Nodejs Generate a keys to sign a piece of data - node.js

Question

I have some blob data for example:
const buffer = Buffer.from('ACDFF12BA','hex');
How I can generate keys in order to sign it?

Answer 1

One way to do that is by using the keypair npm package:
const keypair = require('keypair');
const crypto = require('crypto');
const pair = keypair();
// Create Transmitted Signature
const sign = crypto.createSign('RSA-SHA256');
sign.update('abcdef'); // data from your file would go here
const sig = sign.sign(pair.private, 'hex');
console.log(sig);
// Verifying Signature
const verify = crypto.createVerify('RSA-SHA256');
verify.write('abcdef');
verify.end();
console.log(verify.verify(pair.public, sig,'hex'));
As you can see using the keypair() function I generate the public and the private keys via a sign.sign I generate the signature. Keep in mind to sign with a Private Key. The generated the public key in the following format:
--- RSA BEGIN PUBLIC KEY ---
^some base64 here^
--- RSA END PUBLIC KEY ---
And the generated private key will have the same format:
--- RSA BEGIN PRIVATE KEY ---
^some base64 here^
--- RSA END PRIVATE KEY ---
Now the only thing to do is to stringify the buffer as a hex string and do the job. Keep in mind that the receiving end needs to verify the data as hex string as well.
We can verify the signature with the verify.verify and a public key. Keep in mind on the signature's format as well. In case you generate a hex encoded signature then verify it in the same format.
Also the methodology above is recommended when the native crypto.generateKeyPair is not available (eg. in electron applications)