(Android™) Verify XML Digital Signature with an RSA Key

This example demonstrates how to verify an XML signature, where the RSA public key is embedded in the KeyInfo part of the Signature. When this is the case, nothing external is needed to verify the signature.

This example requires Chilkat v9.5.0.69 or greater.

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);

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

    // The signed XML to be verified in this example contains the following:

    // <?xml version="1.0" encoding="UTF-8"?>
    // <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
    // <SignedInfo>
    //   <CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315" />
    //   <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
    //   <Reference URI="#object">
    //     <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
    //     <DigestValue>OPnpF/ZNLDxJ/I+1F3iHhlmSwgo=</DigestValue>
    //   </Reference>
    // </SignedInfo>
    // <SignatureValue>nihUFQg4mDhLgecvhIcKb9Gz8VRTOlw+adiZOBBXgK4JodEe5aFfCqm8WcRIT8GLLXSk8PsUP4//SsKqUBQkpotcAqQAhtz2v9kCWdoUDnAOtFZkd/CnsZ1sge0ndha40wWDV+nOWyJxkYgicvB8POYtSmldLLepPGMz+J7/Uws=</SignatureValue>
    // <KeyInfo>
    //   <KeyValue>
    //     <RSAKeyValue><Modulus>4IlzOY3Y9fXoh3Y5f06wBbtTg94Pt6vcfcd1KQ0FLm0S36aGJtTSb6pYKfyX7PqCUQ8wgL6xUJ5GRPEsu9gyz8ZobwfZsGCsvu40CWoT9fcFBZPfXro1Vtlh/xl/yYHm+Gzqh0Bw76xtLHSfLfpVOrmZdwKmSFKMTvNXOFd0V18=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>
    //   </KeyValue>
    // </KeyInfo>
    // <Object Id="object">some text
    //   with spaces and CR-LF.</Object>
    // </Signature>

    // The above XML is available at https://www.chilkatsoft.com/exampleData/signedSample1.xml
    // Fetch the XML and then verify it..

    String url = "https://www.chilkatsoft.com/exampleData/signedSample1.xml";
    CkHttp http = new CkHttp();
    CkStringBuilder sbXml = new CkStringBuilder();
    boolean success = http.QuickGetSb(url,sbXml);
    if (success != true) {
        Log.i(TAG, http.lastErrorText());
        return;
        }

    CkXmlDSig dsig = new CkXmlDSig();

    // First load the XML containing the signatures to be verified.
    // Note that this particular Signature already contains the RSA public key that will be used
    // for verification.
    success = dsig.LoadSignatureSb(sbXml);
    if (success != true) {
        Log.i(TAG, dsig.lastErrorText());
        return;
        }

    // The XML in this example contains only 1 signature.
    // It's possible that an XML document can contain multiple signatures.
    // Each can be verified as follows:
    int i = 0;
    while (i < dsig.get_NumSignatures()) {
        // Select the Nth signature by setting the Selector property.
        dsig.put_Selector(i);

        // The bVerifyReferenceDigests argument determines if we want
        // to also verify each reference digest.  If set to false,
        // then only the SignedInfo part of the Signature is verified.
        boolean bVerifyReferenceDigests = true;
        boolean bVerified = dsig.VerifySignature(bVerifyReferenceDigests);
        Log.i(TAG, "Signature " + String.valueOf(i + 1) + " verified = " + String.valueOf(bVerified));

        i = i + 1;
        }


  }

  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."
  }
}