(Android™) RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256.

Note: This example requires Chilkat v9.5.0.67 or greater.

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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);

    // This example requires the Chilkat Crypt API to have been previously unlocked.
    // See Unlock Chilkat Crypt for sample code.

    CkCrypt2 crypt = new CkCrypt2();

    // Get a digital certificate with private key from a .pfx
    // (Chilkat has many different ways to provide a cert + private key for siging.
    // Using a PFX is just one possible option.)
    CkPfx pfx = new CkPfx();
    boolean success = pfx.LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD");
    if (success != true) {
        Log.i(TAG, pfx.lastErrorText());
        return;
        }

    // Get the certificate to be used for signing.
    // (The typical case for a PFX is that it contains a cert with an associated private key,
    // as well as other certificates in the chain of authentication.  The cert with the private
    // key should be in the first position at index 0.)
    CkCert cert = pfx.GetCert(0);
    if (pfx.get_LastMethodSuccess() != true) {
        Log.i(TAG, pfx.lastErrorText());
        return;
        }

    crypt.SetSigningCert(cert);

    // Indicate that RSASSA-PSS with SHA256 should be used.
    crypt.put_SigningAlg("pss");
    crypt.put_HashAlgorithm("sha256");

    crypt.put_EncodingMode("base64");

    // Sign a string and return the base64 PKCS7 detached signature
    String originalText = "This is a test";
    String pkcs7sig = crypt.signStringENC(originalText);
    Log.i(TAG, "Detached Signature:");
    Log.i(TAG, pkcs7sig);

    // This signature looks like this:
    // MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

    // The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
    // then copy-and-paste the Base64 signature into the form and decode..

    // The signature can be verified against the original data like this:
    success = crypt.VerifyStringENC(originalText,pkcs7sig);
    Log.i(TAG, "Signature verified: " + String.valueOf(success));
    success = crypt.VerifyStringENC("Not the original text",pkcs7sig);
    Log.i(TAG, "Signature verified: " + String.valueOf(success));

    // Now we'll create an opaque signature (the opposite of a detached signature). 
    // An opaque signature is a PKCS7 message that contains both the original data and
    // the signature.  The verification process extracts the original data.
    String opaqueSig = crypt.opaqueSignStringENC(originalText);
    Log.i(TAG, "Opaque Signature:");
    Log.i(TAG, opaqueSig);

    // The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
    // then copy-and-paste the Base64 signature into the form and decode..

    // We can verify and extract the original data:
    String origTxt = crypt.opaqueVerifyStringENC(opaqueSig);
    if (crypt.get_LastMethodSuccess() != true) {
        Log.i(TAG, "Signature verification failed.");
        Log.i(TAG, crypt.lastErrorText());

        return;
        }

    Log.i(TAG, "Signature verified.");
    Log.i(TAG, "Extracted text:" + origTxt);


  }

  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."
  }
}