Android™

ECDSA Sign and Verify Data using Different Hash Algorithms

See more ECC Examples

Demonstrates how to create ECDSA signatures on data using different hash algorithms.

Note: This example requires Chilkat v9.5.0.85 or greater because the SignBd and VerifyBd methods were added in v9.5.0.85.

Android™

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    boolean success = false;

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

    // First load an ECDSA private key to be used for signing.
    CkPrivateKey privKey = new CkPrivateKey();
    success = privKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret");
    if (success == false) {
        Log.i(TAG, privKey.lastErrorText());
        return;
        }

    // Load some data to be signed.
    CkBinData bd = new CkBinData();
    success = bd.LoadFile("qa_data/hamlet.xml");
    if (success == false) {
        Log.i(TAG, "Failed to load file to be hashed.");
        return;
        }

    CkEcc ecdsa = new CkEcc();
    CkPrng prng = new CkPrng();

    // Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
    Log.i(TAG, "ECDSA signing the sha256 hash of the data...");
    String sig = ecdsa.signBd(bd,"sha256","base64",privKey,prng);
    Log.i(TAG, "sig = " + sig);

    // Verify the signature against the original data.
    // (We must use the same hash algorithm that was used when signing.)

    // Load the public key that corresponds to the private key used for signing.
    CkPublicKey pubKey = new CkPublicKey();
    success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem");
    if (success == false) {
        Log.i(TAG, pubKey.lastErrorText());
        return;
        }

    CkEcc ecc2 = new CkEcc();
    int result = ecc2.VerifyBd(bd,"sha256",sig,"base64",pubKey);
    if (result != 1) {
        Log.i(TAG, ecc2.lastErrorText());
        return;
        }

    Log.i(TAG, "Verified!");

    // ----------------------------------------------------------------------------------------
    // Let's do the same thing, but with sha384 hashing...

    Log.i(TAG, "--------------------------------------------");
    Log.i(TAG, "ECDSA signing the sha384 hash of the data...");

    sig = ecdsa.signBd(bd,"sha384","base64",privKey,prng);
    Log.i(TAG, "sig = " + sig);

    result = ecc2.VerifyBd(bd,"sha384",sig,"base64",pubKey);
    if (result != 1) {
        Log.i(TAG, ecc2.lastErrorText());
        return;
        }

    Log.i(TAG, "Verified!");

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}