Giấu tin và các ứng dụng trong cuộc sống

C> V j * ^ • # « /^AW il5))\<br /> <br /> <br /> <br /> <br /> ht<br /> ;r<br /> IJCiVJIil<br /> ' ' / ' ' • ' / /<br /> <br /> <br /> <br /> <br /> GIAU TIN<br /> VA CAC LfNG DUNG<br /> TRQNG CUOC SDNG<br /> <br /> <br /> Van de an toan va bao mat thong tin hien<br /> ke ve ky thuat giau thbng tin dupe trayen qua nhieu<br /> nay ludn nhan dUOc su" quan tam dac biet<br /> the he. Nhiing gM chep sdm nhat ve ky thuat giau<br /> trong nhieu Imh vi/c. Cac cong nghe va giai<br /> thdng tin (thdng tin dupe Meu theo nghia nguyen<br /> phap de bao ve thong tin da va dang dUOc<br /> tbiiy eua nd) thubc ve su gia Hy-Lap HerodoMs. KM<br /> nghien ciiTu, phat trien phu hOp vdi dang lu-u<br /> tru' cua thong tin va each thiire truyen tin.<br /> bao chua Hy-Lap Histiaeus bi vua Darius bkt giir d<br /> Susa vao the ky thit nam trade Cbng nguyen, bng ta<br /> Giai phap bao mat thong tin du'Oe sir dung<br /> da gui mbt thdng bko bi mat cho con re cua mlnh la<br /> pho bien nhat la diing cac he mat ma. Day<br /> Aristagoras b MileMs. De lkm viec nky, Histiaeus da<br /> la y tudng cua phUOng phap giau tin (data<br /> hiding) trong moi trudng anh dUdc nghien<br /> cao trpe dau mbt nb le tin cay vk xam mdt thbng bko<br /> eUu gan day va eo nhieu Ung dung trong giau tren da dau cua ngudi nb le ay. KM tbc eiia ngudi nd<br /> tin mat, danh giau ban quyen va nhieu Ung le nay mpc du dki nguoi nb le dupe giil tol MUeMs.<br /> dung khac... Mpt cau chuyen khac ve thbi Hy-Lap cd dai ciing<br /> do HerodoMs gM lai. Mbi trabng de gM van bkn<br /> LICH sis GIAU TIN chinh Ik ckc vien thude dupc bpc trong skp ong.<br /> DemeraMs, mdt ngubi Hy-Lap, can thdng bko eho<br /> Viee giau tin da duoc sir dung M thdi xa xua, va<br /> Sparta rkng Xerxes dinh xam cMem Hy-Lap. De<br /> sau nky dupc phkt trien img dung eho nMeu Unh<br /> tranh bi phkt Men, anh ta da bbc lbp sap ra khdi<br /> vuc. Tir Steganography bkt ngudn M tieng Hi-Lap<br /> ckc vien thude va khkc thbng bko len be mat ckc<br /> vk dupc sii dung cho tbi ngay nay, nb cb ngMa Ik<br /> vien thude nky, sau db bpc lai ckc vien thude bkng<br /> tki Ueu dupc phu (covered writimg). Ckc cau chuyen<br /> mbt lbp sap mbi. Nhkng vien thubc dupc de ngb va<br /> <br /> <br /> TAP CHI CNTT &TTKY 2 (1.2010) 29<br />  AN TOAN - BAO MAT<br /> <br /> <br /> <br /> <br /> Phuong tien Pliuong tien Phan phoi<br /> chiia (audio, chua da duoe<br /> anh, •video) siau tin<br /> <br /> <br /> <br /> <br /> Khoa<br /> <br /> <br /> Hinh 1: Lupc do chung cho qua trinh giau tin<br /> <br /> <br /> <br /> <br /> MO H I N H KY THUAT GIAU T I N<br /> Ipt qua mpi su kiem tra mdt ckch de dkng.<br /> Mb hinh ciia ky thuat giau tin co bkn duoc mb ta<br /> Muc khdng mku Ik phuang tien hiru Meu cho bko<br /> theo hai hinh sau:<br /> mat thbng tin tiong mbt thbi gian dai. Ngubi Romans<br /> cd da biet su dung nhiing chat skn cb nhu nudc qua, - Hlnh 1 bleu diln qua trinh giau tin eo ban.<br /> nudc tieu vk ska de viet cac thbng bao bi mat gika Phuong tien ehira bao gdm ckc ddi Mpng dimg<br /> nhiing hang van tu thbng thubng. KM bi ho nbng, lam mbi trabng de giau tin rihu ckc file text, audio,<br /> nhiing thit muc khbng rihin thay nky tid nen sam video, anh... Thbng tin giau la mbt lupng thdng<br /> mku vk eb the doe de dang. Muc khbng mau ciing tin mang mbt y ngMa nao db nhu anh, logo, doan<br /> duoc sii dung rat gan day, rihu tiong thbi gian cMen van ban, tep du Ueu.. .My thubc vko muc dich cua<br /> ttanh The gibi n. ngubi sit dung. Thbng tin se duoc giau vao tiong<br /> phuong tien ehira nhd mdt bd xii ly thdng tin gpi Ik<br /> Y Mdng ve che giau thbng tin da eb tir hang nghin<br /> bp rihung. Db la nhiing chuong trinh trien khai cac<br /> nam ve trabc rihung ky thukt nky dupe dimg chu<br /> thuat toan de giku tin vk dupe thue Men vbi mpt<br /> yeu tiong qukn dpi vk tiong ckc co quan tinh bao.<br /> khok bl mat gidng nhu eke he ma mat. Sau kM giau<br /> Mai cho tbi vki thap men gan day, "giau tin" mdi<br /> tin ta thu dupe phuang tien ehira ban tin da giku vk<br /> rihan dupc su quan tkm cua eke nhk ngMen cim vk<br /> phkn phdi sii dung tien mang.<br /> ckc vien cbng nghe thbng tin vbi hang loat cbng<br /> trinh ngMen cim gik tri. Cudc ckch mang sd hok Hinh ve 2 cM ra cac cbng viec giai ma thbng tin<br /> thbng tin va su phkt trien nhanh ehbng cua mang da giau. Sau kM nhan dupc ddi Mpng - phuong tien<br /> trayen thdng Ik nguyen nhan chinh dan den sir ehira cd giau thdng tin, qua trtnh giai ma dupe thuc<br /> thay ddi nky. Men thbng qua mbt bb giai ma Mang img vbi bp<br /> nhirng thbng tin eimg vbi khok eiia qua tririh nhirng.<br /> <br /> <br /> <br /> 30 TAP CHI CNTT & TT KY 2 (1.2010)<br />  AIM TOAN - BAO MAT<br /> <br /> <br /> <br /> <br /> Phuong tien<br /> I y chiia da duoc<br /> giau tin<br /> <br /> <br /> <br /> <br /> Hinh 2: Luce do cho qua trinh giai ma.<br /> <br /> <br /> Ket qua thu dupc gdm phuong Uen ehira va thdng phai tdn tai ben viing ciing vbi san pham. Mudn go<br /> tm da giau. Bube tiep theo, trong nhirng trabng hpp bd thuy van nky ma khdng dupc phep cua ngudi<br /> can thiet, thbng tin thu dupc se dupc xir U, kiem chu sd hiiu thi cM cb ckch la phk buy san pham.<br /> dinh hoae so sknh vbi thdng tin giau ban dau.<br /> <br /> Nhan thUe thong tin hay phat hien xuyen<br /> MQT SO UTNG DgNG DANG Dl/Q'C TRIEN tac thong tin<br /> KHAI<br /> Mbt lupng thbng tin se dupc giau trong phuong<br /> Bao ve ban quyen tac gia tien ehira sau dd dupc sit dung de nhan biet xem<br /> Dky Ik img dung co ban nhat cua ky thuat thuy dk Ueu tren phuang Hen gdc db cb bi thay ddi hay<br /> van sd (digital watermarking). Mdt thbng tin nao db khbng. Ckc thuy vkn nen dupe an de trknh dupc<br /> mang y nghia quyen sd hiiu tkc glk (thuang duoc su td md cua ke thii, hon niia viec lkm gia cae thuy<br /> gpi Ik thuy vkn - watermark) se dupc nhung vko vkn hpp le hay xuyen tac thdng tui ngudn cdng can<br /> trong ckc san pham. CM cd ehu sd huu hpp phkp dupe kiem tra thudng xuyen. Trong eke img dung<br /> ckc san pham dd cb quyen tMet ke va nhiing thuy thue te, ngudi ta mong mudn Um dupe vi tri bl xuyen<br /> vkn vko skn pham vbi muc dich mmh chimg cho tac cung nhu phan biet dupc ckc thay ddi (vl du nhu<br /> ban quyen san pham. Gia sit eb mbt thknh pham dir phan biet xem mdt ddi Mpng da phuong Uen ehira<br /> Ueu dang da phuong tien nhu anh, am thanh, video thbng tm giau da bl thay ddi, xuyen tac ndi dung<br /> can dupc luu thdng tren mang. De bao ve eke san hay Ik dtt Ueu hi tdn that tiong quy trUih nen). Yeu<br /> pham, chdng lai eke h^nh vi lay ckp hoae lam nhki, cau chung ddi vbi img dung nay Ik khk nang giau<br /> can phai cd mbt ky thuat de "dkn tern ban quyen" thdng tUi vdi dung lupng Idn. Neu he thdng dam<br /> vko san pham nky. Viec dkn tem hay chinh la viec bao dupc rkng thdi gian trayen thdng tm tren mang<br /> nhung thuy vkn can phai dam bao khbng de lai mbt Ik nhanh ehbng tM yeu eau ve tinh ben vkng trade<br /> anh hubng Ibn nko den viec cam nhan san pham. ckc phep xu ly tren ddi Mpng ehira tm cb the dupe<br /> Yeu cku ky thuat ddi vdi img dung nky la thuy van xem nhe.<br /> <br /> <br /> <br /> TAP CHI CNTT SiTTKY 2 (1.2010) 31<br />  AN T O A N - BAO MAT<br /> <br /> <br /> <br /> <br /> Hinh 3: Hai anh rat kho danh gia anh nao la gia mao.<br /> <br /> <br /> Giau van tay hay dan nhan vkn mang ckc gik tri the Men mire dp eho phep sao<br /> Thuy vkn duoc su dung de nhan dien ngubi gui chep dii Ueu nhu "copy never" - khbng dupe phkp<br /> hay ngudi nhkn cua mbt thdng tui nko dd trong img sao chep hay "copy once" - chi dupe copy mdt lan.<br /> dung phan phdi san pham. Thuy van trong trabng Sau khi copy xong, bd kiem sokt thuy vkn se ghi<br /> hpp nky ciing Mong M nhu sd serial cua skn pham. thuy vkn mdi cM trang thkl mdi len DVD. Ckc img<br /> Mdi mpt san pham se mang mot thuy van rieng. Vi dung loai nay ciing yeu cau thuy vkn phai duoc bao<br /> du rihu ckc thuy van khkc nhau se dupc nhung vao dam an toan vk ciing sit dung phuong phap phat<br /> ckc bkn copy khkc nhau ciia thdng tin gdc trade kM Men thuy van da giau ma khdng can thdng tin gdc.<br /> chuyen cho nMeu nguoi. Vbi nhirng img dung nky<br /> thi yeu eau la dam bao dp an toan cao cho ckc thuy Giau tin m a t<br /> vkn, trknh su sai leeh dku vet trong quk trinh phan Mue tieu cua giau tin mat Ik tdi mi hba dung lupng<br /> phdi. thbng tin duoc giku tren co sd bko toan den mire tol<br /> da chat lupng ciia mdi tradng giku. Viec glal ma de<br /> Oieu khien sao chep nhan duoc thbng tin eiing khbng can phuong Uen<br /> Ddi vbi cac he thdng phan phdi dii Ueu da phuong chita gdc ban dau. Ckc yeu cau ve chdng tan cdng<br /> Uen tM phkt trien cac ky thuat chdng sao chep trai cua ddi phuong cd the dupc giam nhe, thay vko db<br /> phkp dG Ueu dupc quan tam nMeu hon ck. Cb the Ik tang yeu cku ve bao mat vk giam thbi gian luu<br /> su dung thuy van de cM trang thkl sao chep ciia hanh tien dudng trayen.<br /> dii Ueu. Cac thuy van trong tradng hop nay dupc su Trong xa hdi phkt trien thbng tin nhu Men nay,<br /> dung de dieu kMen sao chep ddi vbi thbng tin. Cae viee bao mat thbng tui la vb cung quan trpng. Ki<br /> tMet bi phkt Men ra thuy van thubng dupc gkn sin thuat giau tui se cbn dupc tiep Mc ngMen cim vk<br /> vko trong cae he thdng gM dpc. Vi du nhu he thdng trien khai trong rat nMeu linh vuc khkc nhau cua<br /> quan U sao chep DVD da dupc img dung b Nhat. Thuy cupc sdng.<br /> NNH<br /> <br /> 32 TAP CHI CNTT & TT KY 2 ( 1 . 2 0 1 0 )<br />