a block cipher technique for security of

8/4/2019 A Block Cipher Technique for Security Of

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A BLOCK CIPHER TECHNIQUE FOR SECURITY OFDATA AND COMPUTER NETWORKS

BYKame1H. ahouma*Abstract: A block cipher technique for security of dataandcomputer networks is proposed. The technique can be used fortext, binary and hexadecimal information. It can be placed inany one of the network layers. It is based on changing the systemparameters starting from the block length, includ ing the numberof processing rounds, the used permutation, substitution &arrangement boxes and ending with a disturbance XORsequence which is XORed with the final cipher-text block. Thismakes the system looks like a one-time pad system. These keysare indirectly generated from a' tex t key string either inputtedfrom the key board or read from a file. This happens in adelicate way using two input key numbers L, and L,whichindicate orders of the generated keys. Generated key s are usedto make all the used parameters changeable from a block toanother and from an 8-bit combination to the next. This is doneusing ElGamal discrete logarithm pseudo-random sequencegenerators in a special way. Compared with the exis tingtechniques, the proposed one offers good properties.Index Terms: Cryptography, Block ciphers, Security, Computernetworks, Encryption, Decryption, Crypto-system s.

I. INTRODUCTIONA wide range of applications of Internet andcomputer networks require a secure processing for theirprotocols. For instance, file transfer, data access controland in general file management may have a specialrequirement for such a secure processing. Many of thesecurity systems have been examined and applied. A large

number of them has been proved to be insecure and stillmany are known to be secure. Security of a system can beproved through many of the known tests. If a system issecure, it succeeds against the known attacks for breakingit. On computer networks in general, threats againstsecurity can be classified as passive and active. A passiveattack tries to benefit from the protected informationwithout affecting or changing them. On the other hand,an active attack tries usually to alter the communicatedinformation and data. Therefore, the method of protectiondepends on the type and importance value of thecommunicated data or information. Authentication &digital signature are used to detect any change in thehandled data.Cryptography is the back bone of securitysystems. In all of the security applications, for instance,authentication, encryption and digital signature, a certain

crypto-system stands behind. The crypto-system mightserve and perform the following services and functions:1- Entity security services for different protocols as e-mail, teleconferencing [ ].2- Communication security services which concern withtransferring data and control messages [2].3- Data base security services which are related to anentity's application data, its content, form oforganization, access and usage [3].crypto-systems differ in handling thedata. These are some systems which handle the data inbits or bytes and called stream cipher systems. There aresome other systems which handle the data in blocks andcalled block cipher systems. Each of these systems has itsproperties, advantages and disadvantages. Complexity is amain figure and measurement to the security of the usedcrypto-system. An advantages of a block cipher system isits ability in general to operate faster than a stream cipherone. It can be widely and effectively used in applicationssuch as the services listed above.Block cipher is actually a substitution cipher.This means that it is essential to use blocks of appreciablesizes in order to prevent a crypt-analysis based onfrequency contents of the block types.Shannon identified two significant classes ofcrypto-systems. There are the unconditionally securesystems and the computationally secure ones. The firsttype defies crypt-analysis even though the crypt-analysthas an unlimited computing power available to him. Theone-time pad is proved to be the only unconditionallysecure system if it is used with a truly random key.Computationally secure systems contain sufficientinformation for crypt-analysis but the solution is so largeas to be impossible of execution with the largest availablecomputational power.In mo'st of the known block ciphers, one or twoparameters may be made changeable to increase thecomplexity of the system. These may be the block lengthand/or the key length. However, no-available systemchanges all the parameter of the system. The presentpaper introduces a delicate idea of changing almost all ofthe system parameters. This includes the block length, thenumber of processing rounds, the used permutation,substitution and arrangement boxes. It also generates adisturbing sequence which is XORed with the finalcipher-text block before transmitting it. These parametersare changed such that they are onceusede itheronthe

The used

' he author is an assistant professor at the department of electrical engineering, faculty of engineering, Minia university,Minia, Egypt. Currently, he is visiting the department of computer science, university of Salzburg, Salzburg, Austria. E-mail:[email protected] 0-7803-9939-0/99/$10.000 1999 IEEE25


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level of the whole block or the level of every 8-bitcombination. Some previous work has been done [4-71 tochange some these parameters and an extension to thatwork is carried out here. The keys of generating thesystem parameters are not accessed directly. They aregenerated from a normal text- key string which is fed tothe computer either from a file or from the keyboard. Thishappens using two numbers L l , L, which are representingthe orders of the required keys. The input string shouldnot be less than 6*(L1+L2).Thus, only two input operatingkeys are required in addition to the key string to start theencryptor and decryptor operations.Generation of the system parameters dependsbasically on using discrete logarithm pseudo-randomsequence generators. ElGamal generators are employed ina special way. However, place of the proposedcrypto-system in the architecture of computer networks is shownin section (2)- and ElGamal pseudo-random sequencegenerators are discussed in section (3): Section (4)explains the generation of the system keys and parametersfrom this key string. The encryption and decryptionprocedures are presented in sections (5,6) respectively. Anillustrative example'is introduced in section (7) and someanalysis aspecti and the system properties are given insection (8). Finally, some conciusions are depicted insection (9) and section (10) lists some of the usedreferences and literature.

Seq. Block Number Perm. Sub. Arr. XOR- M 80 25 B1*8 8 8 B1*8~ length(B1) ofrounds boxes boxes boxes se q

11. THE LACE OF ENCIPHERMENT IN TH E NETWORKARCHITECTURE- r

At a casual glance, a computer network can beseen to have a complex strusture. It consists of switchingcenters, often called nodes, connected by communicationlinks and joined to multiplexers or concentrators whichprovide the paths to the network's host computers andterminals. In such a structure, encipherment could beemployed in many differential ways. a more careful studyof network structure reveals that the complexity goesbeyond its communication system. It has further levels ofstructure incorporated in the host computers and theterminals.The OS1 model, for instance, has 6 layers. Theseare the physical layer, the data l ink layer, the network -layer, the session layer, the presentation layer and theapplication layer. The physical layer is the lowest and theapplication layer is the highest. Each of these layers hasits special functions and protocols.. All of the computernetworks have almost the same architecture as the OS1 butwith different names to the corresponding layers [8,9].When encipherment is used in a network, the securityproperties it gives are dependent on the layer at which it isapplied. The OS1 model shows that potentially, it can beapplied at any of six layers and the effect is dependent onthe network structure - and on the responsibility foroperating different parts of the network [8,9].

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In. ELGAMALISCRETE LOGARITHM PSEUDO-RANDOMSEQUENCE GENERA TORS

A pseudo-random sequence is one that looksrandom. Certain generators for these sequences have beendiscussed and tested. All of them have been foundperiodic. With potential periods, they can be used for thelargest applications. The period should be long enough sothat a finite sequence of reasonable length is not periodic.This finite sequence is, actually, the one which is used forthe cryptographic purposes. To have a cryptographicallysecure pseudo-random sequence, it should beunpredictable and incompressible. It must becomputationally, infeasible to predict what the next value,in the sequence will be, given complete knowledge of thealgorithm or hardware generating the sequence and all ofthe previous values in the sequence [10,11]. Discretelogarithm pseudo-random generators constitute a securefamily of generators. They get their security from thedifficulty of computing the discrete logarithms and theirinverses in the finite field. Traditionally, the key ofgenerating these pseudo-random sequences is generallythe seed which is used as the initial state of the generator.ElGamal generators are very familiar types [12]. Here,they are used, in a special way, for constructing therequired sequences. First, choose a prime number P, tworandom numbers (g,x)


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No. Key-pair1 Nl,gl2 N2,g23 N,,g,

Function (s)To generate the block length B1To generate the number of rounds NRTo generate the Permutation box P

~~~~ Table(2): Functions of the system keys.The following procedure is used to generate thesystem six keys from the key string.1- compute the length of the key string (Len).2- For i=l to Len:3- Read the corresponding character to i as A$.4- he character is transformed to an 8-bit binary form.5- The first four bits are XORed with thesecondfour6- The result is transformed to a decimal form and7- Next i10- Divide the obtained number digits equally into six

numbers and then divide each one into two parts NJand g where 1I 16. The numbers N and g are usedas the system keys to generate the block length, thenumber of rounds, the permutation, substitution, &arrangement boxes and the final disturbing XORsequence.Once the system keys are obtained, all of thementioned parameters can be computed. This happens byapplying equation ( 5 ) where N is replaced by NJ, (15j56),

and M is determined according to table (1). The values ofg are changed every time a sequence is generatedaccording to equation (4)using NI instead of P. Thedifferent sequences should not have any repeated valuesand the S-vectors should have no coinmon values at thecorresponding places. To satisfy these conditions,equation (5) may be applied more thgn one time for eachvalue in the sequence.

ones.mod( 10) is computed.

J

v. ENCRYPTIONLGORITHM

456

1 Input the two numbers L,, L,.2- Read or input the key string and obtain the system keysas explained in section (4).

N,,g4N,,g,N,,g,

To generate the substitution box S. To generate the arrangement box A

To generate the final XOR sequence

3- Determine the block length and number of rounds4-Read the block plain-text and transform it into a binaryform if it is not so.Note: Type of the processed data is given to the programas (T or t) for text data or (B or b) for binary data or(H or h) for hexadecimal data.5- Generate both of the permutation box & the disturbingXO R sequence.6- Generate the arrangement & substitution boxes for the

combinations.7- Divide the block into a corresponding number of 8-bitcombinations.8- Each 8-bit combination is replaced by a new one usingthe corresponding substitution box. This happens toobtain the new 8-bit combination Pn from theprocesses combination C as follows:a- Arrange the combination as C=[a, a, .... ,]=[C C1 2C, C,], where;

C,=[a,I, C,=[a, a, a,], C,=[a,l,C,=[aa a7 a*].

b- If C,=O, S I is used for substitution and if C,=l , S,is used.c- Use C,, [=0,1,2 ....,71, as the address of thecorresponding value in the selected substitutionvector. Call that value XI.

d- Repeat the last two steps with (C,,C,) obtainingX,. The corresponding value of X, in the othervector in taken as XZc.

e- Replace the combination C by the new one Pn=[P,p, p as:P,=C, =complement of C,P3=c, a3 c,. P,=X,,. P,=X, @ x,.

9- Collect all the combinations in one block.10-Use the disturbing XOR sequence to disturb the block.11- Arrange the combinations of the block using thearrangement boxes.12- Repeat the steps (7-1 1)NR imes before transmittingthe block or transforming it to a hexadecimal formto store it.13- Repeat the steps (3-12) for the rest of the message.Notes:1- The message file should be ended by a zero (0) on a2- If the last block is not complete, add a number ofseparate line.spaces to complete it.

VI. DECRYPTIONLGORITHM1- Input the two numbers L,, L,.2- Read or input the key string andobtain the systems3- Determine the block length and number of rounds4- Read the block cipher-text and transform it into abinary form.Note that the type of the processed data is given to theprogram as (T or t) for text data or (B orb) for

keys as explained in section (4).

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binary data or (H or h) for hexadecimal data. This isdone for both of the encryptor and decryptor.5- Generate both of the permutation box& the disturbingXOR sequence.6- Generate the arrangement and substitution boxes forthe block combinations.7- Rearrange each combination using the arrangementboxes.8- Use the disturbing XOR sequence to obtain the block

before disturbance.9- Divide the block into a corresponding number of 8-bitcombinations.10- Use the obtained substitution boxes in a reversed wayto obtain the combination C=(C,, C,, C3,C4)which'corresponds to P, as follows:a- C3=Pl=complement of PIb- Using C3and P4(note: P4=X2,) obtain C, & X,.c- Using P, obtain X,=X2B P,.d- Using P3& C3obtain C,=P3B C3e- Using C , & XI obtain C,

11- Collect all the combinations- in one block andrepermute it using the permutation box.12- Repeat the steps (7-1 1)NR imes before transformingi t to the corresponding type (tex or binary orhexadecimal type).

-

13- Repeat the steps (3-12) for the rest of the message.Note: The cipher-text file should be ended by a zero (0)on a separate line.VII. ILLUSTRATIVE EXAMPLE

All of the steps of encryption and decryptionalgorithms are presented here using Ll = l l and L2=5

about 75 years old. He used to the action films. In many of his final tilms, heused to be the kind man or father. He joined not less than 400 films. Also,hehas many theater works.~ and the message, to be processed is:Egyptis anicecounuy locatedat the eastnorthof Africa. It is famous ofagriculture, some new & heavy industries and tourism. If youwant to have agood holiday, then it is better tovisit Egypt specially in the spring time.0

A full description of only the first block is givenwhere nbtl, BL, go,V1,VN $ are respectively the blocknumber, the block length, the generator seed, the ASCIIvalues of the processed bloc characters and the outputstring from the decryptor.

I

us ingthe numbers L, and Lz.

Theencryption results:nbtl= 1, BL,gO= 47 228927V1= [69 103 121 11211632 105 11532973211010599 1013299111 117 110 116 114 12132 108 1 119 997 116 101 100 32 97 11632 116 104 1013210197115116 32 110 111 1141initial block= [I 0 1 0 0 0 1 0 1 1 1 0 0 1 1 0 1 0 0 1 1 1 1 00 0 0 0 1 1 1 0 0 0 1 0 1 1 1 0 0 0 0 0 0 1 0 0 1 0 0 1 0 11 0 1 1 0 0 1 1 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 l l 0 0 0 0 00 1 0 0 0 1 1 1 0 1 1 0 1 0 0 1 0 1 1 0 1 1 0 0 0 l 1 0 l 01 0 0 1 1 0 0 0 0 0 0 1 0 0 1 1 0 0 0 1 1 0 1 l 1 1 0 1 1 01 0 1 0 1 1 1 0 0 1 1 1 0 1 1 0 0 0 1 0 1 1 l 0 0 l 0 0 1 11 0 1 0 0 1 1 1 1 0 0 0 0 0 0 1 0 0 0 0 1 l 0 l 1 0 1 1 1 l0 1 1 0 1 1 0 0 0 1 1 0 1 0 0 0 0 1 1 0 0 0 1 0 1 1 1 0 1 01 0 0 1 1 0 0 0 1 0 0 1 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 1 l 00 0 1 0 1 1 1 0 0 0 0 0 0 1 0 0 0 0 1 0 1 1 1 0 0 0 0 l 0 l1 0 1 0 1 0 0 1 1 0 0 0 0 0 0 1 0 0 1 0 1 0 0 1 1 0 l 0 0 00 l l o l l o o l l l o o o l o l l l o o o o o o l o o o l1 1 0 1 1 0 1 1 1 1 0 1 1 0 0 1 0 0 1 1 l o ]Number of rounds 22permutation box= [258 12 100 323 342 352 201 294 138 2 242 79136 237 7 120 142 216 91 71 144 103 172 63 195 202 351 32043 162 244 124 254 333 72 119 83 297 331 192 343 165 104272 154 233 161 168 88 209 245 290 274 231 247 313 157 361143 178 357 111 241 61 263 296 356 90 365 267 82 222 57 164328 179 134 200 253 173 309 70 47 1 354 36 130 140 150 292350 321 264 262 339 185 255 191 50 360 17 133 148 239 344174 110 48 232 268 118 8 251 204 52 372 293 362 189 370 207217 59 89 218 234 74 44 265 213 326 181 261 334 175 3 116269 291 24 299 141 325 298 280 99 273 5 340 33 31 81 167131 151 349 139 215 221 249 93 194 310 115 180 266 319 2594 335 11 146 78 224 86 159 228 246 23 187 21 145 376 6 60277 332 182 184 348 284 163 32 16 186 338 235 177 286 22362 367 114 112 256 67 282 39 158 133 75 307 38 53 371 305369 51 329 257 14 69 37 49 240 160 169 359 41 341 308 27987 152 96 250 84 337 211 183 303 353 260 199 188 212 27 107147 196 346 318 226 29 312 64 278153300283 295 127 230248 45 19 193 259 68 301 105 281 368 135 108 35 28 225.1764 15 125229 10 285 220 26 227 77 102 243 358 166 156 314 9746 315 238 122 123 270 347 18 304 311 198 54 42 65 149 336101 210 276 271 252 55 327 289 98 219 40 121 66 364 11334374 324 214 95 208 236 22 106 345 92 20 288 206 363 117 80 9109 205 287 366 275 137 58 190 322 316 373 85 56 171 203 17075 126 302 155 306 76 197 128 73 129 132 317 330 355 301substitution maps=SI s 2 s 1 s 2147263 8 1 51 [3 64 1 72 5 811231468751 [874231561 [184635271 [I527 63481[E 7 4 1 6 52 31 [7 54 62 3 1 81[63 7 42 8 1 51 [5 2 3 7 6 84 I][47623158] [ a 37542811 [7854 62311 [37254816][23576841] [E74251361 118563724] [ I47382561[E 7 4 26 1 3 51 [7 18 4 2 3 6 51[632 5 1 74 81 [5 6 7 8 2 4 131[47 2 6 1 5 3 81 [36 2 8 4 7 1 51[231746581 [E74531261 [ I8473 6521 [ I56873241[E 7 42 6 13 51 [7 5 4 1 8 2 3 61[63724851] [47635218] [58247631] [52681473][47 62 1 5 8 31 [37 1 8 5 264)[2 3 5 7 8 6 4 11 [I 4 6 5 8 3 7 21[E 7 4 3 2 6 151 [7 1 3 6 48 2 51[6 37 45 8 2 I] [5 6 4 2 1 37 81[472 15 6 3 81 [34 7 8 5 2 6 I][231756481 [E74261531 [ I84723651 [ I38467521I8 7 2 1 546 31 [7 5 3 2 6 4 1 81[63 7 542 8 I] [5 24 1 3 68 71[476 3 8 5 1 21 [3 7 62 5 8 4 I][23518674] (872415631 118357624] [ I45328761[E 7 4 2 6 1 5 31 [7 1 43 8 56 21[63 2 1 8 7 4 51

(6 34 5 7 2 8 11[2 35 67 1 4 81[4 7 6 2 1 3 5 81

[7 8 1 3 26451[3 8 7 2 1 4 651[5 8 2 3 1 4 7 61

[2 3 1 5 7 68 41[476 15 8 231[6 3 8 4 5 2 I 71[2 3 5 1 76 8 41[637 42 8 1 51[E 7 6 5 2 4 1 31[23 1 5 6 8 7 41[47 2 8 1 6 3 51[63 5 2 4 87 11[23 5 6 7 1 4 81[47 6 3 2 1 5 81[637 8 24 5 11[2 3 1 4 867 51[4 7 6 8 5 3 1 21

[3 8 65 7 2 1 4[5 8 6 7 4 1 3 21[7 8 1 3 2 5 4 61[3 8 7 62 5 1 41[7 8 5 1 34261[I 8 2 3 5 6471[3 8 7 16 5 4 21[5 8 6 1 3 2471[7 8 1 6 2 5 4 31[3 8 7 6 1 2541[5 8 2 4 1 3 7 61[7 8 5 6 4 3 1 21[3 8 1 5 2 7461

anangmentmap=[43562781][E 3 1 2 4 5 7 61[4 36 5 8 1271[83246571][4328 15761[E 3 2 6 1 5471[43 1826751[E31254671[43162785][E 37 4 2 5 1 61[ 4 3 8 5 7 2 161[E 3 4 1 5 27 61

[74138526] [27651384][345 26 1 8 71 [67 5 8 3 42 11(742536811 [27834156][346752811 [67582134][742568131 [27651834][3 4 7 6 1 5281 [675 3 248 I ][7 4 3 5 2 1 8 61 [2 7 5 4 1 8 3 61E348275161 [675283411[7 4 1 8 2 5 3 61 [2 7 4 6 8 3 1 51[348527611 [674183251[745 8 3 1261 [274 16 38 51[3 4 1 2 5 7 8 61 [6 7 4 5 2 3 1 81

[I 4 7 6 5 2 3 81[543 8 2 1 671[I 4 86 2 3 7 51[54786213](1 4 5 8 3 6 7 21[5 4 17 8 3261[I 43 7 62 8 51[5 4 6 8 7 3 2 I][I 4 2 6 7 5 831[5 47 6 12831[1 43 5 6 27 81

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X-ORsequence=[OO 1 1 1 1 1 1 1 1 0 1 1 1 0 1 1 1 1 1 1 0 10 1 1 1 0 0 0 1 0 0 0 0 0 0 0 1 1 1 1 0 1 l l 0 0 1 1 l 0 11 1 0 1 1 1 0 0 1 1 1 0 1 0 1 0 1 0 1 0 0 0 1 0 l 0 0 l l 00 0 1 1 1 1 1 0 1 1 0 0 0 1 1 0 1 0 1 1 0 0 0 l 0 l 0 l l l1 1 0 1 0 1 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 l 0 0 1 1 0 01 0 1 1 1 0 1 1 0 1 1 0 0 0 0 0 0 0 1 1 0 1 0 0 0 0 l 1 0 11 1 1 1 0 0 0 1 0 0 1 0 1 0 0 1 1 1 1 0 0 0 0 l 0 0 0 0 0 00 0 1 0 0 0 0 1 0 1 1 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 00 1 0 0 0 1 0 0 0 0 0 0 1 0 1 0 0 0 1 1 1 l l l 1 0 1 0 0 01 1 1 1 1 1 0 1 1 1 1 0 0 1 0 1 0 1 1 1 1 l 0 0 0 0 1 0 0 l0 0 1 1 0 1 0 0 1 1 0 1 0 0 1 0 0 0 0 1 1 0 1 0 l l 0 1 l 01 1 1 0 1 1 1 0 1 1 0 1 1 0 0 0 1 1 1 1 0 0 l l 0 l 0 l l 01 1 1 1 0 1 1 0 1 1 1 0 1 0 1 1 1 0 0 1 0 0 1 ]Th e@st round results:Permuted sequence= [0 0 1 0 1 0 1 1 1 0 0 1 0 0 1 0 1 0 1 0 01 0 1 1 1 0 0 0 0 0 0 1 1 0 1 0 1 0 0 1 1 0 0 l l o o o l 00 0 1 1 1 0 1 1 0 0 1 0 1 1 0 1 1 0 1 0 1 l 0 0 0 l 0 0 l 01 0 1 1 0 1 1 1 1 1 1 0 1 1 0 0 0 0 0 1 0 0 l 0 1 l 0 0 0 l0 0 1 1 0 0 1 0 1 1 1 0 0 0 0 0 0 0 0 1 1 0 l 1 1 0 1 0 0 10 0 0 0 0 0 0 0 0 1 0 1 0 1 0 1 1 0 0 0 0 1 1 l 0 l 0 l l l0 1 0 1 1 0 1 1 0 1 1 0 0 0 0 0 1 0 0 0 1 0 0 0 0 1 l l l 11 0 0 0 0 0 1 1 0 1 0 1 0 0 0 0 0 1 1 1 0 1 1 0 0 0 l 0 l 00 0 0 0 0 0 0 0 1 1 0 0 1 0 0 0 0 1 1 0 1 0 l 0 0 l 0 0 l l0 1 0 0 0 0 0 0 0 1 0 0 1 0 1 0 0 0 0 1 0 1 l 1 0 0 1 0 1 11 1 1 0 1 1 1 1 0 0 1 0 0 0 0 1 1 0 0 1 0 0 1 0 1 0 1 l 0 00 0 0 0 1 1 0 1 0 1 1 0 0 1 1 0 1 1 0 1 1 0 0 l 0 0 l l 0 l1 1 0 0 1 0 0 0 1 1 0 1 1 1 0 0 0 0 1 1 0 0 1 1 1 ]

Ciphered sequence= [0 1 1 1 1 1 0 1 1 1 1 1 0 0 1 0 0 0 0 1 00 1 1 0 1 1 0 1 0 1 1 0 0 0 1 0 1 1 0 1 0 l 0 0 0 0 1 l 0 l1 0 1 0 1 1 1 0 1 0 0 1 1 0 0 0 0 1 1 1 0 0 1 l l 1 0 0 1 00 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 0 0 1 1 0 1 1 l o l o o l l1 1 0 0 1 0 1 1 1 1 1 1 0 0 1 0 1 0 0 0 0 0 0 l 0 l 0 0 0 l1 1 1 1 1 1 0 0 1 0 1 0 1 0 0 1 1 0 1 1 0 l 1 0 1 1 0 1 0 l1 0 1 0 1 0 0 0 0 1 0 1 1 0 0 1 0 0 0 0 0 1 0 1 1 1 1 1 1 11 1 1 0 1 0 1 1 1 0 0 1 1 1 1 0 0 1 0 1 0 l 0 1 1 1 1 0 l 00 0 1 1 1 0 0 1 1 0 1 0 1 1 1 0 0 0 0 0 1 0 0 1 0 0 1 l 1 11 1 0 0 1 0 0 1 1 1 1 0 0 0 1 0 1 0 0 0 1 0 0 0 0 l 0 l 0 l0 0 1 1 0 1 1 1 0 1 0 1 1 1 1 0 1 0 1 0 0 l 0 0 l 1 0 l 0 10 l o l l o l o l o o l l o o l o l o o l l l l l l o o o l0 0 1 1 0 1 1 0 0 0 1 1 1 1 1 0 0 0 0 0 1 1 1 0 1 ]X - 0 R e d s e q u e n c e = [ 0 1 0 0 0 0 1 0 0 0 1 0 1 I 1 1 1 1 1 0 1 00 1 1 0 0 0 1 0 0 1 0 0 0 1 0 1 0 1 0 1 1 l l l 0 1 0 l 0 11 0 1 1 0 0 1 1 0 1 0 0 0 1 0 1 1 0 1 1 0 l l 0 l l 0 l l l1 0 1 0 1 1 0 0 0 0 1 0 1 0 0 1 0 0 1 1 0 1 1 0 0 0 1 1 0 00 1 1 1 1 1 0 0 1 1 1 0 0 1 0 0 0 0 0 0 0 0 l l 0 0 0 1 0 11 0 1 0 0 1 0 0 1 1 1 0 0 0 1 1 0 1 1 1 0 l l 1 l 0 l 1 0 11 0 1 0 1 0 0 0 0 0 1 0 0 1 1 0 1 1 1 1 1 0 l l 0 l 1 l l l1 1 0 0 0 1 1 1 1 0 0 0 0 1 0 0 0 0 1 0 1 0 l l 1 l 0 0 0 00 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 0 0 0 0 1 l 0 l l 0 l 0 l l1 1 1 0 1 1 0 1 0 0 1 1 0 1 1 1 1 0 1 0 1 1 1 0 l 0 l 1 l 01 1 1 1 0 1 0 0 1 1 0 1 0 1 0 0 0 1 0 0 0 l 0 0 l l 0 0 0 l1 1 0 0 0 0 1 0 0 1 0 1 1 1 1 0 1 1 1 0 0 1 1 0 0 0 1 0 01 0 0 0 1 0 1 1 1 0 0 0 0 1 0 0 1 1 1 0 1 0 1 0 0 ]Arranged block=[O 0 0 0 1 1 0 0 1 0 0 1 1 1 0 1 1 0 0 1 1 1 10 1 0 0 0 1 0 0 1 1 0 0 0 1 0 0 1 1 1 1 1 1 0 l 0 0 1 1 1 01 1 0 0 1 1 0 0 0 1 0 1 0 0 1 1 0 1 1 0 0 1 l l l 1 0 l l l1 0 1 1 0 0 0 0 0 0 0 1 1 1 0 1 0 1 1 0 0 0 0 1 0 1 0 0 1 10 1 0 1 0 1 1 0 0 0 0 1 1 - 1 1 0 0 0 1 0 0 l 0 l l 0 0 1 0 00 0 1 0 0 1 1 0 1 1 0 1 1 0 1 0 0 0 0 1 1 1 l l l 0 1 l 0 l1 1 0 0 1 0 0 0 0 0 1 1 0 0 1 1 1 1 1 1 1 1 l 0 l l 0 0 l l0 1 1 1 0 1 0 0 0 1 1 1 0 0 0 0 1 0 0 0 1 0 l l l 0 l 0 0 01 1 1 0 0 0 0 0 0 1 1 1 0 1 0 1 0 1 1 0 0 0 0 0 l l l 0 l l1 0 1 1 0 0 0 1 1 1 1 1 1 0 0 1 1 1 1 0 0 l 1 0 1 1 1 1 0 11 1 1 0 0 1 1 1 0 1 0 1 0 0 0 0 0 1 0 1 0 0 l 0 1 0 0 1 1 00 0 1 0 0 1 1 0 1 0 1 0 1 0 0 1 1 0 1 1 1 1 0 0 1 0 0 0 11 0 1 0 0 0 1 1 0 0 0 0 1 0 1 0 1 0 1 0 1 0 1 0 ]The lust (22nd) round:permutedsequence=[l 0 1 0 0 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 11 0 1 0 1 1 0 0 0 1 1 0 0 0 1 1 0 1 1 1 0 0 0 0 0 0 0 0 0 00 0 1 0 1 0 0 0 0 1 1 1 0 0 1 1 1 1 0 1 0 1 1 l 0 0 0 0 1 lI 0 1 1 1 1 1 1 1 1 0 0 0 1 0 1 0 1 1 1 0 l 0 l 0 0 1 l l 0

- 0 1 0 1 1 0 1 1 0 0 1 1 1 0 1 1 1 1 1 0 0 0 0 1 0 0 l 0 1 lI 1 0 0 0 1 1 0 1 1 0 0 1 0 0 1 1 0 0 1 0 1 1 0 0 l l l 1 l1 1 0 1 1 1 0 1 0 1 1 1 . 0 1 1 1 1 0 0 1 1 1 0 0 0 0 0 1 1 10 0 1 0 1 0 1 1 1 1 1 1 0 0 1 1 0 1 1 1 0 l 0 l 1 0 0 0 l l

1 0 0 0 1 0 0 0 0 0 0 1 1 1 1 1 0 0 0 1 1 l 0 0 0 0 l 0 0 10 0 0 1 0 0 1 0 0 1 0 0 0 0 1 1 0 1 0 1 0 0 l l 0 l 0 l l l0 0 0 0 0 0 0 1 1 1 0 1 0 1 0 1 1 1 0 1 0 l 1 1 l 1 1 0 0 01 0 1 1 0 0 1 0 1 1 0 1 0 1 1 1 1 1 1 1 0 0 1 0 1 1 0 1 10 1 0 1 1 0 0 0 1 0 1 0 0 0 0 1 0 1 0 1 1 1 1 1 1 0 ]Ciphered sequence= [ I 0 0 1 0 0 0 1 1 0 1 0 1 0 0 1 0 I 1 0 10 1 0 1 1 0 1 0 0 1 1 1 1 1 0 1 0 0 0 0 0 l 0 l 0 l l 1 1 01 0 0 0 1 0 0 1 0 1 0 0 1 0 0 1 1 1 1 1 0 1 0 1 l 0 l 0 1 01 1 0 0 0 1 0 1 0 1 0 1 0 0 1 0 0 0 1 1 0 l 0 l l l l 0 0 l0 0 1 1 1 0 0 1 0 0 1 0 0 0 0 0 0 1 1 0 0 l 0 l 1 0 0 0 l 00 1 0 1 1 0 1 0 1 1 0 1 0 1 0 1 0 1 1 0 0 0 0 l 1 0 0 1 1 00 0 0 1 0 1 0 0 0 1 1 1 1 0 0 0 0 0 1 0 0 0 1 0 1 1 l l 1 l1 1 0 0 1 1 0 0 0 0 0 0 0 1 0 1 0 1 1 1 1 1 0 0 0 1 l 0 0 l1 0 1 0 1 0 0 1 0 0 0 1 1 0 0 0 0 0 1 0 1 l l l o o o l 0 0 0 l 0 11 1 1 1 1 1 1 0 1 0 0 1 0 0 1 0 1 0 0 1 1 l l 0 0 0 0 l 1 10 1 0 1 1 0 0 0 1 0 0 1 0 1 0 0 1 1 0 0 0 l 0 l l l 0 l 0 l0 1 0 0 0 1 0 1 1 0 1 1 1 1 1 1 1 0 0 0 0 1 0 0 1 1 1 1 10 1 0 1 1 0 1 0 0 1 0 0 0 1 0 0 1 1 1 1 0 1 0 0 1 0 ]X-ORedsequence=[lOlOl 1 1 0 0 1 1 1 0 1 0 0 1 0 0 1 0 00 0 0 0 l 1 0 0 0 1 1 1 1 0 1 0 1 1 1 1 1 1 0 1 1 1 0 0 1 11 1 1 1 1 1 0 0 1 1 1 0 0 1 1 0 1 0 1 1 1 0 l 0 0 0 0 1 1 01 o o l o l o l l l o o o l l l o o l l o o l l o l l o o l1 0 0 1 1 0 0 1 0 1 0 0 0 0 0 1 1 1 0 0 1 0 l 0 l 0 0 0 l 01 1 1 0 1 0 0 0 0 0 0 1 1 0 1 0 1 1 0 1 1 0 0 l 0 0 l 0 l 01 1 0 1 0 0 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 l 0 1 0 l l l l l1 0 0 0 1 0 0 0 1 0 1 1 0 0 1 0 0 1 1 1 1 0 0 0 l 1 0 l l 10 1 1 1 0 0 0 0 0 0 1 1 0 1 0 1 0 1 0 0 0 0 0 l l l l 1 l l1 0 0 0 0 0 1 1 1 1 0 1 0 1 1 1 1 0 0 0 0 0 l 0 0 0 l 0 1 00 O l O l O l l O l O O O O O O l O O O O l l o l l o o o l1 1 1 1 1 1 0 0 0 0 0 1 0 0 1 1 0 1 1 1 0 0 0 0 0 1 0 1 10 0 0 0 1 0 0 1 0 0 1 1 0 0 1 1 0 0 0 0 1 1 0 1 1 ]Arranged block=[O 1 1 1 0 1 0 I O 1 0 1 0 0 1 1 0 0 0 0 1 0 01 0 1 0 0 0 0 1 1 1 1 1 1 0 1 1 0 1 1 0 1 l l l 1 l l 1 1 l1 O O l O O O l l l l O l O l l O l l O O o o l o l l o o l1 0 1 0 1 0 1 1 0 1 1 0 0 0 0 1 0 1 1 0 1 0 l 0 0 l l l 1 00 1 1 0 1 0 1 0 0 0 1 0 1 0 0 0 0 1 0 1 1 1 0 1 0 0 l 0 1 10 0 0 0 0 1 0 1 0 0 0 1 1 1 0 1 1 0 1 1 1 0 0 0 0 1 0 0 1 l1 0 1 1 1 0 0 0 0 0 0 1 0 0 1 1 0 1 0 1 0 0 l 1 l l 0 l 0 l0 1 1 0 0 0 0 1 0 0 0 1 1 1 1 0 1 1 0 0 1 l l 0 0 0 l l l l1 0 1 0 0 0 0 1 0 0 0 1 1 1 0 0 0 0 1 0 0 l 0 l l 1 l l l 01 1 0 0 1 0 1 0 1 1 1 1 1 0 0 0 1 0 0 0 0 0 1 0 0 0 l 1 0 00 1 0 1 1 0 0 0 0 1 1 0 0 0 0 0 0 0 1 1 0 0 l 0 1 0 1 l l 11 1 1 0 1 0 0 0 0 0 0 0 1 1 0 1 1 1 0 0 1 0 1 0 0 1 0 1 00 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 0 1 1 1 0 0 0 1 ]

092CF6BFF3 FADODCA634B2FCA82479605CDEO9B309597534CB93EB01784FB9AF802643C089AFBO8D925449~E8The decryption results:nbtl= 1 BL,gO= 94 228927initialblock=[O 1 1 1 0 1 0 1 0 1 0 1 0 0 1 1 0 0 0 0 1 0 0 10 1 0 0 0 0 1 1 1 1 1 1 0 1 1 0 1 1 0 1 l l l l l l 1 1 l 10 0 1 0 0 0 1 1 1 1 0 1 0 1 1 0 1 1 0 0 0 0 l 0 l 1 0 0 1 10 1 0 1 0 1 1 0 1 1 0 0 0 0 1 0 1 1 0 1 0 l 0 0 l l l l 0 01 1 0 1 0 1 0 0 0 1 0 1 0 0 0 0 1 0 1 1 l 0 1 0 0 1 0 1 1 00 0 0 0 1 0 1 0 0 0 1 1 1 0 1 1 0 1 1 1 0 0 0 0 l 0 0 l l l0 1 1 1 0 0 0 0 0 0 1 0 0 1 1 0 1 0 1 0 0 1 l 1 l 0 l 0 l 01 1 0 0 0 0 1 0 0 0 1 1 1 1 0 1 1 0 0 1 l l 0 0 0 l 1 l l l0 1 0 0 0 0 1 0 0 0 1 1 1 0 0 0 0 1 0 0 l 0 1 l l 1 1 1 0 11 0 0 1 0 1 0 1 1 1 1 1 0 0 0 1 0 0 0 0 0 l 0 0 0 l l 0 0 01 0 1 1 0 0 0 0 1 1 0 0 0 0 0 0 0 1 1 0 . 0 1 0 1 0 1 1 1 1 11 1 0 1 0 0 0 0 0 0 0 1 1 0 1 1 1 0 0 1 0 1 0 0 1 0 1 0 0 0 1 00 0 1 0 1 0 0 10 1 0 1 0 1 1 1 0 0 0 I]Number of rounds= 22The first round results:Rearranged sequence [ I 0 1 0 1 1 1 0 0 1 1 1 0 I O 0 1 0 0 I0 0 0 0 0 0 1 1 0 0 0 1 1 1 1 0 1 0 1 1 1 l l l 0 l l 1 0 01 1 1 1 1 1 1 1 0 0 1 1 1 0 0 1 1 0 1 0 1 l l 0 1 0 0 0 0 11 0 1 0 0 1 0 1 0 1 1 1 0 0 0 1 1 1 0 0 1 1 0 0 1 1 0 1 1 00 1 1 0 0 1 1 0 0 1 0 1 0 0 0 0 0 1 1 1 0 0 1 0 l 0 l 0 0 01 0 1 1 1 0 1 0 0 0 0 0 0 1 1 0 1 0 1 1 0 1 l 0 0 l 0 0 l 01 0 1 1 0 1 0 0 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 l 0 1 0 1 l 11 1 1 0 0 0 1 0 0 0 1 0 1 1 0 0 1 0 0 1 1 1 1 0 0 0 l l 0 l1 1 0 1 1 1 0 0 0 0 0 0 1 1 0 1 0 1 0 1 0 0 0 0 0 1 1 1 1 l1 1 1 0 0 0 0 0 1 1 1 1 0 1 0 1 1 1 1 0 0 0 0 0 1 0 0 0 1 01 0 0 0 1 0 1 0 1 1 0 1 0 0 0 0 0 0 1 0 0 0 0 l l 0 l 1 0 0

29


6/7

0 1 1 1 1 1 1 1 0 0 0 0 0 1 0 0 1 1 0 1 1 1 0 0 0 0 0 1 0 1 0 0 0 0 0 1 1 0 1 0 1 0 0 0 0 0 1 1 1 0 1 1 0 0 0 1 0 l 01 1 0 0 0 0 1 0 0 1 0 0 1 1 0 0 1 1 0 0 0 0 1 1 0 1 1 ] 0 0 0 0 0 0 0 0 1 1 0 0 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 1 10 1 0 0 0 0 0 0 0 1 0 0 1 0 1 0 0 0 0 1 0 l l 1 0 0 l 0 1 1X-ORed sequence=[l 0 0 1 0 0 0 1 1 0 1 0 1 0 0 1 0 1 1 0 1 0 1 1 1 0 1 1 1 1 0 0 1 0 0 0 0 1 1 0 0 1 0 0 1 0 l 0 1 l 0 01 0 1 1 0 1 0 0 1 1 1 1 1 0 1 0 0 0 0 0 1 0 l 0 l l l 1 0 1 0 0 0 0 1 1 0 1 0 1 1 0 0 1 1 0 1 1 0 1 1 0 0 1 0 0 1 1 00 0 0 1 0 0 1 0 1 0 0 1 0 0 1 1 1 1 1 0 1 0 1 1 0 1 0 l 0 1 1 1 1 0 0 1 0 0 0 1 1 0 1 1 1 0 0 0 0 1 1 0 0 1 1 1 ]1 0 0 0 1 0 1 0 1 0 1 0 0 1 0 0 0 1 1 0 1 0 l 1 1 l 0 0 1 00 1 1 1 0 0 1 0 0 1 0 0 0 0 0 0 1 1 . 0 0 1 0 1 - 1 0 0 0 1 0 0 Repermutedblock=[l 0 1 0 0 0 1 0 1 1 1 0 0 1 1 0 1 0 0 1 1 11 0 1 1 0 1 0 1 1 0 1 0 1 0 1 0 1 1 0 0 0 0 1 1 0 0 1 1 0 0 1 0 0 0 0 0 1 1 1 0 0 0 1 0 1 1 1 0 0 0 0 0 0 l 0 0 l 0 0 l0 0 1 0 1 0 0 0 1 1 1 1 0 0 0 0 0 1 0 0 0 l 0 1 1 1 1 l l l 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 1 1 0 0 01 0 0 1 1 0 0 0 0 0 0 0 1 0 1 0 1 1 - 1 1 1 0 0 0 1 1 0 0 l l - 0 0 0 1 0 0 0 1 1 1 0 1 1 0 1 0 0 1 0 1 1 0 1 1 0 0 0 1 1 00 1 0 1 0 0 1 0 0 0 1 1 0 0 0 0 0 1 0 1 1 1 1 0 0 0 l 0 1 1 1 0 1 0 0 1 1 0 0 0 0 0 0 1 0 0 1 1 0 0 0 1 l 0 l l l 1 0 11 1 1 1 1 1 0 1 0 0 1 0 0 1 0 1 0 0 1 1 1 1 0 0 0 0 l 1 1 0 1 0 1 0 1 0 1 1 1 0 0 1 1 1 0 1 1 0 0 0 1 0 l 1 1 0 0 1 0 01 0 1 1 0 0 0 1 0 0 1 0 1 0 0 1 1 0 0 0 1 0 1 l l 0 1 0 1 0 1 1 1 0 1 0 0 1 1 1 1 0 0 0 0 0 0 1 0 0 0 0 l l 0 l l 0 1 l1 0 0 0 1 0 1 1 0 1 1 1 1 1 1 1 0 0 0 0 1 0 0 1 1 1 1 1 0 1 1 0 1 1 0 1 1 0 0 0 1 1 0 1 ~ 0 0 0 0 1 1 0 0 0 1 0 1 1 1 01 0 1 1 0 1 0 0 1 0 0 0 1 0 0 1 1 1 1 0 1 0 0 1 0 ] . 1 0 1 0 0 1 1 0 0 0 1 0 0 1 1 0 0 0 0 0 0 1 0 0 l 0 0 0 0 11 0 0 0 1 0 1 1 1 0 0 0 0 0 0 1 0 0 0 0 1 0 1 1 1 0 0 0 0 1Deciphered sequence= [l 0 1 0 0 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 0 1 1 0 1 0 1 0 0 1 1 0 0 0 0 0 0 1 0 0 1 0 l 0 0 1 1 0 l 0I 1 0 1 0 1 1 0 0 0 1 1 0 0 0 1 1 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 0 1 0 1 1 1 0 0 0 0 0 0 1 00 O O l O l O O O O l l l b O l l l l O l o l l l o o o o l 0 0 1 1 1 0 1 1 0 1 1 1 1 0 1 1 0 0 1 0 0 1 1 1 0 ]1 1 0 1 1 1 1 1 1 1 1 0 0 0 1 0 1 0 1 1 1 0 1 0 1 0 0 1 1 l0 o l o l l o l l o o ~ l l l o l l l l l o o o o l o o l o l vln= [69 103 121 112 11632105 1153297 3211010 5991013 2991 1 1 0 0 0 1 1 0 1 1 0 0 1 0 0 1 1 0 0 1 0 l 1 0 0 1 1 1 1 111 117 110116114 121 321081119997 1161011 0032971 16321 1 1 0 1 1 1 0 1 0 1 1 1 0 1 1 1 1 0 0 1 1 1 0 0 0 0 0 l l 11610410132101971151 1632110111 11411 0 0 1 0 1 0 1 1 1 1 1 1 0 0 1 1 0 1 1 1 0 1 0 l 1 0 0 0 l -1 1 0 0 0 1 0 0 0 0 0 0 1 1 1 1 1 0 0 0 1 1 1 0 0 0 0 1 0 0 vn$=Egypt is a nice country located at the eastnor1 0 0 0 1 0 0 1 0 0 1 0 0 - 0 0 1 1 0 1 0 1 0 0 1 1 0 1 0 1 11 0 0 0 0 0 0 0 1 1 1 0 1 0 1 0 1 1 1 0 1 0 l 1 1 1 1 l 0 0 encryption and decryptlon.0 1 0 1 1 0 0 1 0 1 1 0 1 0 1 1 1 1 1 1 1 0 0 1 0 1 1 0 11 0 1 0 1 1 0 0 0 1 0 1 0 0 0 0 1 0 1 0 1 1 1 1 1 1 0 ]Repermuted block=[] 0 0 0 1 0 O-O 0 1 1 01 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 0 0 1 0 1 - 1 0 0 1 0 1 0 1 PROPERTIES0 1 1 0 1 1 1 1 0 1 1 0 0 1 1 ~ 0 0 1 0 1 1 0 0 1 1 0 1 0 11 0 0 1 0 0 1 1 1 1 1 1 0 0 0 0 0 1 1 1 1 0 1 1 0 0 1 0 l l0 0 1 0 0 0 1 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 ~ 0 1 1 1 1 0 1 Differential, linear and linear-differential crypt-0 1 1 1 0 1 1 1 0 0 1 0 0 0 0 1 1 1 0 0 1 l 0 0 0 0 0 1 l 0 analysis attacks are based on using fixed substitutionboxes as well as a fixed number of rounds [14,15].0 1 1 0 0 0 0 0 1 0 0 0 0 0 1 1 0 0 1 0 0 0 0 l l l 0 1 10 0 1 1 0 1 0 1 0 1 1 1 1 1 0 1 0 0 0 1 0 0 1 0 1 0 0 1 10 1 0 0 0 1 0 1 1 0 1 1 0 0 0 0 0 1 1 1 0 0 1 0 l l l 1 0 0 Accordingly, it is very hard and almost impossible to0 0 1 0 0 1 1 0 1 0 1 0 1 . 1 1 0 1 0 0 0 0 1 1 1 0 1 0 0 0 1 apply them to the proposed crypto-system because of

changing both of the substitution boxes and the1 1 1 0 0 1 0 0 0 0 1 1 ~ 1 1 1 1 0 0 1 0 0 1 1 1 1 0 0 10 1 1 0 0 1 1 1 1 1 0 0 - 1 0 0 0 1 0 1 0 1 1 1 1 1 0 0 1 11 0 1 1 1 1 0 0 1 0 1 0 0 1 1 0 0 1 0 0 1 0 0 1 1 ] number of rounds. Note that the number of rounds is -changed between 19 to 25rounds.2- The present crypto-system has the same property ofhe last (22nd) round resulfs:Rearranged sequence= [0 1 0 0 0 0 1 0 0 0 1 0 1 1 1 1 1 1 1 01 0 0 1 1 0 0 0 1 0 0 1 0 0 0 1 0 1 0 1 0 1 1 1 1 1 0 1 0 1 changing the key length as the Blowfish one [16]. It0 1 1 0 1 1 0 0 1 1 0 1 0 0 0 1 0 1 1 0 1 l 0 1 1 0 l 1 0 1 is more distinguished by changing the block length

where the Blowfish has a fixed one (64-bits). Also,0 0 0 1 1 1 1 1 0 0 1 1 1 0 0 1 0 0 0 0 0 0 0 0 l l o o o l0 1 1 0 1 0 0 1 0 0 1 1 1 0 0 0 1 1 0 1 1 1 0 l 1 l l 0 1 1 the proposed system is distinguished by changing the0 1 1 0 1 0 1 0 0 0 0 0 1 0 0 1 1 0 1 1 1 1 ~ 1 0 1 1 0 1 1 1 other parameters as the number or rounds and thedisturbing XOR sequence. This last parameter makes1 1 1 0 0 0 1 1 1 1 0 0 0 0 1 0 0 0 0 1 0 l 0 l 1 1 1 0 00 0 0 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 - 0 0 0 0 1 1 0 1 1 0 1 01 1 1 1 1 0 1 1 0 1 0 0 1 1 0 1 . 1 1 l O l , O l l 1 0 1 0 1 1 the system looks like a one-time pad one. This is- 1 0 1 1 1 1 0 1 0 0 1 1 0 1 0 1 0 0 0 1 0 0 0 l 0 0 l 1 0 0 because the generated sequence is used for0 1 l l O O O O l O O l d l l l l O l l l O O 1 1 0 0 0 1 processing only one block and then it is changed to anew one.0 1 0 0 0 1 0 1 1 - 1 0 0 0 0 1 0 0 1 1 1 0 1 0 1 001X-ORed sequence=[O 1 1 1 1-1 0 1 1 1 1 1 0 0 1 0 0 0 0 1 0 0 3- The proposed crypto-system is distinguished from the1 I 0 1 1 0 1 0 1 1 0 0 0 1 0 1 1 0 1 0 1 0 0 0 0 1 1 0 1 1 SAFER K-64 nd the SAFER K-128 nes [17] by

changing the block length and using the discrete1 0 1 1 1 0 1 0 0 1 1 0 0 0 0 1 1 1 0 0 l l 1 l 0 0 l 0 01 o l l o o l l o l o o ~ l o l o o l l o l l l o l o o l l l1 0 0 1 0 1 1 1 1 1 1 0 0 1 0 1 0 0 0 0 0 0 1 0 1 0 0 0 1 1 logarithm pseudo-random sequence generators toI 1 1 1 1 0 0 1 0 1 0 1 0 0 1 1 0 1 1 0 1 1 0 1 l 0 1 0 1 1 obtain the system keys.. These increase thecomplexity of attacking them.0 1 1 1 0 0 1 1 0 1 0 1 1 1 0 0 0 0 0 1 0 0 ~ 1 0 0 1 1 1 - 1 1 4- The proposed crypto-system has the properties ofI 0 0 1 0 0 1 1 1 1 0 0 0 1 0 1 0 0 0 1 0 0 0 0 1 0 l 0 1 0 changing the block length, key length and number ofrounds as the RC5 one [181. Still i


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IX. CONCLUSIONSA block -cipher technique for securityapplications of data and computer networks has beenproposed. This technique can be used for encrypting anddecrypting text, binary and hexadecimal information. Itcan be placed in any one of the network layers. Thesystem parameters are changed from a block to anotherand from an 8-bit combination to the next. Theseparameters include the block length, the number ofprocessing rounds, the used permutation, substitution &arrangement boxes and a disturbance XOR sequencewhich is XORed with the final cipher-text block. Thesystem keys are indirectly generated from a text key stringeither inputted from the key board or read fr oma file.This happens in a delicate way using two input keynumbers L, and L, which indicate the orders of the

generated keys. The generated keys are used to make allof the system parameters changeable. ElGamal discretelogarithm pseudo-random sequence generators are used ina special way to do that. Comparing the proposedtechnique with the existing ones, it offers good properties.It is distinguished by changing the block length, numberof rounds which are the main factors of applying thedifferential, linear & linear-differential .crypt-analysisattacks. Also, it is distinguished by having the disturbingXOR sequence which makes it looks like a one-time padsystem.

X . REFERENCESMuftic, S:: Security mechanisms for computer networks,John Wiley&Sons, New York, 1989.Voydock, V.L. and Kent, S.T.: Security mechanisms in high levelnetwork protocols, Computing surveys, 15(2), June 1983.Denning, D.E.: Views for multi-level data base security, IEEE trans.software engineering,SE-13(2), Feb. 1987..Rahouma, K.H.: A new system for block cipher data cryptology,Proceedings of the 2nd international conference, Mansoura, Egypt,April 1997.Rahouma, K.H.: A 64-bits ciphering technique for data security;Bulletin of the faculty of engineering, Minia University, Egypt, Vol.16, No. 3, 1997.Rahoka, K.H.: A novel changeable length block cipheringapproach for data and computer security, Presented in the 54thworkshop on General Algebra, May 29-June 1, University ofKlagenfun, Austria, 1997.Rihouma; .K.H.; Mueller, W. and Zinterhof, P.: A data blockcipher crypt-system with pseudo-random permutations andsutistitutions, Accepted for presentation in the 7th Internationalconference on Telecommunication systems, modeling and analysis,to be held March 18 through March 2 1, 1999 Nashville, Tennessee,USA.[SI Tanenbaum, AS.: Computer networks 2nd edihon, Prentlce-Hall,London. 1989

[9] Uyless Blask: Computer networks. Protocols, standards, andinterface. 2nd edition, Prenhce-Hall, nc ,New Jersey, USA, 1993.[lo] Blum, L.; Blum, M. and Shub, M.: A simple unpredictablepseudo-random number generator, SIAM J. Comput., v 15, pp.365-383,1986.[ll] Stinson, D.R.:Cryptography: Theory and practice, CRC Press,London, 1995. .[12] EIGamal, T.: A Public key crypto-system and a signature schemebased on discrete loganthms, IEEE Trans., on Informahon Theory,V. IT-31, no 4, 1985, pp. 469472.[131 Schneier,B.: Applied cryptography, 2nd ed., rotocols, algorithms,and source code in C, John Wiley & Sons, Inc., New York, 1996.

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J(141 Berson, T.: Differential crypt-analysis mod 2 with application oMDY, Advances in cryptology EUROCRYPT92Roc.,pringer-Verlag, 1992, pp. 71-80.[15] Biham,E. and Shamir,A.: Differential crypt-analysisof Feal and Nhash, Advances in cryptology EUROCRYPT91 Roc., Springer-Verlag, 1991, pp. 1-16.[16] Schneier, B.: Descriptionof a new variable length key, 64-bit blockcipher (Blowfish), Fast software encryption, Cambridge securityworkshop proc., Springer-Verlag, 1994, pp. 191-204.[17] Massey, J.L.: SAFER K-64 A byte oriented block cipheringalgorithm, Fast software encryption, Cambridge security workshopproc., Springer-Verlag, 1994, pp.1-17.[IS] Rivest, R.L.: The RC5 encryption algorithm, K.U. Leuvenworkshop on cryptographicalgorithms, Springer-Verlag, 1995.

a block cipher technique for security of

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