(Node.js) Convert RSA Private Key to Public Key

Demonstrates how to get a public RSA key from a private RSA key.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

    var key = new chilkat.PrivateKey();

    // Step 1: Load the private key from a source.
    // (Chilkat can load private keys from all types of formats, and from in-memory bytes or encoded strings.
    // see the online reference documentation for more options.)
    var success = key.LoadPemFile("qa_data/pem/VP_Private.pem");
    if (success !== true) {
        console.log(key.LastErrorText);
        return;
    }

    // Step 2: Get the public key object from the private key object.
    // pubKey: PublicKey
    var pubKey = key.GetPublicKey();
    if (key.LastMethodSuccess !== true) {
        console.log(key.LastErrorText);
        return;
    }

    // Step 3: Save the public key in a desired format. 
    // (Chilkat can load or save public and private keys in many different formats.  See
    // the online reference documentation for more options.)

    // Saves to a PKCS8 PEM file.
    var bPreferPkcs1 = false;
    success = pubKey.SavePemFile(bPreferPkcs1,"qa_data/pem/VP_Public.pem");
    if (pubKey.LastMethodSuccess !== true) {
        console.log(pubKey.LastErrorText);
        return;
    }

    console.log("Extracted and saved public key from private key.");

}

chilkatExample();