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   check_dsa_version()
    Verify the required Crypt::OpenSSL::DSA is installed

    Arguments: none

    Returns: integer (1 True, 0 False) if a valid version of
    Crypt::OpenSSL::DSA is installed

ABOUT DIGITAL SIGNATURES
    Just as one might want to send an email message that is
    cryptographically signed in order to give the recipient the means to
    independently verify who sent the email, one might also want to sign an
    XML document. This is especially true in the scenario where an XML
    document is received in an otherwise unauthenticated context, e.g. SAML.

    However XML provides a challenge that email does not. In XML, two
    documents can be byte-wise inequivalent, and semanticaly equivalent at
    the same time. For example:

        <?xml version="1.0"?>
        <foo>
          <bar />
        </foo>

        And:

        <?xml version="1.0"?>
        <foo>
          <bar></bar>
        </foo>

    Each of these document express the same thing, or in other words they
    "mean" the same thing. However if you were to strictly sign the raw text
    of these documents, they would each produce different signatures.

    XML Signatures on the other hand will produce the same signature for
    each of the documents above. Therefore an XML document can be written
    and rewritten by different parties and still be able to have someone at
    the end of the line verify a signature the document may contain.

    There is a specially subscribed methodology for how this process should
    be executed and involves transforming the XML into its canonical form so
    a signature can be reliably inserted or extracted for verification. This
    module implements that process.

  EXAMPLE SIGNATURE
    Below is a sample XML signature to give you some sense of what they look
    like. First let's look at the original XML document, prior to being
    signed:

      <?xml version="1.0"?>
      <foo ID="abc">
        <bar>123</bar>
      </foo>

    Now, let's insert a signature:

      <?xml version="1.0"?>
      <foo ID="abc">
        <bar>123</bar>
        <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
          <SignedInfo xmlns="http://www.w3.org/2000/09/xmldsig#" xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
            <CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315#WithComments" />
            <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
            <Reference URI="#abc">
              <Transforms>
                <Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
              </Transforms>
              <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
              <DigestValue>9kpmrvv3peVJpNSTRycrV+jeHVY=</DigestValue>
            </Reference>
          </SignedInfo>
          <SignatureValue>
            HXUBnMgPJf//j4ihaWnaylNwAR5AzDFY83HljFIlLmTqX1w1C72ZTuRObvYve8TNEbVsQlTQkj4R
            hiY0pgIMQUb75GLYFtc+f0YmBZf5rCWY3NWzo432D3ogAvpEzYXEQPmicWe2QozQhybaz9/wrYki
            XiXY+57fqCkf7aT8Bb6G+fn7Aj8gnZFLkmKxwCdyGsIZOIZdQ8MWpeQrifxBR0d8W1Zm6ix21WNv
            ONt575h7VxLKw8BDhNPS0p8CS3hOnSk29stpiDMCHFPxAwrbKVL1kGDLaLZn1q8nNRmH8oFxG15l
            UmS3JXDZAss8gZhU7g9T4XllCqjrAvzPLOFdeQ==
          </SignatureValue>
          <KeyInfo>
            <KeyValue>
              <RSAKeyValue>
                <Modulus>
                  1b+m37u3Xyawh2ArV8txLei251p03CXbkVuWaJu9C8eHy1pu87bcthi+T5WdlCPKD7KGtkKn9vq
                  i4BJBZcG/Y10e8KWVlXDLg9gibN5hb0Agae3i1cCJTqqnQ0Ka8w1XABtbxTimS1B0aO1zYW6d+U
                  Yl0xIeAOPsGMfWeu1NgLChZQton1/NrJsKwzMaQy1VI8m4gUleit9Z8mbz9bNMshdgYEZ9oC4bH
                  n/SnA4FvQl1fjWyTpzL/aWF/bEzS6Qd8IBk7yhcWRJAGdXTWtwiX4mXb4h/2sdrSNvyOsd/shCf
                  OSMsf0TX+OdlbH079AsxOwoUjlzjuKdCiFPdU6yAJw==
                </Modulus>
                <Exponent>Iw==</Exponent>
              </RSAKeyValue>
            </KeyValue>
          </KeyInfo>
        </Signature>
      </foo>

SEE ALSO
    <http://www.w3.org/TR/xmldsig-core/>

VERSION CONTROL
    <https://github.com/perl-net-saml2/perl-XML-Sig>

AUTHORS and CREDITS
    Author: Byrne Reese <byrne@majordojo.com>

    Thanks to Manni Heumann who wrote Google::SAML::Response from which this
    module borrows heavily in order to create digital signatures.

    Net::SAML2 embedded version amended by Chris Andrews <chris@nodnol.org>.

    Maintainer: Timothy Legge <timlegge@cpan.org>

AUTHOR
    Timothy Legge <timlegge@gmail.com>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2026 by Byrne Reese, Chris Andrews and
    Others; in detail:

      Copyright 2009       Byrne, Michael Hendricks
                2010       Chris Andrews
                2011       Chris Andrews, Oskari Okko Ojala
                2012       Chris Andrews, Peter Marschall
                2015       Mike Wisener
                2016       Jeff Fearn
                2017       Mike Wisener, xmikew
                2019-2021  Timothy Legge
                2022-2023  Timothy Legge, Wesley Schwengle
                2025-2026  Timothy Legge

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.