(Android™) Encrypt a file to a PKCS7 encrypted message using multiple certificates from different users

Demonstrates how to encrypt a file to a PKCS7 encrypted message using multiple certificates from different users. Any one of the users can decrypt using his/her own certificate + private key.

Note: When doing public key encryption, it is the public key that is used to encrypt. The private key is required for decryption.

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 Crypt API to have been previously unlocked.
    //  See Unlock Chilkat Crypt for sample code.

    CkCrypt2 crypt = new CkCrypt2();

    //  Tell the crypt object to use 3 certificates.
    //  Do this by calling AddEncryptCert for each certificate.

    //  Load a digital certificate.
    //  We don't need the private key for encryption.
    //  Only the public key is needed (which is included in a certificate).
    CkCert cert1 = new CkCert();
    boolean success = cert1.LoadFromFile("qa_data/user1/cert_user1.pem");
    //  Assume success for the example, but make sure your application checks for success/failure...
    crypt.AddEncryptCert(cert1);

    CkCert cert2 = new CkCert();
    success = cert2.LoadFromFile("qa_data/user2/cert_user2.pem");
    crypt.AddEncryptCert(cert2);

    CkCert cert3 = new CkCert();
    success = cert3.LoadFromFile("qa_data/user3/cert_user3.pem");
    crypt.AddEncryptCert(cert3);

    //  Indicate that we want PKI encryption (i.e. public-key infrastructure)
    //  to produce a CMS message (Cryptographic Message Syntax/PKCS7),
    //  that is be created with RSAES-OAEP padding, SHA256, and AES-128 for the
    //  bulk encryption.
    crypt.put_CryptAlgorithm("pki");
    crypt.put_Pkcs7CryptAlg("aes");
    crypt.put_KeyLength(128);
    crypt.put_OaepHash("sha256");
    crypt.put_OaepPadding(true);

    //  Load the file to be encrypted...
    CkBinData fileData = new CkBinData();
    success = fileData.LoadFile("qa_data/jpg/penguins.jpg");
    //  Your app should check for success/failure..

    //  Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
    success = crypt.EncryptBd(fileData);
    if (success != true) {
        Log.i(TAG, crypt.lastErrorText());
        return;
        }

    //  Save the PKCS7 encrypted message to a file..
    success = fileData.WriteFile("qa_output/pkcs7_encrypted.p7");

    //  Now indicate that the PKCS7 output is to be returned in the base64 encoding.
    crypt.put_EncodingMode("base64");

    Log.i(TAG, "OK.");

  }

  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."
  }
}