{"id":15700,"date":"2023-12-06T16:24:57","date_gmt":"2023-12-06T16:24:57","guid":{"rendered":"https:\/\/promoguy.nl\/vocabulary\/proof-of-work\/"},"modified":"2023-12-06T16:24:57","modified_gmt":"2023-12-06T16:24:57","slug":"proof-of-work","status":"publish","type":"entity","link":"https:\/\/promoguy.nl\/pt\/blog\/vocabulary\/proof-of-work\/","title":{"rendered":"Prova de trabalho"},"content":{"rendered":"<p>Um sistema (ou protocolo, ou fun\u00e7\u00e3o) de prova de trabalho (proof-of-work - POW) \u00e9 uma medida econ\u00f3mica para impedir ataques de nega\u00e7\u00e3o de servi\u00e7o e outros abusos de servi\u00e7o, como spam, numa rede, exigindo algum trabalho ao requisitante do servi\u00e7o, o que normalmente significa tempo de processamento por um computador.  O conceito deve-se a Dwork e Naor. Uma carater\u00edstica fundamental destes esquemas \u00e9 a sua assimetria: o trabalho deve ser moderadamente dif\u00edcil (mas exequ\u00edvel) para o requerente, mas f\u00e1cil de verificar para o fornecedor do servi\u00e7o. Esta ideia \u00e9 tamb\u00e9m conhecida como fun\u00e7\u00e3o de custo da CPU, puzzle do cliente, puzzle computacional ou fun\u00e7\u00e3o de pre\u00e7o da CPU. \u00c9 diferente de um CAPTCHA, que se destina a ser resolvido rapidamente por um ser humano e n\u00e3o por um computador. Um sistema popular - usado na minera\u00e7\u00e3o de Bitcoin e no Hashcash - usa invers\u00f5es parciais de hash para provar que o trabalho foi feito, como um s\u00edmbolo de boa vontade para enviar um e-mail. Por exemplo, o seguinte cabe\u00e7alho representa cerca de 252 c\u00e1lculos de hash para enviar uma mensagem para calvin@comics.net em 19 de janeiro de 2038: X-Hashcash: 1:52:380119:calvin@comics.net:::9B760005E92F0DAE \u00c9 verificado com um \u00fanico c\u00e1lculo, verificando que o hash SHA-1 do carimbo (omitir a parte \"X-Hashcash: \") come\u00e7a com 52 zeros bin\u00e1rios, ou seja, 13 zeros hexadecimais: 0000000000000756af69e2ffbdb930261873cd71 A quest\u00e3o de saber se os sistemas de prova de trabalho podem realmente resolver um problema espec\u00edfico de nega\u00e7\u00e3o de servi\u00e7o, como o problema do spam, \u00e9 objeto de debate; o sistema deve tornar o envio de e-mails de spam intrusivamente improdutivo para o spammer, mas tamb\u00e9m n\u00e3o deve impedir que os utilizadores leg\u00edtimos enviem as suas mensagens. Os sistemas de prova de trabalho est\u00e3o a ser utilizados como primitivos por outros sistemas criptogr\u00e1ficos mais complexos, como o Bitcoin, que utiliza um sistema semelhante ao Hashcash.<\/p>","protected":false},"excerpt":{"rendered":"<p>A proof-of-work (POW) system (or protocol, or function) is an economic measure to deter denial of service attacks and other service abuses such as spam on a network by requiring some work from the service requester, usually meaning processing time by a computer. The concept is due to Dwork and Naor. A key feature of [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"","ping_status":"closed","template":"","meta":{"_acf_changed":false,"wl_entities_gutenberg":"","footnotes":""},"categories":[],"wl_entity_type":[39],"class_list":["post-15700","entity","type-entity","status-publish","hentry","wl_entity_type-thing"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v28.0 (Yoast SEO v28.0) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Proof-of-work - Promoguy Digital Marketing Agency<\/title>\n<meta name=\"robots\" content=\"noindex, follow\" \/>\n<meta property=\"og:locale\" content=\"pt_PT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Proof-of-work\" \/>\n<meta property=\"og:description\" content=\"A proof-of-work (POW) system (or protocol, or function) is an economic measure to deter denial of service attacks and other service abuses such as spam on a network by requiring some work from the service requester, usually meaning processing time by a computer. 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