(.NET Core C#) Create XML Digital Signature using a DSA Key

Demonstrates how to create an XML digital signature using a DSA key.

This example requires Chilkat v9.5.0.69 or greater.

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

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

// <?xml version="1.0" encoding="UTF-8" standalone="no"?>
// <Envelope>
//   <Header>
//     <Security>
//     </Security>
//   </Header>
//   <Body Id="abc">
//     <z:FooBar xmlns:z="https://www.example-code.com"/>
//   </Body>
// </Envelope>

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

string url = "https://www.chilkatsoft.com/exampleData/xmlToSign.xml";
Chilkat.Http http = new Chilkat.Http();
Chilkat.StringBuilder sbXml = new Chilkat.StringBuilder();
bool success = http.QuickGetSb(url,sbXml);
if (success != true) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

// This example uses a DSA private key for signing.  
// There are many ways of getting an DSA private key using Chilkat.  This example
// will load it from an encrypted PEM file.

// In case you would like to use it, I put the DSA private key PEM file here:
// https://www.chilkatsoft.com/exampleData/dsa1024_secret.zip
// The password is "secret".
Chilkat.PrivateKey dsaKey = new Chilkat.PrivateKey();
success = dsaKey.LoadEncryptedPemFile("qa_data/dsa/dsa1024_secret.pem","secret");
if (success != true) {
    Debug.WriteLine(dsaKey.LastErrorText);
    return;
}

// To create the XML digital signature (i.e. embed the signature within
// the XML), first specify what is desired, then call the method to 
// create the XML signature.
// 
// For example, the application must provide the following:
//     - Where to put the signature.
//     - What to sign.
//     - The algorithms to be used.
//     - The key to be used for signing.
// 

Chilkat.XmlDSigGen xmlSigGen = new Chilkat.XmlDSigGen();

// In this example, we're going to put the signature within the Security element.
// To specify the location, set the SigLocation property to the XML path to this element,
// using vertical bar characters to separate tags.
xmlSigGen.SigLocation = "Envelope|Header|Security";

// An XML digital signature contains one or more references.  These can be references to the parts
// of the XML document to be signed (a same document reference), or can be external references.
// This example will add a single same-document reference.  We'll add a reference to the XML fragment
// at Body, which is indicated by providing the value of the "ID" attribute (where "ID" is case
// insensitive).  In this case, we specify "abc" because Body has an Id="abc".
// This causes the <Body> ... </Body> XML fragment to be signed.
// 
// For each same-document reference, we must also indicate the hash algorithm and XML canonicalization
// algorithm to be used.  For this example we'll choose SHA1 and Exclusive XML Canonicalization.
xmlSigGen.AddSameDocRef("abc","sha1","EXCL_C14N","","");

// Provide the DSA key to be used for signing:
xmlSigGen.SetPrivateKey(dsaKey);

// We're leaving the following properties at their default values:
// 
//    - SigNamespacePrefix (default is "ds")
//    - SignedInfoCanonAlg  (default is EXCL_C14N)
//    - KeyInfoType (default is "KeyValue", where the DSA public key is included in the Signature)

// Note: Each Reference has it's own specified algorithms for XML canonicalization and hashing,
// and the actual signature part (the SignedInfo) has it's own hash/canonicalization algorithm.
// They may or may not be the same.  In this example, we use Exclusive XML Canonicalization and SHA1 throughout.

// The default SignedInfoDigestMethod is sha256, which is a good choice.  This example will
// change it to sha1.
xmlSigGen.SignedInfoDigestMethod = "sha1";

// OK, everything's specified, so let's create the XML digital signature:
// This in-place signs the XML.  If successful, sbXml will contain the 
// XML with the digital signature at the specified location.
success = xmlSigGen.CreateXmlDSigSb(sbXml);
if (success != true) {
    Debug.WriteLine(xmlSigGen.LastErrorText);
    return;
}

// Examine the signed XML:
Debug.WriteLine(sbXml.GetAsString());

// Below is the signed XML that is produced.
// Chilkat emits the Signature in compact form on a single line.  Whitespace in XML signatures
// matters.  Chilkat's opinion is that writing the Signature without whitespace minimizes the chance
// for problems with whatever software might be verifying the signature.

// <?xml version="1.0" encoding="UTF-8" standalone="no"?>
// <Envelope>
//   <Header>
//     <Security>
//     <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#dsa-sha1"/><ds:Reference URI="#abc"><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/><ds:DigestValue>77X3L6odxTBow1W1dIiqZW1foow=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>Ci/KiAqoQLvNyK94n8TJwdJ6dVpIIy8tJg+9s8utmB92cW8lTd+U7g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:DSAKeyValue><ds:P>AN+Af9FvnqYl84Own8m/MHza9vVFEbpySOiWyeIM8diDjaES9i+UykaX9BGc0oaRJHtrHhe+gboMBGHfP+gYcgbqzeyVCi2kHghRD/TK7uI4jN8Yv8tfM6AO0QrDFfxFq4IV+qTZbSoCkbWaopQ+kEOY6B4btFxJ1YuE48mExMZ3</ds:P><ds:Q>AOCv5pwf4kvMW37Yzt0iH6URKOlD</ds:Q><ds:G>FO3eoDcpuU9Z25OQGFtC+M2ifczcKyRkFwTauGR3mIw0wePPiu3Ocr7A81SA8GQ9x3hWO5jyP//jL3jxYy8fgBg2RXwiic3nwT2rZfu50g6tPUpz1stKz/+Mxjulo6XuaMSOWwjU021IxVMzxQ1/L8QiwiIrwxvfQOaMY8HJgvw=</ds:G><ds:Y>JJmZQvWtrZ+Nb2YV47SfGAave8uOIedGlmg+CseoqKZC2aFcWM6kR0giUwQx834dhxQScRhqzxFxQPk/x+5hyG8LQbXW+BELmT1BiyodobYUAet4rSIt4EU4KU0iYw1drpcWT1jqI07l5xNi28heYSfSF5Odv2qwXxVKDSEeEkM=</ds:Y></ds:DSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></Security>
//   </Header>
//   <Body Id="abc">
//     <z:FooBar xmlns:z="https://www.example-code.com"/>
//   </Body>
// </Envelope>

// The above signed XML contains the DSA public key in the DSAKeyValue fragment (within the ds:KeyInfo).
// The signature can easily be verified like this:

Chilkat.XmlDSig verifier = new Chilkat.XmlDSig();

// First load the XML containing the signature(s) to be verified.
success = verifier.LoadSignatureSb(sbXml);
if (success != true) {
    Debug.WriteLine(verifier.LastErrorText);
    return;
}

bool bVerified = verifier.VerifySignature(true);
if (bVerified != true) {
    Debug.WriteLine(verifier.LastErrorText);
}

Debug.WriteLine("Signature verified = " + Convert.ToString(bVerified));