(Android™) ECDSA Sign Data and Verify Signature

Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// 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);

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

    // To create an ECDSA signature, the data first needs to be hashed.  Then the hash
    // is signed.

    // Use Chilkat Crypt2 to generate a hash for any of the following
    // hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

    CkCrypt2 crypt = new CkCrypt2();
    crypt.put_HashAlgorithm("SHA256");
    crypt.put_Charset("utf-8");
    crypt.put_EncodingMode("base64");

    // Hash a string.
    String hash1 = crypt.hashStringENC("The quick brown fox jumps over the lazy dog");
    Log.i(TAG, "hash1 = " + hash1);

    // Or hash a file..
    String hash2 = crypt.hashFileENC("qa_data/hamlet.xml");
    Log.i(TAG, "hash2 = " + hash2);

    // (The Crypt2 API provides many other ways to hash data..)

    // -----------------------------------------------------------
    // An ECDSA private key is used for signing.  The public key is for signature verification.
    // Load our ECC private key.
    // Our private key file contains this:

    // 	// -----BEGIN PRIVATE KEY-----
    // 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
    // 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
    // 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
    // 	-----END PRIVATE KEY-----

    CkPrivateKey privKey = new CkPrivateKey();
    boolean success = privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem");
    if (success != true) {
        Log.i(TAG, privKey.lastErrorText());
        return;
        }

    // We'll need a PRNG source for random number generation.
    // Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
    CkPrng prng = new CkPrng();

    // Sign the hash..
    CkEcc ecdsa = new CkEcc();
    String ecdsaSigBase64 = ecdsa.signHashENC(hash1,"base64",privKey,prng);
    if (ecdsa.get_LastMethodSuccess() != true) {
        Log.i(TAG, ecdsa.lastErrorText());
        return;
        }

    Log.i(TAG, "ECDSA signature = " + ecdsaSigBase64);

    // -----------------------------------------------------------
    // Now let's verify the signature using the public key.

    CkPublicKey pubKey = new CkPublicKey();
    success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pubkey.pem");
    if (success != true) {
        Log.i(TAG, pubKey.lastErrorText());
        return;
        }

    int result = ecdsa.VerifyHashENC(hash1,ecdsaSigBase64,"base64",pubKey);
    if (result == 1) {
        Log.i(TAG, "Signature is valid.");
        return;
        }

    if (result == 0) {
        Log.i(TAG, "Signature is invalid.");
        return;
        }

    if (result < 0) {
        Log.i(TAG, ecdsa.lastErrorText());
        Log.i(TAG, "The VerifyHashENC method call failed.");
        return;
        }


  }

  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."
  }
}