Android™

Set the OAEP Hash Algorithm for Encrypted Email

Demonstrates the Chilkat Email.OaepHash property, which selects the hash algorithm used by OAEP padding when encrypting email with RSAES-OAEP. Valid values are sha1, sha256, sha384, and sha512; the default is sha256. This property is used only when OaepPadding is true, so this example enables OAEP first.

Background: OAEP ("Optimal Asymmetric Encryption Padding") uses a hash function internally as part of the randomized padding it wraps around the data before RSA encryption. The choice of hash affects security and, importantly, interoperability: the sender and recipient must use the same OAEP hash, or decryption fails. That is why this is exposed as an explicit setting rather than left implicit.

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// 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);

    //  Demonstrates the Email.OaepHash property, which selects the hash algorithm used by
    //  OAEP padding when encrypting email with RSAES-OAEP.  Valid values: sha1, sha256,
    //  sha384, sha512.  The default is sha256.  It is used only when OaepPadding is true.

    CkEmail email = new CkEmail();
    email.put_Subject("Encrypted with RSAES-OAEP");

    //  OAEP padding must be enabled for the OAEP hash to take effect.
    email.put_OaepPadding(true);
    email.put_OaepHash("sha256");

    Log.i(TAG, "OaepHash = " + email.oaepHash());

  }

  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."
  }
}