7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

1/14

LOGO

Tm hiu v phn phi khaan ton vbomt thng tin

Sinh vin thc hin:Nguyn Th LaNguynTh TrangNg Vn

VngVn ThuNguyn Khng Duy

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

2/14

CC MC CHNH

1

2

3 CHNG 3 : CHNG TRNH M T THUT TONDIFFIEHELLMAN

CHNG 2 : PHN PHI KHA

CHNG 1:VAI TR CA KHA TRONG GII PHPAN TON V BO MT THNG TIN

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

3/14

* Vai tr ca cha kha trong cc gii php bo mt v an tonthng tin

Chng 1: VAI TR CA KHA TRONG GIIPHP AN TON V

BO MT THNG TIN

Mt m hay cc gii phpbomtcsdngbov tnh b mtca thng tinkhi chng ctruyn trn cc knh truyn thng cng cng.

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

4/14

Chng 1: VAI TR C A KH A TRONG GI IPHP AN TON V BO MT THNG TIN

Trong h m kha i xng:

Trong h m kha cng khai:

H m loi ny c tn l h m kha ixng v kha lp m v kha gii m l mt,U v V ch c thtruyn tin cvi nhau nuc hai cngbit kha K

=> Cn gi b mt ca kha.

=> Cng b cng khai thng tin cn cho viclp m, bn gi v bn nhn khngcn quy ctrcvi nhau, v cng khng c nhng bmt chung.

Kha Kca bn gi v nhn dng gm haiphn K = (K ' , K") trong K' lphncng khai, cn gi b mt K" .

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

5/14

Chng 1: VAI TR C A KH A TRONG GI IPHP AN TON V BO MT THNG TIN

Trong s xng danh v xc nhn danh tnh:

Trong h xc nhn v ch k in t:

Bom sao cho thng tin truyni l chnh itngang giao tipch khngphiitng khc mo danh thchin no . Ni cch khc, U munchng minh bn kia V xc nhn danh tnh ca mnh m khng lbt kthng tin g v mnh.

=> Xng danh v xc nhn danh tnh rt cn thit trong cc hot ngthng tin, c bit l khi cc hot ng ny thng qua mng.

Kimth tnh xc thcngungcca thng tin, cngnhchcchn l thng tin

khng b thay i trong qu trnh truyni, v nht l cn rngbuc danh tnhca bn gi thng tin i sau bn gi khng th thoi thc l mnhkhng givnbn.

=> Xng danh v xc nhn danh tnh rt cn thit trong cc hot ngthng tin, c bit l khi cc hot ng ny thng qua mng.

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

6/14

Phn phi kha l g?

L qu trnh nhmt bn to ra hocngclinhncmt gi tr dng lm b mt (kha), v chuyn chobn kia mt cch an ton.

- Tithiimkt thc thtc, hai nhm u ccng kho K xong khng cho nhm no khcbitc(trkhnng TA).

Chng 2: PHN PHI KHA

Ti sao phi phn phi kha?

- Mth m ha ph thuc vo kha, kha nyc truyn cng khai hay truyn b mt. Phnphi kha b mt th chi ph s cao hn so vi ccthut ton m ha kha cng khai.

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

7/14

Chng 2: PHN PHI KHA

2.1. S phn phi kha Blom(k=1):

Bc 1: Cng khai s nguyn t p ca h thng, mi c th U cng khai gi trrU Zp, gi tr ny ca mi ngi l khc nhau.

Bc 2: TA ly 3 gi tr ngu nhin a,b,c Zp sau xy dng a thc:f(x,y) a b(x y) cxy) modp

Bc 3: TA xc nh ri chuyn cho mi ngi dng U mta thc:gU(x) f(x, rU) modp

Vi cch xc nh nh trn th gU(x) l a thc tuyn tnh bin x, v th tac th vit:

gU(x) = aU+ bUx

Trong : aU a brU modp , bU b crU modp

Bc 4: U v V mun truyn tin vi nhau, hai ngi s dng kha chung:

KU,V KV,U f(rU, rV) a b(rU rV) crUrV modp

Trong U tnh KU, Vbng : f(rU, rV) gU(rV)

cn V tnh KU, V: f(rU, rV) gV(rU)

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

8/14

Chng 2: PHN PHI KHA

* Vn an ton ca s Blom:

- S Blom vi k=1 l an ton tuytiivibtkngi dng no.

-Tuy nhin, nu hai thnh vin W, X no sao cho{W, X} {U,V} = lin minh vi nhau th h cth xc nhc a, b, c.Mt khi h xc nhc cc gi tr ny th hstnh cttc cc kha ca hai bn no .

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

9/14

Chng 2: PHN PHI KHA

2.2. H phn phi kha Kerberos:

Bc 1: U yu cu TA cung cp kha phin truyn tin vi V

Bc 2: TA sinh ngu nhin kha phin K, tem thi gian T, v thi gian sng L

Bc 3: TA tnh : m1 = eKu(K||ID(V) || T||L)m2 = eKv(K||ID(V) || T||L)

Bc 4: U dng hm dKv gii m thu c K, T, L v ID(V). Sau tnh:

ri gi m1, m2 cho U

m3 = eK(ID(U) || T) ri gi m2, m3 cho V

Bc 5: Vs dng dKv gii m m2 xc nh K, T, L v ID(U), dK gii m thuc T v ID(U). Nu thy cc gi tr T v ID(U) gii m c khp nhauth V tnh:

m4 = eK(T+1) ri gi U

Bc 6: U dng dK gii m m4 v kim tra xem kt qu thu c c ng l T+1hay khng.

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

10/14

Chng 2: PHN PHI KHA

* Vn an ton ca s Kerberos :

- Tr ngi chnh ca Kerboros l tt c mi ngi

trong mngphi c mt ng h ngb, v giaothc cnphi xc nh thi im hin ti tnhton khong thi gian cn hp l ca kha. Trongthctthchiniu ny l rt kh, v th lun c chnh lchnhtnh.

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

11/14

Chng 2: PHN PHI KHA

2.3. H phn phi kha Diffie Hellman:

Bc 1: V tnh:

KU,VbaV modpU

aUaV modp

Trong gi tr bU ly t chng ch ca U

Bc 2: U tnh:

KU,VbaV modpU

aUaV modp

gi tr bV ly t chng ch ca V.

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

12/14

Chng 2: PHN PHI KHA

* Vn an ton ca s Diffie Hellman :

- Ch k trn chng chcangi dng chng licc tn cng ch ng, v r rng khng ai c ththay i c gi tr bU (hay bV) c TA ktrong chngch.

- ivi cc tn cngbng,nu bi ton DiffieHellman giic th giao thc khng an ton vitn cng thng.

- Cnggingnh giao thc Diffie-Hellman v mtvi giao thc da trn n, tnh an ton ca s trc cc tn cng bngnm trong tnh kh giica bi ton DiffieHellman.

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

13/14

Chng 3: CHNG TRNH M T THUTTON

3.2 Cc bc thc hin chng trnh:

Bc 1

Ban u ta cn nhp thng tinvo cho chng trnh...

Bc 2 Bc 3

7/27/2019 SLIDE BAO CAO ATBMTT-PHN PHI KHA

14/14

LOGO