Solana Testnet Wallet Private Keys Length

Question

what is the correct length for the Solana testnet wallet private keys, 64 or 88? Also, I am using the Phantom browser extension for my wallet. Is there anything else that is best and creates the secret key of 64 length?

Answer 1

All Private Keys are 64 bytes, and the first 32 are the Public-Key.

You can use the KeyPair class as well.

https://solana-labs.github.io/solana-web3.js/classes/Keypair.html

Here is some more info about it: https://solana.com/docs/clients/javascript-reference

const { Keypair } = require("@solana/web3.js");
 
let account = Keypair.generate();
 
console.log(account.publicKey.toBase58());
console.log(account.secretKey);
 
// 2DVaHtcdTf7cm18Zm9VV8rKK4oSnjmTkKE6MiXe18Qsb
// Uint8Array(64) [
//   152,  43, 116, 211, 207,  41, 220,  33, 193, 168, 118,
//    24, 176,  83, 206, 132,  47, 194,   2, 203, 186, 131,
//   197, 228, 156, 170, 154,  41,  56,  76, 159, 124,  18,
//    14, 247,  32, 210,  51, 102,  41,  43,  21,  12, 170,
//   166, 210, 195, 188,  60, 220, 210,  96, 136, 158,   6,
//   205, 189, 165, 112,  32, 200, 116, 164, 234
// ]
 
let seed = Uint8Array.from([
  70, 60, 102, 100, 70, 60, 102, 100, 70, 60, 102, 100, 70, 60, 102, 100, 70,
  60, 102, 100, 70, 60, 102, 100, 70, 60, 102, 100, 70, 60, 102, 100,
]);
let accountFromSeed = Keypair.fromSeed(seed);
 
console.log(accountFromSeed.publicKey.toBase58());
console.log(accountFromSeed.secretKey);
 
// 3LDverZtSC9Duw2wyGC1C38atMG49toPNW9jtGJiw9Ar
// Uint8Array(64) [
//    70,  60, 102, 100,  70,  60, 102, 100,  70,  60, 102,
//   100,  70,  60, 102, 100,  70,  60, 102, 100,  70,  60,
//   102, 100,  70,  60, 102, 100,  70,  60, 102, 100,  34,
//   164,   6,  12,   9, 193, 196,  30, 148, 122, 175,  11,
//    28, 243, 209,  82, 240, 184,  30,  31,  56, 223, 236,
//   227,  60,  72, 215,  47, 208, 209, 162,  59
// ]
 
let accountFromSecret = Keypair.fromSecretKey(account.secretKey);
 
console.log(accountFromSecret.publicKey.toBase58());
console.log(accountFromSecret.secretKey);
 
// 2DVaHtcdTf7cm18Zm9VV8rKK4oSnjmTkKE6MiXe18Qsb
// Uint8Array(64) [
//   152,  43, 116, 211, 207,  41, 220,  33, 193, 168, 118,
//    24, 176,  83, 206, 132,  47, 194,   2, 203, 186, 131,
//   197, 228, 156, 170, 154,  41,  56,  76, 159, 124,  18,
//    14, 247,  32, 210,  51, 102,  41,  43,  21,  12, 170,
//   166, 210, 195, 188,  60, 220, 210,  96, 136, 158,   6,
//   205, 189, 165, 112,  32, 200, 116, 164, 234
// ]

In case you wonder how to generate a SEED: e.g, using a combination of words or strings provided by the user.

//*************/
async function DeriveUserRootKey(email, key_seed, output_bits_length = 256) {
  const inner_digest = 'constant-string-whatever-but-constant' + key_seed;
  const enc = new TextEncoder();

  const seed_key = await crypto.subtle.importKey('raw', enc.encode(inner_digest), 'PBKDF2', false, [
    'deriveBits',
    'deriveKey',
  ]);

  if (seed_key == undefined || seed_key == null) {
    console.log('ERROR: Failed to derive seed_key');
    return null;
  }

  
  var buffer = new TextEncoder('utf-8').encode('user_salt:' + email);
  const salt = new Uint8Array(buffer);

  let root_key = await crypto.subtle.deriveBits(
    {
      name: 'PBKDF2',
      salt: salt,
      iterations: 3000000,
      hash: 'SHA-512',
    },
    seed_key,
    output_bits_length,
  );

  if (root_key == undefined || root_key == null) {
    console.log('ERROR: Failed to derive primary key bits from seed key.');
    return null;
  }

  return buf2hex(root_key);
}
//*************/
async function DeriveUserPrivateKey(root_key, key_name) {
  
  let inner_digest = root_key + ':' + key_name; 
  
  var buffer = new TextEncoder().encode(inner_digest);
  let derived_bits = await crypto.subtle.digest('SHA-256', buffer);

  if (derived_bits == undefined || derived_bits == null) {
    console.log('ERROR: Failed to derive secondary key bits from root key.');
    return null;
  }
 
  let private_key = new Uint8Array(derived_bits);

  return private_key;
}
//*************/
function buf2hex(buffer) {
  
  return [...new Uint8Array(buffer)].map((x) => x.toString(16).padStart(2, '0')).join('');
}

This returns a Buffer or Uint8Array(64) that you use to feed the KeyPair.fromSeed() method.

  let sol_keypair = Keypair.fromSeed(sol_private_key);
  accountAddress.value = sol_keypair.publicKey.toBase58();
  privateKey.value = bs58.encode(sol_keypair.secretKey);

Security NOTE:

The above custom method does not use a SALT, using a random salt is recommended to avoid collisions. e.f. if 2 users provide the same set of random words, they would get the same KeyPair, adding a random salt prevents that but requires the users to save the RandomSalt in order to recover or regenerate the Pairs.