Dart Requires Chilkat v11.0.0+

How to Generate an Elliptic Curve Shared Secret

See more ECC Examples

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. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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...

  // -----------------------------------------------------------------
  // (Client-Side) Generate an ECC key, save the public part to a file.
  // -----------------------------------------------------------------
  final prngClient = CkPrng();
  final eccClient = CkEcc();
  final privKeyClient = CkPrivateKey();
  try {
    eccClient.genKey('secp256r1', prngClient, privKeyClient);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final pubKeyClient = CkPublicKey();
  privKeyClient.toPublicKey(pubKeyClient);
  pubKeyClient.savePemFile(false, 'qa_output/eccClientPub.pem');

  // -----------------------------------------------------------------
  // (Server-Side) Generate an ECC key, save the public part to a file.
  // -----------------------------------------------------------------
  final prngServer = CkPrng();
  final eccServer = CkEcc();
  final privKeyServer = CkPrivateKey();
  eccServer.genKey('secp256r1', prngServer, privKeyServer);

  final pubKeyServer = CkPublicKey();
  privKeyServer.toPublicKey(pubKeyServer);
  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.
  final pubKeyFromServer = CkPublicKey();
  pubKeyFromServer.loadFromFile('qa_output/eccServerPub.pem');
  final 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.
  final pubKeyFromClient = CkPublicKey();
  pubKeyFromClient.loadFromFile('qa_output/eccClientPub.pem');
  final 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.
  // ---------------------------------------------------------
  print(sharedSecret1);
  print(sharedSecret2);
}