How to convert ed25519 bytes to Tezos public key

Question

I tried to do that by base58 encoding ed255191 public key bytes. Consider a following code sample:

const seed = crypto.randomBytes(32);
const keyPair = ed25519.MakeKeypair(seed);
const base58encoded = base58.encode(keyPair.publicKey);

console.log('ed25519 pub key bytes len: ' + keyPair.publicKey.length);
console.log('base58 pub key: ' + base58encoded);
console.log('base58 pub key len: ' + base58encoded.length);
console.log('actual key: edpktx799pgw7M4z8551URER52VcENNCSZwE9f9cst4v6h5vCrQmJE');
console.log('actual key len: ' + 'edpktx799pgw7M4z8551URER52VcENNCSZwE9f9cst4v6h5vCrQmJE'.length);

It prints:

ed25519 pub key bytes len: 32
base58 pub key: 6jRoreKb7RXAQZBuKZs7WDzsFHHrg62GkMmkXuiWqtKm
base58 pub key len: 44
actual key: edpktx799pgw7M4z8551URER52VcENNCSZwE9f9cst4v6h5vCrQmJE
actual key len: 54

A base58 string that I got is 10 characters shorter than an actual Tezos public key. This, and also that topic suggests I need to prefix my ed25519 data with some magical bytes before encoding it with base58. What are those magical bytes? Is there a documentation about that?

Thanks.

---

EDIT after Arthur B's answer:

I tried appending prefix bytes: \013\015\037\217 to ed25519 bytes before base58 encoding them. Still, I got 49 characters when a real Tezos public key has 54 characters. After appending additional 4 random bytes, I got desired 54 chars and a value that starts with edpk. Clearly this means that prefix is correct - but where do I get remaining 4 bytes from?

---

EDIT after discussion in comments:

4 bytes were missing due to me using base58 instead of base58check that has additional 4 bytes as a checksum. After using base58check I got 55 bytes starting with 1edpk - so something looking like a valid public Tezos address prepended with a 1 .

Current problem is: when working with the key (specifically - computing its hash) I removed a leading 1 and got 54 characters. As a result, a library I'm using to hash a key threw an Invalid checksum error. Clearly, 1 is a part of base58check checksum. Still, if not removed the key is going to have an invalid prefix. An updated code sample looks like this:

const realKey = 'edpktx799pgw7M4z8551URER52VcENNCSZwE9f9cst4v6h5vCrQmJE';
const seed = crypto.randomBytes(32);
const keyPair = ed25519.MakeKeypair(seed);
const directPubKeyBytes = keyPair.publicKey;

const tezosPublicKeyPrefix = Buffer.from([13, 15, 37, 217]);
const prefixedPublicKey = Buffer.concat([tezosPublicKeyPrefix, directPubKeyBytes]);
const base58checkEncoded = base58check.encode(prefixedPublicKey).substr(1);

console.log('ed25519 pub key bytes len: ' + prefixedPublicKey.length);
console.log('base58 pub key: ' + base58checkEncoded);
console.log('base58 pub key len: ' + base58checkEncoded.length);
console.log('actual key len: ' + realKey.length);

const publicKey = new Key({ key: base58checkEncoded });
await publicKey.ready;
return publicKey.publicKeyHash();

It prints:

ed25519 pub key bytes len: 36
base58 pub key: edpkvCRxvpVG6FYAevL5Kqf4cQhaVAdyovGqrSCezHhNnav5BwjhuZ
base58 pub key len: 54
actual key len: 54
(node:12395) UnhandledPromiseRejectionWarning: Error: Invalid checksum
    at Object.decode (/home/kspisacki/coding/wallets/node_modules/bs58check/base.js:41:25)
    at Object.b58cdecode (/home/kspisacki/coding/wallets/node_modules/sotez/dist/node/index.js:1:12743)
    at z.<anonymous> (/home/kspisacki/coding/wallets/node_modules/sotez/dist/node/index.js:1:15122)
    at Generator.next (<anonymous>)
    at o (/home/kspisacki/coding/wallets/node_modules/sotez/dist/node/index.js:1:13324)

Any further help with that would be greatly appreciated as I don't understand how to get this to work despite reading up A LOT on the topic ;)

Answer 1

You can find those bytes at the bottom of this file

https://gitlab.com/tezos/tezos/blob/master/src/lib_crypto/base58.ml

In your case, "\013\015\037\217"