a review on cryptography mechanisms -...
TRANSCRIPT
A Review on Cryptography Mechanisms
Prof ML Sharma Department of Electronics & Communication
Bhai Gurdas Institute of Engineering & Technology, Sangrur, India [email protected]
Er. Sheetal Atri
Department of Electronics & Communication Bhai Gurdas Institute of Engineering & Technology, Sangrur India
Abstract
In today's information age, communications play an important role which is becoming widespread as well. The same aspects of cryptography that make it useful for security and privacy make it particularly troublesome for law enforcement. The use of cryptography by criminals can prevent law enforcement from obtaining information needed for the prevention and prosecution of crime. The international organizations have acted to regulate cryptography and protect the legitimate interests of law enforcement, while attempting to balance the needs of legitimate users of cryptography. Cryptography can be classifies into Symmetric and asymmetric encryption algorithms as shown in Figure. A symmetric encryption algorithm consists of a pair of functions, encrypt and decrypt. If plaintext is encrypted with key K and the resulting cipher text is decrypted with key K then the original plaintext is contributed to the growth of technologies. Electronic security is increasingly involved in making communications more prevalent. Therefore, a mechanism is needed to assure the security and privacy of information that is sent over the electronic communications media is in need. Whether the communications media is wired or wireless, both can be not protected from unauthorized reception or interception of transmission. The, method
of transforming the original information into the unreadable format is called encryption and decryption of information. The study of encryption and decryption is known as Cryptography. This paper focuses on the analysis of the two types of key cryptography exists, based on the availability of the key publicly: Private key Cryptography, and Public Key Cryptography. Index Terms: Cryptography, Encryption, Decryption. 1. Introduction Cryptography, in G reek, literally m eans hidden writing, or t he art of c hanging plain text message [1][4][5]. Cryptography is u sed increasingly by businesses, i ndividuals a nd t he go vernment f or ensuring t he s ecurity a nd pr ivacy of information and communications. The most popular s ymmetric encryption algorithm is t he D ata E ncryption Standard (DES). It was developed by IBM in 1976 in response to the challenge to produce an encryption [6][7][81. Algorithm that could be made public and still is secure. Even t hough repeated attempts have been made t o replace it, remains s ecure w hen pr operly us ed. Asymmetric encryption algorithm, also known as a public key cryptosystem (PKS), the ke ys us ed for the encrypt and decrypt functions are different, and it is co mputationally infeasible t o obtain t he decryption key from the encryption key. This allows the encryption key to be made public while the decryption k ey i s kept private. The ke ys ar e known as the public key and the private key. The corresponding terminology for a ke y in a symmetric cr yptosystem is s ecret ke y. T hus anyone ca n enc rypt m essages, b ut only t he
Er.Sheetal Atri et al, Int. J. Comp. Tech. Appl., Vol 2 (4), 1048-1050
IJCTA | JULY-AUGUST 2011 Available [email protected]
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ISSN:2229-6093
holder o f the pr ivate ke y ca n r ead them. T he most p opular publ ic key c ryptosystem is R SA, named after i ts i nventors Rivest, S hamir, a nd Adleman [9][101[11]. It was produced in 1978 in response to a challenge in 1976 to find PKS. 2. Cryptography Objectives Cryptography is t he s cience o f w riting in s ecret code w ithin t he co ntext of any app lication-to-application co mmunication, there ar e s ome specific security requirements, including: - Authentication: The pr ocess of pr oving one’s identity. - Privacy/confidentiality: Ensuring that no one can r ead the message except t he intended receiver. - Integrity: Assuring the r eceiver t hat t he received message has n ot b een a ltered in a ny way from the original. - Non-repudiation: A m echanism t o prove that the sender really sent this message. Cryptography, t hen, not only pr otects da ta f rom theft or alteration, but can also be us ed for user authentication. There are, in general, three types of cr yptographic s chemes t ypically u sed to accomplish t hese go als: s ecret ke y ( or symmetric) c ryptography, pu blic-key ( or asymmetric) cr yptography, an d hash functions, each o f w hich is de scribed below. I n a ll ca ses, the initial u nencrypted data i s r eferred to as daintext. It i s enc rypted into cipher text, which will in t urn ( usually) b e e ncrypted -into us able plaintext 3. Cryptographic Algorithms Cryptography h as s everal d ifferences f rom pur e mathematics. While a mathematician may use A and B t o e xplain a n a lgorithm, a c ryptographer may u se t he fictious n ames A lpha a nd Beta Suppose A lpha w ants to send a message t o hi s bank to transfer money. H e w ould like t he message t o b e pr ivate, s ince it includes information s uch a s hi s a ccount nu mber a nd transfer a mount. O ne s olution is t o us e a cryptographic a lgorithm, a t echnique t hat would transform his message into an e ncrypted form, unreadable e xcept by t hose f or w hom it is intended. When encrypted, the message can only be interpreted t hrough the us e o f t he corresponding secret ke y. Wi thout the ke y t he message is u seless: goo d C ryptographic algorithms make it s o di fficult for i ntruders t o decode the or iginal te xt that i t i sn't w orth their effort [8][9][1 I]. Some of Encryption Algorithm is shown in Table.1. There are two categories of cryptographic a lgorithms: c onventional a nd
public ke y C onventional c ryptography. Also known a s symmetric cr yptography r equires t hat the s ender an d receiver s hare a ke y: a s ecret piece o f information t hat i s us ed to encrypt or decrypt a message. I f t his ke y is s ecret t hen nobody other than the sender or receiver can read the message. If A lpha a nd t he ba nk e ach have a Secret ke y, t hen t hey may s end each ot her private messages. The task of privately choosing a ke y b efore c ommunicating P ublic ke y cryptography, a lso kn own as asymmetric cryptography s olves t he ke y e xchange pr oblem by de fining a n a lgorithm w hich u ses t wo ke ys, each of which can be used to encrypt a message. If one key is used to encrypt a message, then the other must b e us ed t o de crypt it. T his makes it possible t o receive s ecure messages by s imply publishing one key (the public key) and keeping the other s ecret (the pr ivate ke y). A nyone may encrypt a message using the public key, but only the owner of the private key is able to read it. In this w ay, Alpha may send pr ivate m essages t o the owner of a ke y-pair (the bank) by encrypting it us ing t heir p ublic ke y. O nly t he ba nk can decrypt it.
4. Data Encryption Standard (DES) Goal o f DES is to completely scramble t he da ta and key so that every bit o f c ipher t ext depends on e very bit o f d ata a nd ever bit o f ke y. I t i s a block Cipher Algorithm, encodes p laintext in 64 bit chunks, One parity bit for each of the 8 bytes thus it r educes t o 56 bi ts. I t i s t he most us ed algorithm. D ES de veloped by I BM in t he e arly 1970s. S tandard a pproved by U S N ational Bureau of S tandards for C ommercial a nd no classified US government use in 1993. DES is an
Er.Sheetal Atri et al, Int. J. Comp. Tech. Appl., Vol 2 (4), 1048-1050
IJCTA | JULY-AUGUST 2011 Available [email protected]
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ISSN:2229-6093
iterated block cipher, iterated m eans multiple repetitions o f a s imple e ncryption a lgorithm. DES has 16 rounds. Wh ere B lock cipher encrypts i n fixed-size bl ocks, D ES us es 64 -bit (&byte) bl ocks. At i ts s implest le vel, DES is a combination o f t he two basic t echniques o f cryptography: c onfusion a nd d iffusion. D ES follows strict avalanche cr iteria. Every bit of the key and every bit o f t he p laintext af fects e very bit o f th e c ipher te xt. It h as d ifferent ke ys for encryption and decryption. E avesdropper s ees the ci pher t ext an d one of t he ke ys. A ll o f t he security is in o ne ke y; t here i s no ne in t he algorithm or in the second key. 5. Discussions and Conclusions Cryptography i s a particularly i nteresting field because o f t he amount of w ork that i s, by necessity, done in secret. The irony is that today, secrecy i s not the ke y t o the goo dness o f a cryptographic a lgorithm. Regardless o f t he mathematical t heory behind an a lgorithm, t he best al gorithms ar e t hose t hat ar e w ell-known and well documented because they are also well-tested and well-studied! In fact, time is the only Vue t est of goo d c ryptography; a ny cryptographic scheme that stays in use year after year is most l ikely a goo d one. T he s trength of cryptography l ies i n the choice ( and management) of the keys; longer keys will resist attack b etter than s horter ke ys. The basic concepts, ch aracteristics, an d goals o f various cryptographic have been discussed. The essential parts of C ryptography in c ommunications systems a re s hown. H ow this makes t hem especially at tractive as a pot ential p latform t o implement cryptographic algorithms. 6. References [1].Atul Kahate, Cryptography and Network security, Tata Mc Graw Hill Publishing Company Limited, 2003 [2] F erguson, N. and B. Schneier, Proclicol Cryptography. New York John Wiley & Sons, 2003 [3]Barr, T.H. hitation to Cryptologv. Upper Saddle River (NJ): Prentice Hall, 2002. [4] Bauer, F .L. Decrypted Secrets: Methods and Maxims of Cryptology. 2nd ed. New York Springer Verlag, 2002. [5] D.E.R. Denning, Cryptography and Data Securi@, Addison-Wesley, 1982. [6] E. Kranakis, Primaliry and Cryptography, Wiley, 1986. [7] A .G. K onheim, Cryptogrophy: A Primer, John Wiley, 1981. [8] J. Seberry a nd J. P ieprzyk, Cryptography: An Introduction to Computer Security, Prentice-Hall, 1989.
[9] D. W elsh, Codes and Cryptography, Oxford Science Publications, 1988. [I0] D . R . S tinson, Cryptography: Theory and Practice. CRC Press, 1995. [11] M. Y . Rhee, cryptography and .%cure Communications, McGraw-Hill, 1994.
Author’s Profile Madan Lal received his three years Diploma from the Department of Electronics a nd
Communication Engineering of Bo ard of Technical E ducation, New Delhi in 1990. H e
received his B .Tech ( amie) from D epartment of Electronics and Communication Engineering of the Institution of Engineers (India) Kolkata in 1996. He received his Master o f Tec hnology f rom N ational Institute of Technology, Bhopal in 1999. He is currently purs uing hi s P h.D. de gree f rom Department of Electronics and Telecommunication Engineering. He i s a C hartered Engineer; H e was the Principal of CRR In stitute of Technology New Delhi from 2007 to 2008. He is presently Professor and Head, Department o f E lectronics a nd Communication E ngineering of Bh ai G urdas Institute of En gineering a nd T echnology, S angrur, Punjab, India. He is a life member of the Institution of E lectronics a nd T elecommunication E ngineers, New Delhi. H e i s a lso a life m ember of I ndian Society of Technical Education, New Delhi. He is also a life m ember of t he Institution of E ngineers Kolkata. His a rea of interest i s w ireless communication and circuit theory. He has contributed ov er 75 pa pers publ ished in re ferred journals a nd presented in various i nternational & national conferences."
Sheetal Atri received her four years B achelors o f Technology from t he Department o f Electronics E ngineering from K urukshetra University Kurukshetra in 2008. S he is c urrently
pursuing her M asters o f T echnology from B hai Gurdas I nstitute of E ngineering & T echnology, Sangrur. She has contributed up to some papers in i nternational & na tional c onferences. Her areas o f interest ar e S ecurity in C omputer Networks, F uzzy L ogic S ystem, an d VHDL System. N ow s he is do ing her t hesis w ork o n Security in Computer Networks.
Er.Sheetal Atri et al, Int. J. Comp. Tech. Appl., Vol 2 (4), 1048-1050
IJCTA | JULY-AUGUST 2011 Available [email protected]
1050
ISSN:2229-6093