ECDSAKeyCheck.js

/* Checking encoding of public keys for ECDSA
   Keys from RFC6979 and draft did:key document
   https://w3c-ccg.github.io/did-method-key/#p-384
*/

import { P256 } from '@noble/curves/p256';
import {P384} from '@noble/curves/p384';
import { hexToBytes, bytesToHex, concatBytes } from '@noble/hashes/utils';
import { base58btc } from "multiformats/bases/base58";
import varint from 'varint';
import { mkdir, writeFile } from 'fs/promises';

// Create output directory for the results
const baseDir = "./output/KeyCheck/";
let status = await mkdir(baseDir, {recursive: true});

// Multicodec information from https://github.com/multiformats/multicodec/
/*
name        tag     code    status      description
p256-pub	key	    0x1200	draft	    P-256 public Key (compressed)
p384-pub	key	    0x1201	draft	    P-384 public Key (compressed)
p256-priv key	    0x1306	draft	    P-256 private key
p384-priv key	    0x1307	draft	    P-384 private key
*/

const P256_PUB_PREFIX = 0x1200;
const P384_PUB_PREFIX = 0x1201;
const P256_PRIV_PREFIX = 0x1306;
const P384_PRIV_PREFIX = 0x1307;

console.log("Multicodec leading bytes in hex for P-256 and P-384 compressed public keys:");
let myBytes = new Uint8Array(varint.encode(P256_PUB_PREFIX));
console.log(`Public P-256 leading bytes: ${bytesToHex(myBytes)}`);
myBytes = new Uint8Array(varint.encode(P384_PUB_PREFIX));
console.log(`Public P-384 leading bytes: ${bytesToHex(myBytes)}\n`);

console.log("Multicodec leading bytes in hex for P-256 and P-384 private keys:");
myBytes = new Uint8Array(varint.encode(P256_PRIV_PREFIX));
console.log(`Private P-256 leading bytes: ${bytesToHex(myBytes)}`);
myBytes = new Uint8Array(varint.encode(P384_PRIV_PREFIX));
console.log(`Private P-384 leading bytes: ${bytesToHex(myBytes)}\n`);

// Example keys from RFC6979

console.log("P256 key example:");
let privateKey = hexToBytes("C9AFA9D845BA75166B5C215767B1D6934E50C3DB36E89B127B8A622B120F6721");
let publicKey = P256.getPublicKey(privateKey);
console.log(`P-256 private key length: ${privateKey.length}`);
console.log('P-256 private key hex:');
console.log(bytesToHex(privateKey));
let priv256Prefix = new Uint8Array(varint.encode(P256_PRIV_PREFIX)); // Need to use varint on the multicodecs code
let priv256Encoded = base58btc.encode(concatBytes(priv256Prefix, privateKey));
console.log('Private P-256 encoded multikey:');
console.log(priv256Encoded, '\n'); // Should start with z42 characters
console.log(`P-256 Pubic key length ${publicKey.length}`);
console.log('P-256 public key in hex:');
console.log(bytesToHex(publicKey));
let p256Prefix = new Uint8Array(varint.encode(P256_PUB_PREFIX)); // Need to use varint on the multicodecs code
let pub256Encoded = base58btc.encode(concatBytes(p256Prefix, publicKey));
console.log('Public P-256 encoded multikey:');
console.log(pub256Encoded, '\n'); // Should start with zDn characters
let p256KeyPair = {
   "publicKeyMultibase": pub256Encoded,
   "privateKeyMultibase": priv256Encoded
};
await writeFile(baseDir + 'p256KeyPair.json', JSON.stringify(p256KeyPair, null, 2));

let privateKey384 = hexToBytes("6B9D3DAD2E1B8C1C05B19875B6659F4DE23C3B667BF297BA9AA47740787137D896D5724E4C70A825F872C9EA60D2EDF5");
let publicKey384 = P384.getPublicKey(privateKey384);
console.log(`P-384 private key length: ${privateKey384.length}`);
console.log(bytesToHex(privateKey384));
let priv384Prefix = new Uint8Array(varint.encode(P384_PRIV_PREFIX)); // Need to use varint on the multicodecs code
let priv384Encoded = base58btc.encode(concatBytes(priv384Prefix, privateKey384));
console.log('Private P-384 encoded multikey:');
console.log(priv384Encoded, '\n'); // Should start with z2f characters

console.log(`P-384 Pubic key length ${publicKey384.length}`);
console.log('P-384 public key in hex:');
console.log(bytesToHex(publicKey384));
let p384Prefix = new Uint8Array(varint.encode(P384_PUB_PREFIX)); // Need to use varint on the multicodecs code
let pub384Encoded = base58btc.encode(concatBytes(p384Prefix, publicKey384));
console.log('P-384 encoded multikey:');
console.log(pub384Encoded, '\n'); // Should start with z82

let p384KeyPair = {
   "publicKeyMultibase": pub384Encoded,
   "privateKeyMultibase": priv384Encoded
};
await writeFile(baseDir + 'p384KeyPair.json', JSON.stringify(p384KeyPair, null, 2));

// From example 1 ECDSA-2019 P-384 public key
// "zsJV1eTDACogBS8FMj5vXSa51g1CY1y88DR2DGDwTsMTotTGELVH1XTEsFP8ok9q22ssAaqHN5fMgm1kweTABZZNRSc"
// This does not appear to be a valid P-384 key...
// Try: did:key:z82Lm1MpAkeJcix9K8TMiLd5NMAhnwkjjCBeWHXyu3U4oT2MVJJKXkcVBgjGhnLBn2Kaau9
let ex384multi = "z82Lm1MpAkeJcix9K8TMiLd5NMAhnwkjjCBeWHXyu3U4oT2MVJJKXkcVBgjGhnLBn2Kaau9";
let ex384bytes = base58btc.decode(ex384multi);
console.log("DID:key example P384 key in hex bytes:");
console.log(bytesToHex(ex384bytes));
console.log(`Length of example P-384 key without prefix: ${ex384bytes.length-2}`);