Java

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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Chilkat2 Java

import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Dkim;

public class ChilkatExample {

    public static void main(String[] args) {
        // 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.

        Dkim dkim = new Dkim();

        // 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.
        try {
            dkim.prefetchPublicKey("myselector", "example.com");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Public key prefetched from DNS and cached.");
    }
}