Fayilo system steganography

Pa Habr.

Ndikufuna ndikuwonetseni kantchito kakang'ono steganography, yopangidwa mu nthawi yanga yopuma pophunzira.

Ndidapanga pulojekiti pakusungirako zobisika zamafayilo (kupitilira apo FS).
Izi zitha kugwiritsidwa ntchito kuba zinsinsi pazolinga zamaphunziro.

Linux FS yakale kwambiri idasankhidwa kukhala choyimira ext2.

Реализация

Kuganizira za Kukhazikitsa

Ngati kuli bwino "kutsegula" muyezo wa ext2, ndiye kuti mutha kusinthanso kuti mu FS pali zomwe zimatchedwa Superblocks, yomwe imapereka chidziwitso chofunikira chokhudza dongosolo. Nditapezeka Tsegulani Bitmap и Inode Table. Pafupifupi nthawi yomweyo, lingaliro lojambulira zidziwitso muzitsulo zopanda kanthu za FS lidabadwa. Tsopano zinali zoyenera kuganizira za chitetezo kuchokera kwa wopanga mapulogalamu okhala ndi zida hex mkonzi.

Ngati musunga zidziwitso zobisika popanda kubisa, ndiye, ngakhale zili zowoneka bwino mu FS, zidzakhalabe zowonekera kwambiri, makamaka ngati wopanga mapulogalamu akudziwa zoyenera kuyang'ana. Chifukwa chake, zidasankhidwa kubisa midadada yonse ya fayilo yoyambira. Ndinasankha block cipher AES, koma monga mukumvetsetsa, izi sizofunikira.

Kuti alekanitse midadada yofunikira kuchokera kwa ena onse powerenga, adaganiza kuwonjezera chikhomo chapadera ku chipika chilichonse kumayambiriro kwa chipikacho. Chizindikirochi chidabisidwa kutengera nambala ya block mufayilo yoyambira. Chinyengochi nthawi yomweyo chinapangitsa kuti zitheke kupeza midadada yofunikira, komanso kuzindikira dongosolo lawo lolondola.

General ntchito mfundo ya dongosolo.

Kujambula algorithm

Mfundo:

• Choyamba lembani zambiri ku gwero la fayilo;
• Chotsani izi (osati zonse);
• Fayilo yomwe iyenera kubisika imagawidwa muzitsulo zautali wofanana, ndikuwonjezera chikhomo;
• Lembani midadada iyi;
• Ikani midadada yobisidwa mu midadada yopanda kanthu ya FS.

Kwa okonda zojambula za block

Pansipa pali chithunzi cha block cha algorithm yojambulira. Algorithm imalandira mafayilo anayi monga zolowetsa:
- Chithunzi cha fayilo yosinthika yosinthika;
-Fayilo yolembedwa ndi steganography;
-Fayilo yokhala ndi chinsinsi chachinsinsi cha AES;
-Fayilo yokhala ndi chikhomo.

Ndikoyenera kudziwa nthawi yomweyo kuti aligorivimu ili ndi vuto limodzi: mutatha kulemba fayilo ku FS, sangathe lembani chilichonse chatsopano mu FS, popeza chidziwitso chilichonse chatsopano chitha kukhala m'malire omwe tapereka ku fayilo yathu ya zip, ngakhale izi zimatsegulanso mwayi "wophimba nyimbo zathu mwachangu."

Koma ndizodziwikiratu momwe izi zingakhazikitsire: ndikofunikira kulembanso algorithm yolembera midadada mu FS. Izi ndi zomveka, koma ntchito yowononga nthawi.
Chifukwa cha Umboni Wa Consept sindinagwiritse ntchito izi.

Zotsatira zake, zosintha zotsatirazi zidzapangidwa ku FS; izi ndi zomwe FS imawonekera pamaso pa steganography (fayilo yomvera idajambulidwa kale).

Ndipo izi ndi momwe FS imawonekera ndi chidziwitso chomwe chatsekedwa kale.

Kuwerenga algorithm

Mfundo:

• Ndi chidziwitso cha fungulo ndi njira yopangira zikhomo, lembani zizindikiro zoyamba za N, ndi chitsimikizo chakuti N kuchulukitsa ndi kutalika kwa chipika cha fayilo ndi chachikulu kuposa kutalika kwa fayilo ya steganographed;
• Sakani midadada mu FS kuyambira ndi zolembera;
• Tsimikizirani midadada yolandilidwa ndikulekanitsa zolembera;
• Sonkhanitsani midadada yotsatira mu dongosolo lolondola ndikupeza fayilo yoyambira.

Kwa okonda zojambula za block

Pansipa pali chithunzi cha block cha algorithm yojambulira. Algorithm imalandira mafayilo atatu monga cholowera:
-Fayilo dongosolo chithunzi;
-Fayilo yokhala ndi chinsinsi chachinsinsi cha AES;
-Fayilo yokhala ndi chikhomo.

Pulogalamuyo ikatha, fayilo ya Read imawonekera, yomwe idzakhala fayilo yochotsedwa ku fayilo ya steganographed; ngati kiyi kapena chikhomo sichinatchulidwe molakwika, ndiye kuti fayilo ya Read idzakhala yopanda kanthu.
(kwa okonda kukongola, mutha kuyika osati fayilo yokhayo, komanso "mutu" wokhala ndi chidziwitso: dzina lafayilo, maufulu, nthawi yosinthidwa yomaliza, ndi zina zambiri.)

Makina oyambira

Kuti zitheke, zolemba za bash zidalembedwa kuti zisinthe kukhazikitsidwa kwa Linux (kuyesedwa pa Ubuntu 16.04.3 LTS).
Tiyeni tiwone poyambira sitepe ndi sitepe.
Lembani:

1. sudo Copy_Flash.sh "DEVICE" - pezani chithunzi cha FS kuchokera ku DEVICE (kung'anima);
2. ./Write.sh "FILE" "KEY" "MARKER" - pangani malo enieni, tsitsani malaibulale ofunikira ndikuyendetsa zolemba;
3. sudo ./Write_Flash.sh "DEVICE" - lembaninso FS yosinthidwa ku DEVICE.

Kuwerenga:

1. sudo Copy_Flash.sh "DEVICE" - pezani chithunzi cha FS kuchokera ku DEVICE (kung'anima);
2. ./Read.sh "KEY" 'MARKER' - pangani malo enieni, tsitsani malaibulale ofunikira ndikuthamanga kuti muwerenge;
3. Pachikwatu chomwe chilipo, tsegulani fayilo ya Read - iyi ndiye zip.

Pomaliza

Njira iyi ya steganography mwina ikufunika kuwongolera, kuyezetsa kwina kowonjezera ndikuwonjeza kumafayilo otchuka kwambiri, monga Fat32, NTFS и ext4.
Koma cholinga cha ntchitoyi chinali kusonyeza mfundo imene n'zotheka kuchita zobisika kusungirako zambiri mu dongosolo wapamwamba.
Mothandizidwa ndi ma aligorivimu oterowo, mutha kusunga zidziwitso mopanda mantha, ndipo ngati, ngati mukudziwa fungulo, ndizotheka kuthyolako dongosolo loterolo osati mwankhanza (koma ndi algorithm yayitali), ndiye popanda kudziwa fungulo, izi. dongosolo likuwoneka kwa ine kukhala lokhazikika, komabe, izi zitha kukhala chifukwa cha nkhani ina.

Khodi yonse ikugwiritsidwa ntchito mu mtundu wa Python 3.5.2. Chitsanzo cha ntchito zowonetsedwa pa kanema wanga wa youtube. Khodi yonse ya polojekitiyi imayikidwa github.
(Inde, inde, ndikudziwa kuti pamapangidwe opanga muyenera kulemba china chake "mwachangu", mwachitsanzo C 😉)
Pakukhazikitsa uku, kukula kwa fayilo yolowera kwa steganography sikuyenera kupitilira 1000 kB.

Ndikufuna kuthokoza kwa ogwiritsa ntchito PavelMSTU kuti mupeze malangizo ofunikira pokonzekera phunzirolo ndi malingaliro pa kapangidwe ka nkhaniyo.

Source: www.habr.com