80 lines
1.5 KiB
JavaScript
80 lines
1.5 KiB
JavaScript
'use strict';
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/*global crypto*/
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var Hashcash = module.exports;
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var textEncoder = new TextEncoder();
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Hashcash.solve = async function solveHc(hc) {
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var solution = 0;
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var parts = hc.split(':').slice(0, 6);
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if (parts.length < 6) {
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throw new Error('invalid Hashcash-Challenge: ' + hc);
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}
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var bits = parseInt(parts[1], 10) || -1;
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if (bits > 10 || bits < 0) {
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throw new Error('bad bit values');
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}
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console.log('bits:', bits);
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hc = parts.join(':') + ':';
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async function next() {
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var answer = hc + int52ToBase64(solution);
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var u8 = textEncoder.encode(answer);
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// REALLY SLOW due to async tasks and C++ context switch
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var hash = await crypto.subtle.digest('SHA-256', u8);
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hash = new Uint8Array(hash);
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if (checkHc(hash, bits)) {
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return answer;
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}
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solution += 1;
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return next();
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}
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return next();
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};
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function int52ToBase64(n) {
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var hex = n.toString(16);
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if (hex.length % 2) {
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hex = '0' + hex;
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}
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var bin = [];
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var i = 0;
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var d;
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var b;
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while (i < hex.length) {
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d = parseInt(hex.slice(i, i + 2), 16);
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b = String.fromCharCode(d);
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bin.push(b);
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i += 2;
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}
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return btoa(bin.join('')).replace(/=/g, '');
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}
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function checkHc(hash, bits) {
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var n = Math.floor(bits / 8);
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var m = bits % 8;
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var i;
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if (m > 0) {
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n += 1;
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}
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for (i = 0; i < n && i < hash.length; i += 1) {
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if (bits > 8) {
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bits -= 8;
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if (0 !== hash[i]) {
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return false;
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}
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continue;
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}
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if (0 !== hash[i] >> (8 - bits)) {
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return false;
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}
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return true;
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}
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}
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