Abacwaningi basePoland bahlongoze indlela entsha ye-steganography yenethiwekhi ngokusekelwe ezicini zokusebenza zephrothokholi ye-TCP yesendlalelo sezokuthutha esetshenziswa kabanzi. Ababhali balo msebenzi bakholelwa ukuthi uhlelo lwabo, ngokwesibonelo, lungasetshenziswa ukuthumela imilayezo efihliwe emazweni anobushiqela aphoqelela ukucutshungulwa okuqinile kwe-inthanethi. Ake sizame ukuthola ukuthi iyini ngempela into entsha nokuthi iwusizo kangakanani.
Okokuqala, udinga ukuchaza ukuthi iyini i-steganography. Ngakho-ke, i-steganography isayensi yokudlulisa umyalezo ofihliwe. Okusho ukuthi, ngokusebenzisa izindlela zakhe, amaqembu azama ukucasha lona kanye iqiniso lokudlulisa. Lona umehluko phakathi kwale sayensi kanye ne-cryptography, ezamayo yenza okuqukethwe komlayezo kungafundeki. Kuyaphawuleka ukuthi umphakathi wochwepheshe wabadwebi be-cryptographers uyadelela impela i-steganography ngenxa yokusondelana kwemibono yawo nesimiso esithi “Ukuphepha ngokufiphala” (angazi ukuthi kuzwakala kanjani kahle ngesiRashiya, into efana nokuthi “Ukuphepha ngokungazi. ”). Lesi simiso, isibonelo, sisetshenziswa yi-Skype Inc. - ikhodi yomthombo yesidayeli esidumile ivaliwe futhi akekho owaziyo ngempela ukuthi idatha ibethelwe kanjani. Muva nje, ngendlela, i-NSA yakhononda ngalokhu, njengoba kuphawulwe uchwepheshe odumile uBruce Schneier. kubhulogi yami.
Ukubuyela ku-steganography, sizophendula umbuzo: kungani kuyadingeka nhlobo uma kukhona i-cryptography? Ngempela, ungakwazi ukubethela umlayezo usebenzisa i-algorithm ethile yesimanje futhi uma usebenzisa ukhiye omude ngokwanele, akekho ozokwazi ukufunda lo mlayezo ngaphandle uma uwufuna. Noma kunjalo, ngezinye izikhathi kusiza kakhulu ukufihla iqiniso lokudlulisa okuyimfihlo. Isibonelo, uma iziphathimandla ezifanele zibambe umlayezo wakho obethelwe futhi zingakwazi ukuwuchaza, kodwa zifuna ngempela, khona-ke, ngemuva kwakho konke, kunezindlela ezingezona zekhompyutha zokuthonya kanye nokuthola ulwazi. Kuzwakala i-dystopian, kodwa, uyabona, lokhu kungenzeka ngokomthetho. Ngakho-ke, kungaba ngcono ukwenza isiqiniseko sokuthi labo okungafanele bazi nhlobo ukuthi ukudluliselwa kwenzeke. Abacwaningi basePoland bahlongoze indlela enjalo nje. Ngaphezu kwalokho, bahlongoza ukwenza lokhu kusetshenziswa iphrothokholi wonke umsebenzisi we-inthanethi ayisebenzisa izikhathi eziyinkulungwane ngosuku.
Lapha sisondela ku-Transmission Control Protocol (TCP). Ukuchaza yonke imininingwane yayo, yebo, akunangqondo - yinde, iyadina, futhi labo abayidingayo sebeyazi kakade. Ngamafuphi, singasho ukuthi i-TCP iyiphrothokholi yesendlalelo sezokuthutha (okungukuthi, isebenza "ngaphezu" kwe-IP kanye "ngaphansi" kwezivumelwano zesendlalelo sohlelo lokusebenza, njenge-HTTP, i-FTP noma i-SMTP), eqinisekisa ukulethwa okuthembekile kwedatha kusuka kumthumeli kuya. umemukeli. Ukulethwa okuthembekile kusho ukuthi uma iphakethe lilahleka noma lifika lilungisiwe, i-TCP izonakekela ukudlulisela lelo phakethe. Qaphela ukuthi izinguquko ephaketheni lapha azisho ukuhlanekezelwa kwamabomu kwedatha, kodwa amaphutha okudlulisela okwenzeka ezingeni lomzimba. Isibonelo, ngenkathi iphakethe lihamba ngezintambo zethusi, izingcezu ezimbalwa zashintsha inani lazo kwaba ngokuphambene noma zalahleka ngokuphelele phakathi komsindo (ngendlela, ku-Ethernet inani le-Bit Error Rate livame ukuthathwa ngokuthi licishe libe ngu-10-8. ). Ukulahleka kwephakethe kwezokuthutha nakho kuyisenzakalo esivamile ku-inthanethi. Kungenzeka, isibonelo, ngenxa yomthwalo kuma-routers, okuholela ekuchichimeni kwe-buffer futhi, ngenxa yalokho, ukulahlwa kwawo wonke amaphakethe asanda kufika. Ngokuvamile, ingxenye yamaphakethe alahlekile icishe ibe ngu-0.1%, futhi ngenani lamaphesenti ambalwa, i-TCP iyeka ukusebenza ngendlela evamile - yonke into izohamba kancane kakhulu kumsebenzisi.
Ngakho, siyabona ukuthi ukudlulisa (ukudluliselwa kabusha) kwamaphakethe kuyinto evamile ye-TCP futhi, ngokuvamile, iyadingeka. Ngakho kungani ungayisebenzisi ngezidingo ze-steganography, njengoba kuphawulwe ngenhla, isetshenziswa yonke indawo (ngokusho kwezilinganiso ezihlukahlukene, namuhla isabelo se-TCP ku-intanethi sifinyelela ku-80-95%). Ingqikithi yendlela ehlongozwayo iwukuthumela umlayezo odlulisiwe hhayi okwakusephaketheni eliyinhloko, kodwa idatha esizama ukuyifihla. Nokho, ukuthola ukushintshwa okunjalo akulula kangako. Ngemuva kwakho konke, udinga ukwazi ukuthi ubheke kuphi - inombolo yokuxhumana ye-TCP ngesikhathi esisodwa edlula kumhlinzeki inkulu kakhulu. Uma ulazi izinga elilinganiselwe lokudlulisela kabusha kunethiwekhi, ungalungisa indlela yokudlulisela phambili ye-steganographic ukuze uxhumo lwakho lungefani nolunye.
Yiqiniso, le ndlela ayikhululekile ezinkingeni. Isibonelo, ngokombono osebenzayo, ukukusebenzisa ngeke kube lula kakhulu - kuzodinga ukushintsha isitaki senethiwekhi ezinhlelweni zokusebenza, nakuba kungekho lutho olunzima kakhulu ngalokhu. Ngaphezu kwalokho, uma unezinsiza ezanele, kusengenzeka ukuthola amaphakethe "ayimfihlo" ngokubuka nokuhlaziya wonke amaphakethe kunethiwekhi. Kodwa njengomthetho, lokhu akunakwenzeka, ngakho-ke ngokuvamile babheka amaphakethe nokuxhumana okuvelele ngandlela thile, futhi indlela ehlongozwayo iyona kanye eyenza uxhumano lwakho lungabonakali. Futhi akekho okuvimbelayo ekubetheleni idatha eyimfihlo uma kwenzeka. Ngesikhathi esifanayo, uxhumo ngokwalo lungahlala lungabethelwe ukuze kuvuse ukusola okuncane.
Ababhali bomsebenzi (ngendlela, kulabo abanentshisekelo, she) ukhombise ezingeni lokulingisa ukuthi indlela ehlongozwayo isebenza ngendlela ehlosiwe. Mhlawumbe esikhathini esizayo othile uzosebenzisa umqondo wabo ekusebenzeni. Bese-ke, ngethemba, kuzoba nokuncishiswa okuncane ku-inthanethi.
Source: www.habr.com