{"id":31079,"date":"2019-10-31T21:39:19","date_gmt":"2019-10-31T18:39:19","guid":{"rendered":"https:\/\/prohoster.info\/blog\/tcp-steganografiya-ili-kak-skryt-peredachu-dannyh-v-internete\/"},"modified":"2019-10-31T21:39:19","modified_gmt":"2019-10-31T18:39:19","slug":"tcp-steganografiya-ili-kak-skryt-peredachu-dannyh-v-internete","status":"publish","type":"post","link":"https:\/\/prohoster.info\/ro\/blog\/administrirovanie\/tcp-steganografiya-ili-kak-skryt-peredachu-dannyh-v-internete","title":{"rendered":"Steganografie TCP sau cum s\u0103 ascunzi transmiterea de date pe internet","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"Steganografie
\n
\nCercet\u0103torii polonezi au propus o nou\u0103 metod\u0103 de steganografie \u00een re\u021bea, bazat\u0103 pe particularit\u0103\u021bile func\u021bion\u0103rii protocolului de transport TCP, foarte r\u0103sp\u00e2ndit. Autorii studiului consider\u0103 c\u0103 schema lor ar putea fi utilizat\u0103, de exemplu, pentru a trimite mesaje ascunse \u00een \u021b\u0103rile totalitare care impun o cenzur\u0103 strict\u0103 pe internet. S\u0103 \u00eencerc\u0103m s\u0103 ne d\u0103m seama \u00een ce const\u0103, de fapt, inova\u021bia \u0219i c\u00e2t de util\u0103 este aceasta.<\/p>\n

<\/a><\/noindex><\/p>\n

\u00cen primul r\u00e2nd, trebuie s\u0103 definim ce este steganografia. A\u0219adar, steganografia este \u0219tiin\u021ba transmiterii ascunse a mesajelor. Adic\u0103, folosind metodele sale, p\u0103r\u021bile \u00eencearc\u0103 s\u0103 ascund\u0103 faptul \u00een sine al transmiterii<\/b>. Acesta este \u0219i motivul pentru care aceast\u0103 \u0219tiin\u021b\u0103 se deosebe\u0219te de criptografie, care \u00eencearc\u0103 s\u0103 fac\u0103 con\u021binutul mesajului inaccesibil pentru citire<\/b>. Este important de men\u021bionat c\u0103 comunitatea profesional\u0103 de criptografi are o atitudine destul de dispre\u021buitoare fa\u021b\u0103 de steganografie, av\u00e2nd \u00een vedere apropierea ideologiei sale de principiul \u201eSecuritate prin obscuritate\u201d (nu \u0219tiu cum sun\u0103 exact \u00een rom\u00e2n\u0103, ceva de genul \u201eSecuritate prin ignoran\u021b\u0103\u201d). Acest principiu, de exemplu, este folosit de compania Skype Inc. \u2014 codul surs\u0103 al celebrei aplica\u021bii de apeluri este \u00eenchis, iar nimeni nu \u0219tie cu adev\u0103rat cum se realizeaz\u0103 criptarea datelor. Apropo, recent, acest lucru a fost subliniat \u0219i de NSA, despre care cunoscutul specialist Bruce Schneier Jurnalistul Bloomberg Jason Schreier<\/a><\/noindex> a scris pe blogul s\u0103u. <\/p>\n

\u00centorc\u00e2ndu-ne la steganografie, s\u0103 r\u0103spundem la \u00eentrebarea de ce este necesar\u0103, dac\u0103 exist\u0103 criptografie. De fapt, se poate cripta un mesaj folosind un algoritm modern \u0219i, av\u00e2nd o cheie suficient de lung\u0103, nimeni nu va putea citi acest mesaj, dec\u00e2t dac\u0103 dori\u021bi. Cu toate acestea, uneori este mai util s\u0103 ascunzi chiar \u0219i faptul c\u0103 se face o transmisie secret\u0103. De exemplu, dac\u0103 autorit\u0103\u021bile competente \u00ee\u021bi intercept\u0103 mesajul criptat, nu pot s\u0103-l decripteze, dar totu\u0219i \u00ee\u0219i doresc foarte mult acest lucru, \u00een cele din urm\u0103 exist\u0103 \u0219i metode necomputeroizate de influen\u021bare \u0219i ob\u021binere a informa\u021biilor. Sun\u0103 distopic, dar, recunoa\u0219te\u021bi, este \u00een principiu posibil. Prin urmare, ar fi mai bine ca cei care nu au dreptul s\u0103 nu \u0219tie deloc c\u0103 transmisia a avut loc. Cercet\u0103torii polonezi au propus tocmai o astfel de metod\u0103. Mai mult, ei sugereaz\u0103 s\u0103 o fac\u0103 printr-un protocol pe care fiecare utilizator al internetului \u00eel folose\u0219te de o mie de ori pe zi.<\/p>\n

Aici am ajuns la Protocolul de Control al Transmisiunii (TCP). Explicarea tuturor detaliilor acestuia, desigur, nu are sens - ar fi prea lung\u0103 \u0219i plictisitoare, cei care trebuie s\u0103 \u0219tie, deja \u0219tiu. Pe scurt, TCP este un protocol de nivel de transport (adic\u0103 func\u021bioneaz\u0103 \u201epeste\u201d IP \u0219i \u201esub\u201d protocoalele de nivel aplica\u021bie, precum HTTP, FTP sau SMTP), care asigur\u0103 livrarea fiabil\u0103 a datelor de la expeditor la destinatari. Livrarea sigur\u0103 \u00eenseamn\u0103 c\u0103, dac\u0103 un pachet s-a pierdut sau a sosit cu modific\u0103ri, TCP se va asigura c\u0103 acel pachet este retransmis. Este important de men\u021bionat c\u0103 modific\u0103rile din pachet nu se refer\u0103 la o distorsionare inten\u021bionat\u0103 a datelor, ci la erori de transmisie care apar la nivel fizic. De exemplu, pe parcursul c\u0103l\u0103toriei unui pachet prin cabluri de cupru, c\u00e2\u021biva bi\u021bi \u0219i-au schimbat valoarea \u00een opusul lor sau, pur \u0219i simplu, s-au pierdut \u00een zgomot (de altfel, pentru Ethernet, rata de eroare a bi\u021bilor este de obicei considerat\u0103 a fi \u00een jurul valorii de 10-8). Pierderile de pachete pe drum sunt, de asemenea, un fenomen relativ frecvent pe internet. Acestea se pot \u00eent\u00e2mpla, de exemplu, din cauza aglomer\u0103rii routez\u0103torilor, care duce la umplerea buffer-elor \u0219i, drept urmare, la eliminarea tuturor pachetelor care sosesc ulterior. De obicei, procentul pachetelor pierdute este de aproximativ 0.1%, iar la un procent de c\u00e2teva procente, TCP \u00eenceteaz\u0103 s\u0103 func\u021bioneze corespunz\u0103tor - utilizatorul va experimenta \u00eent\u00e2rzieri severe.<\/p>\n

Astfel, vedem c\u0103 retransmisia pachetelor este un fenomen frecvent \u0219i \u00een general necesar pentru TCP. Atunci, de ce s\u0103 nu-l folosim pentru nevoile steganografiei av\u00e2nd \u00een vedere c\u0103 TCP, a\u0219a cum s-a men\u021bionat mai sus, este utilizat pe scar\u0103 larg\u0103 (conform unor estim\u0103ri, la ora actual\u0103, cota de pia\u021b\u0103 a TCP pe internet ajunge la 80-95%). Esen\u021ba metodei propuse const\u0103 \u00een a trimite \u00een mesajul retransmis nu ceea ce a fost \u00een pachetul ini\u021bial, ci datele pe care \u00eencerc\u0103m s\u0103 le ascundem. \u00cen acest sens, descoperirea unei astfel de \u00eenlocuiri nu este chiar at\u00e2t de simpl\u0103. Trebuie s\u0103 \u0219tii unde s\u0103 te ui\u021bi - num\u0103rul conexiunilor TCP simultane care trec prin furnizor este pur \u0219i simplu uria\u0219. Dac\u0103 se cunoa\u0219te nivelul aproximativ al retransmisiilor \u00een re\u021bea, se poate ajusta mecanismul de transmisie steganografic\u0103 astfel \u00eenc\u00e2t conexiunea ta s\u0103 nu se deosebeasc\u0103 deloc de altele. <\/p>\n

Desigur, aceast\u0103 metod\u0103 nu este lipsit\u0103 de defecte. De exemplu, din punct de vedere practic, implementarea ei nu va fi deloc simpl\u0103 \u2014 va necesita modificarea stivei de re\u021bea \u00een sistemele de operare, de\u0219i nu este nimic extrem de complicat \u00een acest sens. \u00cen plus, av\u00e2nd un num\u0103r suficient de resurse, este totu\u0219i posibil s\u0103 descoperi\u021bi pachetele \u201esecrete\u201d, pentru aceasta trebuie s\u0103 analiza\u021bi fiecare pachet din re\u021bea. Dar, de obicei, acest lucru este practic imposibil, a\u0219a c\u0103 de obicei se caut\u0103 pachete \u0219i conexiuni care se eviden\u021biaz\u0103, iar metoda propus\u0103 face exact ca conexiunea dumneavoastr\u0103 s\u0103 nu fie remarcabil\u0103. \u0218i nimic nu v\u0103 opre\u0219te s\u0103 cripta\u021bi datele secrete, pentru orice eventualitate. \u00cen plus, conexiunea \u00een sine poate r\u0103m\u00e2ne necriptat\u0103 pentru a provoca mai pu\u021bine suspiciuni.<\/p>\n

Autorii lucr\u0103rii (de altfel, pentru cei interesa\u021bi, iat\u0103<\/a><\/noindex> ea) la nivel de simul\u0103ri au demonstrat c\u0103 metoda propus\u0103 func\u021bioneaz\u0103 a\u0219a cum a fost g\u00e2ndit\u0103. Poate, \u00een viitor, cineva se va ocupa de implementarea ideii lor \u00een practic\u0103. \u0218i atunci, s\u0103 sper\u0103m, \u00een internet va fi pu\u021bin mai pu\u021bin cenzur\u0103.
\n
Sursa: habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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