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8/6/2019 BAO CAO MD5
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BO CO M HA V CRACKING MD5
TRNG H K THUT CNG NGH TP.HCM
KHOA CNG NGH THNG TIN
*************************
MN: BO MT MNG
BO CO M HA V
CRACKING MD5
GVHD: NGUYN C QUANG
SINH VIN MNG KHO 2008 THC HIN
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THC HIN BI CC NHM SINH VIN08DTHM:
1. L GIA T 0851020220
2. NGUYN MINH QUANG 0851020161
3. NUYN VN THNH 0851020187
4. TRN MINH TN 0851020197
5. H S QUANG 0851020162
6. PHM ANH QUANG 0851020157
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M HA MD5I. GII THIU V M HA V THUT TON MD5:
1. M HA L G?
M ha l phng php bin thng tin t nh dng bnh thng sangdng thng tin khng th hiu c nu khng c phng tin gii m.
VD: T ngn xa ng cha ta bit dng cc cch m ha truyn thngtin c mt nh ghi ch ngc, c ch thng qua gng,dch chuyn ch ci
V sao chng ta cn phi m ha?- Nhu cu ring t, tnh bo mt- Ton vn ca thng tin
M ha cng l nn tng ca ch k in t, h thng PKI
Ch k in t l thng tin i km theo d liu (vn bn, hnh nh,video...) nhm mc ch xc nh ngi ch ca d liu .
Kha cng khai (PKI) thng c dng ch ton b h thngbao gm nh cung cp chng thc s (CA) cng cc c ch lin quanng thi vi ton b vic s dng cc thut ton mt m ha kha cngkhai trong trao i thng tin.
2. MD 5 L G?
MD5 (Message - Digest - algorithm 5)gii thut tiu ha tp tin l mtchun Internet (RFC 1321). C kh nng bmm ha tp tin bt k thnh chui HEX 32 kt, 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 l cch cn bn ly chm k t ( ldigest, alphabeic hay g khc ), c gi l
string nhp vo 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 vo nm 1991 thay th cho hmbm trc , MD4. Vo nm 1996, ngi ta pht hin ra mt l hng trong MD5;trong khi vn cha bit n c phi l li nghim trng hay khng, nhng chuyn
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http://vi.wikipedia.org/wiki/Internethttp://tools.ietf.org/html/1321http://tools.ietf.org/html/1321http://vi.wikipedia.org/wiki/Internet8/6/2019 BAO CAO MD5
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BO CO M HA V CRACKING MD5
gia m ha bt u ngh s dng nhng gii thut khc, nh SHA-1 (khi cng b xem l khng an ton). Trong nm 2004, nhiu l hng hn b khm phkhin cho vic s dng gii thut ny cho mc ch bo mt ang b t nghi vn.
3. C IM MD5
Vic tnh MD n gin, c kh nng xc nh c file c kch thc nhiuGb.
Khng c kh nng tnh ngc, khi tm ra MD.
Do bn cht ngu nhin ca hm bm v s lng cc ln cc gi tr hashc th, nn hu nh khng c kh nng hai bn tin phn bit c cng gi trhash.
Gi tr MD ph thuc vo bn tin tng ng.
Mt chui ch c duy nht mt hash.
Gi tr MD ph thuc vo tt c cc bit ca bn tin tng ng.
V d :
love is blue 03d4ad6e7fee3f54eb46b5ccde58249c
love is Blue 82b76f8eeb4a91aa640f9a23016c7b1c
II. NG DNG1. BO TON THNG TIN
MD5 c dng rng ri trong cc phn mm trn ton th gii m bovic truyn tp tin c nguyn vn. Cc nh pht trin ng dng thng dngMD5 trong vic cho php download file. H s cho xut bn mt tn hiu MDca file download. Khi chng ta ti file v , th file chng ta va download s cmt chui MD:
Nu tn hiu ny khp vi tn hiu cc nh pht trin ng dng xut
bn trn. Th OK, ko c vn . Nu hai tn hiu ny khc nhau, c th c trong file download c virut hay
tp tin b thay i.
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tng tnh bo mt, ta c th thm key vo mt khu trc khi bmchng. Bm nhiu ln hn, .
Tuy nhin, hin nay d dng to ra xung t MD5, mt ngi c th to ramt tp tin to ra tp tin th hai vi cng mt checksum, do k thut nykhng th chng li mt vi dng gi mo nguy him. Ngoi ra, trong mt strng hp checksum khng th tin tng c (v d, nu n c ly t mtlnh nh tp tin ti v), trong trng hp MD5 ch c th c chc nng kimtra li: n s nhn ra mt li hoc ti v cha xong, rt d xy ra khi ti tp tin ln.
2. BO MT
Mc ch ca vic m ha ny l bin i mt chui mt khu thnh mt on
m khc, sao cho t on m khng th no ln tr li mt khu. C ngha lvic gii m l khng th hoc phi mt mt khong thi gian v tn ( lmnn lng cc hacker).
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Qu trnh chng thc ca mt User vi Webserver
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64 bit tip theo s c thm vo biu th chiu di ca chui bit ban u.
(B bit + bit 1 + k bit 0 + 64 bit chiu di) mod 512 = 0
V d: Ta c chui 384bit
Qu trnh thm bit
Bc 2: Khi to b m MD
Mt b m 4 word (A,B,C,D) c dng tnh m s thng ip. y miA,B,C,D l mt thanh ghi 32 bit. Nhng thanh ghi ny c khi to theo nhng gi trhex sau ( cc byte thp trc ) :
word A : 01 23 45 67
word B : 89 ab cd efword 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 bit v tora mt word 32 bit.
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Vi ln lt l XOR, 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 sin. Gi
T[i] l phn t th i ca bng, th T[i]l phn nguyn ca 4294967296*|sin(i)| , i ctnh 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
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 increment eachof the four registers by the value it had before this block was started.) */
/* Sau lm cc php cng sau. ( Ngha l cng vo mi thanh ghi gi trca n trc khi vo vng lp ) */
A = A + AAB = B + BBC = C + CCD = D + DD
end /* of loop on i */
Bc 4: In ra
M s thng ip c to ra l A,B,C,D. Ngha l chng ta bt u t bytethp ca A, kt thc vi byte cao ca D.
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M GI
M gi cho gii thut MD5 nh sau.
//Ch : Tt c cc bin u l bin khng du 32 bit v bao ph m un 2^32
khi tnh ton
varint[64] r, k
//r xc nh s dch chuyn mi vng
r[ 0..15] := {7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22}
r[16..31] := {5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20}
r[32..47] := {4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23}
r[48..63] := {6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21}
//S dng phn nguyn nh phn ca sin ca s nguyn lm hng s:
for i from0 to 63k[i] := floor(abs(sin(i + 1)) (2pow 32))
//Khi to bin:
varint h0 := 0x67452301
varint h1 := 0xEFCDAB89
varint h2 := 0x98BADCFE
varint h3 := 0x10325476
//Tin x l:
append"1" bit to message
append"0" bits until message length in bits 448 (mod 512)
appendbit (bit, not byte) length of unpadded message as64-bit little-endian
integerto message
//X l mu tin trong on 512-bit tip theo:
for each512-bit chunk of message
break chunk into sixteen 32-bit little-endian words w[i], 0 i 15
//Khi to gi tr bm cho on ny:
varint a := h0
varint b := h1
varint c := h2
varint d := h3
//Vng lp chnh:
for i from0 to 63
if 0 i 15 then
f := (b andc) or ((not b) andd)
g := i
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http://vi.wikipedia.org/wiki/M%C3%A3_gi%E1%BA%A3http://vi.wikipedia.org/wiki/M%C3%A3_gi%E1%BA%A38/6/2019 BAO CAO MD5
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BO CO M HA V CRACKING MD5
else if 16 i 31
f := (d andb) or ((not d) andc)
g := (5i + 1)mod16
else if 32 i 47
f := b xor c xor d
g := (3i + 5)mod16 else if 48 i 63
f := c xor (b or (not d))
g := (7i)mod16
temp := d
d := c
c := b
b := b + leftrotate((a + f + k[i] + w[g]) , r[i])
a := temp
//Thm bng bm ca on vo kt qu:
h0 := h0 + a
h1 := h1 + b
h2 := h2 + c
h3 := h3 + d
varint digest := h0 appendh1 appendh2 appendh3 //(expressed as little-
endian)
//nh ngha hm dch tri
leftrotate (x, c)
return (x > (32-c));
Ghi ch: Thay v hm ha RFC 1321 gc nh trn, phn sau c th c dng tng hiu qu (hu
ch nu ngn ng assembly c dng - cn khng, chng trnh dch s t ng ti u ha on m
trn):
(0 i 15): f := d xor (b and(c xor d))
(16 i 31): f := c xor (d and(b xor c))
IV. CC GII PHP THAY TH TNG TBt c thut ton m ha no ri cng b gii m. Vi MD5, ngay t nm1996, ngi ta tm thy l hng ca n. Mc d lc cn cha r rng lm nhngcc chuyn gia m ha ngh n vic phi a ra mt thut gii khc, nh l SHA-1
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BO CO M HA V CRACKING MD5
SHA-1 c coi l chun mc "vng" v thut ton. N c tch hp bntrong rt nhiu chng trnh thng dng nh PGP v SSL, c chng thc bi VinChun Cng ngh Quc gia v l thut ton ch k in t duy nht c C quanChun Ch k S ca chnh ph M ph chun.
V. KT LUN
Thut ton s ha thng ip MD5 kh n gin thc hin, cung cp mt dngvn tay hay m s ca thng ip vi di ty .
Ngi ta cho rng kh tm c 2 thng ip c cng m s l khong 2^64bc tnh, v kh tim c mt thng ip vi m s cho trc l 2^128 bctnh.
- Vi bt k gi tr x, khng th tnh c y x sao cho H(y) = H(x).
- Khng th tnh c mt cp (x, y) sao cho H(x) = H(y).
Do MD5 c s dng rng ry trong cc ng dng, web, bo mt, v chngthc
Tuy nhin mt mc no th md 5 vn c th crack c.
VI.DEMO SNIFF & CRACK MD5:
Tuy mc bo mt ca MD5 c nh gi l kh tt v khng th dch ngc. Nhngcn vic crack on Hash MD5 l c th thc hin c. Trong bi demo ny ti s thchin vic bc gi tin login ng nhp ca din n http://ithutech.net vi thng tin
password c m ha bng MD5.
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BO CO M HA V CRACKING MD5
ngh cn chun b:
Trnh duyt internet Wireshark bt lu lng login. Cain & Abel
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Cc bc thc hin:
B1:
Dng trnh duyt m trang web cn tn cng.
B2: M wireshark v chn card mng ang s dng
B3: Tr li trang din n v tin hnh login
B4: Lc gi tin http login.php
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Xem ni dung bt c
B4: Tin hnh cracking on password MD5 va bt c bng cain & Abell davo gii thut Brute-force attack
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Cho on hash MD5 vo
nh dng pass c th l a-z, A-Z, 0-9, !@#...
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nh dng pass cn tim
Gii hn chiu di pass
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BO CO M HA V CRACKING MD5
V kt qu
Kt qu tim c l: 0989612220
Th nghim thnh cng vi mt s kiu password kiu tn ngi, s in thoi,ngy thng nm sinh
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