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GIAU TIN VA CAC LfNG DUNG TRQNG CUOC SDNG
Van de an toan va bao mat thong tin hien nay ludn nhan dUOc su" quan tam dac biet trong nhieu Imh vi/c. Cac cong nghe va giai phap de bao ve thong tin da va dang dUOc nghien ciiTu, phat trien phu hOp vdi dang lu-u tru' cua thong tin va each thiire truyen tin.
Giai phap bao mat thong tin du'Oe sir dung pho bien nhat la diing cac he mat ma. Day la y tudng cua phUOng phap giau tin (data hiding) trong moi trudng anh dUdc nghien eUu gan day va eo nhieu Ung dung trong giau tin mat, danh giau ban quyen va nhieu Ung dung khac...
LICH sis GIAU TIN
Viee giau tin da duoc sir dung M thdi xa xua, va sau nky dupc phkt trien img dung eho nMeu Unh vuc. Tir Steganography bkt ngudn M tieng Hi-Lap vk dupc sii dung cho tbi ngay nay, nb cb ngMa Ik tki Ueu dupc phu (covered writimg). Ckc cau chuyen
ke ve ky thuat giau thbng tin dupe trayen qua nhieu the he. Nhiing gM chep sdm nhat ve ky thuat giau thdng tin (thdng tin dupe Meu theo nghia nguyen tbiiy eua nd) thubc ve su gia Hy-Lap HerodoMs. KM bao chua Hy-Lap Histiaeus bi vua Darius bkt giir d Susa vao the ky thit nam trade Cbng nguyen, bng ta da gui mbt thdng bko bi mat cho con re cua mlnh la Aristagoras b MileMs. De lkm viec nky, Histiaeus da cao trpe dau mbt nb le tin cay vk xam mdt thbng bko tren da dau cua ngudi nb le ay. KM tbc eiia ngudi nd le nay mpc du dki nguoi nb le dupe giil tol MUeMs.
Mpt cau chuyen khac ve thbi Hy-Lap cd dai ciing do HerodoMs gM lai. Mbi trabng de gM van bkn chinh Ik ckc vien thude dupc bpc trong skp ong.
DemeraMs, mdt ngubi Hy-Lap, can thdng bko eho Sparta rkng Xerxes dinh xam cMem Hy-Lap. De tranh bi phkt Men, anh ta da bbc lbp sap ra khdi ckc vien thude va khkc thbng bko len be mat ckc vien thude nky, sau db bpc lai ckc vien thude bkng mbt lbp sap mbi. Nhkng vien thubc dupc de ngb va
TAP CHI CNTT &TTKY 2 (1.2010) 2 9
AN TOAN - BAO MAT
Phuong tien chiia (audio, anh, •video)
Khoa
Pliuong tien chua da duoe
siau tin
Phan phoi
Hinh 1: Lupc do chung cho qua trinh giau tin
Ipt qua mpi su kiem tra mdt ckch de dkng.
Muc khdng mku Ik phuang tien hiru Meu cho bko mat thbng tin tiong mbt thbi gian dai. Ngubi Romans cd da biet su dung nhiing chat skn cb nhu nudc qua, nudc tieu vk ska de viet cac thbng bao bi mat gika nhiing hang van tu thbng thubng. KM bi ho nbng, nhiing thit muc khbng rihin thay nky tid nen sam mku vk eb the doe de dang. Muc khbng mau ciing duoc sii dung rat gan day, rihu tiong thbi gian cMen ttanh The gibi n.
Y Mdng ve che giau thbng tin da eb tir hang nghin nam ve trabc rihung ky thukt nky dupe dimg chu yeu tiong qukn dpi vk tiong ckc co quan tinh bao.
Mai cho tbi vki thap men gan day, "giau tin" mdi rihan dupc su quan tkm cua eke nhk ngMen cim vk ckc vien cbng nghe thbng tin vbi hang loat cbng trinh ngMen cim gik tri. Cudc ckch mang sd hok thbng tin va su phkt trien nhanh ehbng cua mang trayen thdng Ik nguyen nhan chinh dan den sir thay ddi nky.
MO H I N H KY THUAT G I A U T I N
Mb hinh ciia ky thuat giau tin co bkn duoc mb ta theo hai hinh sau:
- Hlnh 1 bleu diln qua trinh giau tin eo ban.
Phuong tien ehira bao gdm ckc ddi Mpng dimg lam mbi trabng de giau tin rihu ckc file text, audio, video, anh... Thbng tin giau la mbt lupng thdng tin mang mbt y ngMa nao db nhu anh, logo, doan van ban, tep du Ueu.. .My thubc vko muc dich cua ngubi sit dung. Thbng tin se duoc giau vao tiong phuong tien ehira nhd mdt bd xii ly thdng tin gpi Ik bp rihung. Db la nhiing chuong trinh trien khai cac thuat toan de giku tin vk dupe thue Men vbi mpt khok bl mat gidng nhu eke he ma mat. Sau kM giau tin ta thu dupe phuang tien ehira ban tin da giku vk phkn phdi sii dung tien mang.
Hinh ve 2 cM ra cac cbng viec giai ma thbng tin da giau. Sau kM nhan dupc ddi Mpng - phuong tien ehira cd giau thdng tin, qua trtnh giai ma dupe thuc Men thbng qua mbt bb giai ma Mang img vbi bp nhirng thbng tin eimg vbi khok eiia qua tririh nhirng.
3 0 TAP CHI CNTT & TT KY 2 (1.2010)
AIM TOAN - BAO MAT
Phuong tien I y chiia da duoc
giau tin
Hinh 2: Luce do cho qua trinh giai ma.
Ket qua thu dupc gdm phuong Uen ehira va thdng tm da giau. Bube tiep theo, trong nhirng trabng hpp can thiet, thbng tin thu dupc se dupc xir U, kiem dinh hoae so sknh vbi thdng tin giau ban dau.
MQT SO UTNG DgNG DANG Dl/Q'C TRIEN KHAI
Bao ve ban quyen tac gia
Dky Ik img dung co ban nhat cua ky thuat thuy van sd (digital watermarking). Mdt thbng tin nao db mang y nghia quyen sd hiiu tkc glk (thuang duoc gpi Ik thuy vkn - watermark) se dupc nhung vko trong ckc san pham. CM cd ehu sd huu hpp phkp ckc san pham dd cb quyen tMet ke va nhiing thuy vkn vko skn pham vbi muc dich mmh chimg cho ban quyen san pham. Gia sit eb mbt thknh pham dir Ueu dang da phuong tien nhu anh, am thanh, video can dupc luu thdng tren mang. De bao ve eke san pham, chdng lai eke h^nh vi lay ckp hoae lam nhki, can phai cd mbt ky thuat de "dkn tern ban quyen"
vko san pham nky. Viec dkn tem hay chinh la viec nhung thuy vkn can phai dam bao khbng de lai mbt anh hubng Ibn nko den viec cam nhan san pham.
Yeu cku ky thuat ddi vdi img dung nky la thuy van
phai tdn tai ben viing ciing vbi san pham. Mudn go bd thuy van nky ma khdng dupc phep cua ngudi chu sd hiiu thi cM cb ckch la phk buy san pham.
Nhan thUe thong tin hay phat hien xuyen tac thong tin
Mbt lupng thbng tin se dupc giau trong phuong tien ehira sau dd dupc sit dung de nhan biet xem dk Ueu tren phuang Hen gdc db cb bi thay ddi hay khbng. Ckc thuy vkn nen dupe an de trknh dupc su td md cua ke thii, hon niia viec lkm gia cae thuy vkn hpp le hay xuyen tac thdng tui ngudn cdng can dupe kiem tra thudng xuyen. Trong eke img dung thue te, ngudi ta mong mudn Um dupe vi tri bl xuyen tac cung nhu phan biet dupc ckc thay ddi (vl du nhu phan biet xem mdt ddi Mpng da phuong Uen ehira thbng tm giau da bl thay ddi, xuyen tac ndi dung hay Ik dtt Ueu hi tdn that tiong quy trUih nen). Yeu cau chung ddi vbi img dung nay Ik khk nang giau thdng tUi vdi dung lupng Idn. Neu he thdng dam bao dupc rkng thdi gian trayen thdng tm tren mang Ik nhanh ehbng tM yeu eau ve tinh ben vkng trade ckc phep xu ly tren ddi Mpng ehira tm cb the dupe xem nhe.
TAP CHI CNTT SiTTKY 2 (1.2010) 3 1
A N T O A N - BAO MAT
Hinh 3: Hai anh rat kho danh gia anh nao la gia mao.
Giau van t a y hay dan nhan
Thuy vkn duoc su dung de nhan dien ngubi gui hay ngudi nhkn cua mbt thdng tui nko dd trong img dung phan phdi san pham. Thuy van trong trabng hpp nky ciing Mong M nhu sd serial cua skn pham.
Mdi mpt san pham se mang mot thuy van rieng. Vi du rihu ckc thuy van khkc nhau se dupc nhung vao ckc bkn copy khkc nhau ciia thdng tin gdc trade kM chuyen cho nMeu nguoi. Vbi nhirng img dung nky thi yeu eau la dam bao dp an toan cao cho ckc thuy vkn, trknh su sai leeh dku vet trong quk trinh phan phdi.
Oieu khien sao chep
Ddi vbi cac he thdng phan phdi dii Ueu da phuong Uen tM phkt trien cac ky thuat chdng sao chep trai phkp dG Ueu dupc quan tam nMeu hon ck. Cb the su dung thuy van de cM trang thkl sao chep ciia dii Ueu. Cac thuy van trong tradng hop nay dupc su dung de dieu kMen sao chep ddi vbi thbng tin. Cae tMet bi phkt Men ra thuy van thubng dupc gkn sin vko trong cae he thdng gM dpc. Vi du nhu he thdng quan U sao chep DVD da dupc img dung b Nhat. Thuy
vkn mang ckc gik tri the Men mire dp eho phep sao chep dii Ueu nhu "copy never" - khbng dupe phkp sao chep hay "copy once" - chi dupe copy mdt lan.
Sau khi copy xong, bd kiem sokt thuy vkn se ghi thuy vkn mdi cM trang thkl mdi len DVD. Ckc img dung loai nay ciing yeu cau thuy vkn phai duoc bao dam an toan vk ciing sit dung phuong phap phat Men thuy van da giau ma khdng can thdng tin gdc.
Giau tin m a t
Mue tieu cua giau tin mat Ik tdi mi hba dung lupng thbng tin duoc giku tren co sd bko toan den mire tol da chat lupng ciia mdi tradng giku. Viec glal ma de nhan duoc thbng tin eiing khbng can phuong Uen chita gdc ban dau. Ckc yeu cau ve chdng tan cdng cua ddi phuong cd the dupc giam nhe, thay vko db Ik tang yeu cku ve bao mat vk giam thbi gian luu hanh tien dudng trayen.
Trong xa hdi phkt trien thbng tin nhu Men nay, viee bao mat thbng tui la vb cung quan trpng. Ki thuat giau tui se cbn dupc tiep Mc ngMen cim vk trien khai trong rat nMeu linh vuc khkc nhau cua cupc sdng.
NNH
3 2 TAP CHI CNTT & TT KY 2 ( 1 . 2 0 1 0 )