Cheesebaron.MvxPlugins.SimpleWebToken.SimpleWebToken.ValidateSignature C# (CSharp) Method

        public bool ValidateSignature(string keyString)
        {
            if (keyString == null) throw new ArgumentNullException(nameof(keyString));

            if (string.IsNullOrEmpty(RawToken) || string.IsNullOrEmpty(RawToken))
                throw new Exception("The token does not have a signature to verify");

            var serializedToken = RawToken;
            string unsignedToken = null;

            // Find the last parameter. The signature must be last per SWT specification.
            var lastSeparator = serializedToken.LastIndexOf(ParameterSeparator);

            // Check whether the last parameter is an hmac.
            if (lastSeparator > 0)
            {
                var lastParamStart = ParameterSeparator + SimpleWebTokenConstants.Signature + "=";
                var lastParam = serializedToken.Substring(lastSeparator);

                // Strip the trailing hmac to obtain the original unsigned string for later hmac verification.               
                if (lastParam.StartsWith(lastParamStart, StringComparison.Ordinal))
                {
                    unsignedToken = serializedToken.Substring(0, lastSeparator);
                }
            }
            var generatedSignature = GenerateSignature(unsignedToken, Convert.FromBase64String(keyString));

            return string.CompareOrdinal(generatedSignature, Signature) == 0;
        }