Kompania Kudelski Security, e specializuar n\u00eb auditimin e siguris\u00eb, publikoi mjetin Shufflecake, q\u00eb lejon krijimin e sistemeve t\u00eb fshehta t\u00eb skedar\u00ebve, t\u00eb shp\u00ebrndara n\u00eb hap\u00ebsir\u00ebn e lir\u00eb ekzistuese n\u00eb pjes\u00ebt aktuale dhe t\u00eb padallueshme nga t\u00eb dh\u00ebnat e rast\u00ebsishme. Pjes\u00ebt krijohen n\u00eb nj\u00eb m\u00ebnyr\u00eb q\u00eb, pa e ditur \u00e7el\u00ebsin e qasjes, \u00ebsht\u00eb e v\u00ebshtir\u00eb t\u00eb provohet ekzistenca e tyre, madje edhe gjat\u00eb analiz\u00ebs kriminalistike. Kodi i utiliteteve (shufflecake-userland) dhe modulit t\u00eb kernelit Linux (dm-sflc) \u00ebsht\u00eb shkruar n\u00eb gjuh\u00ebn C dhe shp\u00ebrndahen 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 kernelit Linux p\u00ebr shkak t\u00eb q\u00ebllimeve t\u00eb pafavorshme me licenc\u00ebn GPLv2, n\u00ebn t\u00eb cil\u00ebn shp\u00ebrndahet 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 natively p\u00ebr platform\u00ebn Linux dhe lejon vendosjen e deri n\u00eb 15 pjes\u00ebve t\u00eb fshehta n\u00eb pajisje, t\u00eb vendosura nj\u00eb brenda tjetr\u00ebs p\u00ebr t\u00eb ngat\u00ebrruar zbardhjen e ekzistenc\u00ebs s\u00eb tyre. N\u00ebse aplikimi i vet\u00eb Shufflecake nuk paraqet sekrete, \u00e7ka mund t\u00eb gjykohet, p\u00ebr shembull, nga prania e utiliteteve p\u00ebrkat\u00ebse n\u00eb sistem, numri i p\u00ebrgjithsh\u00ebm i pjes\u00ebve t\u00eb krijuara t\u00eb fshehta \u00ebsht\u00eb i pamundur t\u00eb p\u00ebrcaktohet. Pjes\u00ebt e fshehta t\u00eb krijuara sipas d\u00ebshires s\u00eb p\u00ebrdoruesit mund t\u00eb formatahen p\u00ebr t\u00eb mbajtur \u00e7do sistem skedar\u00ebsh, p\u00ebr shembull, ext4, xfs ose btrfs. \u00c7do pjes\u00eb trajtohet si nj\u00eb pajisje virtuale t\u00eb ve\u00e7ant\u00eb me \u00e7el\u00ebsin e saj t\u00eb zhbllokimit. <\/p>\n
P\u00ebr t\u00eb ngat\u00ebrruar gjurm\u00ebt, sugjerohet t\u00eb p\u00ebrdoret modeli i sjelljes \u201emohim i besuesh\u00ebm\u201d (plausible deniability), ku thelbi \u00ebsht\u00eb se t\u00eb dh\u00ebnat e vlefshme fshihen si shtresa t\u00eb tjera n\u00eb pjes\u00eb t\u00eb kriptuara me t\u00eb dh\u00ebna q\u00eb kan\u00eb vler\u00eb m\u00eb t\u00eb ul\u00ebt, duke krijuar nj\u00eb lloj hierarkie t\u00eb fsheht\u00eb t\u00eb pjes\u00ebve. N\u00eb rast presioni, pronari i pajisjes mund t\u00eb zbuloj\u00eb \u00e7el\u00ebsin p\u00ebr pjes\u00ebn e kriptuar, por ndoshta n\u00eb at\u00eb pjes\u00eb mund t\u00eb fshihen pjes\u00eb t\u00eb tjera (deri n\u00eb 15 nivele t\u00eb vendosura brenda), dhe t\u00eb p\u00ebrcaktohet ekzistenca e tyre dhe t\u00eb provohet \u00ebsht\u00eb e v\u00ebshtir\u00eb. <\/p>\n
Fshehja sigurohet p\u00ebrmes formimit t\u00eb \u00e7do pjese si nj\u00eb grup shiresh t\u00eb kriptuara, t\u00eb vendosura n\u00eb pozita t\u00eb rast\u00ebsishme n\u00eb pajisjen e ruajtjes. \u00c7do shire krijohet dinamikiisht n\u00eb momentin kur n\u00eb pjes\u00eb k\u00ebrkohet hap\u00ebsir\u00eb shtes\u00eb p\u00ebr ruajtje. P\u00ebr t\u00eb v\u00ebshtir\u00ebsuar analiz\u00ebn, shires t\u00eb pjes\u00ebve t\u00eb ndryshme alternojn\u00eb, pra, pjes\u00ebt Shufflecake nuk lidh\u00ebn me zona t\u00eb vazhdueshme dhe shires t\u00eb t\u00eb gjitha pjes\u00ebve shp\u00ebrndahen. Informacioni mbi shiret e p\u00ebrdorura dhe ato t\u00eb lira ruhet n\u00eb nj\u00eb hart\u00eb lokacioni t\u00eb lidhur me \u00e7do pjes\u00eb, e cila referohet nga titulli i kriptuar. Harta dhe titulli jan\u00eb t\u00eb kriptuara dhe pa njohuri t\u00eb \u00e7el\u00ebsit t\u00eb qasjes nuk dallohen nga t\u00eb dh\u00ebnat e rast\u00ebsishme. <\/p>\n
Titulli ndahen n\u00eb vende, \u00e7do nj\u00ebri prej t\u00eb cilave p\u00ebrcakton pjes\u00ebn e tij dhe shires e lidhura me t\u00eb. Vendet n\u00eb titull jan\u00eb vendosur n\u00eb rendin stack dhe lidhur n\u00eb m\u00ebnyr\u00eb rekursive \u2014 vendi aktual p\u00ebrmban \u00e7el\u00ebsin p\u00ebr dekodimin e parametrave t\u00eb pjes\u00ebs s\u00eb m\u00ebparshme n\u00eb hierarki (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 pjes\u00ebn e zgjedhur. \u00c7do pjes\u00eb m\u00eb pak e fshehur e konsideron shiret e pjes\u00ebve t\u00eb brendshme si t\u00eb lira. <\/p>\n
N\u00eb parazgjedhje, t\u00eb gjitha pjes\u00ebt e brendshme t\u00eb Shufflecake kan\u00eb t\u00eb nj\u00ebjtin madh\u00ebsi t\u00eb dukshme si pjesa e nivelit t\u00eb lart\u00eb. P\u00ebr shembull, n\u00ebse n\u00eb nj\u00eb pajisje prej 1 GB jan\u00eb t\u00eb angazhuara tri pjes\u00eb, secila prej tyre do t\u00eb duket p\u00ebr sistemin si nj\u00eb pjes\u00eb me madh\u00ebsi 1 GB dhe hap\u00ebsira e p\u00ebrgjithshme e disponueshme do t\u00eb p\u00ebrdoret p\u00ebr t\u00eb gjitha pjes\u00ebt \u2014 n\u00ebse summa e madh\u00ebsis\u00eb s\u00eb t\u00eb dh\u00ebnave t\u00eb ruajtura kalon madh\u00ebsin\u00eb aktuale t\u00eb pajisjes, do t\u00eb filloj\u00eb t\u00eb jepet nj\u00eb gabim input\/output. <\/p>\n
Pjes\u00ebt e brendshme t\u00eb pa hapura nuk marrin pjes\u00eb n\u00eb shp\u00ebrndarjen e hap\u00ebsir\u00ebs, pra, p\u00ebrpjekja p\u00ebr t\u00eb mbushur pjes\u00ebn e nivelit t\u00eb lart\u00eb do t\u00eb \u00e7onte n\u00eb fshirjen e t\u00eb dh\u00ebnave n\u00eb pjes\u00ebt e brendshme, por nuk do t\u00eb ofronte mund\u00ebsi p\u00ebr t\u00eb zbuluar ekzistenc\u00ebn e tyre p\u00ebrmes analiz\u00ebs s\u00eb madh\u00ebsis\u00eb s\u00eb t\u00eb dh\u00ebnave, t\u00eb cilat mund t\u00eb vendosen n\u00eb pjes\u00eb para fillimit t\u00eb gabimit (supozimi \u00ebsht\u00eb se pjes\u00ebt e sip\u00ebrme 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 b\u00ebhet gjithmon\u00eb me pjes\u00ebn m\u00eb t\u00eb 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 humbja e k\u00ebtyre t\u00eb dh\u00ebnave). <\/p>\n
N\u00eb fakt, krijohen gjithmon\u00eb 15 seksione Shufflecake \u2014 seksionet e p\u00ebrdorura lidhen me fjal\u00ebkalimin e p\u00ebrdoruesit, nd\u00ebrsa seksionet e pap\u00ebrdorura furnizohen me nj\u00eb fjal\u00ebkalim t\u00eb gjeneruar n\u00eb m\u00ebnyr\u00eb t\u00eb rast\u00ebsishme (nuk \u00ebsht\u00eb e mundur t\u00eb kuptohet sa realmente seksione po p\u00ebrdoren). Gjat\u00eb inicializimit t\u00eb seksioneve Shufflecake, disku, seksioni ose pajisja virtuale e bllokut q\u00eb \u00ebsht\u00eb dedikuar p\u00ebr vendosjen e tyre mbushet me t\u00eb dh\u00ebna t\u00eb rast\u00ebsishme, gj\u00eb q\u00eb nuk lejon t\u00eb p\u00ebrcaktohet n\u00eb sfond metadata dhe t\u00eb dh\u00ebnat e Shufflecake. <\/p>\n
Realizimi i Shufflecake ka nj\u00eb performanc\u00eb t\u00eb mjaftueshme t\u00eb lart\u00eb, por p\u00ebr shkak t\u00eb kostove shtes\u00eb, p\u00ebson rreth dyfish n\u00eb aft\u00ebsin\u00eb e kalimit n\u00eb krahasim me enkriptimin e disqeve n\u00eb baz\u00eb t\u00eb n\u00ebnstruktur\u00ebs 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 sh\u00ebrbyese n\u00eb dysheme. Shpenzimi i memories vler\u00ebsohet n\u00eb 60 MB p\u00ebr \u00e7do seksion, nd\u00ebrsa hap\u00ebsira n\u00eb disk n\u00eb 1% t\u00eb madh\u00ebsis\u00eb totale. P\u00ebr krahasim, teknika e ngjashme WORAM \u00e7on n\u00eb ngadal\u00ebsim prej 5 deri n\u00eb 200 her\u00eb me nj\u00eb humbje prej 75% t\u00eb hap\u00ebsir\u00ebs t\u00eb dobishme n\u00eb disk. <\/p>\n