Android™

Verify Opaque Signature and Retrieve Signing Certificates

See more Digital Signatures Examples

Demonstrates how to verify a PCKS7 opaque digital signature (signed data), extract the original file/data, and then extract the certificate(s) that were used to sign. 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.

    CkCrypt2 crypt = new CkCrypt2();

    // Verify a PKCS7 signed-data (opaque signature) file and extract the original content to a file.
    success = crypt.VerifyP7M("qa_data/p7m/opaqueSig.p7","qa_output/originalData.dat");
    if (success == false) {
        Log.i(TAG, crypt.lastErrorText());
        return;
        }

    // Alternatively, we can do it in memory...
    CkBinData binData = new CkBinData();
    success = binData.LoadFile("qa_data/p7m/opaqueSig.p7");
    // Your app should check for success, but we'll skip the check for brevity..

    // If verified, the signature is unwrapped and binData is replaced with the original data that was signed.
    success = crypt.OpaqueVerifyBd(binData);
    if (success == false) {
        Log.i(TAG, crypt.lastErrorText());
        return;
        }

    // For our testing, we signed some text, so we can get it from the binData..
    Log.i(TAG, "Original Data:");
    Log.i(TAG, binData.getString("utf-8"));

    // After any method call that verifies a signature, the crypt object will contain the certificate(s)
    // that were used for signing (assuming the X.509 certs were available in the signature, which is typically the case).

    // Get each signing certificate, and build the certificate chain for each.
    CkCert cert = new CkCert();
    CkCertChain certChain = new CkCertChain();
    int numCerts = crypt.get_NumSignerCerts();
    int i = 0;
    while (i < numCerts) {
        crypt.LastSignerCert(i,cert);
        Log.i(TAG, cert.subjectDN());

        success = cert.BuildCertChain(certChain);
        if (success == false) {
            Log.i(TAG, cert.lastErrorText());
            return;
            }

        i = i + 1;
        }


  }

  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."
  }
}