96 lines
2.8 KiB
JavaScript
96 lines
2.8 KiB
JavaScript
/**
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* Implements proof of work.
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* @see {@link https://bitmessage.org/wiki/Proof_of_work}
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* @module bitmessage/pow
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*/
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// TODO(Kagami): Find a way how to document object params properly.
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"use strict";
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var objectAssign = Object.assign || require("object-assign");
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var bmcrypto = require("./crypto");
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var platform = require("./platform");
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var DEFAULT_TRIALS_PER_BYTE = 1000;
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var DEFAULT_EXTRA_BYTES = 1000;
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/**
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* Calculate target
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* @param {Object} opts - Target options
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* @return {number} Target.
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*/
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// Just a wrapper around platform-specific implementation.
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exports.getTarget = function(opts) {
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var payloadLength = opts.payloadLength || opts.payload.length;
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var nonceTrialsPerByte = opts.nonceTrialsPerByte;
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// Automatically raise lower values per spec.
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if (!nonceTrialsPerByte || nonceTrialsPerByte < DEFAULT_TRIALS_PER_BYTE) {
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nonceTrialsPerByte = DEFAULT_TRIALS_PER_BYTE;
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}
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var payloadLengthExtraBytes = opts.payloadLengthExtraBytes;
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if (!payloadLengthExtraBytes || payloadLengthExtraBytes < DEFAULT_EXTRA_BYTES) {
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payloadLengthExtraBytes = DEFAULT_EXTRA_BYTES;
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}
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return platform.getTarget({
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ttl: opts.ttl,
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payloadLength: payloadLength,
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nonceTrialsPerByte: nonceTrialsPerByte,
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payloadLengthExtraBytes: payloadLengthExtraBytes,
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});
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};
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/**
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* Check a POW.
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* @param {Object} opts - Proof of work options
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* @return {boolean} Is the proof of work sufficient.
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*/
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exports.check = function(opts) {
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var initialHash;
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var nonce;
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if (opts.data) {
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nonce = opts.data.slice(0, 8);
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initialHash = bmcrypto.sha512(opts.data.slice(8));
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} else {
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if (typeof opts.nonce === "number") {
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nonce = new Buffer(8);
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// High 32 bits.
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nonce.writeUInt32BE(Math.floor(opts.nonce / 4294967296), 0, true);
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// Low 32 bits.
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nonce.writeUInt32BE(opts.nonce % 4294967296, 4, true);
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} else {
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nonce = opts.nonce;
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}
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initialHash = opts.initialHash;
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}
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var targetHi = Math.floor(opts.target / 4294967296);
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var targetLo = opts.target % 4294967296;
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var dataToHash = Buffer.concat([nonce, initialHash]);
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var resultHash = bmcrypto.sha512(bmcrypto.sha512(dataToHash));
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var trialHi = resultHash.readUInt32BE(0, true);
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if (trialHi > targetHi) {
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return false;
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} else if (trialHi < targetHi) {
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return true;
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} else {
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var trialLo = resultHash.readUInt32BE(4, true);
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return trialLo <= targetLo;
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}
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};
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/**
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* Do a POW.
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* @param {Object} opts - Proof of work options
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* @return {Promise.<Buffer>} A promise that contains computed nonce for
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* the given target when fulfilled.
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*/
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exports.doAsync = function(opts) {
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var initialHash;
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if (opts.payload) {
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initialHash = bmcrypto.sha512(opts.payload);
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} else {
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initialHash = opts.initialHash;
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}
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opts = objectAssign({}, opts, {initialHash: initialHash});
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return platform.pow(opts);
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};
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