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Create XML Digital Signature using a DSA Key

See more XML Digital Signatures Examples

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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LOCAL nSuccess
LOCAL cUrl
LOCAL oHttp
LOCAL oSbXml
LOCAL oDsaKey
LOCAL oXmlSigGen
LOCAL oVerifier
LOCAL nBVerified

nSuccess := 0

//  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..

cUrl := "https://www.chilkatsoft.com/exampleData/xmlToSign.xml"
oHttp := CreateObject("Chilkat.Http")
oSbXml := CreateObject("Chilkat.StringBuilder")
nSuccess := oHttp:QuickGetSb(cUrl, oSbXml)
IF (nSuccess != 1)
    ? oHttp:LastErrorText
    oHttp:destroy()
    oSbXml:destroy()
    RETURN
ENDIF

//  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".
oDsaKey := CreateObject("Chilkat.PrivateKey")
nSuccess := oDsaKey:LoadEncryptedPemFile("qa_data/dsa/dsa1024_secret.pem", "secret")
IF (nSuccess != 1)
    ? oDsaKey:LastErrorText
    oHttp:destroy()
    oSbXml:destroy()
    oDsaKey:destroy()
    RETURN
ENDIF

//  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.
//  

oXmlSigGen := CreateObject("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.
oXmlSigGen: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.
oXmlSigGen:AddSameDocRef("abc", "sha1", "EXCL_C14N", "", "")

//  Provide the DSA key to be used for signing:
oXmlSigGen:SetPrivateKey(oDsaKey)

//  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.
oXmlSigGen: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.
nSuccess := oXmlSigGen:CreateXmlDSigSb(oSbXml)
IF (nSuccess != 1)
    ? oXmlSigGen:LastErrorText
    oHttp:destroy()
    oSbXml:destroy()
    oDsaKey:destroy()
    oXmlSigGen:destroy()
    RETURN
ENDIF

//  Examine the signed XML:
? oSbXml: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:

oVerifier := CreateObject("Chilkat.XmlDSig")

//  First load the XML containing the signature(s) to be verified.
nSuccess := oVerifier:LoadSignatureSb(oSbXml)
IF (nSuccess != 1)
    ? oVerifier:LastErrorText
    oHttp:destroy()
    oSbXml:destroy()
    oDsaKey:destroy()
    oXmlSigGen:destroy()
    oVerifier:destroy()
    RETURN
ENDIF

nBVerified := oVerifier:VerifySignature(1)
IF (nBVerified != 1)
    ? oVerifier:LastErrorText
ENDIF

? "Signature verified = " + Str(nBVerified)

oHttp:destroy()
oSbXml:destroy()
oDsaKey:destroy()
oXmlSigGen:destroy()
oVerifier:destroy()