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TRNG I HC K THUT CNG NGH

KHOA CNG NGH THNG TIN

Mn: Bo Mt Thng Tin

Bi thc hnh s 3

Bi 1: Hin thc thut ton hm bm MD5 vi yu cu sau:

1.1 Cho php ngi dng nhp username v password.

1.2 Dng thut ton MD5 bm username , password v lu vo File

1.3 Dng username v password ng nhp , chng thc vi File ghiusername, password.

I. GII THIU THUT TON MD5:MD5 (Message - Digest - algorithm 5) gii

thut tiu ha tp tin l mt chunInternet(RFC1321). C kh nng bm m ha tp tin bt kthnh chui HEX 32 k t, tng ng 128-bit(mi k t hex 4-bit x 32 k t = 128 bit).Hoc c th nh ngha theo cch khc. MD5 lcch cn bn ly chm k t ( l digest,alphabeic hay g khc ), c gi l string nhpvo v cho ra l 32 k t hexa.(0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f).

MD5 c thit k bi Ronald Rivest vonm 1991 thay th cho hm bm trc , MD4. Vo nm 1996, ngi ta phin ra mt l hng trong MD5; trong khi vn cha bit n c phi l li nghi

trng hay khng, nhng chuyn gia m ha bt u ngh s dng nhng gthut khc, nh SHA-1 (khi cng b xem l khng an ton). Trong nm 200nhiu l hng hn b khm ph khin cho vic s dng gii thut ny cho mc bo mt ang b t nghi vn.

C IM MD5Vic tnh MD n gin, c kh nng xc nh c file c kch thc nhiu Gb.

http://vi.wikipedia.org/wiki/Internethttp://tools.ietf.org/html/1321http://tools.ietf.org/html/1321http://tools.ietf.org/html/1321http://tools.ietf.org/html/1321http://vi.wikipedia.org/wiki/Internet

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word C : fe dc ba 98word D : 76 54 32 10

Bc 3: X l thng ip theo tng khi 16 word

Trc ht ta nh ngha cc hm ph, cc hm ny nhn u vo l 3 word 32 v to ra mt word 32 bit.

Vi ln lt lXOR, AND, OR, NOT

y l qu trnh thc hin x l ca 4 hm F trn:

Qu trnh ny s dng mt bng c 64 gi tr T[1 .. 64] c to ra t hm sinGi T[i] l phn t th i ca bng, th T[i]l phn nguyn ca 4294967296*|sin(i c tnh theo radian.

Thc hin:

/* X l mi khi 16 word */

For (i = 0 to N/16-1) do

/* Copy block i into X. */

For j = 0 to 15 do

Set X[j] to M[i*16+j].

end /* of loop on j */

/* Lu A vo AA, B vo BB, C vo CC, D v DD . Lm buffer */

AA = A

BB = B

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CC = C

DD = D

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Qu trnh thc hin qua cc vng

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/* Then perform the following additions. (That is incrementeachof the four registers by the value it had before this block wasstarted.) */

/* Sau lm cc php c ng sau. ( Ngh a l c ng vo m i thanh ghi gi tr c a n tr c khi vo vng l p ) */

A = A + AAB = B + BBC = C + CCD = D + DD

end /* of loop on i */

Bc 4: In ra

M s thng i p c t o ra l A,B,C,D. Ngh a l chng ta b t u t byte th p c a A, k t thc v i byte cao c a D.

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III. THUT TONIII.1 Thit K Form

III.2 Th Vin cn s dng

III.3 Vit hm x l s kin

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III.3.1 X l s kin ng K

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III.3.2 X l s kin ng nhp

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Bi 2: Hin thc thut ton hm bm SHA vi yu cu sau:

Nhp chui v s dng thut ton SHA bm chui theo 2 cch.

Hng dn Thut TonThit k Frame:

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X l s kin thot Form

Kt Qu

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