(Node.js) How to Generate an Elliptic Curve Shared Secret

Demonstrates how to generate an ECC (Elliptic Curve Cryptography) shared secret. Imagine a cilent has one ECC private key, the server has another. A shared secret is computed by each side providing it's public key to the other. The private keys are kept private.

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() {

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example includes both client-side and server-side code.
    // Each code segment is marked as client-side or server-side.
    // Imagine these segments are running on separate computers...

    var success;

    // -----------------------------------------------------------------
    // (Client-Side) Generate an ECC key, save the public part to a file.
    // -----------------------------------------------------------------
    var prngClient = new chilkat.Prng();
    var eccClient = new chilkat.Ecc();
    // privKeyClient: PrivateKey
    var privKeyClient = eccClient.GenEccKey("secp256r1",prngClient);
    if (eccClient.LastMethodSuccess !== true) {
        console.log(eccClient.LastErrorText);
        return;
    }

    // pubKeyClient: PublicKey
    var pubKeyClient = privKeyClient.GetPublicKey();
    pubKeyClient.SavePemFile(false,"qa_output/eccClientPub.pem");

    // -----------------------------------------------------------------
    // (Server-Side) Generate an ECC key, save the public part to a file.
    // -----------------------------------------------------------------
    var prngServer = new chilkat.Prng();
    var eccServer = new chilkat.Ecc();
    // privKeyServer: PrivateKey
    var privKeyServer = eccServer.GenEccKey("secp256r1",prngServer);
    if (eccServer.LastMethodSuccess !== true) {
        console.log(eccServer.LastErrorText);
        return;
    }

    // pubKeyServer: PublicKey
    var pubKeyServer = privKeyServer.GetPublicKey();
    pubKeyServer.SavePemFile(false,"qa_output/eccServerPub.pem");

    // -----------------------------------------------------------------
    // (Client-Side) Generate the shared secret using our private key, and the other's public key.
    // -----------------------------------------------------------------

    // Imagine that the server sent the public key PEM to the client.
    // (This is simulated by loading the server's public key from the file.
    var pubKeyFromServer = new chilkat.PublicKey();
    pubKeyFromServer.LoadFromFile("qa_output/eccServerPub.pem");
    var sharedSecret1 = eccClient.SharedSecretENC(privKeyClient,pubKeyFromServer,"base64");

    // -----------------------------------------------------------------
    // (Server-Side) Generate the shared secret using our private key, and the other's public key.
    // -----------------------------------------------------------------

    // Imagine that the client sent the public key PEM to the server.
    // (This is simulated by loading the client's public key from the file.
    var pubKeyFromClient = new chilkat.PublicKey();
    pubKeyFromClient.LoadFromFile("qa_output/eccClientPub.pem");
    var sharedSecret2 = eccServer.SharedSecretENC(privKeyServer,pubKeyFromClient,"base64");

    // ---------------------------------------------------------
    // Examine the shared secrets.  They should be the same.
    // Both sides now have a secret that only they know.
    // ---------------------------------------------------------
    console.log(sharedSecret1);
    console.log(sharedSecret2);

}

chilkatExample();