{"id":34101,"date":"2019-10-31T21:56:25","date_gmt":"2019-10-31T18:56:25","guid":{"rendered":"https:\/\/prohoster.info\/blog\/ob-anonimnosti-v-account-based-blokchejnah\/"},"modified":"2019-10-31T21:56:25","modified_gmt":"2019-10-31T18:56:25","slug":"ob-anonimnosti-v-account-based-blokchejnah","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/administrirovanie\/ob-anonimnosti-v-account-based-blokchejnah","title":{"rendered":"O anonymit\u011b v bloc\u00edch zalo\u017een\u00fdch na \u00fa\u010dtech","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Dlouho se zaj\u00edm\u00e1me o anonymitu v kryptom\u011bn\u00e1ch a sna\u017e\u00edme se sledovat v\u00fdvoj technologi\u00ed v t\u00e9to oblasti. V na\u0161ich \u010dl\u00e1nc\u00edch jsme ji\u017e podrobn\u011b prozkoumali principy fungov\u00e1n\u00ed konfiden\u010dn\u00edch transakc\u00ed<\/a><\/noindex> v Monero a tak\u00e9 jsme uskute\u010dnili srovn\u00e1vac\u00ed p\u0159ehled<\/a><\/noindex> technologi\u00ed, kter\u00e9 v tomto oboru existuj\u00ed. Nicm\u00e9n\u011b v\u0161echny anonymn\u00ed kryptom\u011bny sou\u010dasnosti jsou postaveny na modelu dat navr\u017een\u00e9m Bitcoinem \u2014 Unspent Transaction Output (d\u00e1le UTXO). Pro blockchainy zalo\u017een\u00e9 na \u00fa\u010dtech jako Ethereum existuj\u00ed st\u00e1vaj\u00edc\u00ed \u0159e\u0161en\u00ed pro implementaci anonymity a d\u016fv\u011brnosti (nap\u0159\u00edklad Mobius<\/a><\/noindex> nebo Aztec<\/a><\/noindex>) se sna\u017eila replikovat model UTXO ve smart kontraktech.<\/p>\n

V \u00fanoru 2019 vy\u0161la skupina v\u00fdzkumn\u00edk\u016f ze Stanfordovy univerzity a Visa Research<\/a><\/noindex> vydal preprint<\/a><\/noindex> \u201eZether: Sm\u011brem k soukrom\u00ed ve sv\u011bt\u011b smart kontrakt\u016f\u201c. Auto\u0159i poprv\u00e9 navrhli p\u0159\u00edstup k zaji\u0161t\u011bn\u00ed anonymity v blockchainu na b\u00e1zi \u00fa\u010dt\u016f a p\u0159edstavili dva varianty smart kontrakt\u016f: pro d\u016fv\u011brn\u00e9 (skryt\u00ed z\u016fstatk\u016f a \u010d\u00e1stek transakc\u00ed) a anonymn\u00ed (skryt\u00ed p\u0159\u00edjemce a odes\u00edlatele) transakce. Pova\u017eujeme navr\u017eenou technologii za zaj\u00edmavou a r\u00e1di bychom se s v\u00e1mi pod\u011blili o jej\u00ed fungov\u00e1n\u00ed a probrali, pro\u010d je probl\u00e9m anonymity v blockchainu na b\u00e1zi \u00fa\u010dt\u016f pova\u017eov\u00e1n za velmi slo\u017eit\u00fd a zda se autor\u016fm poda\u0159ilo jej vy\u0159e\u0161it zcela.<\/p>\n

O fungov\u00e1n\u00ed t\u011bchto datov\u00fdch model\u016f<\/h3>\n

\nV modelu UTXO se transakce skl\u00e1d\u00e1 z \u201evstup\u016f\u201c a \u201ev\u00fdstup\u016f\u201c. P\u0159\u00edm\u00fd analog k \u201ev\u00fdstup\u016fm\u201c jsou bankovky ve va\u0161\u00ed pen\u011b\u017eence: ka\u017ed\u00fd \u201ev\u00fdstup\u201c m\u00e1 ur\u010ditou hodnotu. Kdy\u017e plat\u00edte n\u011bkomu (tvo\u0159\u00edte transakci), utr\u00e1c\u00edte jeden nebo v\u00edce \u201ev\u00fdstup\u016f\u201c, kter\u00e9 se st\u00e1vaj\u00ed \u201evstupy\u201c transakce, a blockchain je ozna\u010d\u00ed jako utracen\u00e9. P\u0159\u00edjemce va\u0161\u00ed platby (nebo vy sami, pokud pot\u0159ebujete vr\u00e1tit pen\u00edze) pak z\u00edsk\u00e1v\u00e1 nov\u011b vygenerovan\u00e9 \u201ev\u00fdstupy\u201c. Sch\u00e9maticky lze toto zn\u00e1zornit takto:<\/p>\n

\"O
\n
\nBlockchainy na b\u00e1zi \u00fa\u010dt\u016f funguj\u00ed p\u0159ibli\u017en\u011b jako v\u00e1\u0161 bankovn\u00ed \u00fa\u010det. Ovl\u00e1daj\u00ed pouze \u010d\u00e1stku na va\u0161em \u00fa\u010dtu a \u010d\u00e1stku p\u0159evodu. Kdy\u017e p\u0159ev\u00e1d\u00edte n\u011bjakou \u010d\u00e1stku ze sv\u00e9ho \u00fa\u010dtu, nesp\u00e1l\u00edte \u017e\u00e1dn\u00e9 \u201ev\u00fdstupy\u201c, s\u00ed\u0165 si nemus\u00ed pamatovat, kter\u00e9 mince byly utraceny, a kter\u00e9 ne. V nejjednodu\u0161\u0161\u00edm p\u0159\u00edpad\u011b se ov\u011b\u0159en\u00ed transakce omezuje na kontrolu podpisu odes\u00edlatele a \u010d\u00e1stky na jeho z\u016fstatku:<\/p>\n

\"O
\n<\/p>\n

Anal\u00fdza technologie<\/h3>\n

\nD\u00e1le se budeme zab\u00fdvat t\u00edm, jak Zether skr\u00fdv\u00e1 \u010d\u00e1stky transakc\u00ed, p\u0159\u00edjemce a odes\u00edlatele. B\u011bhem popisu princip\u016f jeho fungov\u00e1n\u00ed budeme upozor\u0148ovat na rozd\u00edly v d\u016fv\u011brn\u00e9m a anonymn\u00edm variant\u011b. Jeliko\u017e je zaji\u0161t\u011bn\u00ed d\u016fv\u011brnosti v blockchainech zalo\u017een\u00fdch na \u00fa\u010dtech mnohem jednodu\u0161\u0161\u00ed, n\u011bkter\u00e1 z omezen\u00ed spojen\u00fdch s anonymizac\u00ed nebudou pro d\u016fv\u011brnou verzi technologie relevantn\u00ed.<\/p>\n

Skr\u00fdv\u00e1n\u00ed z\u016fstatk\u016f a \u010d\u00e1stek p\u0159evod\u016f<\/h4>\n

\nPro \u0161ifrov\u00e1n\u00ed z\u016fstatk\u016f a \u010d\u00e1stek p\u0159evod\u016f v Zether se pou\u017e\u00edv\u00e1 \u0161ifrovac\u00ed sch\u00e9ma El-Gamala<\/a><\/noindex>. Funguje to n\u00e1sledovn\u011b. Kdy\u017e chce Alice poslat Bobovi b<\/b><\/i> mince na adresu (jeho ve\u0159ejn\u00fd kl\u00ed\u010d) Y<\/b><\/i>, vybere si n\u00e1hodn\u00e9 \u010d\u00edslo jsou rovny nule.<\/b><\/i> a \u0161ifruje \u010d\u00e1stku:<\/p>\n

\"O
\nkde C<\/b><\/i> \u2014 za\u0161ifrovan\u00e1 \u010d\u00e1stka, DDoS<\/b><\/i> \u2014 pomocn\u00e1 hodnota pot\u0159ebn\u00e1 k de\u0161ifrov\u00e1n\u00ed t\u00e9to \u010d\u00e1stky, G<\/b><\/i> \u2014 pevn\u00fd bod na eliptick\u00e9 k\u0159ivce, p\u0159i n\u00e1soben\u00ed tajn\u00fdm kl\u00ed\u010dem, kter\u00fd produkuje ve\u0159ejn\u00fd kl\u00ed\u010d.<\/p>\n

Kdy\u017e Bob obdr\u017e\u00ed tyto hodnoty, jednodu\u0161e je p\u0159i\u010dte k sv\u00e9mu za\u0161ifrovan\u00e9mu z\u016fstatku stejn\u00fdm zp\u016fsobem, a to je v\u00fdhodou tohoto sch\u00e9matu.<\/p>\n

Analogicky Alice ode\u010d\u00edt\u00e1 ze sv\u00e9ho z\u016fstatku stejn\u00e9 hodnoty, pouze jako Y<\/b><\/i> pou\u017e\u00edv\u00e1 sv\u016fj ve\u0159ejn\u00fd kl\u00ed\u010d.<\/p>\n

Skr\u00fdv\u00e1n\u00ed adres\u00e1ta a odes\u00edlatele<\/h4>\n

\nM\u00edch\u00e1n\u00ed \u201ev\u00fdstup\u016f\u201c v UTXO se objevilo ji\u017e na po\u010d\u00e1tku kryptom\u011bn a pom\u00e1h\u00e1 skr\u00fdt odes\u00edlatele. K tomu s\u00e1m odes\u00edlatel p\u0159i prov\u00e1d\u011bn\u00ed p\u0159evodu vyb\u00edr\u00e1 n\u00e1hodn\u00e9 \u201ev\u00fdstupy\u201c v blockchainu a m\u00edch\u00e1 je se sv\u00fdmi. N\u00e1sledn\u011b podep\u00ed\u0161e \u201ev\u00fdstupy\u201c kruhov\u00fdm podpisem \u2014 kryptografick\u00fdm mechanismem, kter\u00fd umo\u017e\u0148uje p\u0159esv\u011bd\u010dit kontrolora, \u017ee mezi zam\u00edchan\u00fdmi \u201ev\u00fdstupy\u201c jsou mince odes\u00edlatele. Samoz\u0159ejm\u011b, zam\u00edchan\u00e9 mince se neutrat\u00ed.<\/p>\n

Pro skr\u00fdv\u00e1n\u00ed p\u0159\u00edjemce v\u0161ak nebudeme schopni generovat fale\u0161n\u00e9 \u201ev\u00fdstupy\u201c. Proto m\u00e1 v UTXO ka\u017ed\u00fd \u201ev\u00fdstup\u201c svou jedine\u010dnou adresu, a ta je kryptograficky spojena s adresou p\u0159\u00edjemce t\u011bchto minc\u00ed. V sou\u010dasnosti neexistuje zp\u016fsob, jak odhalit spojen\u00ed mezi jedine\u010dnou adresou \u201ev\u00fdstupu\u201c a adresou p\u0159\u00edjemce, ani\u017e bychom znali jeho tajn\u00e9 kl\u00ed\u010de.<\/p>\n

V modelu zalo\u017een\u00e9m na \u00fa\u010dtech nem\u016f\u017eeme pou\u017e\u00edt jednor\u00e1zov\u00e9 adresy (jinak bychom u\u017e mluvili o modelu \u201ev\u00fdstup\u016f\u201c). Proto je t\u0159eba zam\u00edchat p\u0159\u00edjemce a odes\u00edlatele mezi dal\u0161\u00ed \u00fa\u010dty v blockchainu. P\u0159itom se z zam\u00edchan\u00fdch \u00fa\u010dt\u016f ode\u010d\u00edt\u00e1 za\u0161ifrovan\u00fd 0 minc\u00ed (nebo se p\u0159id\u00e1v\u00e1 0 \u2014 v p\u0159\u00edpad\u011b zam\u00edch\u00e1n\u00ed p\u0159\u00edjemce), co\u017e vlastn\u011b nem\u011bn\u00ed jejich skute\u010dn\u00fd z\u016fstatek.<\/p>\n

Jeliko\u017e m\u00e1 odes\u00edlatel i p\u0159\u00edjemce v\u017edy st\u00e1lou adresu, vznik\u00e1 pot\u0159eba pou\u017e\u00edvat pro zam\u00edch\u00e1n\u00ed stejn\u00e9 skupiny p\u0159i p\u0159evodech na stejn\u00e9 adresy. Sn\u00e1ze se to uk\u00e1\u017ee na p\u0159\u00edkladu.<\/p>\n

P\u0159edstavme si, \u017ee Alice se rozhodla prov\u00e9st p\u0159\u00edsp\u011bvek do charitativn\u00edho fondu Boba, ale preferuje, aby tento p\u0159evod z\u016fstal anonymn\u00ed pro vn\u011bj\u0161\u00edho pozorovatele. Aby zamaskovala sebe v poli odes\u00edlatele, uvede tak\u00e9 \u00fa\u010dty Adama a Ad\u00e9le. A aby skryla Boba \u2014 v poli p\u0159\u00edjemce uvede nav\u00edc \u00fa\u010dty Bena a Billa. P\u0159i dal\u0161\u00edm p\u0159\u00edsp\u011bvku se Alice rozhodla vedle sebe uv\u00e9st Alexe a Amandu, a vedle Boba \u2014 Bruce a Banjena. V tomto p\u0159\u00edpad\u011b se p\u0159i anal\u00fdze blockchainu v t\u011bchto dvou transakc\u00edch najde pouze jedna spole\u010dn\u00e1 dvojice \u00fa\u010dastn\u00edk\u016f \u2014 Alice a Bob, co\u017e deanonimizuje tyto transakce.<\/p>\n

\"O
\n<\/p>\n

Z\u00e1vody transakc\u00ed<\/h4>\n

\nJak jsme ji\u017e zm\u00ednili, pro skryt\u00ed sv\u00e9ho z\u016fstatku v syst\u00e9mech zalo\u017een\u00fdch na \u00fa\u010dtech u\u017eivatel \u0161ifruje sv\u016fj z\u016fstatek a \u010d\u00e1stku p\u0159evodu. P\u0159i tom mus\u00ed dok\u00e1zat, \u017ee zbytek na jeho \u00fa\u010dtu z\u016fst\u00e1v\u00e1 nez\u00e1porn\u00fd. Probl\u00e9m spo\u010d\u00edv\u00e1 v tom, \u017ee p\u0159i vytv\u00e1\u0159en\u00ed transakce u\u017eivatel sestavuje d\u016fkaz o sv\u00e9m aktu\u00e1ln\u00edm stavu \u00fa\u010dtu. Co se v\u0161ak stane, pokud Bob po\u0161le Alici transakci a ta bude p\u0159ijata d\u0159\u00edve, ne\u017e je odesl\u00e1na Alice? Potom bude transakce Alice pova\u017eov\u00e1na za neplatnou, proto\u017ee d\u016fkaz o z\u016fstatku byl sestaven p\u0159ed p\u0159ijet\u00edm transakce Boba.<\/p>\n

\"O
\n
\nPrvn\u00ed \u0159e\u0161en\u00ed, kter\u00e9 v takov\u00e9 situaci napadne, je zmrazit \u00fa\u010det do doby proveden\u00ed transakce. Ale tento p\u0159\u00edstup nen\u00ed vhodn\u00fd, proto\u017ee krom\u011b slo\u017eitosti vy\u0159e\u0161en\u00ed takov\u00e9ho \u00fakolu v distribuovan\u00e9m syst\u00e9mu bude v anonymn\u00edm sch\u00e9matu nejasn\u00e9, \u010d\u00ed \u00fa\u010det zablokovat.<\/p>\n

Pro vy\u0159e\u0161en\u00ed tohoto probl\u00e9mu technologie odd\u011bluje p\u0159\u00edchoz\u00ed a odchoz\u00ed transakce: v\u00fddaje maj\u00ed okam\u017eit\u00fd \u00fa\u010dinek na stav z\u016fstatku, zat\u00edmco p\u0159\u00edjmy maj\u00ed odlo\u017een\u00fd \u00fa\u010dinek. Proto se zav\u00e1d\u00ed pojem \u201eepochy\u201c \u2013 skupiny blok\u016f pevn\u00e9 velikosti. Aktu\u00e1ln\u00ed \u201eepocha\u201c je ur\u010dena d\u011blen\u00edm v\u00fd\u0161ky bloku velikost\u00ed skupiny. P\u0159i zpracov\u00e1n\u00ed transakce s\u00ed\u0165 okam\u017eit\u011b aktualizuje z\u016fstatek odes\u00edlatele, zat\u00edmco prost\u0159edky p\u0159\u00edjemce jsou ulo\u017eeny do \u00falo\u017ei\u0161t\u011b. Nahromad\u011bn\u00e9 prost\u0159edky p\u0159ijdou do dispozice p\u0159\u00edjemce platby a\u017e s p\u0159\u00edchodem nov\u00e9 \u201eepochy\u201c.<\/p>\n

V\u00fdsledkem je, \u017ee u\u017eivatel m\u016f\u017ee odes\u00edlat transakce bez ohledu na to, jak \u010dasto mu p\u0159ich\u00e1zej\u00ed prost\u0159edky (co\u017e samoz\u0159ejm\u011b z\u00e1vis\u00ed na jeho z\u016fstatku). Velikost epochy je ur\u010dena podle toho, jak rychle se bloky \u0161\u00ed\u0159\u00ed po s\u00edti a jak rychle transakce vstoup\u00ed do bloku. <\/p>\n

Toto \u0159e\u0161en\u00ed dob\u0159e funguje v p\u0159\u00edpad\u011b d\u016fv\u011brn\u00fdch p\u0159evod\u016f, av\u0161ak s anonymn\u00edmi transakcemi, jak uvid\u00edme d\u00e1le, vytv\u00e1\u0159\u00ed v\u00e1\u017en\u00e9 probl\u00e9my.<\/p>\n

Ochrana proti replay \u00fatok\u016fm<\/h4>\n

\nV blockchainov\u00fdch syst\u00e9mech zalo\u017een\u00fdch na \u00fa\u010dtech je ka\u017ed\u00e1 transakce podeps\u00e1na priv\u00e1tn\u00edm kl\u00ed\u010dem odes\u00edlatele, co\u017e p\u0159esv\u011bd\u010duje ov\u011b\u0159ovatele, \u017ee transakce nebyla zm\u011bn\u011bna a \u017ee ji vytvo\u0159il vlastn\u00edk tohoto kl\u00ed\u010de. Co se v\u0161ak stane, kdy\u017e \u00fato\u010dn\u00edk, kter\u00fd odposlouch\u00e1val p\u0159enosov\u00e9 kan\u00e1ly, zachyt\u00ed tuto zpr\u00e1vu a ode\u0161le identickou druhou? Ov\u011b\u0159ovatel porovn\u00e1 podpis transakce a bude p\u0159esv\u011bd\u010den o jej\u00edm autorstv\u00ed, a s\u00ed\u0165 znovu ode\u010dte stejnou \u010d\u00e1stku ze z\u016fstatku odes\u00edlatele.<\/p>\n

Tento \u00fatok se naz\u00fdv\u00e1 replay \u00fatok. V modelu UTXO nejsou takov\u00e9 \u00fatoky aktu\u00e1ln\u00ed, proto\u017ee \u00fato\u010dn\u00edk by se pokusil pou\u017e\u00edt utracen\u00e9 v\u00fdstupy, co\u017e samo o sob\u011b nen\u00ed platn\u00e9 a je odm\u00edtnuto s\u00edt\u00ed.<\/p>\n

Aby k tomu nedo\u0161lo, do transakce se vkl\u00e1d\u00e1 pole se n\u00e1hodn\u00fdmi daty, kter\u00e9 se naz\u00fdv\u00e1 nonce nebo jednodu\u0161e \u201es\u016fl\u201c. P\u0159i op\u011btovn\u00e9m odes\u00edl\u00e1n\u00ed transakce s \u201esol\u00ed\u201c ov\u011b\u0159ovatel zkontroluje, zda byl tento nonce pou\u017eit d\u0159\u00edve, a pokud ne, pova\u017euje tuto transakci za platnou. Aby nebylo nutn\u00e9 uchov\u00e1vat v blockchainu celou historii nonce u\u017eivatel\u016f, obvykle se v samotn\u00e9 prvn\u00ed transakci p\u0159ijme jako nulov\u00fd a d\u00e1le se zvy\u0161uje o jedna. S\u00ed\u0165 m\u00e1 za \u00fakol jen zkontrolovat, \u017ee nonce nov\u00e9 transakce se li\u0161\u00ed od p\u0159edchoz\u00ed o jednu.<\/p>\n

V anonymn\u00edm sch\u00e9matu p\u0159evod\u016f se objevuje probl\u00e9m validace nonce transakc\u00ed. Nelze p\u0159\u00edmo p\u0159i\u0159adit nonce k adrese odes\u00edlatele, proto\u017ee by to zjevn\u011b de-anonymizovalo p\u0159evod. Tak\u00e9 nem\u016f\u017eeme p\u0159i\u010d\u00edtat jedni\u010dku k nonce v\u0161ech z\u00fa\u010dastn\u011bn\u00fdch \u00fa\u010dt\u016f, proto\u017ee to m\u016f\u017ee kolidovat s jin\u00fdmi p\u0159evody, kter\u00e9 jsou v procesu zpracov\u00e1n\u00ed. <\/p>\n

Auto\u0159i Zether navrhuj\u00ed generovat nonce kryptograficky \u2014 v z\u00e1vislosti na \u201eepoch\u011b\u201c. Nap\u0159\u00edklad:<\/p>\n

\"O
\nZde x<\/i><\/b> \u2014 tajn\u00fd kl\u00ed\u010d odes\u00edlatele, a Gepoch<\/i><\/b> \u2014 dodate\u010dn\u00fd gener\u00e1tor pro epochu, z\u00edskan\u00fd hashov\u00e1n\u00edm \u0159et\u011bzce ve form\u00e1tu ‘Zether + ‘. Zd\u00e1lo se, \u017ee probl\u00e9m je vy\u0159e\u0161en \u2014 nezve\u0159ej\u0148ujeme nonce odes\u00edlatele a nezasahujeme do nonce nez\u00fa\u010dastn\u011bn\u00fdch \u00fa\u010dastn\u00edk\u016f. Tento p\u0159\u00edstup v\u0161ak klade v\u00e1\u017en\u00e1 omezen\u00ed: jeden \u00fa\u010det m\u016f\u017ee odeslat maxim\u00e1ln\u011b jednu transakci v \u201eepoce\u201c. Tento probl\u00e9m z\u016fst\u00e1v\u00e1, bohu\u017eel, nevy\u0159e\u0161en a v sou\u010dasnosti \u010din\u00ed anonymn\u00ed verzi Zether, podle na\u0161eho n\u00e1zoru, sotva pou\u017eitelnou.<\/p>\n

Obt\u00ed\u017enost d\u016fkaz\u016f s nulov\u00fdm odhalov\u00e1n\u00edm<\/h4>\n

\nV UTXO mus\u00ed odes\u00edlatel dok\u00e1zat s\u00edti, \u017ee netrat\u00ed negativn\u00ed \u010d\u00e1stku, jinak by bylo mo\u017en\u00e9 generovat nov\u00e9 mince z ni\u010deho (pro\u010d je to mo\u017en\u00e9, jsme popisovali v jednom z p\u0159edchoz\u00edch \u010dl\u00e1nk\u016f<\/a><\/noindex>). A tak\u00e9 podepsat \u201evstupy\u201c kruhov\u00fdm podpisem, aby dok\u00e1zal, \u017ee mezi m\u00edsen\u00fdmi mincemi jsou prost\u0159edky, kter\u00e9 mu pat\u0159\u00ed.<\/p>\n

V anonymn\u00ed verzi blockchainu zalo\u017een\u00e9ho na \u00fa\u010dtech jsou v\u00fdrazy pro d\u016fkaz mnohem slo\u017eit\u011bj\u0161\u00ed. Odes\u00edlatel dokazuje, \u017ee:<\/p>\n

    \n
  1. Odes\u00edlan\u00e1 \u010d\u00e1stka je kladn\u00e1;<\/li>\n
  2. Z\u016fstatek z\u016fst\u00e1v\u00e1 nez\u00e1porn\u00fd;<\/li>\n
  3. Odes\u00edlatel spr\u00e1vn\u011b za\u0161ifroval \u010d\u00e1stky p\u0159evod\u016f (v\u010detn\u011b nulov\u00fdch);<\/li>\n
  4. Z\u016fstatek na \u00fa\u010dtu se m\u011bn\u00ed pouze u odes\u00edlatele a p\u0159\u00edjemce;<\/li>\n
  5. Odes\u00edlatel vlastn\u00ed tajn\u00fd kl\u00ed\u010d k sv\u00e9mu \u00fa\u010dtu a skute\u010dn\u011b se nach\u00e1z\u00ed v seznamu odes\u00edlatel\u016f (mezi m\u00edsen\u00fdmi);<\/li>\n
  6. Nonce pou\u017eit\u00fd v transakci je spr\u00e1vn\u011b slo\u017een.<\/li>\n<\/ol>\n

    \nPro takto slo\u017eit\u00fd d\u016fkaz auto\u0159i pou\u017e\u00edvaj\u00ed sm\u011bs Bulletproof<\/a><\/noindex> (jeden z autor\u016f, mimochodem, se pod\u00edlel na jej\u00edm vytvo\u0159en\u00ed) a Sigma protocol<\/a><\/noindex>, kterou naz\u00fdvaj\u00ed Sigma-bullets. Form\u00e1ln\u00ed d\u016fkaz takov\u00e9ho tvrzen\u00ed je pom\u011brn\u011b slo\u017eit\u00fd \u00fakol a siln\u011b omezuje po\u010det t\u011bch, kte\u0159\u00ed maj\u00ed z\u00e1jem o realizaci technologie.<\/p>\n

    Jak\u00fd je v\u00fdsledek?<\/h4>\n

    \nPodle na\u0161eho n\u00e1zoru m\u016f\u017ee \u010d\u00e1st Zether, kter\u00e1 p\u0159in\u00e1\u0161\u00ed soukrom\u00ed do blockchain\u016f zalo\u017een\u00fdch na \u00fa\u010dtech, b\u00fdt pou\u017e\u00edv\u00e1na ji\u017e nyn\u00ed. Nicm\u00e9n\u011b v sou\u010dasnosti anonymn\u00ed verze technologie klade v\u00e1\u017en\u00e1 omezen\u00ed na jej\u00ed pou\u017eit\u00ed a jej\u00ed slo\u017eitost na implementaci. Je v\u0161ak d\u016fle\u017eit\u00e9 nezapom\u00ednat, \u017ee auto\u0159i ji vydali teprve p\u0159ed n\u011bkolika m\u011bs\u00edci a mo\u017en\u00e1 n\u011bkdo jin\u00fd nalezne \u0159e\u0161en\u00ed pro dne\u0161n\u00ed probl\u00e9my. Takto se p\u0159ece d\u011bl\u00e1 v\u011bda.
    \n
    Zdroj:     habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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