System.Security.dll 4.6.1073.0

        [ComVisible(false)]
        [SecuritySafeCritical]
        public bool CheckSignature(X509Certificate2 certificate, bool verifySignatureOnly) {
            if (!CheckSignature(certificate.PublicKey.Key)) {
                return false;
            }

            if (verifySignatureOnly) {
                SignedXmlDebugLog.LogVerificationResult(this, certificate, true);
                return true;
            }

            // Check key usages to make sure it is good for signing.
            foreach (X509Extension extension in certificate.Extensions) {
                if (String.Compare(extension.Oid.Value, CAPI.szOID_KEY_USAGE, StringComparison.OrdinalIgnoreCase) == 0) {
                    X509KeyUsageExtension keyUsage = new X509KeyUsageExtension();
                    keyUsage.CopyFrom(extension);
                    SignedXmlDebugLog.LogVerifyKeyUsage(this, certificate, keyUsage);

                    bool validKeyUsage = (keyUsage.KeyUsages & X509KeyUsageFlags.DigitalSignature) != 0 ||
                                         (keyUsage.KeyUsages & X509KeyUsageFlags.NonRepudiation) != 0;

                    if (!validKeyUsage) {
                        SignedXmlDebugLog.LogVerificationFailure(this, SecurityResources.GetResourceString("Log_VerificationFailed_X509KeyUsage"));
                        return false;
                    }
                    break;
                }
            }

            // Do the chain verification to make sure the certificate is valid.
            X509Chain chain = new X509Chain();
            chain.ChainPolicy.ExtraStore.AddRange(BuildBagOfCerts());
            bool chainVerified = chain.Build(certificate);
            SignedXmlDebugLog.LogVerifyX509Chain(this, chain, certificate);

            if (!chainVerified) {
                SignedXmlDebugLog.LogVerificationFailure(this, SecurityResources.GetResourceString("Log_VerificationFailed_X509Chain"));
                return false;
            }

            SignedXmlDebugLog.LogVerificationResult(this, certificate, true);
            return true;
        }