is further divided into two categories: a. Synchronous Stream Ciphers: In this technique a randomly generated streams of binary digits are added to the plain text at type of encryption and to cipher text at the time of decryption.

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C. Hash Functions: It is also called One way Encryption or Message Digests. These techniques were developed to ensure that data can only be encrypted, and cannot be decrypted back to plain text. Unlike the other techniques the Cryptographic Hash Functions may or may not use Key for encryption of plain text [4]. A hash function has 3 main properties [1]:  Preimage resistance  Second-preimage resistance  Collision resistance

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ISSN: 2312-7694 Prabhsimran et al, / International Journal of Computer and Communication System Engineering (IJCCSE), Vol. 2 (1), 2015, 117-120

The most commonly used hash functions are MD4, MD5, SHA1, SHA3 etc. Figure 5 shows results of applying MD5 hash function on plain text. Figure 6, shows detailed flowchart of different cryptography techniques and their sub types [1]. The main idea behind all the 3 techniques i.e. Secret-Key Cryptography, Public-Key Cryptography and Hash Functions, is protection/security of the user data. All these techniques have their own advantages and disadvantages and therefore are used in different applications based upon functionality. But many researchers believe One-Time Pad is the only technique which is fully secure i.e. cannot be cracked if used correctly [1,6]. Fig. 5, Applying MD5 on Plain Text

Fig. 6, Types of Cryptography [1]

V. APPLICATIONS OF CRYPTOGRAPHY The various fields where cryptography is used are as following: A. Database encryption: Now days everything is stored in databases including sensitive data, so encryption of this data is very important. B. Authentication/Authorization: To get access to any website or service we need a username/password, if

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this gets to wrong hands it can really hamper once image, so encryption of these is one of the main priorities. C. Secure Network Communication: Sending data over a network can be really dangerous, as data can be intercepted or can be manipulated. So it’s very important to send data in encrypted form so that the intruder cannot understand it. D. Military Application: Military and Security are backbone of any nation, so cryptography plays a very important role in keeping them safe and secure.

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ISSN: 2312-7694 Prabhsimran et al, / International Journal of Computer and Communication System Engineering (IJCCSE), Vol. 2 (1), 2015, 117-120

E. Banking Transactions: Online Money Transactions and ATM services are some banking services where cryptography is used. VI. CONCLUSIONS This paper discus the various type Cryptographic techniques used in the modern world. Each technique has its own merits and demerits, and is used for specific applications. This paper also discusses the various goals and applications of cryptography. This paper was just an overview of Cryptographic techniques, researchers are still working to make these technique perfect so that security of user data can be enhanced.

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REFERENCES [1] Menezes, Alfred J., Paul C. Van Oorschot, and Scott A. Vanstone. “Handbook of applied cryptography”. CRC press, 2001. [2] Liddell, Henry George, and Robert Scott. “A GreekEnglish Lexicon”, Oxford: Clarendon Press, 1984. [3] David, Kahn. "The codebreakers: the story of secret writing." (1966), ISBN: 0-684-83130-9. [4] Kessler, Gary C. "An Overview of Cryptography." (2013). [5] Andress, Jason. “The Basics of Information Security: Understanding the Fundamentals of InfoSec in Theory and Practice”. Elsevier, 2011.

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