private bool VerifySignature(RSACryptoServiceProvider publicKey)
{
var signatureValueElement =
_xDocument.Root?.XPathSelectElement(SignatureValueExpression, _namespaceManager);
if (null == signatureValueElement)
{
throw new CryptographicException("null == signatureValueElement");
}
byte[] signature;
try
{
signature = Convert.FromBase64String(signatureValueElement.Value);
}
catch (Exception exception) when(exception is FormatException || exception is ArgumentNullException)
{
throw new CryptographicException("Wrong format of signature value!");
}
var signedInfoElement = _xDocument.Root.XPathSelectElement(SignedInfoExpression, _namespaceManager);
var xDocument = new XDocument();
xDocument.Add(signedInfoElement);
var canonizedSignedInfo = Canonicalizer.Canonize(xDocument);
return(publicKey.VerifyData(Encoding.UTF8.GetBytes(canonizedSignedInfo), new SHA256Managed(), signature));
}
private byte[] ComputeDigest()
{
var xDocument = new XDocument(_xDocument);
var signatureElement = xDocument.Root?.XPathSelectElement(SignatureElementExpression, _namespaceManager);
if (null == signatureElement)
{
throw new CryptographicException("null == signatureElement");
}
signatureElement.Remove();
var canonizedXml = Canonicalizer.Canonize(xDocument);
byte[] hash;
using (var sha256 = new SHA256Managed())
{
hash = sha256.ComputeHash(Encoding.UTF8.GetBytes(canonizedXml));
}
return(hash);
}
