Kompania Kudelski Security, e specializuar n\u00eb auditimin e siguris\u00eb, publikoi mjetin Shufflecake, i cili lejon krijimin e sistemeve t\u00eb fshehura t\u00eb skedar\u00ebve, t\u00eb shp\u00ebrndara n\u00eb hap\u00ebsir\u00ebn e lir\u00eb ekzistuese n\u00eb partit\u00eb aktuale dhe t\u00eb pa dallueshme nga t\u00eb dh\u00ebnat rast\u00ebsore mbet\u00ebse. Partit\u00eb krijohen n\u00eb nj\u00eb m\u00ebnyr\u00eb q\u00eb, pa ditur \u00e7el\u00ebsin e aksesit, \u00ebsht\u00eb problematike t\u00eb provohet ekzistenca e tyre, madje edhe n\u00ebse b\u00ebhet nj\u00eb analiz\u00eb kriminalistike. Kodi i utilites (shufflecake-userland) dhe modulit t\u00eb b\u00ebrtham\u00ebs Linux (dm-sflc) \u00ebsht\u00eb shkruar n\u00eb gjuh\u00ebn C dhe distribuohet n\u00ebn licenc\u00ebn GPLv3, e cila e b\u00ebn t\u00eb pamundur p\u00ebrfshirjen e modulit t\u00eb publikuar n\u00eb b\u00ebrtham\u00ebn kryesore t\u00eb Linux-it p\u00ebr shkak t\u00eb pap\u00ebrputhshm\u00ebris\u00eb me licenc\u00ebn GPLv2, n\u00ebn t\u00eb cil\u00ebn ofrohet b\u00ebrthama. <\/p>\n
Projekti pozicionohet si nj\u00eb zgjidhje m\u00eb e avancuar se Truecrypt dhe Veracrypt p\u00ebr fshehjen e t\u00eb dh\u00ebnave q\u00eb k\u00ebrkojn\u00eb mbrojtje, e cila ka mb\u00ebshtetje native p\u00ebr platform\u00ebn Linux dhe lejon vendosjen e deri n\u00eb 15 partish t\u00eb fshehura n\u00eb nj\u00eb pajisje, t\u00eb nd\u00ebrlikuara nj\u00ebra me tjetr\u00ebn p\u00ebr t\u00eb ngat\u00ebrruar analiz\u00ebn e ekzistenc\u00ebs s\u00eb tyre. N\u00ebse aplikimi i vet\u00eb Shufflecake-it nuk paraqet nj\u00eb sekret, si\u00e7 mund t\u00eb gjykohet nga pranija n\u00eb sistem e utiliteteve p\u00ebrkat\u00ebse, numri total i partive t\u00eb krijuara t\u00eb fshehura \u00ebsht\u00eb e pamundur t\u00eb p\u00ebrcaktohet. Partit\u00eb e fshehura t\u00eb krijuara mund t\u00eb formatojn\u00eb sipas d\u00ebshir\u00ebs s\u00eb p\u00ebrdoruesit p\u00ebr t\u00eb vendosur \u00e7do FS, si\u00e7 jan\u00eb ext4, xfs ose btrfs. \u00c7do parti trajtohet si nj\u00eb pajisje virtuale e ve\u00e7ant\u00eb blloku me \u00e7el\u00ebsin e saj p\u00ebr \u00e7eljen. <\/p>\n
P\u00ebr t\u00eb maskuar gjurm\u00ebt, sugjerohet p\u00ebrdorimi i modelit t\u00eb sjelljes \"mohoja e besueshme\" (plausible deniability), thelbi i s\u00eb cil\u00ebs \u00ebsht\u00eb se t\u00eb dh\u00ebnat me vler\u00eb fshihen si shtesa n\u00eb pjes\u00eb t\u00eb koduara me t\u00eb dh\u00ebna m\u00eb pak t\u00eb vlefshme, duke krijuar nj\u00eb hierarki t\u00eb fsheht\u00eb t\u00eb veprave. N\u00eb rast presioni, pronari i pajisjes mund t\u00eb zbuloj\u00eb \u00e7el\u00ebsin p\u00ebr pjes\u00ebn e koduar, por n\u00eb at\u00eb pjes\u00eb mund t\u00eb fshihen pjes\u00eb t\u00eb tjera (deri n\u00eb 15 nivele t\u00eb vendosura), dhe t\u00eb p\u00ebrcaktosh pranin\u00eb e tyre dhe t\u00eb provosh ekzistenc\u00ebn \u00ebsht\u00eb e v\u00ebshtir\u00eb. <\/p>\n
Fshehja sigurohet p\u00ebrmes formimit t\u00eb \u00e7do seksioni si nj\u00eb grupi t\u00eb shllizave t\u00eb enkriptuara, t\u00eb vendosura n\u00eb pozita t\u00eb rastit n\u00eb pajisjen e ruajtjes. \u00c7do shlliz krijohet dinamikisht n\u00eb momentin kur n\u00eb seksion nevojitet hap\u00ebsir\u00eb shtes\u00eb p\u00ebr ruajtje. P\u00ebr t\u00eb v\u00ebshtir\u00ebsuar analiz\u00ebn, shllizat e seksioneve t\u00eb ndryshme alternohen, pra seksionet Shufflecake nuk lidhen me zona t\u00eb vazhdueshme dhe shllizat e t\u00eb gjitha seksioneve p\u00ebrzihen. Informacioni mbi shllizat e p\u00ebrdorura dhe ato t\u00eb lira ruhet n\u00eb nj\u00eb hart\u00eb lokacioni t\u00eb lidhur me secilin seksion, e cila referohet n\u00eb kok\u00ebn e enkriptuar. Hartat dhe koka jan\u00eb t\u00eb enkriptuara dhe pa njohjen e \u00e7el\u00ebsit t\u00eb qasjes nuk jan\u00eb t\u00eb dallueshme nga t\u00eb dh\u00ebnat e rast\u00ebsishme. <\/p>\n
Kapoja \u00ebsht\u00eb e ndar\u00eb n\u00eb hap\u00ebsira, \u00e7do nj\u00ebra prej t\u00eb cilave p\u00ebrcakton pjes\u00ebn e saj dhe lidhjet e saj me pjes\u00ebt p\u00ebrkat\u00ebse. Hap\u00ebsirat n\u00eb kapak jan\u00eb vendosur n\u00eb nj\u00eb rend t\u00eb stack dhe jan\u00eb t\u00eb lidhura n\u00eb m\u00ebnyr\u00eb rekursive - hap\u00ebsira aktuale p\u00ebrmban \u00e7el\u00ebsin p\u00ebr dekodimin e parametrave t\u00eb pjes\u00ebs paraprake n\u00eb hierarkin\u00eb (m\u00eb pak t\u00eb fshehur), q\u00eb lejon p\u00ebrdorimin e nj\u00eb fjal\u00ebkalimi p\u00ebr dekodimin e t\u00eb gjitha pjes\u00ebve m\u00eb pak t\u00eb fshehura q\u00eb lidhen me zgjedhjen e pjes\u00ebs. \u00c7do pjes\u00eb m\u00eb pak t\u00eb fshehur shqyrton pjes\u00ebt e sub-pjes\u00ebve si t\u00eb lira. <\/p>\n
N\u00eb variantin e saj standard, t\u00eb gjitha n\u00ebn-pjes\u00ebt e Shufflecake kan\u00eb t\u00eb nj\u00ebjtin madh\u00ebsi t\u00eb dukshme si dhe pjesa kryesore. P\u00ebr shembull, n\u00ebse n\u00eb nj\u00eb pajisje me madh\u00ebsi 1 GB p\u00ebrdoren tre pjes\u00eb, secila do t\u00eb duket p\u00ebr sistemin si nj\u00eb pjes\u00eb me madh\u00ebsi 1 GB dhe hap\u00ebsira e disponueshme totale do t\u00eb p\u00ebrdoret ngusht\u00eb n\u00eb t\u00eb gjitha pjes\u00ebt - n\u00ebse bashk\u00ebrisht madh\u00ebsia e t\u00eb dh\u00ebnave t\u00eb ruajtura tejkalon madh\u00ebsin\u00eb faktike t\u00eb pajisjes, do t\u00eb filloj\u00eb t\u00eb shfaqet nj\u00eb gabim input\/output. <\/p>\n
Nd\u00ebrmarrjet e pambikqyrura nuk marrin pjes\u00eb n\u00eb shp\u00ebrndarjen e hap\u00ebsir\u00ebs, pra, p\u00ebrpjekja p\u00ebr t\u00eb mbushur nj\u00eb ndarje t\u00eb nivelit t\u00eb lart\u00eb do t\u00eb \u00e7oj\u00eb n\u00eb fshirjen e t\u00eb dh\u00ebnave n\u00eb ndarjet e brendshme, por nuk do t\u00eb ofroj\u00eb mund\u00ebsin\u00eb p\u00ebr t\u00eb zbuluar ekzistenc\u00ebn e tyre p\u00ebrmes analiz\u00ebs s\u00eb madh\u00ebsis\u00eb s\u00eb t\u00eb dh\u00ebnave q\u00eb do t\u00eb vendosen n\u00eb ndarje para fillimit t\u00eb shfaqjes s\u00eb gabimit (supozimi \u00ebsht\u00eb se ndarjet e larta p\u00ebrmbajn\u00eb t\u00eb dh\u00ebna t\u00eb pandryshueshme p\u00ebr t\u00eb shp\u00ebrqendruar v\u00ebmendjen dhe kurr\u00eb nuk p\u00ebrdoren ve\u00e7mas, nd\u00ebrsa puna normale kryhet gjithmon\u00eb me ndarjen e fundit t\u00eb brendshme, skema vet\u00eb n\u00ebnkupton se \u00ebsht\u00eb m\u00eb e r\u00ebnd\u00ebsishme t\u00eb ruhet sekreti i ekzistenc\u00ebs s\u00eb t\u00eb dh\u00ebnave sesa t\u00eb humbasin k\u00ebto t\u00eb dh\u00ebna). <\/p>\n
N\u00eb fakt, gjithmon\u00eb krijohen 15 pjes\u00eb Shufflecake - pjes\u00ebve t\u00eb p\u00ebrdorura i bashk\u00ebngjitet fjal\u00ebkalimi i p\u00ebrdoruesit, nd\u00ebrsa pjes\u00ebt e pa p\u00ebrdorura pajisen me nj\u00eb fjal\u00ebkalim t\u00eb gjeneruar rast\u00ebsisht (nuk \u00ebsht\u00eb e mundur t\u00eb kuptohet se sa pjes\u00eb realisht p\u00ebrdoren). Kur inicializohen pjes\u00ebt e Shufflecake, disku, pjesa ose pajisja virtuale e bllokut e dedikuar p\u00ebr vendosjen e tyre mbushet me t\u00eb dh\u00ebna t\u00eb rast\u00ebsishme, \u00e7ka nuk lejon p\u00ebrcaktimin e sfondit t\u00eb p\u00ebrgjithsh\u00ebm t\u00eb metadatat dhe t\u00eb dh\u00ebnave t\u00eb Shufflecake. <\/p>\n
Implementimi i Shufflecake ka nj\u00eb performanc\u00eb mjaft t\u00eb lart\u00eb, por p\u00ebr shkak t\u00eb kostove t\u00eb mbik\u00ebqyrjes, ai mbetet rreth dy her\u00eb m\u00eb posht\u00eb n\u00eb kapacitetin e p\u00ebr\u00e7imit krahasuar me enkriptimin e diskeve bazuar n\u00eb n\u00ebn-sistemin LUKS. P\u00ebrdorimi i Shufflecake gjithashtu \u00e7on n\u00eb shpenzime shtes\u00eb t\u00eb memories operative dhe hap\u00ebsir\u00ebs p\u00ebr ruajtjen e t\u00eb dh\u00ebnave ndihm\u00ebse n\u00eb disk. Shpenzimet e memories jan\u00eb rreth 60 MB p\u00ebr \u00e7do ndarje, nd\u00ebrsa hap\u00ebsira n\u00eb disk \u00ebsht\u00eb rreth 1% e madh\u00ebsis\u00eb totale. P\u00ebr krahasim, nj\u00eb teknik\u00eb e ngjashme si WORAM \u00e7on n\u00eb ngadal\u00ebsim nga 5 deri n\u00eb 200 her\u00eb me nj\u00eb humbje prej 75% t\u00eb hap\u00ebsir\u00ebs s\u00eb dobishme n\u00eb disk. <\/p>\n