bitmessage-js/lib/pow.js

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/**
* Implements proof of work.
* @see {@link https://bitmessage.org/wiki/Proof_of_work}
* @module bitmessage/pow
*/
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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");
var util = require("./_util");
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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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* @function
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* @static
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*/
// Just a wrapper around platform-specific implementation.
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var getTarget = exports.getTarget = function(opts) {
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var payloadLength = opts.payloadLength || opts.payload.length;
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return platform.getTarget({
ttl: opts.ttl,
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payloadLength: payloadLength,
nonceTrialsPerByte: util.getTrials(opts),
payloadLengthExtraBytes: util.getExtraBytes(opts),
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});
};
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/**
* Check a POW.
* @param {Object} opts - Proof of work options
* @return {boolean} Is the proof of work sufficient.
*/
exports.check = function(opts) {
var initialHash;
var nonce;
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var target = opts.target;
if (target === undefined) {
target = getTarget(opts);
}
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if (opts.payload) {
nonce = opts.payload.slice(0, 8);
initialHash = bmcrypto.sha512(opts.payload.slice(8));
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} else {
if (typeof opts.nonce === "number") {
nonce = new Buffer(8);
// High 32 bits.
nonce.writeUInt32BE(Math.floor(opts.nonce / 4294967296), 0, true);
// Low 32 bits.
nonce.writeUInt32BE(opts.nonce % 4294967296, 4, true);
} else {
nonce = opts.nonce;
}
initialHash = opts.initialHash;
}
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var targetHi = Math.floor(target / 4294967296);
var targetLo = target % 4294967296;
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var dataToHash = Buffer.concat([nonce, initialHash]);
var resultHash = bmcrypto.sha512(bmcrypto.sha512(dataToHash));
var trialHi = resultHash.readUInt32BE(0, true);
if (trialHi > targetHi) {
return false;
} else if (trialHi < targetHi) {
return true;
} else {
var trialLo = resultHash.readUInt32BE(4, true);
return trialLo <= targetLo;
}
};
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/**
* Do a POW.
* @param {Object} opts - Proof of work options
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* @param {?Buffer} opts.data - Object message payload without nonce to
* get the initial hash from
* @param {?Buffer} opts.initialHash - Or already computed initial hash
* @param {number} opts.target - POW target
* @return {Promise.<number>} A promise that contains computed nonce for
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* the given target when fulfilled.
*/
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exports.doAsync = function(opts) {
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var initialHash;
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if (opts.data) {
initialHash = bmcrypto.sha512(opts.data);
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} else {
initialHash = opts.initialHash;
}
opts = objectAssign({}, opts, {initialHash: initialHash});
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return platform.pow(opts);
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};