7/30/2019 Thut ton bo mt d liu DES.pptx

1/13

LOGO

Thut ton bo mt d liu DES

(Data Encryption Standard)GVHD : on Duy Bnh

7/30/2019 Thut ton bo mt d liu DES.pptx

2/13

w

ww.t

hemegallery.com

Data Encryption Standard

Ni dung

Gii thiu v thut ton1

Phn tch thut ton

2

Chc nng chng trnh3

Demo4

7/30/2019 Thut ton bo mt d liu DES.pptx

3/13

w

ww.t

hemegallery.com

Data Encryption Standard

Gii thiu v thut ton

Chun m ha dliu DES cVn phng tiu chun

caM cng b nm 1971 s dng trong cc cquan chnh ph lin bang.

Hin nay DES c xem l khng an ton cho nhiungdng. Nguyn nhn ch yu l di 56 bit ca

kha l qu nh (Kha DES tngb ph trong vngchay 24 gi).

Thut ton c tin tng l an ton trong thctin cdng Triple DES (thchin DES ba ln).

7/30/2019 Thut ton bo mt d liu DES.pptx

4/13

w

ww.t

hemegallery.com

Gii thiu v thut ton

ngdng: DES thng c dng m ho bo mt cc

thng tin trong qu trnh truyn tin cngnh lu trthng tin

Kim tra tnh xc thccamtkhu truy nhp vo

mththng(hthngqun l bn hng) To v kim tnh hp lcamt m s b mt (th

internet, thin thoi di ng tr trc),hoccamtth thng minh (th tn dng,th payphone).

Data Encryption Standard

7/30/2019 Thut ton bo mt d liu DES.pptx

5/13

w

ww.t

hemegallery.com

Phn tch thut ton

DES l thut ton m ho khi (block algrithm):

Viccamtkhi l 64 bit. Mtkhi 64 bit bn r ca vo, sau khi m ho d liu

a ra l mtkhibn m 64 bit.

Kho m c di 64 bit, trong : C 8 bit chnlcsdngkim sot li.

Cc bit chnlnm cc v tr 8, 16, 24, ... , 64. Tc l c 8 bitkho th trong c 1 bit kim sot li.

Nntngxy dngkhica DES l: Skthpnginca cc kthut thay th v hon vbn

r da trn kho. l cc vng lp. DES sdng 16 vng lp, n p dng cng mtkiukthp

ca cc kthut trn khibn r 16 ln.

Data Encryption Standard

7/30/2019 Thut ton bo mt d liu DES.pptx

6/13

w

ww.t

hemegallery.com

Data Encryption Standard

Phn tch thut tonHon v khi u (IP)

Hon v cui cng (Hon v ngc - IP1)

Bng kha chuyn i

7/30/2019 Thut ton bo mt d liu DES.pptx

7/13

w

ww.t

hemegallery.com

Phn tch thut ton

Data Encryption Standard

Mt vng lp DES

Bng s bit dch ca mt vng

Bng hon v nn (hon v la chn)

Bng hon v m rng (E)

Bng hp hon v (P)

8 hp S

7/30/2019 Thut ton bo mt d liu DES.pptx

8/13

w

ww.t

hemegallery.com

Chc nng chng trnh

Chng trnh m ha c vit bng Java,c thao tc : Nhp vo bng r (Plain text) vi di 64 bit. Nhp kha key vi di 64 bit.

Kt qu nhn c sau khi m ha: Bng r dng nh phn. Kha dng nh phn. Kt qu ca tng vng lp (trong 16 vng lp). Bng nh phn cui cng sau khi m ha v bn m

(Cipher Text).

V d :

Data Encryption Standard

7/30/2019 Thut ton bo mt d liu DES.pptx

9/13

w

ww.t

hemegallery.com

Demo

Data Encryption Standard

7/30/2019 Thut ton bo mt d liu DES.pptx

10/13

LOGO

SVTH : Trn Thu ThoNguyn Th Thanh Thy

7/30/2019 Thut ton bo mt d liu DES.pptx

11/13

w

ww.t

hemegallery.com

Hon vmrng

Mcch : To ra ktqu l d liu cng cvi kha thchin thao

tc XOR.

nhngha : Vimib 4bit cakhid liu vo, bit u tin v bit tht

mi bit tngngvi 2bit cakhidliu ra, trong khi bit thhai v bit th ba mi bit tngngvi 1bit cakhidliu ra.

V d : Bit v tr th 3 cakhidliu vo cchuyntiv tr th

4. V bit v tr 21 chuyntiv tr 30 v 32 trong khidliu

ra.

Data Encryption Standard

7/30/2019 Thut ton bo mt d liu DES.pptx

12/13

w

ww.t

hemegallery.com

Kha chuyni

Kha 64 bit cgimxung thnh kha 56 bit

bng cch b qua 8 bit chn l theo phngphp sdngbng kha chuyni:

Mcch : mbo rng khng c li noxy ra khi a kha vo.

Data Encryption Standard

Bngkhachuyni

7/30/2019 Thut ton bo mt d liu DES.pptx

13/13

w

ww.t

hemegallery.com

Hp thay th S

V d: Khid liu sau khi nn, kha c

XORvikhimrng ta c 48 bit ktqu:

Hp S2:

Gista chnkhi 2: Tm hng : af 00(2) = 0(10)Chn hng 1

Tm ct : bcde 1011(2) = 11(10)Chnct 12

Ktqu l : 13(10)=1101(2) Thay 010110 =1101

Data Encryption Standard