const crypto = require('crypto');
const fs = require('fs');

//Calculate the signature of the test.txt file.
//const buffer = fs.readFileSync('test.txt');

//Calculate the signature of the string "your content 12345".
const buffer = Buffer.from('your content 12345', 'utf8');    

// The content of the private key used for encryption should be...
//-----BEGIN RSA PRIVATE KEY-----
//        Private key content.
//-----END RSA PRIVATE KEY-----
// Read the private key.
const privateKey = fs.readFileSync('mytproof.key');

// Convert the private key to KeyObject.
const keyObject = crypto.createPrivateKey(privateKey);

// Sign the buffer using the private key.
const signature = crypto.sign('sha256', buffer, { key: keyObject, padding: crypto.constants.RSA_PKCS1_PADDING });

// Display the obtained signature value (displayed in hex format with 512 characters)
console.log(signature.toString('hex'));