Sample code for 30+ languages & platforms
B4X

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.

Chilkat B4X Downloads

Download Chilkat for B4X
B4X 
Dim success As Boolean = False

'  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..

Dim url As String = "https://www.chilkatsoft.com/exampleData/xmlToSign.xml"
Dim http As ChilkatHttp
http.Initialize("http")
Dim sbXml As ChilkatStringBuilder
sbXml.Initialize
success = http.QuickGetSb(url, sbXml)
If success <> True Then
    Log(http.LastErrorText)
    Return
End If


'  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".
Dim dsaKey As ChilkatPrivateKey
dsaKey.Initialize("dsaKey")
success = dsaKey.LoadEncryptedPemFile("qa_data/dsa/dsa1024_secret.pem", "secret")
If success <> True Then
    Log(dsaKey.LastErrorText)
    Return
End If


'  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.
'  

Dim xmlSigGen As ChilkatXmlDSigGen
xmlSigGen.Initialize("xmlSigGen")

'  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 Then
    Log(xmlSigGen.LastErrorText)
    Return
End If


'  Examine the signed XML:
Log(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:

Dim verifier As ChilkatXmlDSig
verifier.Initialize

'  First load the XML containing the signature(s) to be verified.
success = verifier.LoadSignatureSb(sbXml)
If success <> True Then
    Log(verifier.LastErrorText)
    Return
End If


Dim bVerified As Boolean = verifier.VerifySignature(True)
If bVerified <> True Then
    Log(verifier.LastErrorText)
End If

Log("Signature verified = " & bVerified)