{"id":34823,"date":"2019-10-31T22:00:35","date_gmt":"2019-10-31T19:00:35","guid":{"rendered":"https:\/\/prohoster.info\/blog\/ispolzovanie-sluchajnogo-orakula-na-primere-loterei\/"},"modified":"2019-10-31T22:00:35","modified_gmt":"2019-10-31T19:00:35","slug":"ispolzovanie-sluchajnogo-orakula-na-primere-loterei","status":"publish","type":"post","link":"https:\/\/prohoster.info\/pt\/blog\/administrirovanie\/ispolzovanie-sluchajnogo-orakula-na-primere-loterei","title":{"rendered":"Uso de um or\u00e1culo aleat\u00f3rio usando o exemplo da loteria","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Certa manh\u00e3, me deparei com um artigo sobre um gerador de n\u00fameros aleat\u00f3rios verificado<\/a><\/noindex> na blockchain da Waves platform. <\/p>\n

O quadro geral estava claro, mas o m\u00e9todo de implementa\u00e7\u00e3o espec\u00edfico n\u00e3o. Quais c\u00f3digos, assinaturas, o que, para onde, por qu\u00ea?<\/p>\n

Ap\u00f3s v\u00e1rias consultas com o autor do or\u00e1culo, consegui unir a l\u00f3gica do sorteio (implementada em PHP) com o algoritmo de gera\u00e7\u00e3o de n\u00fameros aleat\u00f3rios.
\n<\/a><\/noindex><\/p>\n

    \n
  1. No in\u00edcio do torneio\/rodada, pedimos ao or\u00e1culo a primeira parte do c\u00f3digo (R-code).\n

    Nesse momento, n\u00e3o h\u00e1 informa\u00e7\u00f5es sobre o n\u00famero de jogadores, nem sobre a quantidade de pr\u00eamios, nem sobre o valor das recompensas e at\u00e9 mesmo sobre a exist\u00eancia da loteria. O or\u00e1culo emite um c\u00f3digo aleat\u00f3rio pessoal atrav\u00e9s de uma transa\u00e7\u00e3o, que poder\u00e1 ser utilizado apenas uma vez e somente por quem o solicitou. A prop\u00f3sito, o R-code pode ser \"adquirido\" (entenda-se o custo da transa\u00e7\u00e3o de solicita\u00e7\u00e3o + compensa\u00e7\u00e3o ao or\u00e1culo pela transa\u00e7\u00e3o de resposta, que soma cerca de $0.015 com a taxa atual, e o c\u00f3digo em si \u00e9 fornecido gratuitamente) com anteced\u00eancia, em quantidades m\u00faltiplas, para n\u00e3o precisar esperar pela transa\u00e7\u00e3o de resposta. Eu criei um pequeno buffer regularmente atualizado no banco de dados.<\/li>\n

  2. O torneio normalmente dura 60 blocos na blockchain da Waves platform, o que atualmente equivale a aproximadamente 1 hora. O torneio \u00e9 considerado realizado e fechado se, ap\u00f3s 60 blocos, houver pelo menos dois ingressos, caso contr\u00e1rio, o tempo de atividade do torneio \u00e9 estendido por mais 60 blocos.<\/li>\n
  3. Imediatamente ap\u00f3s o fechamento do torneio, formamos e enviamos a transa\u00e7\u00e3o de dados (tamb\u00e9m pagamos uma taxa por isso, de aproximadamente $0.005), se necess\u00e1rio \u2014 v\u00e1rias transa\u00e7\u00f5es, nas quais est\u00e3o fixadas todas as condi\u00e7\u00f5es do sorteio e uma lista ordenada de jogadores (ingressos) de onde precisamos selecionar os vencedores.<\/li>\n
  4. Neste est\u00e1gio, j\u00e1 temos a primeira parte do c\u00f3digo (R-code) e o ID da transa\u00e7\u00e3o de dados (TXID). N\u00f3s os enviamos para assinatura ao or\u00e1culo na forma de concatena\u00e7\u00e3o (R-code + TXID), novamente pagando a taxa e a compensa\u00e7\u00e3o. O or\u00e1culo verifica os dados recebidos quanto \u00e0 exclusividade e propriedade, e em resposta nos envia a segunda parte do c\u00f3digo (S-code) no formato sha256, que se torna o ponto de partida para o gerador de n\u00fameros aleat\u00f3rios.<\/li>\n
  5. Para obter um n\u00famero aleat\u00f3rio que indicar\u00e1 o n\u00famero do bilhete vencedor, transformamos o S-code de dados bin\u00e1rios sha256 em uma representa\u00e7\u00e3o hexadecimal (HEX). Em seguida, a partir da string HEX resultante, obtemos um n\u00famero. Calculamos o resto da divis\u00e3o do n\u00famero obtido pelo n\u00famero de bilhetes (all_tickets) e adicionamos 1 ao resultado (para obter um n\u00famero de 1 at\u00e9 all_tickets). No final, obtemos o n\u00famero do vencedor.<\/li>\n
  6. Se, de acordo com as condi\u00e7\u00f5es do sorteio, houver v\u00e1rios vencedores, repetimos as opera\u00e7\u00f5es anteriores na quantidade correspondente ao n\u00famero de pr\u00eamios. Cada vez, removemos da lista o bilhete que j\u00e1 ganhou e diminu\u00edmos all_tickets em 1, enquanto substitu\u00edmos o S-code pelo n\u00famero anteriormente obtido.<\/li>\n<\/ol>\n

    \nVamos analisar um exemplo real, torneio n\u00ba 119:<\/p>\n

    Um total de 7 bilhetes (all_tickets)
    \nCusto do bilhete 50 moedas (Bet)
    \nTaxa de jogo 10% (Fee)<\/p>\n

    De acordo com as regras da loteria, 30% v\u00e3o para os pr\u00eamios, ou seja, neste caso, 2 bilhetes devem receber um pr\u00eamio, cujo valor \u00e9 calculado pela f\u00f3rmula (Bet*all_tickets-Fee)\/2.<\/p>\n

    1. Recebemos o R-code: RdbAiAhKhveAtR4eyTKq75noMxdcEoxbE6BvojJjM13VE<\/a><\/noindex><\/p>\n

    2. Ap\u00f3s o fechamento do torneio, temos uma lista de bilhetes na forma de pares: n\u00famero + endere\u00e7o (endere\u00e7o da carteira de onde foi feito o pagamento da participa\u00e7\u00e3o no torneio). Note que os endere\u00e7os podem se repetir, isso significa que um participante comprou v\u00e1rios bilhetes em um \u00fanico torneio, o que n\u00e3o \u00e9 proibido pelas regras.<\/p>\n

    Enviamos a data da transa\u00e7\u00e3o: 82JTMzhHM5xEA2fQ9Qscd5QAJU3DAd8nShLjdVHTer5S<\/a><\/noindex><\/p>\n

    3. Solicitamos o S-code: FTF3uRyaa4F2uAyD6z5a3CNbTXbQLc7fSR6CFNVjgZYV<\/a><\/noindex> com o coment\u00e1rio (R-code + TXID):
    \nRdbAiAhKhveAtR4eyTKq75noMxdcEoxbE6BvojJjM13VE 82JTMzhHM5xEA2fQ9Qscd5QAJU3DAd8nShLjdVHTer5S<\/p>\n

    4. Recebemos o S-code: Ri89jHB4UXZDXY6gT1m4LBDXGMTaYzHozMk4nxiuqVXdC<\/a><\/noindex><\/p>\n

    5. Determinamos os vencedores.<\/p>\n

    6. Enviamos os pagamentos<\/a><\/noindex><\/p>\n

    Como resultado, temos no blockchain um registro passo a passo do procedimento de sorteio de pr\u00eamios, com a possibilidade de verific\u00e1-lo a qualquer momento. Manipular os resultados por parte do organizador \u00e9 praticamente imposs\u00edvel, ao menos que seja de forma impercept\u00edvel.<\/p>\n

    determinar o vencedor n\u00ba 1\n\nTodos_ticket:\n\u00cdndice: 1 Bilhete:139\n\u00cdndice: 2 Bilhete:141\n\u00cdndice: 3 Bilhete:143\n\u00cdndice: 4 Bilhete:145\n\u00cdndice: 5 Bilhete:147\n\u00cdndice: 6 Bilhete:149\n\u00cdndice: 7 Bilhete:151\n\n1. bin -> hex (bin2hex(sha256(S-code))): Ri89jHB4UXZDXY6gT1m4LBDXGMTaYzHozMk4nxiuqVXdC -> 0xdaf5802953dcb27f89972e38e8900b898733f6a613e6e1c6c5491362c1832596\n\n2. hex -> n\u00famero gmp: 0xdaf5802953dcb27f89972e38e8900b898733f6a613e6e1c6c5491362c1832596 -> 99037963059744689166154019807924045947962565922868104113173478160267437352342\n\n3. gmp -> m\u00f3dulo (mod=7): 99037963059744689166154019807924045947962565922868104113173478160267437352342 -> 4\n\n4. m\u00f3dulo -> bilhete: 4 -> 145\n\ndeterminar o vencedor n\u00ba 2\n\nTodos_ticket:\n\n\u00cdndice: 1 Bilhete:139\n\u00cdndice: 2 Bilhete:141\n\u00cdndice: 3 Bilhete:143\n\u00cdndice: 4 Bilhete:147\n\u00cdndice: 5 Bilhete:149\n\u00cdndice: 6 Bilhete:151\n\n1. bin -> hex (bin2hex(sha256(hex anterior))): daf5802953dcb27f89972e38e8900b898733f6a613e6e1c6c5491362c1832596 -> 0x9560e77525e9ea2db92cdb8484dc52046ccafac7c719b8859ff55f0eb92834a0\n2. hex -> n\u00famero gmp: 0x9560e77525e9ea2db92cdb8484dc52046ccafac7c719b8859ff55f0eb92834a0 -> 67565829218838067182838043983962684143266386786567427968312120473742580659360\n3. gmp -> m\u00f3dulo (mod=6): 67565829218838067182838043983962684143266386786567427968312120473742580659360 -> 1\n4. m\u00f3dulo -> bilhete: 1 -> 139\n\nFim.<\/code><\/pre>\n
    Fonte: habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"
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