SignedXml Class

SignedXml Class

 

Provides a wrapper on a core XML signature object to facilitate creating XML signatures.

Namespace:   System.Security.Cryptography.Xml
Assembly:  System.Security (in System.Security.dll)

System.Object
  System.Security.Cryptography.Xml.SignedXml

[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
public class SignedXml

NameDescription
System_CAPS_pubmethodSignedXml()

Initializes a new instance of the SignedXml class.

System_CAPS_pubmethodSignedXml(XmlDocument)

Initializes a new instance of the SignedXml class from the specified XML document.

System_CAPS_pubmethodSignedXml(XmlElement)

Initializes a new instance of the SignedXml class from the specified XmlElement object.

NameDescription
System_CAPS_pubpropertyEncryptedXml

Gets or sets an EncryptedXml object that defines the XML encryption processing rules.

System_CAPS_pubpropertyKeyInfo

Gets or sets the KeyInfo object of the current SignedXml object.

System_CAPS_pubpropertyResolver

Sets the current XmlResolver object.

System_CAPS_pubpropertySafeCanonicalizationMethods

[Supported in the .NET Framework 4.5.1 and later versions]

Gets the names of methods whose canonicalization algorithms are explicitly allowed.

System_CAPS_pubpropertySignature

Gets the Signature object of the current SignedXml object.

System_CAPS_pubpropertySignatureFormatValidator

Gets a delegate that will be called to validate the format (not the cryptographic security) of an XML signature.

System_CAPS_pubpropertySignatureLength

Gets the length of the signature for the current SignedXml object.

System_CAPS_pubpropertySignatureMethod

Gets the signature method of the current SignedXml object.

System_CAPS_pubpropertySignatureValue

Gets the signature value of the current SignedXml object.

System_CAPS_pubpropertySignedInfo

Gets the SignedInfo object of the current SignedXml object.

System_CAPS_pubpropertySigningKey

Gets or sets the asymmetric algorithm key used for signing a SignedXml object.

System_CAPS_pubpropertySigningKeyName

This API supports the product infrastructure and is not intended to be used directly from your code. Gets or sets the name of the installed key to be used for signing the SignedXml object.

NameDescription
System_CAPS_pubmethodAddObject(DataObject)

Adds a DataObject object to the list of objects to be signed.

System_CAPS_pubmethodAddReference(Reference)

Adds a Reference object to the SignedXml object that describes a digest method, digest value, and transform to use for creating an XML digital signature.

System_CAPS_pubmethodCheckSignature()

Determines whether the Signature property verifies using the public key in the signature.

System_CAPS_pubmethodCheckSignature(AsymmetricAlgorithm)

Determines whether the Signature property verifies for the specified key.

System_CAPS_pubmethodCheckSignature(KeyedHashAlgorithm)

Determines whether the Signature property verifies for the specified message authentication code (MAC) algorithm.

System_CAPS_pubmethodCheckSignature(X509Certificate2, Boolean)

Determines whether the Signature property verifies for the specified X509Certificate2 object and, optionally, whether the certificate is valid.

System_CAPS_pubmethodCheckSignatureReturningKey(AsymmetricAlgorithm)

Determines whether the Signature property verifies using the public key in the signature.

System_CAPS_pubmethodComputeSignature()

Computes an XML digital signature.

System_CAPS_pubmethodComputeSignature(KeyedHashAlgorithm)

Computes an XML digital signature using the specified message authentication code (MAC) algorithm.

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetIdElement(XmlDocument, String)

Returns the XmlElement object with the specified ID from the specified XmlDocument object.

System_CAPS_protmethodGetPublicKey()

Returns the public key of a signature.

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodGetXml()

Returns the XML representation of a SignedXml object.

System_CAPS_pubmethodLoadXml(XmlElement)

Loads a SignedXml state from an XML element.

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

NameDescription
System_CAPS_protfieldm_signature

This API supports the product infrastructure and is not intended to be used directly from your code. Represents the Signature object of the current SignedXml object.

System_CAPS_protfieldm_strSigningKeyName

This API supports the product infrastructure and is not intended to be used directly from your code. Represents the name of the installed key to be used for signing the SignedXml object.

System_CAPS_pubfieldSystem_CAPS_staticXmlDecryptionTransformUrl

Represents the Uniform Resource Identifier (URI) for the XML mode decryption transformation. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigBase64TransformUrl

Represents the Uniform Resource Identifier (URI) for the base 64 transformation. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigC14NTransformUrl

Represents the Uniform Resource Identifier (URI) for the Canonical XML transformation. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigC14NWithCommentsTransformUrl

Represents the Uniform Resource Identifier (URI) for the Canonical XML transformation, with comments. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigCanonicalizationUrl

Represents the Uniform Resource Identifier (URI) for the standard canonicalization algorithm for XML digital signatures. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigCanonicalizationWithCommentsUrl

Represents the Uniform Resource Identifier (URI) for the standard canonicalization algorithm for XML digital signatures and includes comments. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigDSAUrl

Represents the Uniform Resource Identifier (URI) for the standard DSA algorithm for XML digital signatures. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigEnvelopedSignatureTransformUrl

Represents the Uniform Resource Identifier (URI) for enveloped signature transformation. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigExcC14NTransformUrl

Represents the Uniform Resource Identifier (URI) for exclusive XML canonicalization. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigExcC14NWithCommentsTransformUrl

Represents the Uniform Resource Identifier (URI) for exclusive XML canonicalization, with comments. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigHMACSHA1Url

Represents the Uniform Resource Identifier (URI) for the standard HMACSHA1 algorithm for XML digital signatures. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigMinimalCanonicalizationUrl

Represents the Uniform Resource Identifier (URI) for the standard minimal canonicalization algorithm for XML digital signatures. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigNamespaceUrl

Represents the Uniform Resource Identifier (URI) for the standard namespace for XML digital signatures. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigRSASHA1Url

Represents the Uniform Resource Identifier (URI) for the standard RSA signature method for XML digital signatures. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigSHA1Url

Represents the Uniform Resource Identifier (URI) for the standard SHA1 digest method for XML digital signatures. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigXPathTransformUrl

Represents the Uniform Resource Identifier (URI) for the XML Path Language (XPath). This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlDsigXsltTransformUrl

Represents the Uniform Resource Identifier (URI) for XSLT transformations. This field is constant.

System_CAPS_pubfieldSystem_CAPS_staticXmlLicenseTransformUrl

Represents the Uniform Resource Identifier (URI) for the license transform algorithm used to normalize XrML licenses for signatures.

The SignedXml class is the main class used for XML signing and verification (XMLDSIG) in the .NET Framework. XMLDSIG is a standards-based, interoperable way to sign and verify all or part of an XML document or other data that is addressable from a Uniform Resource Identifier (URI). The .NET Framework XMLDSIG classes implement the World Wide Web Consortium (W3C) specification for XML signing and verification located at http://www.w3.org/TR/xmldsig-core/.

Use the SignedXml class whenever you need to share signed XML data between applications or organizations in a standard way. Any data signed using this class can be verified by any conforming implementation of the W3C specification for XMLDSIG.

XMLDSIG creates a <Signature> element, which contains a digital signature of an XML document or other data that is addressable from a URI. The <Signature> element can optionally contain information about where to find a key that will verify the signature and which cryptographic algorithm was used for signing.

The SignedXml class allows you to create the following three kinds of XML digital signatures:

Signature Type

Description

Enveloped signature

The signature is contained within the XML document being signed.

Enveloping signature

The signed XML is contained within the <Signature> element.

Detached signature

The signature is in a separate document from the data being signed.

Use one of the following methods to exchange key information:

  • Do not include any key information. If you choose this option, both parties must agree on an algorithm and key before they exchange a digital signature.

  • Include a public key in the <EncryptedKey> element.

  • Include the location of the key in the URI attribute of the <RetrievalMethod> element. Both parties must agree on the key location ahead of time and this location must be kept secret.

  • Include a string name that maps to a key in the <KeyName> element. Both parties must agree on the key name mapping before they exchange encrypted data and this mapping must be kept secret.

The following code example shows how to sign and verify an entire XML document using an enveloped signature.

//
// This example signs an XML file using an
// envelope signature. It then verifies the 
// signed XML.
//
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;

public class SignVerifyEnvelope
{

    public static void Main(String[] args)
    {
        try
        {
           // Generate a signing key.
           RSACryptoServiceProvider Key = new RSACryptoServiceProvider();

           // Create an XML file to sign.
           CreateSomeXml("Example.xml");
           Console.WriteLine("New XML file created."); 

           // Sign the XML that was just created and save it in a 
           // new file.
           SignXmlFile("Example.xml", "signedExample.xml", Key);
           Console.WriteLine("XML file signed."); 

           // Verify the signature of the signed XML.
           Console.WriteLine("Verifying signature...");
           bool result = VerifyXmlFile("SignedExample.xml", Key);

           // Display the results of the signature verification to 
           // the console.
           if(result)
           {
               Console.WriteLine("The XML signature is valid.");
           }
           else
           {
            Console.WriteLine("The XML signature is not valid.");
           }
        }
        catch(CryptographicException e)
        {
            Console.WriteLine(e.Message);
        }
    }


    // Sign an XML file and save the signature in a new file. This method does not  
    // save the public key within the XML file.  This file cannot be verified unless  
    // the verifying code has the key with which it was signed.
    public static void SignXmlFile(string FileName, string SignedFileName, RSA Key)
    {
        // Create a new XML document.
        XmlDocument doc = new XmlDocument();

        // Load the passed XML file using its name.
        doc.Load(new XmlTextReader(FileName));

        // Create a SignedXml object.
        SignedXml signedXml = new SignedXml(doc);

        // Add the key to the SignedXml document. 
        signedXml.SigningKey = Key;

        // Create a reference to be signed.
        Reference reference = new Reference();
        reference.Uri = "";

        // Add an enveloped transformation to the reference.
        XmlDsigEnvelopedSignatureTransform env = new XmlDsigEnvelopedSignatureTransform();
        reference.AddTransform(env);

        // Add the reference to the SignedXml object.
        signedXml.AddReference(reference);

        // Compute the signature.
        signedXml.ComputeSignature();

        // Get the XML representation of the signature and save
        // it to an XmlElement object.
        XmlElement xmlDigitalSignature = signedXml.GetXml();

        // Append the element to the XML document.
        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, true));

        if (doc.FirstChild is XmlDeclaration)  
        {
            doc.RemoveChild(doc.FirstChild);
        }

        // Save the signed XML document to a file specified
        // using the passed string.
        XmlTextWriter xmltw = new XmlTextWriter(SignedFileName, new UTF8Encoding(false));
        doc.WriteTo(xmltw);
        xmltw.Close();
    }

    // Verify the signature of an XML file against an asymetric 
    // algorithm and return the result.
    public static Boolean VerifyXmlFile(String Name, RSA Key)
    {
        // Create a new XML document.
        XmlDocument xmlDocument = new XmlDocument();

        // Load the passed XML file into the document. 
        xmlDocument.Load(Name);

        // Create a new SignedXml object and pass it
        // the XML document class.
        SignedXml signedXml = new SignedXml(xmlDocument);

        // Find the "Signature" node and create a new
        // XmlNodeList object.
        XmlNodeList nodeList = xmlDocument.GetElementsByTagName("Signature");

        // Load the signature node.
        signedXml.LoadXml((XmlElement)nodeList[0]);

        // Check the signature and return the result.
        return signedXml.CheckSignature(Key);
    }


    // Create example data to sign.
    public static void CreateSomeXml(string FileName)
    {
        // Create a new XmlDocument object.
        XmlDocument document = new XmlDocument();

        // Create a new XmlNode object.
        XmlNode  node = document.CreateNode(XmlNodeType.Element, "", "MyElement", "samples");

        // Add some text to the node.
        node.InnerText = "Example text to be signed.";

        // Append the node to the document.
        document.AppendChild(node);

        // Save the XML document to the file name specified.
        XmlTextWriter xmltw = new XmlTextWriter(FileName, new UTF8Encoding(false));
        document.WriteTo(xmltw);
        xmltw.Close();
    }
}

The following code example shows how to sign and verify an object that is addressable from a Uniform Resource Identifier (URI), using a detached signature..

//
// This example signs a file specified by a URI 
// using a detached signature. It then verifies  
// the signed XML.
//

using System;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;



class XMLDSIGDetached
{

    [STAThread]
    static void Main(string[] args)
    {
        // The URI to sign.
        string resourceToSign = "http://www.microsoft.com";

        // The name of the file to which to save the XML signature.
        string XmlFileName = "xmldsig.xml";

        try
        {

            // Generate a signing key.
            RSACryptoServiceProvider Key = new RSACryptoServiceProvider();

            Console.WriteLine("Signing: {0}", resourceToSign);

            // Sign the detached resourceand save the signature in an XML file.
            SignDetachedResource(resourceToSign, XmlFileName, Key);

            Console.WriteLine("XML Signature was succesfully computed and saved to {0}.", XmlFileName);

            // Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...");

            //Verify the XML signature in the XML file against the key.
            bool result = VerifyDetachedSignature(XmlFileName, Key);

            // Display the results of the signature verification to 
            // the console.
            if(result)
            {
                Console.WriteLine("The XML signature is valid.");
            }
            else
            {
                Console.WriteLine("The XML signature is not valid.");
            }
        }
        catch(CryptographicException e)
        {
            Console.WriteLine(e.Message);

        }

    }

    // Sign an XML file and save the signature in a new file. This method does not  
    // save the public key within the XML file.  This file cannot be verified unless  
    // the verifying code has the key with which it was signed.
    public static void SignDetachedResource(string URIString, string XmlSigFileName, RSA Key)
    {
        // Create a SignedXml object.
        SignedXml signedXml = new SignedXml();

        // Assign the key to the SignedXml object.
        signedXml.SigningKey = Key;

        // Create a reference to be signed.
        Reference reference = new Reference();

        // Add the passed URI to the reference object.
        reference.Uri = URIString;

        // Add the reference to the SignedXml object.
        signedXml.AddReference(reference);

        // Compute the signature.
        signedXml.ComputeSignature();

        // Get the XML representation of the signature and save
        // it to an XmlElement object.
        XmlElement xmlDigitalSignature = signedXml.GetXml();

        // Save the signed XML document to a file specified
        // using the passed string.
        XmlTextWriter xmltw = new XmlTextWriter(XmlSigFileName, new UTF8Encoding(false));
        xmlDigitalSignature.WriteTo(xmltw);
        xmltw.Close();

    }

    // Verify the signature of an XML file against an asymetric 
    // algorithm and return the result.
    public static Boolean VerifyDetachedSignature(string XmlSigFileName, RSA Key)
    {	
        // Create a new XML document.
        XmlDocument xmlDocument = new XmlDocument();

        // Load the passedXML file into the document.
        xmlDocument.Load(XmlSigFileName);

        // Create a new SignedXml object.
        SignedXml signedXml = new SignedXml();

        // Find the "Signature" node and create a new
        // XmlNodeList object.
        XmlNodeList nodeList = xmlDocument.GetElementsByTagName("Signature");

        // Load the signature node.
        signedXml.LoadXml((XmlElement)nodeList[0]);

        // Check the signature against the passed asymetric key
        // and return the result.
        return signedXml.CheckSignature(Key);
    }

}

The following code example shows how to sign and verify a single element of an XML document using an enveloping signature.

//
// This example signs an XML file using an
// envelope signature. It then verifies the 
// signed XML.
//
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;

public class SignVerifyEnvelope
{

    public static void Main(String[] args)
    {
        // Generate a signing key.
       RSACryptoServiceProvider Key = new RSACryptoServiceProvider();

       try
       {
           // Specify an element to sign. 
           string[] elements =  { "#tag1" };

           // Sign an XML file and save the signature to a 
           // new file.
           SignXmlFile("Test.xml", "SignedExample.xml", Key, elements);
           Console.WriteLine("XML file signed.");

           // Verify the signature of the signed XML.
           Console.WriteLine("Verifying signature...");

           bool result = VerifyXmlFile("SignedExample.xml");

           // Display the results of the signature verification to 
           // the console.
           if (result)
           {
               Console.WriteLine("The XML signature is valid.");
           }
           else
           {
               Console.WriteLine("The XML signature is not valid.");
           }
       }
       catch (CryptographicException e)
       {
           Console.WriteLine(e.Message);
       }
       finally
       {
           // Clear resources associated with the 
           // RSACryptoServiceProvider.
           Key.Clear();
       }
   }

    // Sign an XML file and save the signature in a new file.
    public static void SignXmlFile(string FileName, string SignedFileName, RSA Key, string[] ElementsToSign)
    {
        // Check the arguments.  
        if (FileName == null)
            throw new ArgumentNullException("FileName");
        if (SignedFileName == null)
            throw new ArgumentNullException("SignedFileName");
        if (Key == null)
            throw new ArgumentNullException("Key");
        if (ElementsToSign == null)
            throw new ArgumentNullException("ElementsToSign");

        // Create a new XML document.
        XmlDocument doc = new XmlDocument();

        // Format the document to ignore white spaces.
        doc.PreserveWhitespace = false;

        // Load the passed XML file using it's name.
        doc.Load(new XmlTextReader(FileName));

        // Create a SignedXml object.
        SignedXml signedXml = new SignedXml(doc);

        // Add the key to the SignedXml document. 
        signedXml.SigningKey = Key;

        // Loop through each passed element to sign 
        // and create a reference.
        foreach (string s in ElementsToSign)
        {
            // Create a reference to be signed.
            Reference reference = new Reference();
            reference.Uri = s;

            // Add an enveloped transformation to the reference.
            XmlDsigEnvelopedSignatureTransform env = new XmlDsigEnvelopedSignatureTransform();
            reference.AddTransform(env);

            // Add the reference to the SignedXml object.
            signedXml.AddReference(reference);

        }



        // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        KeyInfo keyInfo = new KeyInfo();
        keyInfo.AddClause(new RSAKeyValue((RSA)Key));
        signedXml.KeyInfo = keyInfo;

        // Compute the signature.
        signedXml.ComputeSignature();

        // Get the XML representation of the signature and save
        // it to an XmlElement object.
        XmlElement xmlDigitalSignature = signedXml.GetXml();

        // Append the element to the XML document.
        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, true));


        if (doc.FirstChild is XmlDeclaration)
        {
            doc.RemoveChild(doc.FirstChild);
        }

        // Save the signed XML document to a file specified
        // using the passed string.
        XmlTextWriter xmltw = new XmlTextWriter(SignedFileName, new UTF8Encoding(false));
        doc.WriteTo(xmltw);
        xmltw.Close();
    }
    // Verify the signature of an XML file and return the result.
    public static Boolean VerifyXmlFile(String Name)
    {
        // Check the arguments.  
        if (Name == null)
            throw new ArgumentNullException("Name");

        // Create a new XML document.
        XmlDocument xmlDocument = new XmlDocument();

        // Format using white spaces.
        xmlDocument.PreserveWhitespace = true;

        // Load the passed XML file into the document. 
        xmlDocument.Load(Name);

        // Create a new SignedXml object and pass it
        // the XML document class.
        SignedXml signedXml = new SignedXml(xmlDocument);

        // Find the "Signature" node and create a new
        // XmlNodeList object.
        XmlNodeList nodeList = xmlDocument.GetElementsByTagName("Signature");

        // Load the signature node.
        signedXml.LoadXml((XmlElement)nodeList[0]);

        // Check the signature and return the result.
        return signedXml.CheckSignature();
    }
}

.NET Framework
Available since 1.1

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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