{"id":93794,"date":"2020-09-10T07:42:27","date_gmt":"2020-09-10T05:42:27","guid":{"rendered":"https:\/\/prohoster.info\/blog\/administrirovanie\/town-crier-vs-deco-kakoj-orakul-ispolzovat-v-blokchejne"},"modified":"2020-09-10T07:42:27","modified_gmt":"2020-09-10T05:42:27","slug":"town-crier-vs-deco-kakoj-orakul-ispolzovat-v-blokchejne","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sq\/blog\/administrirovanie\/town-crier-vs-deco-kakoj-orakul-ispolzovat-v-blokchejne","title":{"rendered":"Town Crier vs DECO: cili orakull t\u00eb p\u00ebrdor\u00ebt n\u00eb blockchain?","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Sot \u00ebsht\u00eb q\u00eb vet\u00ebm nj\u00eb person i len\u00eb nuk ka shkruar p\u00ebr teknologjin\u00eb blockchain, kriptovalutat dhe sa t\u00eb mrekullueshme jan\u00eb k\u00ebto. Por n\u00eb k\u00ebt\u00eb artikull nuk do t\u00eb ket\u00eb lavd\u00ebrime p\u00ebr k\u00ebt\u00eb teknologji, do t\u00eb flasim pik\u00ebrisht p\u00ebr disavantazhet e saj dhe m\u00ebnyrat p\u00ebr t'i kaluar ato. <\/p>\n

<\/p>\n

\"Town<\/p>\n

<\/p>\n

Gjat\u00eb pun\u00ebs n\u00eb nj\u00eb nga projektet n\u00eb kompanin\u00eb Altiriks Systems, doli nevoja p\u00ebr nj\u00eb konfirmim t\u00eb sigurt, t\u00eb q\u00ebndruesh\u00ebm ndaj censur\u00ebs t\u00eb t\u00eb dh\u00ebnave nga nj\u00eb burim t\u00eb jasht\u00ebm n\u00eb blockchain. Duhej t\u00eb konfirmoheshin ndryshimet n\u00eb regjistrimet e nj\u00eb sistemi t\u00eb tret\u00eb dhe n\u00eb baz\u00eb t\u00eb k\u00ebtyre ndryshimeve t\u00eb ekzekutohej nj\u00eb deg\u00eb specifike n\u00eb logjik\u00ebn e kontrat\u00ebs smart. Detyra n\u00eb shikim t\u00eb par\u00eb duket mjaft triviale, por kur rezultati i saj ndikon n\u00eb gjendjen financiare t\u00eb nj\u00eb prej pal\u00ebve pjes\u00ebmarr\u00ebse n\u00eb proces, dalin k\u00ebrkesa shtes\u00eb. Para s\u00eb gjithash, kjo \u00ebsht\u00eb besimi p\u00ebrfundimtar n\u00eb nj\u00eb mekaniz\u00ebm t\u00eb till\u00eb validimi. Por le t\u00eb shkojm\u00eb sipas radh\u00ebs. <\/p>\n

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

Problemi q\u00ebndron n\u00eb faktin se blockchain \u00ebsht\u00eb nj\u00eb objekt autonom, i mbyllur, prandaj kontratat smart brenda blockchain-it nuk din\u00eb asgj\u00eb p\u00ebr bot\u00ebn e jashtme. N\u00eb t\u00eb nj\u00ebjt\u00ebn koh\u00eb, kushtet e kontratave smart shpesh lidhen me informacionin p\u00ebr ngjarje t\u00eb v\u00ebrteta (vonesa fluturimi, kursi i valutor\u00ebve, etj.). P\u00ebr t\u00eb funksionuar si\u00e7 duhet, informacioni i marra jasht\u00eb blockchain-it duhet t\u00eb jet\u00eb i besuesh\u00ebm dhe i verifikuar. Ky problem zgjidhet duke p\u00ebrdorur orakuj, t\u00eb till\u00eb si Town Crier dhe DECO. K\u00ebta orakuj lejojn\u00eb q\u00eb kontratat smart n\u00eb rrjetin blockchain t\u00eb besojn\u00eb informacionin nga nj\u00eb server web t\u00eb verifikuar, mund t\u00eb thuhet se jan\u00eb furnizues t\u00eb informacionit t\u00eb besuesh\u00ebm. <\/p>\n

<\/p>\n

Orakuj<\/h1>\n

<\/p>\n

Mendoni se kontrata smart kryen nj\u00eb transferim prej 0.001 btc n\u00eb portofolin tuaj bitcoin n\u00eb rastin e fitores s\u00eb klubit tuaj t\u00eb preferuar t\u00eb futbollit n\u00eb Kup\u00ebn e Rusis\u00eb. N\u00eb rastin e nj\u00eb fitoreje t\u00eb v\u00ebrtet\u00eb, kontrat\u00ebs smart i nevojitet t\u00eb kaloj\u00eb informacionin mbi cilin klub ka fituar, dhe k\u00ebtu lind nj\u00eb s\u00ebr\u00eb problemesh: ku ta gjejm\u00eb k\u00ebt\u00eb informacion, si ta kalojm\u00eb at\u00eb n\u00eb m\u00ebnyr\u00eb t\u00eb sigurt n\u00eb kontrat\u00ebn smart dhe si t\u00eb sigurohemi q\u00eb informacioni q\u00eb ka arritur n\u00eb kontrat\u00ebn smart n\u00eb t\u00eb v\u00ebrtet\u00eb p\u00ebrputhet me realitetin? <\/p>\n

<\/p>\n

N\u00eb \u00e7\u00ebshtjen e burimit t\u00eb informacionit mund t\u00eb jen\u00eb 2 skenar\u00eb: lidhja e nj\u00eb smart kontrate me nj\u00eb uebfaqe t\u00eb besuar, e cila ruan informacionin p\u00ebr rezultatet e ndeshjeve n\u00eb m\u00ebnyr\u00eb t\u00eb centralizuar, dhe opsioni i dyt\u00eb \u2014 lidhja e disa uebfaqeve n\u00eb t\u00eb nj\u00ebjt\u00ebn koh\u00eb dhe m\u00eb pas zgjedhja e informacionit nga shumica e burimeve q\u00eb ofrojn\u00eb t\u00eb dh\u00ebna t\u00eb nj\u00ebjta. P\u00ebr t\u00eb siguruar sakt\u00ebsin\u00eb e informacionit, p\u00ebrdoren orakuj, p\u00ebr shembull Oraclize, q\u00eb p\u00ebrdor TLSNotary (modifikimi i TLS p\u00ebr t\u00eb provuar origjinalitetin e t\u00eb dh\u00ebnave). Por p\u00ebr Oraclize ka mjaft informacion n\u00eb Google, dhe n\u00eb Habr ka disa artikuj, sot do t\u00eb flas p\u00ebr orakujt q\u00eb p\u00ebrdorin nj\u00eb qasje pak m\u00eb ndryshe p\u00ebr t\u00eb transmetuar informacion: Town Crier dhe DECO. Artikulli p\u00ebrmban p\u00ebrshkrimin e principeve t\u00eb funksionimit t\u00eb dy orakujve, si dhe nj\u00eb krahasim t\u00eb detajuar. <\/p>\n

<\/p>\n

Town Crier<\/h1>\n

<\/p>\n

Town Crier (TC) u paraqit nga IC3 (Iniciativa p\u00ebr Kriptovalutat dhe Kontratat) n\u00eb vitin 2016 n\u00eb CCS\u201916. Ideja kryesore e TC: t\u00eb transmetoj\u00eb informacionin nga uebfaqja te smart kontrata dhe t\u00eb siguroj\u00eb se informacioni i dor\u00ebzuar nga TC \u00ebsht\u00eb i nj\u00ebjt\u00eb me at\u00eb n\u00eb uebfaqe. TC p\u00ebrdor TEE (Mjedisi i Besuesh\u00ebm i Ekzekutimit) p\u00ebr t\u00eb garantuar autenticitetin e pron\u00ebsis\u00eb s\u00eb t\u00eb dh\u00ebnave. N\u00eb versionin origjinal, TC p\u00ebrshkruan funksionimin me Intel SGX.
\nTown Crier p\u00ebrb\u00ebhet nga nj\u00eb pjes\u00eb brenda blockchain dhe nj\u00eb pjes\u00eb brenda vet\u00eb sistemit operativ \u2014 TC Server.
\n\"Town
\nTC Contract ndodhet n\u00eb blockchain dhe vepron si front end p\u00ebr TC. Ai pranon k\u00ebrkesat nga CU (smart kontrata e p\u00ebrdoruesit) dhe kthen p\u00ebrgjigjen nga TC Server. Brenda TC Server ndodhet Relay, i cili krijon nj\u00eb lidhje midis enklav\u00ebs dhe internetit (trafik me dy drejtime) dhe lidh enklav\u00ebn me blockchain. Enclave p\u00ebrmban progencl, i cili \u00ebsht\u00eb kodi q\u00eb ekzekuton k\u00ebrkesat nga blockchain dhe kthen mesazhe n\u00eb blockchain me nj\u00eb n\u00ebnshkrim digjital, progencl p\u00ebrmban nj\u00eb pjes\u00eb t\u00eb kodit t\u00eb smart kontrat\u00ebs dhe n\u00eb thelb ekzekuton disa nga funksionet e saj. <\/p>\n

<\/p>\n

Enklava Intel SGX mund t\u00eb konsiderohet si nj\u00eb bibliotek\u00eb e p\u00ebrbashk\u00ebt me API, e cila funksionon p\u00ebrmes ecall. Ecall transferon kontrollin n\u00eb enklav\u00eb. Enklava ekzekuton kodin e saj derisa t\u00eb p\u00ebrfundoj\u00eb ose t\u00eb ndodh\u00eb nj\u00eb p\u00ebrjashtim. P\u00ebr thirrjen e funksioneve, t\u00eb p\u00ebrcaktuara jasht\u00eb enklav\u00ebs, p\u00ebrdoren ocall. Ocall ekzekutohet jasht\u00eb enklav\u00ebs dhe trajtohet prej saj si nj\u00eb thirrje e pasigurt. Pas p\u00ebrfundimit t\u00eb ocall, kontrolli kthehet n\u00eb enklav\u00eb.
\n\"Town
\nN\u00eb pjes\u00ebn Enclave konfigurimi i kanalit t\u00eb sigurt me serverin web, Enclave vet\u00eb kryen TLS handshake me serverin e synuar dhe kryen t\u00eb gjitha operacionet kriptografike brenda vetes. Biblioteka TLS (mbedTLS) dhe kodi HTTP n\u00eb versionin e reduktuar jan\u00eb eksportuar n\u00eb mjedisin SGX. Po ashtu, Enclave p\u00ebrmban certifikatat e root CA (koleksion t\u00eb certifikatave) p\u00ebr t\u00eb verifikuar certifikatat e server\u00ebve t\u00eb larg\u00ebt. Request Handler pranon k\u00ebrkesat datagram n\u00eb formatin e siguruar nga Ethereum, e dekripton dhe analizojn\u00eb. Pastaj gjeneron nj\u00eb transaksion Ethereum, q\u00eb p\u00ebrmban datagramin e k\u00ebrkuar, e n\u00ebnshkruan at\u00eb me skTC dhe e d\u00ebrgon n\u00eb Relay.<\/p>\n

<\/p>\n

Pjesa Relay p\u00ebrfshin Client Interface, TCP, Blockchain Interface. Client Interface \u00ebsht\u00eb i nevojsh\u00ebm p\u00ebr attestimin e kodit t\u00eb Enclave dhe komunikimin me klientin. Klienti d\u00ebrgon nj\u00eb k\u00ebrkes\u00eb p\u00ebr attestim p\u00ebrmes ecall dhe merr nj\u00eb timestamp, i n\u00ebnshkruar me skTC, s\u00eb bashku me att (n\u00ebnshkrimin e attestimit), m\u00eb pas att konfirmohet p\u00ebrmes Intel Attestation Service (IAS), dhe timestamp verifikohet nga sh\u00ebrbimi i besuesh\u00ebm t\u00eb koh\u00ebs. Blockchain Interface kontrollon k\u00ebrkesat e pranuara dhe vendos transaksionet n\u00eb blockchain p\u00ebr d\u00ebrgimin e datagram\u00ebve. Geth \u00ebsht\u00eb klienti zyrtar i Ethereum dhe lejon Relay t\u00eb nd\u00ebrveproj\u00eb me blockchain p\u00ebrmes thirrjeve RPC. <\/p>\n

<\/p>\n

Duke punuar me TEE, TC lejon t\u00eb aktivizohen disa Enclaves paralelisht, duke rritur k\u00ebshtu shpejt\u00ebsin\u00eb e p\u00ebrpunimit t\u00eb informacionit me 3 her\u00eb. N\u00ebse me nj\u00eb Enclave n\u00eb pun\u00eb shpejt\u00ebsia ishte 15 tx\/sec, at\u00ebher\u00eb me 20 Enclaves t\u00eb aktivizuara paralelisht shpejt\u00ebsia rritet deri n\u00eb 65 tx\/sec; p\u00ebr krahasim, shpejt\u00ebsia maksimale e pun\u00ebs n\u00eb blockchain bitcoin \u00ebsht\u00eb 26 tx\/sec.<\/p>\n

<\/p>\n

DECO<\/h1>\n

<\/p>\n

DECO (Decentralized Oracles for TLS) u prezantua n\u00eb CCS\u201920, punon me faqet q\u00eb p\u00ebrkrahin lidhjen TLS. Siguron konfidencialitetin dhe integritetin e t\u00eb dh\u00ebnave.
\nDECO me TLS p\u00ebrdor enkriptimin simetrik, k\u00ebshtu q\u00eb klienti dhe serveri web kan\u00eb \u00e7el\u00ebsat e enkriptimit, dhe klienti, n\u00ebse d\u00ebshiron, mund t\u00eb falsifikoj\u00eb t\u00eb dh\u00ebnat e sesionit TLS. P\u00ebr t\u00eb zgjidhur k\u00ebt\u00eb problem, DECO p\u00ebrdor nj\u00eb protokoll t\u00eb trefisht\u00eb t\u00eb dor\u00ebzimit midis prover (kontrakt\u00ebs inteligjente), verifier (orakulli) dhe serverit web (burimi i t\u00eb dh\u00ebnave).<\/p>\n

<\/p>\n

\"Town<\/p>\n

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Parimi i funksionimit t\u00eb DECO p\u00ebrfshin q\u00eb provuesi (prover) t\u00eb marr\u00eb nj\u00eb pjes\u00eb t\u00eb t\u00eb dh\u00ebnave D dhe t\u00eb konfirmoj\u00eb p\u00ebrverifikuesin (verifier) q\u00eb D ka ardhur nga serveri TLS S. Nj\u00eb tjet\u00ebr problem \u00ebsht\u00eb se TLS nuk n\u00ebnshkruan t\u00eb dh\u00ebna dhe \u00ebsht\u00eb e v\u00ebshtir\u00eb p\u00ebr klientin TLS t\u00eb provoj\u00eb se t\u00eb dh\u00ebnat jan\u00eb marr\u00eb pik\u00ebrisht nga ai server (v\u00ebshtir\u00ebsia e provananc\u00ebs). <\/p>\n

<\/p>\n

N\u00eb protokollin DECO, p\u00ebrdoren \u00e7el\u00ebsat e enkriptimit KEnc dhe KMac. Klienti d\u00ebrgon nj\u00eb k\u00ebrkes\u00eb Q n\u00eb serverin web<\/a>, p\u00ebrgjigja nga serveri R vjen n\u00eb form\u00eb t\u00eb enkriptuar, por klienti dhe serveri kan\u00eb t\u00eb nj\u00ebjt\u00ebt KMac, dhe klienti mund t\u00eb falsifikoj\u00eb mesazhin TLS. Zgjidhja nga DECO \u00ebsht\u00eb q\u00eb t\u00eb \"fsheh\u00eb\" KMac nga klienti (prover), derisa ai t\u00eb p\u00ebrgjigjet n\u00eb k\u00ebrkes\u00eb. Tani KMac \u00ebsht\u00eb i ndar\u00eb midis prover dhe verifier \u2014 KpMac dhe KvMac. Serveri merr KMac p\u00ebr enkriptimin e p\u00ebrgjigjes duke p\u00ebrdorur operacionin mbi pjes\u00ebt e \u00e7el\u00ebsit KpMac \u2295 KvMac = KMac.<\/p>\n

<\/p>\n

Duke vendosur nj\u00eb dor\u00ebheqje trefisht\u00eb, shk\u00ebmbimi i t\u00eb dh\u00ebnave midis klientit dhe serverit do t\u00eb zhvillohet me nj\u00eb garantim sigurie.
\n\"Town
\nDuke folur p\u00ebr sistemet e oracleve t\u00eb decentralizuara, nuk mund t\u00eb mos p\u00ebrmendim Chainlink, i cili synon t\u00eb krijoj\u00eb nj\u00eb rrjet oracle t\u00eb decentralizuar t\u00eb nyjeve, t\u00eb pajtueshme me Ethereum, Bitcoin dhe Hyperledger, duke marr\u00eb parasysh modularitetin: \u00e7do pjes\u00eb e sistemit mund t\u00eb p\u00ebrdit\u00ebsohet. N\u00eb t\u00eb nj\u00ebjt\u00ebn koh\u00eb, p\u00ebr t\u00eb siguruar sigurin\u00eb, Chainlink ofron q\u00eb \u00e7do oracle q\u00eb merr pjes\u00eb n\u00eb detyr\u00eb t\u00eb l\u00ebshoj\u00eb nj\u00eb kombinim \u00e7el\u00ebsash (t\u00eb hapur dhe t\u00eb mbyllur). \u00c7el\u00ebsi i mbyllur p\u00ebrdoret p\u00ebr t\u00eb gjeneruar nj\u00eb n\u00ebnshkrim t\u00eb pjessh\u00ebm, i cili p\u00ebrmban zgjidhjen e tyre p\u00ebr k\u00ebrkes\u00ebn e t\u00eb dh\u00ebnave. P\u00ebr t\u00eb marr\u00eb p\u00ebrgjigjen, \u00ebsht\u00eb e nevojshme kombinimi i t\u00eb gjitha n\u00ebnshkrimeve t\u00eb pjes\u00ebshme t\u00eb oracleve t\u00eb rrjetit.<\/p>\n

<\/p>\n

Chainlink planifikon t\u00eb realizoj\u00eb nj\u00eb PoC fillestar DECO me fokus n\u00eb aplikacionet e financave t\u00eb decentralizuara, si Mixicles. N\u00eb momentin e shkruar t\u00eb k\u00ebtij artikulli, doli nj\u00eb lajm n\u00eb Forbes, se Chainlink kishte bler\u00eb DECO nga Universitete Cornell.<\/p>\n

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Sulmet ndaj oracleve<\/h1>\n

<\/p>\n

\"Town<\/p>\n

<\/p>\n

Nga perspektiva e siguris\u00eb informative, jan\u00eb shqyrtuar sulmet e m\u00ebposhtme ndaj Town Crier:<\/p>\n

<\/p>\n

    \n
  1. \n

    Injeksioni i kodit t\u00eb paligjsh\u00ebm t\u00eb kontratave t\u00eb zgjuara n\u00eb nyjat TEE.
    \nThelbi i sulmit: d\u00ebrgimi n\u00eb TEE i nj\u00eb kodi t\u00eb dh\u00ebn\u00eb gabim t\u00eb kontrat\u00ebs s\u00eb zgjuar, n\u00eb k\u00ebt\u00eb m\u00ebnyr\u00eb, q\u00eb nj\u00eb sulmues, i cili ka akses n\u00eb nyj\u00eb, do t\u00eb kishte mund\u00ebsi t\u00eb realizonte kontrat\u00ebn e tij (t\u00eb mashtruar) mbi t\u00eb dh\u00ebnat e dekoduar. Megjithat\u00eb, vlerat e kthyera do t\u00eb jen\u00eb t\u00eb enkriptuara me \u00e7el\u00ebsin privat, dhe opsioni i vet\u00ebm p\u00ebr akses n\u00eb t\u00eb tilla t\u00eb dh\u00ebna \u00ebsht\u00eb rrjedhja e tekstit t\u00eb enkriptuar gjat\u00eb kthimit\/ekstraktimit.
    \nMbrojtja nga ky sulm p\u00ebrfshin verifikimin nga enklava e sakt\u00ebsis\u00eb s\u00eb kodit n\u00eb adres\u00ebn aktuale. Kjo mund t\u00eb arrihet p\u00ebrmes nj\u00eb skeme adresimi, ku adresa e kontrat\u00ebs p\u00ebrcaktohet duke hash-uar kodin e kontrat\u00ebs. <\/p>\n

    \n<\/li>\n

  2. \n

    Ndryshimet n\u00eb enkriptimin e gjendjes s\u00eb kontrat\u00ebs l\u00ebshojn\u00eb.
    \nThe essence of the attack: Node owners, where smart contracts are executed, have access to the contract state in encrypted form outside the enclave. An attacker who gains control of a node can compare the contract state before and after the transaction execution and can determine which arguments were input and which specific method of the smart contract was used, as the smart contract code and its technical specifications are publicly available.
    \nProtection in ensuring the reliability of the node itself.<\/p>\n

    \n<\/li>\n

  3. \n

    Ataqet mbi kanalin an\u00ebsor.
    \nNj\u00eb tip i ve\u00e7ant\u00eb sulmesh q\u00eb p\u00ebrdor mbik\u00ebqyrjen e aksesit n\u00eb memorien dhe cache-in e enklav\u00ebs n\u00eb skenar\u00eb t\u00eb ndrysh\u00ebm. Nj\u00eb shembull i till\u00eb sulmi \u00ebsht\u00eb Prime and Probe.
    \n\"Town
    \nProcedura e kryerjes s\u00eb sulmit:<\/p>\n

    <\/p>\n