Android™

Prefetch a DKIM Public Key from DNS

Demonstrates the Chilkat Dkim.PrefetchPublicKey method, which retrieves a DKIM public key from DNS and caches it for a specific selector and domain. The arguments are the selector and the domain. The TXT lookup is made at selector._domainkey.domain.

Background: DkimVerify already fetches the key from DNS on demand, so prefetching is about when the lookup happens: doing it up front lets you separate a potentially slow network step from the verification itself, warm the cache before a batch of messages from the same domain, or confirm the key is publishable before relying on it. After a successful prefetch, verification of a matching signature uses the cached key with no further DNS traffic.

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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;

    //  Demonstrates the Dkim.PrefetchPublicKey method, which retrieves a DKIM public key from DNS and
    //  caches it for a specific selector and domain.  The 1st argument is the selector and the 2nd is
    //  the domain.

    CkDkim dkim = new CkDkim();

    //  Retrieve the public key from the DNS TXT record at selector._domainkey.domain and cache it.
    //  A later DkimVerify for the same selector and domain then uses the cached key.
    success = dkim.PrefetchPublicKey("myselector","example.com");
    if (success == false) {
        Log.i(TAG, dkim.lastErrorText());
        return;
        }

    Log.i(TAG, "Public key prefetched from DNS and cached.");

  }

  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."
  }
}