TRNG I HC K THUT CNG NGHKHOA CNG NGH THNG TIN Mn: Bo Mt Thng Tin

Bi thc hnh s 1

Bi 1: Vit chng trnh m ha v gii m vn bn vi thut ton m ha Ceasar. Chng trnh c th thc hin cc chc nng sau: Cho php nhp vn bn vo h thng. Cho php nhp kha bo v vn bn. Cho php ghi File v m File. Hng dn m dch chuyn Caesar: -Ta ln lt nh ch s cho cc ch ci bt u t 0. - Gi k l 1 s nguyn t 0 ->25 c gi l kha. -Hm m ha: E(p,k)=(p+k)mod26 vi p l ch s ca k t cn m ha. -Hm gii m: D(c,k)=|c-k|mod26 vi c l ch s ca k t cn gii m.

Bc 1: To project mi: File New Project

Bc 2: To mi jFrame Form thit k:

Giao din thit k Frame:

Bc 3: Thit k Form

Bc 4: Vit hm x l s kin a. Hm x l s kin Encypt

b. Hm x l s kin Ghi File

c. Hm x l s kin Dencypt

d. Hm x l s kin M File

Bi 2: Vit chng trnh m ha v gii m vn bn vi thut ton m ha Vigenere. Chng trnh c th thc hin cc chc nng sau: Cho php nhp vn bn vo h thng. Cho php nhp kha bo v vn bn.

Cho php m File v Ghi File. Hng Dn: Mt m Vigenere cn gi l mt m nhiu bng m. u im ca m ny l vic s dng 26 bng m khc nhau. Do m khng b ph trong mt thi gian di. Ngoi ra m ny cn h tr vic s dng t kha v cng tin li. Thut ton: Kho K l mt b gm nhiu kho cono

K = (k1, k2, , km)

M ho:o

eK(x1, x2, , xm) = (x1 + k1, x2 + k2, , xm + km)

Gii m:o

dK(y1, y2, , ym) = (y1 k1, y2 k2, , ym km)

o (cng, tr theo modulo 26)

M KHI (block cipher)

V d:

{A, B, C, , X, Y, Z} = Z26={0, 1, , 25}.

K = (2, 8, 15, 7, 4, 17) (CIPHER).

p = thiscryptosy. c = VPXZGIAXIVWP

Bc 1: Thit K Form :

Bc 2: Vit hm x l s kin a. Hm x l s kin Encypt

b. Hm x l s kin Dencypt

Kt qu:

Bi Tp V Nh: Yu cu vit phn mm m ha v gii m vi 2 thut ton trn bao gm: - Menu m ha: Thut ton Ceasar, Thut Ton Vigenere - Menu gii m: Thut ton Ceasar, Thut Ton Vigenere - Cc chc nng m ha v gii m u phi c mc m ha v gii m theo File( File c th l .txt, .dat,)

Bi 3: Vit chng trnh m ha v gii m vn bn vi thut ton m ha Rail Fence. Chng trnh c th thc hin cc chc nng sau: Cho php nhp vn bn vo h thng.

Cho php nhp kha bo v vn bn. Cho php m File v Ghi File. Hng Dn :M Rail Fence cn c gi l m zig zag l mt hnh thc ca m chuyn v: Thng ip c vit ln lt t tri qua phi trn cc ct (rail) ca mt hng do tng tng theo ng cho t trn xung di. Theo ng cho t di ln khi t ti ct thp nht. V khi t ti ct cao nht, li vit theo ng cho t trn xung. C lp i lp li nh th no cho n khi vit ht ton b ni dung ca thng ip. V d: m ha chui HUTECH TECHNOLOGY vi kha l 2.

Bc 1: Thit K Form :

Bc 2: Vit hm x l s kin a. Hm x l s kin Encypt

b. Hm x l s kin Dencypt: ( Bi tp v nh Sinh vin )

Bc 3: Kim Tra

Bi 4: Vit chng trnh m ha v gii m vn bn vi thut ton m ha PLayFail. Chng trnh c th thc hin cc chc nng sau: Cho php nhp vn bn vo h thng. Cho php nhp kha bo v vn bn. Cho php m File v Ghi File. Hng dn:

Phng php l lp ma trn 5x5 da trn t kha cho trc v cc k t trn bng ch ci : - Trc ht vit cc ch ca t kho vo cc hng ca ma trn bt t hng th nht. - Nu ma trn cn trng, vit cc ch khc trn bng ch ci cha c s dng vo cc cn li. C th vit theo mt trnh t qui c trc, chng hn t u bng ch ci cho n cui. - V c 26 ch ci ting Anh, nn thiu mt . Thng thung ta dn hai ch no vo mt chung, chng hn I v J. - Gi s s dng t kho MORNACHY. Lp ma trn kho Playfair tng ng nh sau:

Quy tc m ha v gii mo

Chia bn r thnh tng cp ch. Nu mt cp no c hai ch nh nhau, th ta chn thm mt ch lc chng hn X. V d, trc khi m balloon bin i thnh ba lx lo on. Nu c hai ch trong cp u ri vo cng mt hng, th m mi ch bng ch pha bn phi n trong cng hng ca ma trn kha (cun vng quanh t cui v u), chng hn ar bin i thnh RM . Nu c hai ch trong cp u ri vo cng mt ct, th m mi ch bng ch pha bn di n trong cng ct ca ma trn kha (cun vng quanh t cui v u), chng hn mu bin i thnh CM. Trong cc trng hp khc, mi ch trong cp c m bi ch cng hng vi n v cng ct vi ch cng cp vi n trong ma trn kha. Chng hn, hs m thnh BP, v ea m thnh IM hoc JM .

o

o

o

Bc 1: Thit K Form :

Bc 2: Vit hm x l s kin a. Hm x l s kin Encypt

b. Hm x l s kin Dencypt

} c. Hm FindIndex

Bc 3: Kt qu

Bi 5: Vit chng trnh m ha v gii m vn bn vi thut ton m ha Transposition cipher. Chng trnh c th thc hin cc chc nng sau: Cho php nhp vn bn vo h thng. Cho php nhp kha bo v vn bn. Cho php m File v Ghi File. Hng dn :H m ha i ch ( Transposition Cipher) L h m ha trong cc k t ca bn gc c gi nguyn, nhng v tr b thay i.

o ngc ton b plaintex : ngha l bn gc c vit theo th t ngc li t sau ra trc. V d Plaintext: SECURE EMAIL Bn m: LIAMEERUCES M ha theo mu hnh hc: bn gc c sp xp li theo mt mu hnh hc no , thng l mt mng hoc ma trn hai chiu. V d: bn gc ban u l BAO MAT V d m ho theo mu hnh hc. Ct 1 Ct 2 Ct 3 B A O M A T Nu ly cc ct theo th t 2, 3, 1. Bn m s l AAOTBM i ch ct: i ch cc k t trong plaintext thnh dng hnh ch nht theo ct. V d : Bn gc BAO MAT THU DIEN TU Bn gc c chuyn thnh ma trn 3x5 nh sau: Bng v d m ha bng phng php i ch ct Ct 1 Ct 2 Ct 3 Ct 4 Ct 5 B M T D N A A H I T O T U E U V c 5 ct nn chng c th c sp li theo 5! = 120 cch khc nhau Nu ta chuyn v cc ct theo th t 3, 5, 2, 4, 1 ri ly cc k t theo hng ngang ta s thu c bn m: TNMDBHTAIAUUTEO. Hon v cc k t ca bn gc theo chu k c nh d: Nu hm f l hon v ca mt khi gm d k t th kha m ha c biu din bi K(d, f) V d: vi d = 5, f hon v ca dy 12345 thnh 35142

Bng Hon v cc k t ca bn gc theo chu k c nh d V tr ban u V tr hon v Ni dung m ha M ha 1 3 G O 2 5 R P 3 1 O G 4 4 U U 5 2 P R Theo bng trn bn gc ban u c m ha thnh OPGUP. Bc 1: Thit K Form :

Bc 2: Vit hm x l s kin a. Hm x l s kin Encypt

b. Hm x l s kin Dencypt

Bi Tp: Vit phn mm m ha vn bn vi cc thut ton m ha trn. Chng trnh c th thc hin cc chc nng sau:

Cho php nhp vn bn vo h thng. Cho php nhp kha bo v vn bn. Cho php m File v Ghi File. Cho php bn gi m ha d liu v bn nhn m ha d liu vi kha K.