Changing a Private Ethereum Key into a PEM or HMAC algorithm in NodeJS

Question

I have a private key, which is:

0x66228b427f07b168c7cb1380aa5554403b9e24bf935a9364c89711a306a23ddb

NOTE: The Original Key was the Public Key when the question was posted: 0x6a2043113D5640F9F50dC593D0DcD8CC1c970EB1
I generated it randomly for this question, so don't worry that it's public on the Internet.

I want to use it as the encryption scheme for a JWT token, using the ES256 algorithm.

To get it into my library, I have to have it in one these formats.

secretOrPrivateKey is a string, buffer, or object containing either the secret for HMAC algorithms or the PEM encoded private key for RSA and ECDSA. In case of a private key with passphrase an object { key, passphrase } can be used (based on crypto documentation), in this case be sure you pass the algorithm option.

Is there any easy way to move the hex value to one of these formats? Or, will this not work because I'm not understanding the difference between an Ethereum Private key and a ES256?

Answer 1

Etherium keys are actually ES256K and not ES256 so in this case it might not be possible.

If you need to turn the key in PEM in NodeJS there is a library called key-encoder for this specific purpose. Which can be accomplished with the following code.

var KeyEncoder = require('key-encoder');
console.log(KeyEncoder.default);
let keyEncoder = new KeyEncoder.default('secp256k1')

var pemPrivateKey = keyEncoder.encodePrivate('0x66228b427f07b168c7cb1380aa5554403b9e24bf935a9364c89711a306a23ddb', 'raw', 'pem')
console.log(pemPrivateKey);