(Android™) Decrypt S/MIME and Verify S/MIME Signatures

Android™ example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting.

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.

    CkMime mime = new CkMime();

    // Load an S/MIME message from a file:
    boolean success = mime.LoadMimeFile("signedMime.txt");
    if (success != true) {
        Log.i(TAG, mime.lastErrorText());
        return;
        }

    // The ContainsEncryptedParts/ContainsSignedParts methods
    // can be called to determine if the MIME is encrypted and/or signed:
    boolean isEncrypted = mime.ContainsEncryptedParts();
    boolean isSigned = mime.ContainsSignedParts();

    // We don't want the "unwrap extras".  You'll see what those
    // are in a few moments...
    mime.put_UnwrapExtras(false);

    // To verify the signature, call UnwrapSecurity.  This will
    // verify the signature(s) and decrypt the S/MIME and restore
    // the MIME to the unsigned/unencrypted state.
    // The results of what was found are present in the MIME object's
    // properties, as well as extra header fields that are added
    // to the unwrapped MIME.
    success = mime.UnwrapSecurity();
    if (success != true) {
        // UnwrapSecurity returns true if all signatures were
        // verified and all parts decrypted.
        Log.i(TAG, mime.lastErrorText());
        return;
        }

    // The mime.UnwrapExtras property controls whether or not
    // these additional fields are added to the unwrapped MIME:
    // 
    // X-NumPartsSigned: 1
    // X-SignaturesValid: yes
    // X-NumPartsEncrypted: 1
    // X-Decrypted: no
    // 
    // The X-NumPartsSigned/X-SignaturesValid headers are added
    // if the MIME was signed.  
    // 
    // The X-NumPartsEncrypted/X-Decrypted headers are added
    // if the MIME was encrypted.
    // 

    // If the MIME was signed, get the certificate used for signing.
    if (isSigned == true) {
        // The NumSignerCerts property indicates how many certificates
        // were used for signing.  This example will assume the value is 1.
        // To get the 1st signer cert, call GetSignerCert with an index of 0:
        CkCert signerCert = mime.GetSignerCert(0);
        if (mime.get_LastMethodSuccess() == true) {
            Log.i(TAG, "**** Signer Cert: " + signerCert.subjectCN());

            }

        }

    // If the MIME was encrypted, get the certificate used for encryption:
    if (isEncrypted == true) {
        // The NumEncryptCerts property indicates how many certificates
        // were used for encrypting.  This example will assume the value is 1.
        // To get the 1st encrypt cert, call GetEncryptCert with an index of 0:
        CkCert encryptCert = mime.GetEncryptCert(0);
        if (mime.get_LastMethodSuccess() == true) {
            Log.i(TAG, "**** Encrypt Cert: " + encryptCert.subjectCN());

            }

        }

    // Display the unwrapped MIME:
    Log.i(TAG, mime.getMime());

    // Save the unwrapped MIME to a file:
    success = mime.SaveMime("unwrappedMime.txt");

  }

  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."
  }
}