(Android™) RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

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Demonstrates how RSA sign the utf-8 byte representation of a string to get the signature in base64 format.

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);

    // Assuming the smartcard/USB token is installed with the correct drivers from the manufacturer,
    // this code can work on multiple platforms including Windows, MacOS, Linux, and iOS.

    // Chilkat automatically detects and determines the way in which the HSM is used,
    // which can be by PKCS11, Apple Keychain, Microsoft CNG / Crypto API, or ScMinidriver.

    CkCert cert = new CkCert();

    // Set the token/smartcard PIN prior to loading.
    cert.put_SmartCardPin("123456");

    // Specify the certificate by its common name.
    boolean success = cert.LoadFromSmartcard("cn=chilkat-rsa-2048");
    if (success == false) {
        Log.i(TAG, cert.lastErrorText());
        return;
        }

    Log.i(TAG, "Signing with cert: " + cert.subjectCN());

    // Create a string to be hashed and signed.
    CkStringBuilder sb = new CkStringBuilder();
    boolean crlfLineEnding = true;
    int i;
    for (i = 0; i <= 10; i++) {
        sb.AppendLine("This is a test.",crlfLineEnding);
        }

    CkRsa rsa = new CkRsa();

    // Use the certificate's private key for signing.
    success = rsa.SetX509Cert(cert,true);
    if (success == false) {
        Log.i(TAG, rsa.lastErrorText());
        return;
        }

    // Sign the SHA-256 hash of the utf-8 byte representation of the contents of sb
    // Return the signature in base64 format.
    rsa.put_EncodingMode("base64");
    rsa.put_Charset("utf-8");
    String stringToSign = sb.getAsString();
    String sigBase64 = rsa.signStringENC(stringToSign,"sha256");
    if (rsa.get_LastMethodSuccess() == false) {
        Log.i(TAG, rsa.lastErrorText());
        return;
        }

    Log.i(TAG, "RSA signature as base64: " + sigBase64);

  }

  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."
  }
}