Android™

Compute a Public Key's JWK Thumbprint

Demonstrates the Chilkat PublicKey.GetJwkThumbprint method, which returns the RFC 7638 JWK thumbprint for the public key. The only argument is the hash algorithm (for example sha256).

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: A JWK thumbprint is a canonical hash of the key's public parameters — a compact fingerprint that identifies the key regardless of formatting. It is the standard way to derive a stable key ID (kid) and to check whether two representations are the same key. Chilkat builds the required canonical JSON, hashes it with the named algorithm, and returns the result.

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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;

    //  Load a public key to export.  LoadFromFile inspects the content, so it accepts DER, PEM, XML,
    //  JWK, and other supported representations.
    CkPublicKey pubKey = new CkPublicKey();
    success = pubKey.LoadFromFile("qa_data/public.pem");
    if (success == false) {
        Log.i(TAG, pubKey.lastErrorText());
        return;
        }

    //  Compute the RFC 7638 JWK thumbprint of the public key using the named hash algorithm.  Common
    //  values include "sha256".
    String thumbprint = pubKey.getJwkThumbprint("sha256");
    if (pubKey.get_LastMethodSuccess() == false) {
        Log.i(TAG, pubKey.lastErrorText());
        return;
        }

    Log.i(TAG, "JWK thumbprint: " + thumbprint);

  }

  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."
  }
}