Use naive, slow implementation
This commit is contained in:
+178
-18
@@ -1,21 +1,159 @@
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width,initial-scale=1">
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<title>PoW Shield</title>
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</head>
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<script>
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function getCookie(name) {
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const cookies = document.cookie.split("; ");
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for (const c of cookies) {
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if (c.startsWith(name + "=")) {
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return decodeURIComponent(c.substring(name.length + 1));
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}
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}
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return null;
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}
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function b64ToBytes(b64) {
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const bin = atob(b64);
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const out = new Uint8Array(bin.length);
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for (let i = 0; i < bin.length; i++) out[i] = bin.charCodeAt(i);
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return out;
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}
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function bytesToB64(bytes) {
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let s = "";
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for (let i = 0; i < bytes.length; i++) {
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s += String.fromCharCode(bytes[i]);
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}
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return btoa(s);
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}
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function checkDifficulty(hash, bits) {
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const full = bits >> 3;
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const rem = bits & 7;
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for (let i = 0; i < full; i++) {
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if (hash[i] !== 0) return false;
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}
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if (rem) {
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const mask = 0xff << (8 - rem);
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if ((hash[full] & mask) !== 0) return false;
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}
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return true;
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}
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async function sha256(buf) {
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const h = await crypto.subtle.digest("SHA-256", buf);
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return new Uint8Array(h);
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}
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async function minePow(cookieB64, {
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timeoutMs = 5000,
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startNonce = 0,
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littleEndian = true
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} = {}) {
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const start = performance.now();
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// decode challenge once
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const challenge = b64ToBytes(cookieB64);
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const challengeLen = challenge.length;
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// layout:
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// [ challenge | nonce | hash ]
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const NONCE_OFFSET = challengeLen;
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const HASH_OFFSET = challengeLen + 4;
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const TOTAL_SIZE = challengeLen + 4 + 32;
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// single working buffer (NO reallocation in loop)
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const work = new Uint8Array(TOTAL_SIZE);
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work.set(challenge, 0);
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const view = new DataView(work.buffer);
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// extract difficulty once
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const difficulty = view.getUint32(12, littleEndian);
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for (nonce = startNonce; ; nonce++) {
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// timeout throttle (cheap check)
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if ((nonce & 2047) === 0) {
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if (performance.now() - start > timeoutMs) {
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throw new Error("PoW timeout");
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}
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}
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// Set nonce (this still copies the nonce)
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view.setUint32(NONCE_OFFSET, nonce, littleEndian);
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// Calculate sha256
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const input = work.subarray(0, challengeLen + 4);
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const hash = new Uint8Array(
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await crypto.subtle.digest("SHA-256", input)
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);
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// Set hash (this still copies the hash)
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work.set(hash, HASH_OFFSET);
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if (checkDifficulty(hash, difficulty)) {
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return {
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nonce,
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hash,
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resultBytes: work,
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resultB64: bytesToB64(work)
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};
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}
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}
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}
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const powChallengeCookie = getCookie('pow-challenge');
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console.log(powChallengeCookie);
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minePow(powChallengeCookie)
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.then(pow => {
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console.log(pow);
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document.cookie = `pow = ${pow.resultB64}`
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})
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.catch(e => console.log(e));
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</script>
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<!-- script>
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const SHA256_MD_LENGTH = 64;
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const POW_RANDOM_LENGTH = 64;
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class PowChallenge {
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constructor(cookie) {
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const bytes = Uint8Array.from(atob(b64), c => c.charCodeAt(0));
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const view = new DataView(powChallengeBytes.buffer);
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let offset = 0;
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this.version = view.getUint32(offset, true); offset += 4;
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this.created = view.getUint32(offset, true); offset += 4;
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this.ttl = view.getUint32(offset, true); offset += 4;
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this.difficulty = view.getUint32(offset, true); offset += 4;
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this.random = view.buffer.slice(offset, offset + POW_RANDOM_LENGTH); offset += POW_RANDOM_LENGTH;
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this.digest = view.buffer.slice(offset);
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}
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getBytes() {
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}
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}
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function base64ToBytes(b64) {
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return Uint8Array.from(atob(b64), c => c.charCodeAt(0));
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}
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function deserializePowChallenge(b64) {
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const bytes = base64ToBytes(b64);
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const view = new DataView(bytes.buffer);
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function deserializePowChallenge(powChallengeBytes) {
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const view = new DataView(powChallengeBytes.buffer);
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let offset = 0;
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@@ -53,10 +191,10 @@
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return new Uint8Array(hashBuffer);
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}
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function hasLeadingBytes(buf, numBits) {
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function hasLeadingBits(buf, numBits) {
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const zeroBytes = numBits / 8;
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const remainingBits = numBits % 8;
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const lut = Uint8Array([
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const lut = new Uint8Array([
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0b11111111, 0b01111111, 0b00111111, 0b00011111,
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0b00001111, 0b00000111, 0b00000011, 0b00000001
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]);
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@@ -67,29 +205,51 @@
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}
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}
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if (buf[zeroBytes + 1] ^ lut[remainingBytes]) {
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if (buf[zeroBytes + 1] ^ lut[remainingBits]) {
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return false;
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}
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return true;
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}
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function pow(challenge) {
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const difficulty = deserializePowChallenge(challenge).difficulty
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const pow = Uint32
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function powSolve(powChallengeBytes, difficulty) {
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const powBytes = new Uint8Array(powChallengeBytes.length
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+ 4 // Nonce length
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+ SHA256_MD_LENGTH);
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powBytes.set(powChallengeBytes, 0);
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let digest;
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let nonce = 0;
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for (
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nonce = 0 >>> 0; // Force nonce to be uint32
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(!hasLeadingBits(powBytes.slice(powChallengeBytes.length), difficulty)
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&& nonce < 100)
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|| nonce != 0;
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nonce++
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) {
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powBytes[powChallengeBytes.length + 0] = nonce & 0xFF;
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powBytes[powChallengeBytes.length + 1] = (nonce >>> 8) & 0xFF;
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powBytes[powChallengeBytes.length + 2] = (nonce >>> 16) & 0xFF;
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powBytes[powChallengeBytes.length + 3] = (nonce >>> 24) & 0xFF;
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do {
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sha256(challenge).then(d => digest = d);
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} while (hasLeadingBytes(digest, difficulty))
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sha256(powBytes.slice(0, powChallengeBytes.length + 4))
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.then(s => powBytes.set(s, powChallengeBytes + 4))
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.catch(e => console.log(e));
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}
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console.log(digest)
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return powBytes;
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}
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const powChallengeCookie = getCookie("pow-challenge");
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const powChallenge = deserializePowChallenge(powChallengeCookie);
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console.log(powChallenge, powChallenge.length)
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</script>
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console.log(powChallengeCookie);
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const powChallengeBytes = base64ToBytes(powChallengeCookie);
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console.log(powChallengeBytes);
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const powChallenge = deserializePowChallenge(powChallengeBytes);
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console.log(powChallenge);
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const pow = powSolve(powChallengeBytes, powChallenge.difficulty);
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console.log(pow);
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</script -->
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</html>
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