Adobe® Flex® 4 Language Reference
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flash.security 
XMLSignatureValidator 
Packageflash.security
Classpublic class XMLSignatureValidator
InheritanceXMLSignatureValidator Inheritance EventDispatcher Inheritance Object

Language Version: ActionScript 3.0
Runtime Versions: AIR 1.0

The XMLSignatureValidator class validates whether an XML signature file is well formed, unmodified, and, optionally, whether it is signed using a key linked to a trusted digital certificate.

XMLSignatureValidator implements a subset of the W3C Recommendation for XML-Signature Syntax and Processing and should not be considered a conforming implementation. The supported subset of the recommendation includes:

  • All of the core signature syntax except KeyInfo element.
  • The KeyInfo element only supports the X509Data element.
  • The X509Data element only supports the X509Certificate element.
  • The SHA256 digest method algorithm.
  • The PKCS1 signing algorithm.
  • The "Canonical XML without comments" Canonicalization Method and Transform algorithm.
  • The Manifest element in additional signature syntax.

You must provide an IURIDereferencer implementation in order to verify an XML signature. This implementation class is responsible for resolving the URIs specified in the SignedInfo elements of the signature file and returning the referenced data in an object, such as a ByteArray, that implements the IDataInput interface.

In order to verify that the signing certificate chains to a trusted certificate, either the XML signature must contain the certificates required to build the chain in X509Certificate elements, or you must supply the certificates required to build the chain using the addCertificate() method.

To verify an XMLSignature:

  1. Create an instance of the XMLSignatureValidator class.
  2. Set the uriDereferencer property of the instance to an instance of your IURIDereferencer implementation class.
  3. Supply DER-encoded certificates for building the certificate trust chain, if desired, using the addCertificate() method.
  4. Call the XMLSignatureValidator verify method, passing in the signature to be verified.
  5. Check the validityStatus property after the XMLSignatureValidator object dispatches a complete event.

About signature status:

The validity of an XML signature can be valid, invalid, or unknown. The overall status depends on the verification status of the individual components of the signature file:

  • digestStatus — The validity of the cryptographic of the signature computed over the SignedInfo element. Can be valid, invalid, or unknown.
  • identityStatus — The validity of the signing certificate. If the certificate has expired, has been revoked, or altered, the status is invalid. If the certificate cannot be chained to a trusted root certificate, the status is unknown. The certificate is not checked if the digest is invalid. If not checked, the status will be reported as unknown.
  • referencesStatus — The validity of the data addressed by the references in the SignedInfo element of the signature file. Can be valid, invalid, or unknown. The references are not checked if the digest or certificate is invalid. Reference checking can also be skipped based on the setting of the referencesValidationSetting property. If not checked, the status will be reported as unknown.

The signature validity reported by the validityStatus property can be:

  • valid — If referencesStatus, digestStatus, and identityStatus are all valid.
  • invalid — If any individual status is invalid.
  • unknown — If referencesStatus, digestStatus, or identityStatus is unknown.

Canonicalization limitations:

The XML engine in AIR does not always produce the expected XML string when canonicalizing an XML document. For this reason, it is recommended that you avoid putting inter-element whitespace in enveloped or detached signature documents and do not redefine namespaces inside a signature document. In both cases, AIR may not recreate the document with the same character sequence as the original and, therefore, validation will fail.

View the examples

See also



Public Properties
 PropertyDefined By
 Inheritedconstructor : Object
A reference to the class object or constructor function for a given object instance.
Object
  AIR-only digestStatus : String
[read-only] The validity status of the cryptographic signature computed over the SignedInfo element.
XMLSignatureValidator
  AIR-only identityStatus : String
[read-only] The validity status of the signing certificate.
XMLSignatureValidator
 Inheritedprototype : Object
[static] A reference to the prototype object of a class or function object.
Object
  AIR-only referencesStatus : String
[read-only] The validity status of the data in the references in the SignedInfo element.
XMLSignatureValidator
  AIR-only referencesValidationSetting : String
Specifies the conditions under which references are checked.
XMLSignatureValidator
  AIR-only revocationCheckSetting : String
Specifies how certificate revocation is checked.
XMLSignatureValidator
  AIR-only signerCN : String
[read-only] The Common Name field of the signing certificate.
XMLSignatureValidator
  AIR-only signerDN : String
[read-only] The Distinguished Name field of the signing certificate.
XMLSignatureValidator
  AIR-only signerExtendedKeyUsages : Array
[read-only] An array containing the Extended Key Usages OIDs listed in the signing certificate.
XMLSignatureValidator
  AIR-only signerTrustSettings : Array
[read-only] An array containing the trust settings of the signing certificate.
XMLSignatureValidator
  AIR-only uriDereferencer : IURIDereferencer
The IURIDereferencer implementation.
XMLSignatureValidator
  AIR-only useSystemTrustStore : Boolean
Specifies that certificates in the system trust store are used for chain building.
XMLSignatureValidator
  AIR-only validityStatus : String
[read-only] The validity status of a verified XML signature.
XMLSignatureValidator
Public Methods
 MethodDefined By
  
Creates an XMLSignatureValidator object.
XMLSignatureValidator
  
Adds an x509 certificate for chain building.
XMLSignatureValidator
 Inherited
addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0, useWeakReference:Boolean = false):void
Registers an event listener object with an EventDispatcher object so that the listener receives notification of an event.
EventDispatcher
 Inherited
Dispatches an event into the event flow.
EventDispatcher
 Inherited
Checks whether the EventDispatcher object has any listeners registered for a specific type of event.
EventDispatcher
 Inherited
Indicates whether an object has a specified property defined.
Object
 Inherited
Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.
Object
 Inherited
Indicates whether the specified property exists and is enumerable.
Object
 Inherited
removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void
Removes a listener from the EventDispatcher object.
EventDispatcher
 Inherited
Sets the availability of a dynamic property for loop operations.
Object
 Inherited
Returns the string representation of this object, formatted according to locale-specific conventions.
Object
 Inherited
Returns the string representation of the specified object.
Object
 Inherited
Returns the primitive value of the specified object.
Object
  
AIR-only verify(signature:XML):void
Verifies the specified signature.
XMLSignatureValidator
 Inherited
Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type.
EventDispatcher
Events
 Event Summary Defined By
 Inherited[broadcast event] Dispatched when the Flash Player or AIR application gains operating system focus and becomes active.EventDispatcher
  Dispatched when verification is complete.XMLSignatureValidator
 Inherited[broadcast event] Dispatched when the Flash Player or AIR application operating loses system focus and is becoming inactive.EventDispatcher
  Dispatched if verification cannot complete because of errors.XMLSignatureValidator
Property Detail
AIR-only 

digestStatus

property
digestStatus:String  [read-only]

Runtime Versions: AIR 1.0

The validity status of the cryptographic signature computed over the SignedInfo element.

The status is:

  • valid — If signature is cryptographically valid.
  • invalid — If the digest has been altered after signing.
  • unknown — If the verify() method has not been called.

Note: If the digestStatus is invalid, the identityStatus and referencesStatus are not checked and will be reported as unknown.



Implementation
    public function get digestStatus():String

Throws
IllegalOperationError — If accessed while a signature is being validated.
AIR-only 

identityStatus

property 
identityStatus:String  [read-only]

Runtime Versions: AIR 1.0

The validity status of the signing certificate.

The status can be:

  • valid — The certificate has not expired, has not failed a revocation check and chains to a trusted root certificate.
  • unknown — The certificate has not expired and has not failed a revocation check, but does not chain to a trusted root certificate. A status of unknown will also be reported when the status has not been verified, either because the verify() method has not been called or because the cryptographic signature of the SignedInfo element (digestStatus) is invalid.
  • invalid — The certificate has expired or fails a revocation check.

The certificates added using the addCertificate() method and the settings of the revocationCheckSetting and the useSystemTrustStore properties can change whether a certificate is considered valid.

Note: If the identityStatus is invalid, the referencesStatus is not checked and will be reported as unknown. In addition, references are not checked when the identityStatus is unknown unless the referencesValidationSetting is validOrUnknownIdentity



Implementation
    public function get identityStatus():String

Throws
IllegalOperationError — If accessed while a signature is being validated.

See also


Example  ( How to use this example )
The following example gets the result of validating the signing certificate (after a signature has been validated):
 import flash.security.XMLSignatureValidator;
 
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator();
 //validate a signature...
  
 var identityResult:String = verifier.identityStatus;
AIR-only 

referencesStatus

property 
referencesStatus:String  [read-only]

Runtime Versions: AIR 1.0

The validity status of the data in the references in the SignedInfo element.

The status can be:

  • valid — If all references are valid.
  • invalid — If any reference is invalid.
  • unknown — If not verified. References can remain unverified in the following circumstances:
    • the verify() method has not been called
    • the cryptographic signature of the SignedInfo element (digestStatus) is invalid.
    • the signing certificate (identityStatus) is invalid
    • referencesValidationSetting is validIdentity (which is the default setting) and the identityStatus of the signing certificate is unknown.
    • the referencesValidationSetting is never.

Important: External resources are not validated unless they are referenced directly in a SignedInfo element within the signature document. External resources referred to by a secondary reference are not validated. For example, if an XML signature signs a manifest element, only the integrity of the manifest element itself is verified. The files listed in the manifest are not checked.



Implementation
    public function get referencesStatus():String

Throws
IllegalOperationError — If accessed while a signature is being validated.

See also


Example  ( How to use this example )
The following example gets the result of validating the references in the signature (after a signature has been validated):
 import flash.security.XMLSignatureValidator;
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator();
 //validate a signature...
  
 var dataResult:String = verifier.referencesStatus;
AIR-only 

referencesValidationSetting

property 
referencesValidationSetting:String

Runtime Versions: AIR 1.5

Specifies the conditions under which references are checked.

Use constants defined in the ReferencesValidationSetting class to set this property. The settings include:

  • ReferencesValidationSetting.VALID_IDENTITY — Check references only if the signing certificate is valid and chains to a trusted root. This is the default setting.
  • ReferencesValidationSetting.VALID_OR_UNKNOWN_IDENTITY — Check references if the signing certificate is valid, even if it does not chain to a trusted root.
  • ReferencesValidationSetting.NEVER — Never check references.

Use the default, validIdentity, setting with signatures signed with a commercial certificate or when you supply your own certificate as a trust anchor with the addCertificate() method. This setting avoids the overhead of checking reference validity when the signed document will be rejected anyway.

Use the validOrUnknownIdentity setting with signatures signed with self-signed certificates. This setting allows you to validate that the signed data has not been altered, but does not provide any assurances about the identity of the signer.

Use the never setting to avoid the overhead of validating references when such validation is not important in the context of your application.



Implementation
    public function get referencesValidationSetting():String
    public function set referencesValidationSetting(value:String):void

Throws
IllegalOperationError — If set while a signature is being validated.
 
ArgumentError — if the setting parameter contains a value not defined in the ReferencesValidationSetting class.

See also


Example  ( How to use this example )
The following example sets the XMLSignatureValidator object to check references only if the signing certificate chains to a trust anchor:
 import flash.security.ReferencesValidationSetting;
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator(); 
 verifier.referencesValidationSetting = ReferencesValidationSetting.VALID_OR_UNKNOWN_IDENTITY;
AIR-only 

revocationCheckSetting

property 
revocationCheckSetting:String

Runtime Versions: AIR 1.0

Specifies how certificate revocation is checked.

Use constants defined in the RevocationSettings class to set this property. The settings include:

  • RevocationCheckSettings.NEVER — Do not check certificate revocation.
  • RevocationCheckSettings.BEST_EFFORT — Check certificate revocation, if revocation information is available and the revocation status can be obtained. If revocation status cannot be positively determined, the certificate is not rejected.
  • RevocationCheckSettings.REQUIRED_IF_AVAILABLE — If the certificate includes revocation information, the revocation status must be positively determined to validate the certificate.
  • RevocationCheckSettings.ALWAYS_REQUIRED — Always check certificate revocation. Certificates without revocation information are rejected.



Implementation
    public function get revocationCheckSetting():String
    public function set revocationCheckSetting(value:String):void

Throws
IllegalOperationError — If set while a signature is being validated.

See also

AIR-only 

signerCN

property 
signerCN:String  [read-only]

Runtime Versions: AIR 1.0

The Common Name field of the signing certificate.



Implementation
    public function get signerCN():String

Example  ( How to use this example )
The following example reads the common name of the signing certificate (after a signature has been validated):
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator();
 //validate a signature...
  
 var commonName:String = verifier.signerCN;
AIR-only 

signerDN

property 
signerDN:String  [read-only]

Runtime Versions: AIR 1.0

The Distinguished Name field of the signing certificate.



Implementation
    public function get signerDN():String

Example  ( How to use this example )
The following example reads the distinguished name of the signing certificate (after a signature has been validated):
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator();
 //validate a signature...
  
 var distinguishedName:String = verifier.signerDN;
AIR-only 

signerExtendedKeyUsages

property 
signerExtendedKeyUsages:Array  [read-only]

Runtime Versions: AIR 1.0

An array containing the Extended Key Usages OIDs listed in the signing certificate.

Each extended key usage is reported in numeric OID form.



Implementation
    public function get signerExtendedKeyUsages():Array

Throws
IllegalOperationError — If accessed while a signature is being validated.

Example  ( How to use this example )
The following example reads the extended key OIDs of the signing certificate (after a signature has been validated):
 import flash.security.XMLSignatureValidator;
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator();
 //validate a signature...
  
 var extendedKeyOIDs:Array = verifier.signerExtendedKeyUsages;
AIR-only 

signerTrustSettings

property 
signerTrustSettings:Array  [read-only]

Runtime Versions: AIR 1.0

An array containing the trust settings of the signing certificate.

Trust settings are derived from the system and the key usage OIDs embedded in the certificate. Constants for the strings representing the recognized trust settings are defined in the SignerTrustSettings class.

The signerTrustSettings array of an unknown or invalid certificate is empty.

Modifying the array does not change the certificate trust settings.



Implementation
    public function get signerTrustSettings():Array

Throws
IllegalOperationError — If accessed while a signature is being validated.

See also


Example  ( How to use this example )
The following example reads the trust settings of the signing certificate (after a signature has been validated):
 import flash.security.XMLSignatureValidator;
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator();
 //validate a signature...
  
 var certificateTrustedFor:Array = verifier.signerTrustSettings;
AIR-only 

uriDereferencer

property 
uriDereferencer:IURIDereferencer

Runtime Versions: AIR 1.0

The IURIDereferencer implementation.

An IURIDereferencer implementation must be provided before attempting to verify a signature.



Implementation
    public function get uriDereferencer():IURIDereferencer
    public function set uriDereferencer(value:IURIDereferencer):void

Throws
IllegalOperationError — If set while a signature is being validated.

See also


Example  ( How to use this example )
The following example creates an instance of SignedMessageDereferencer, which implements the IURIDereferencer interface, and sets it as the dereferencer to use for signature validation:
 import com.example.SignedMessageDereferencer; //A custom class implementing IURIDereferencer
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator(); 
 verifier.uriDereferencer = new SignedMessageDereferencer();
AIR-only 

useSystemTrustStore

property 
useSystemTrustStore:Boolean

Runtime Versions: AIR 1.0

Specifies that certificates in the system trust store are used for chain building.

If true, then the trust anchors in the system trust store are used as trusted roots. The system trust store is not used by default.



Implementation
    public function get useSystemTrustStore():Boolean
    public function set useSystemTrustStore(value:Boolean):void

Throws
IllegalOperationError — If set while a signature is being validated.

Example  ( How to use this example )
The following example creates an XMLSignatureValidator instance and sets it to use the system repository of trusted certificates when validating an XML signature:
 var verifier:XMLSignatureValidator = new XMLSignatureValidator(); 
 verifier.useSystemTrustStore = true;
AIR-only 

validityStatus

property 
validityStatus:String  [read-only]

Runtime Versions: AIR 1.0

The validity status of a verified XML signature.

The XML signature is verified by validating the the cryptographic signature of the SignedInfo element, the signing certificate, and the data addressed by the references in the SignedInfo element. The validity of each of these elements is reported individually by the digestStatus, identityStatus(), and referencesStatus properties, respectively.

The validity of an XML signature can be valid, invalid, or unknown. The overall status depends on the verification status of the individual components of the signature file:

  • digestStatus — The validity of the cryptographic signature computed over the SignedInfo element.
  • identityStatus — The validity of the signing certificate.
  • referencesStatus — The validity of the digest of the references in the signature SignedInfo element.

The signature validity reported by the validityStatus property can be:

  • valid — If referencesStatus, digestStatus, and identityStatus are all valid.
  • invalid — If any individual status is invalid.
  • unknown — If any individual status is unknown.



Implementation
    public function get validityStatus():String

Throws
IllegalOperationError — If accessed while a signature is being validated.

See also


Example  ( How to use this example )
The following example gets the result of validating the XML signature
 import flash.security.XMLSignatureValidator;
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator();
 //validate the signature...
  
 var validationResult:String = verifier.validityStatus;
Constructor Detail
AIR-only 

XMLSignatureValidator

()Constructor
public function XMLSignatureValidator()

Runtime Versions: AIR 1.0

Creates an XMLSignatureValidator object.

You must set the uriDereferencer property before calling the verify() method of the new object.

See also


Example  ( How to use this example )

The following example creates and sets up a new XMLSignatureValidator object:
 
import com.example.EnvelopedDereferencer; //Your custom IURIDereferencer implementation

//Create the object
var verifier:XMLSignatureValidator = new XMLSignatureValidator();

//Provide the IURIDerferencer
verifier.uriDereferencer = new EnvelopedDereferencer(xmlDoc);

//Set validation options
verifier.referencesValidationSetting = ReferencesValidationSetting.VALID_OR_UNKNOWN_IDENTITY;
verifier.revocationCheckSetting = RevocationCheckSettings.NEVER;
verifier.useSystemTrustStore = true;

//Add listeners to handle results
verifier.addEventListener(Event.COMPLETE, verificationComplete);
verifier.addEventListener(ErrorEvent.ERROR, verificationError);
Method Detail

AIR-only addCertificate

()method
public function addCertificate(cert:ByteArray, trusted:Boolean):*

Runtime Versions: AIR 1.0

Adds an x509 certificate for chain building.

The certificate added must be a DER-encoded x509 certificate.

If the trusted parameter is true, the certificate is considered a trust anchor.

Note: An XML signature may include certificates for building the signer's certificate chain. The XMLSignatureValidator class uses these certificates for chain building, but not as trusted roots (by default).

Parameters

cert:ByteArray — A ByteArray object containing a DER-encoded x509 digital certificate.
 
trusted:Boolean — Set to true to designate this certificate as a trust anchor.

Returns
*

Throws
IllegalOperationError — If called while a signature is being validated.

Example  ( How to use this example )

The following example loads a certificate from the file system and adds it as a trusted anchor.
 import flash.utils.ByteArray;
 
 var verifier:XMLSignatureValidator = new XMLSignatureValidator();
 var certificate:ByteArray = new ByteArray();
 
 var certFile:File = new File("certificate.cer");
 var certFileStream:FileStream = new FileStream();
 certFileStream.open(certFile, FileMode.READ);
 certFileStream.readBytes(certificate, 0, certFileStream.bytesAvailable);

 verifier.addCertificate(certificate, true);

AIR-only verify

()method 
public function verify(signature:XML):void

Language Version: ActionScript 3.0
Runtime Versions: AIR 1.0

Verifies the specified signature.

Verification is asynchronous. The XMLSignatureValidator object dispatches a complete event when verification completes successfully or an error event if verification cannot complete because of errors.

The verification process cannot be cancelled. While a verification process is under way, subsequent calls to the verify() method fail. After the current verification check is complete, you can call the verify() method again.

Note: Because the XMLSignatureValidator only implements a subset of the W3C recommendation for XML Signature Syntax and Processing, not all valid XML signatures can be verified.

Parameters

signature:XML — The XML signature to verify.


Events
complete:Event — Dispatched when verification completes successfully.
 
error:ErrorEvent — Dispatched if the verification of references encounters an error.

Throws
IllegalOperationError — If called while a signature is being validated.
 
Error — If other errors are encountered, such as non-well-formed XML or unsupported elements in the signature file.

Example  ( How to use this example )

The following example reads a file containing an XML signature and validates it by calling the verify() method. (The example assumes that the IURIDereferencer implementation is appropriate for the signature.)
import flash.filesystem.File;
import flash.filesystem.FileStream;
import com.example.SignedMessageDereferencer; //Your IURIDereferencer implementation
 
const xmlSignatureNS:Namespace = new Namespace( "http://www.w3.org/2000/09/xmldsig#" );

var verifier:XMLSignatureValidator = new XMLSignatureValidator();
verifier.uriDereferencer = new SignedMessageDereferencer();

var signatureFile:File = new File( "path/to/XMLSignatureDocument.xml" );
var sigFileStream:FileStream = new FileStream();
sigFileStream.open( signatureFile, FileMode.READ );

var xmlDoc:XML = XML( sigFileStream.readUTFBytes(sigFileStream.bytesAvailable) );
var xmlSig:XML = XML( xmlDoc..xmlSignatureNS::Signature );

verifier.verify( xmlSig );
Event Detail
AIR-only 

complete

Event
Event Object Type: flash.events.Event
property Event.type = flash.events.Event.COMPLETE

Language Version: ActionScript 3.0
Runtime Versions: AIR 1.0

Dispatched when verification is complete.

A complete event does not imply that the signature is valid. Check the validityStatus property of the XMLSignatureValidator object to determine the outcome of the signature verification.

The Event.COMPLETE constant defines the value of the type property of a complete event object.

This event has the following properties:

PropertyValue
bubblesfalse
cancelablefalse; there is no default behavior to cancel.
currentTargetThe object that is actively processing the Event object with an event listener.
targetThe network object that has completed loading.

Example  ( How to use this example )

The following example listens for the complete event dispatched by an XMLSignatureValidator object and traces the validation results:
private function verificationComplete(event:Event):void{
    var validator:XMLSignatureValidator = event.target as XMLSignatureValidator;
    trace("Digest status: " + validator.digestStatus);
    trace("Identity status: " + validator.identityStatus);
    trace("Reference status: " + validator.referencesStatus);
    trace("Signature status: " + validator.validityStatus);    
}

See also

AIR-only 

error

Event  
Event Object Type: flash.events.ErrorEvent
property ErrorEvent.type = flash.events.ErrorEvent.ERROR

Language Version: ActionScript 3.0
Runtime Versions: AIR 1.0

Dispatched if verification cannot complete because of errors.

Defines the value of the type property of an error event object.

This event has the following properties:

PropertyValue
bubblesfalse
cancelablefalse; there is no default behavior to cancel.
currentTargetThe object that is actively processing the Event object with an event listener.
targetThe object experiencing a network operation failure.
textText to be displayed as an error message.

Example  ( How to use this example )

The following example listens for the error event dispatched by an XMLSignatureValidator object and traces the error message:
private function verificationError(event:ErrorEvent):void{
    trace("Verification error: " + event.text);                
}
XMLSignatureValidatorExample.as

The following example loads and verifies a file containing an XML signature. To use this example, you must implement an IURIDereferencer appropriate for the signatures to be validated (replacing the SignedMessageDereferencer class used in the example). Run the example by calling SignatureValidatorExample.validateSignature( signatureFile ), passing in the file referencing the XML signature document to validate.
import flash.events.Event;
import flash.filesystem.File;
import flash.filesystem.FileStream;
import flash.security.ReferencesValidationSetting;
import flash.security.XMLSignatureValidator; 

import com.example.SignedMessageDereferencer; //A custom class implementing IURIDereferencer

public class SignatureValidatorExample{ 
    private var xmlSig:XML;
    private const signatureNS:Namespace = new Namespace( "http://www.w3.org/2000/09/xmldsig#" );
    
    public static function validateSignature( signatureFile:File ):void{
        try{
            //Set up the XMLSignatureValidator
            var verifier:XMLSignatureValidator = new XMLSignatureValidator();
            verifier.addEventListener( Event.COMPLETE, verificationComplete );
            verifier.uriDereferencer = new SignedMessageDereferencer();
            verifier.referencesValidationSetting = ReferencesValidationSetting.VALID_OR_UNKNOWN_IDENTITY;
    
            //Load the signed document
            var sigFileStream:FileStream = new FileStream();
            sigFileStream.open( signatureFile, FileMode.READ );
            var xmlDoc:XML = XML( sigFileStream.readUTFBytes(sigFileStream.bytesAvailable) );
            
            //Get the last Signature element in the document
            if( xmlDoc.name().localName != "Signature" ){
                var signatureList:XMLList = xmlDoc..signatureNS::Signature;
                xmlSig = XML( signatureList[ signatureList.length()-1 ] );
            } else{
                xmlSig = xmlDoc;
            }
    
            //Validate the signature
            verifier.verify( xmlSig );
            
        }catch (e:Error){
            statusDisplay.text = "Verification error.\n" + e;
        }
    }
    
    private static function verificationComplete(event:Event):void{
        trace( "Signature Validity: " + verifier.validityStatus );
        trace( "Digest validity: " + verifier.digestStatus );
        trace( "Certificate validity: " + verifier.identityStatus );
        trace( "Data validity: " + verifier.referencesStatus );
    }
}