A Comparative Analysis of Encryption Algorithms for Better Utilization

Transcription

1 A Comparatve Analyss of Encrypton Algorthms for Better Utlzaton Anuj Kumar M.tech(IT) Sapna Snha Astt. Professor Rahul Chaudhary M.tech(CSE) ABSTRACT Cryptographc algorthms provde securty aganst attacks durng encrypton of data. However, they are computatonally ntensve applcaton and consume large amount of CPU tme [1] and space at tme of encrypton. The goal of ths paper s to compare the dfferent encrypton algorthm and to fnd space complexty of the encrypted and decrypted data y usng complextes of encrypton algorthm.. In ths paper provde comparson etween fve most wdely used algorthms. Based on followng expermental t can e seen that TDES n general perform etter than other algorthms. In ths, fnd that how these algorthms etter utlze for mprovng performances of algorthms n terms of space complexty. General Terms Algorthms Key words Cryptographc algorthm, encrypton, lock cpher, stream cpher, space complexty INTRODUCTION Encrypton s ascally hdng of data whle eng transmtted or stored [2].The encrypton process conssts of an algorthm and a key. The key controls the algorthm. The ojectve s to desgn an encrypton technque so that t would e very dffcult or mpossle for an authorzed party to understand the content of the cpher text. A use can recover the orgnal message only y decryptng the cpher text usng securty key. Dependng upon the secret key used, the algorthm wll produce a dfferent output. If the secret key changes then the output of the algorthm also changes. A key s used for performng encrypton and decrypton. Key s a specfc numer (usually large one) whch s usually used y the algorthms and ts calculaton [2]. There are two types of encrypton algorthms. These are dscussed n detal elow- 1. Symmetrc key encrypton 2. Asymmetrc key encrypton 1. SYMMETRIC KEY ENCRYPTION In symmetrc key encrypton algorthm can e used only one secret key for encryptng and decryptng data. Whle usng symmetrc key cryptographc encrypton algorthms, key can e calculated from decrypton key and also ther vce versa. When mplementng symmetrc key encrypton t can e very effcent, due to ths user cannot face any sgnfcant tme delays durng encryptng and decryptng data. It provde a degree of authentcaton.e. data cannot e decrypted through other key. It s only enefcal for the user f encrypton key s kept secret. The authorty of symmetrc key encrypton depends upon sze of the key [1]. Symmetrc key encrypton algorthm s of two types- 1.1 Block cpher 1.2 Stream cpher 1.1 Block cpher A lock cpher can operates on lock of data. Block cpher algorthms that permute N-t lock of plantext data encrypted any other [2]. In ths algorthm reaks nto lock and perform operaton on each lock ndependently. It uses locks of 8 or 16 ytes long. Securty of lock cpher s ascally dependng upon the encrypton functon. Software mplementaton of lock cpher runs faster than software mplementaton of stream cpher. Error transmttng n one lock generally does not affect other lock. The data contans n each lock s encrypted ndependently, usng the same key, dentcal plantext locks produce dentcal cpher text locks. Suppose that plan text s 227 yte long and the cpher text you are usng operates on 16- yte locks. Algorthm takes the frst 16-ytes of data, encrypts them usng the key tale. Algorthm provdes 16-yte of cpher text. After frst lock, algorthm takes next lock. The key tale doesn t change from lock to lock. Plan text= 227 ytes Block sze= 16 ytes = = 14 locks plus 3 ytes Algorthm encrypts 14 ytes and 3 ytes reman. For encrypton last 3 ytes data paddng s used. Extra ytes are added to make the last lock sze of 16 ytes. Whoever decrypts the cpher text must e ale to recognze the paddng. One prolem wth lock cphers s that f the same lock of plan text appears n two places, t encrypts to the same cpher text. To avod havng these knds of copes n the cpher text, feedack modes are used. Cpher lock channg s not contanng the extra nformaton that acqures t space, so every t n the lock s part of the massage. Before plan text s encphered, that lock s XORed wth precedng cpher text lock. It requres an ntalzaton vector to XOR the ntal plan text lock n addton of a key. For decryptng the data, copy a lock of cpher text, decrypt t and XOR the result wth the precedng lock of cpher text. Up to now, there have een numer of research artcles pontng out the performance of the compared algorthms [2]. Takng E to e the decpherment algorthm wth key and ntalzng vector s I, technque used n ths algorthm s- C Ek m ) 0 ( 0 I Ek ( m C 1 C For > 0 There are dfferent lock cpher algorthm- 1. One tme pad 2. IDEA 3. Blowfsh 19

2 4. RC2 5. Serpen 6. CAST-5 7. RC6 1.2 Stream cpher Desgnng of these algorthms to accept a crypto key and a stream of plan text to produce a stream of cpher text. Stream cpher comprses of two man components: a mxng functon and a key stream [2]. Mxng functon s usually exactly an XOR functon, whereas key stream generator s the man unt n stream cpher encrypton [1, 3]. Stream cpher ascally operates on small unts of plan text. It s faster than lock cpher. Stream cpher produces the nput element contnuously producng one output at a tme. It uses fewer amounts of codes and key s uses only once. Many stream cpher algorthms are used for hardware mplementaton. Stream cpher encrypts smaller lock of data, typcally ts or ytes. A key stream generator outputs a stream of ts K1, K2,K3.K. Ths key stream s XORed wth a stream of plan ts p1, P2,P3.P to produce the stream of cpher text ts. C P K.At the descrpton end, the cpher text ts are XORed wth an dentcal key stream to recover the plan text ts. Y1. Wth the message X and encrypton x and encrypton key Ku as nput, X1 forms the cpher text. Y= (Y1, Y2, Y3. Y ) n Y E (X ) Ku The recever, n possesson of the matchng prvate key s ale to nvert the transformaton. Y D (Y) KRB An opponent, oservng y and access to pulc key ( not havng access to prvate key ( K R K u ), ut ), must attempt to recover X. It s assumed that the opponent does have knowledge of the encrypton (E) and decrypton algorthms (D). Pulc key cryptography requres each user to have two keys: A pulc key used y anyone for encryptng messages to e sent to that user and a prvate key, whch the user need to decryptng messages. There s dfferent asymmetrc key encrypton algorthms- 1. RSA encrypton algorthm 2. Dffe Hellman key exchange 3. Dgtal sgnature algorthm 4. ElGamal P C K The system securty depend s entrely on the nsde of keys team generator. There are dfferent stream cpher algorthms- 1. Salasa2 2. HC VMP 4. RC4 5. HC25 6. Gran 2. Asymmetrc key encrypton Asymmetrc key encrypton algorthm also called pulc key encrypton algorthm. It s used n message authentcaton and key dstruton. These algorthms are ased on mathematcal functons. It uses two separate keys.e. encrypton key and decrypton oth are dfferent and the decrypton key could not e derved from the encrypton key. Only the authorzed person can e ale to decrypt the cpher text through hs own prvate key [4]. Followng steps are requred for ths algorthm. 1. Each end system n a computer network generates a par of keys to e used for encrypton and decrypton of messages that I wll receve. 2. Each system pulshes ts encrypton key.e. ths s pulc key. The companon key s kept prvate. 3. If X1 wshes to send a message to Y1, t encrypts the message usng Y1 s pulc key. After Y1 receves the message, t decrypts the message y usng Y1 s prvate key. The pulc key s accessed to all partcpants and prvate key us generated locally y each partcpant. System controls ts prvate key. At any tme, a system can change ts prvate key. Fgure 1 shows the process of pulc key algorthm. A message from source whch s n a plan text, X=(X1, X2, X3 X ). The message s ntended for destnaton m whch generates a related par of keys a pulc key Ku, and a prvate key KR. Prvate Key s secret key and known only to Fg1: Model of cryptographc system for Encrypton and Decrypton 3. IMPLEMENTED ALGORITHMS These are followng encrypton algorthm that are chosen for the mplementaton- 3.1 DES 3.2 TDES 3.3 RSA 3.4 Blowfsh 3.5 XOR 3.1 DES encrypton In may 1973, NIST (then NBS) called for possle encrypton algorthms for use n unclassfed adopted encrypton algorthm and s many standard around the world (e.g. Australan standards AS ) [5]. The plantext locks of data n and put through an ntal permutaton. 1. Put plantext K= {} 2. Dvde plantext K nto n 64-t lock 3. Repeat for each lock for =0 to n-1 4. Performed calculaton of ntal permutaton 5. After that dvded nto two parts 6. Po= left sde su part 7. Qo= rght sde su part 20

3 8. round I has nputs P-1, Q-1 9. Output of t wll e P= Q-1, Q=P-1 XOR f(q-1,m) 10. For th round M s the su key where After completon of round 16, nterchange Lo and Ro// whch conforms decrypton algorthm has same structure as encrypton algorthm At last, compute IP 13. The output wll e cphertext.e. output=cphertext Fg3: TDES Encrypton/Decrypton [7] Fg2: DES Encrypton [7] 3.2 TDES encrypton Trple DES s one of the other modes of encrypton and decrypton. It requres three 64-t keys and havng overall key length s 192 ts. TDES s a proposal ased on the Exstng DES, and was standardzed n ANSI X9.17 & ISO 8732 and n PEM for key management [5]. The procedure for encrypton s exactly the same as regular DES, ut repeat t three tmes. The data s encrypted wth the key (K1), decrypted wth the second key (K2), and fnally encrypted agan wth the thrd key (K3). Trple DES wth three keys s requred quet extensvely n many products ncludng PGP and S/MIME. Brute force search mpossle on trple DES. Meet-n-mddle attacks needs 256 Plantext-Cpher text pars per key. Cpher text s produced as C=Ek3 [Dk2 [Ek1 [P]]]. 3.3 RSA encrypton The RSA algorthm s developed n 1977 y Rvest, Shamr, Adleman (RSA) at MPT. It has een wdely used for many years on the nternet for securty and authentcaton n many applcatons ncludng credt card payments, emal and remote logn sessons [6]. RSA algorthm s pulc key encrypton type algorthm. In ths algorthm, one user (party) uses a pulc key and other user uses a secret key (prvate key) key. In the RSA algorthm each staton ndependently and randomly chooses two large prmes p and q numer, and multples them to produce n=pq whch s the modulus used n the arthmetc calculatons of the algorthm. The process of RSA algorthm s as follows. 1. Select p and q ut oth r prme numers. 2. Calculate n= pq 3. Calculate z= (p-1)(q-1) 4. Select nteger D whch s relatvely prme to 2. gcd ɸ (n)d= 1 (ɸ(n)= z) 5. Calculate ED= 1 mod (ɸ (n)) For encrypton: C P E modn Where P s plan text, C s cpher text(encrypton) For decrypton (for calculatng plan text) P C D modn 3.4 Blowfsh encrypton Many of the encrypton algorthms n today s tme do not, show to pulc- most of them are protected y patents [1] (e.g. Khufu, REDOCII, and IDEA) n whch secrecy provde y the governments. A lowfsh algorthm s a symmetrc lock cpher whch can take a key of varale length, from 32(4 Bytes) to 448t (56 Bytes) [2] that makes t enefcal for exportale and domestc use. The elementary operator of Blowfsh algorthm ncludes tale lookup, addton and XOR [5]. Blowfsh algorthm manly contans two parts- the key expanson part and the data-encrypton part [2]. Key expanson part changes a key length from 48 ts nto 4168 ytes. It 21

4 contans P-array and havng four S-oxes. P-array contans 18 of 32 ts su keys, whle each S-ox contans 256 entres. Encrypton of data performs y 16-round Festal structure. The su keys are calculated y usng followng steps- 1. Frst ntalze P-array and S-oxes. 2. Usng two XOR P-arrays of key ts 32 ts each. 3. Perform aove methods for encryptng all zeros. 4. Otan new output s P1 and P2. 5. Usng su keys encrypts new otan output P1 and P2. 6. Then otan new output s P3 and P4. 7. Repeat same steps upto 521 tmes n order to calculate new su keys for P-array and the four S-oxes. 2. Perform XOR y usng same key 3. Convertng otaned nary code to hexadecmal code 4. After, converts t nto ASCII code 5. Otanng the plan text 4. RESULT ANALYSIS Analyzng of dfferent algorthms can performng y encrypton and decrypton on varous sze of data. An XOR algorthm converts the plan text nto ASCII value and after that converts t nto hexadecmal and then nary. In last, performng XORng wth key whch s easly performed. Whle n lowfsh technque, frst dvde plan text nto 64 ts locks and then separated nto left and rght halves and performng teratve process usng 8 to 448 wth 16 Festal round wth four S-oxes. Due to ths t takes more space than XOR, DES and TDES. Tale1: space complextes of encrypton algorthms of dfferent sze of data Algorthm efore encrypton After encrypton After Decrypton XOR 160 KB 160 KB 160 KB DES 160 KB 218 KB 160 KB TDES 160 KB 390 KB 160 KB BLOWFISH 160 KB 574 KB 160 KB DES can also 16 rounds of Festal usng 56 key wth permutaton whch takes large space than XOR and TDES ut less space than Blowfsh whch s varaton of DES uses 168 key, that requre large space than DES and XOR ut smaller than Blowfsh. Assume that, encryptng same fle y dfferent encrypton technques then results are- Fg4: each round acton n Blowfsh [8] 3.5 XOR encrypton In cryptography, a smple cpher s XOR cpher. Encrypton algorthm can e operate on followng prncples- A 0 = A, A A = 0, (A B) C = A (B C), (B A) A = B 0 = B Where s an exclusve dsjuncton (XOR). Sometmes t can e sad that say that modulus 2 addtons or sutracton. Usng ths logc text of a strng can e encrypted usng twse XOR operator to every character usng a every key. In ths, encrypton s done y- 1. Frst any plan text s nput 2. Plan text s converted nto ASCII representaton. 3. after that converts nto hexadecmal representaton. 4. Converts t nto nary equvalent representaton. 5. Usng XOR wth key that converted nto same plan text. 6. Cpher text s otaned. Decrypton s done y- 1. Input a cpher text Fg5: Comparson encrypton algorthms n terms of space 22

5 5. CONCLUSION AND FUTURE SCOPE On the ass of mplementaton and ther results, notced that XOR s the fastest technque ut t s very smple and acqure less space for storng ntermedate cpher text whch s approxmately same as orgnal plan text whle other two.e. DES and TDES are advanced technque then XOR, these are fast and secure due to ts large sze of the key length and havng 16 Festal rounds wth permutaton n each round. Whle usng Blowfsh s faster than oth DES and TDES ecause t uses four S-oxes n 16 Festel rounds t t has more space complexty. After comparson of all algorthms fnd that TDES s more secure and technque can e chosen accordng to requrement. XOR algorthm s enhances as same as TDES ecause t s less secure and acqure less space than other algorthm. The space complexty s also compared wth other algorthm such as RSA, DES, IDEA. 6. REFERENCES [1] Suhala Omer Sharf, S.P. Mansoor Performance analyss of Stream and Block cpher algorthms. 3 rd Internatonal Conference on Advanced Computer Theory and Engneerng (ICACTE) [2] Allam Mousa Data Encrypton Performance Based on Blowfsh. 47 th Internatonal symposum ELMAR, Zadar, Crota [3] P.Krshnamurthy Encrypton and Power Consumpton n Wreless LANs-N. The Thrd IEEE Workshop on Wreless LANs - - Newton, Massachusetts [4] Monka Agrawal, Pradeep Mshra A Comparatve Survey on Symmetrc Key Encrypton Technques. Internatonal Journal on Computer Scence and Engneerng (IJCSE) [5] Aamer Nadeem, dr M.Younus javed A Performance Comparson of data Encrypton Algorthms. Insttute of Electrcal and Electroncs Engneers (IEEE) [6] Wllam Stallngs Cryptography and Network Securty: Prncples and practces. Dorlng Kndersley (nda) pvt ltd. [7] Krut R. Shah, Bhavka Gamhava New Approach of Data Encrypton Standard Algorthm. Internatonal Journal of Soft Computng and Engneerng (IJSCE) ISSN: Volume-2, Issue-1 [8] Jawahar Thakur and Nagesh Kumar DES, AES and Blowfsh: Symmetrc Key Cryptography Algorthms Smulaton Based Performance Analyss. Internatonal Journal of Emergng Technology and Advanced Engneerng, ISSN Volume 1, Issue 2 IJCA TM : 23