private void btnValidateLicense_Click(object sender, EventArgs e)
{
LicenseInformation info = LicenseEncryption.Decrypt(txtLicense.Text, txtPublicKey.Text);
txtProduct.Text = info.Product;
txtExpiration.Text = info.Expiration.HasValue ? info.Expiration.Value.ToString("yyyy-MM-dd HH:mm:ss") : "never";
txtIsValid.Text = info.IsValid.ToString();
}
internal static LicenseInformation Decrypt(string license, string publicKey)
{
using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
{
rsa.PersistKeyInCsp = false;
rsa.FromXmlString(publicKey);
var doc = XDocument.Parse(license);
if (doc.Root.Name != "license")
{
throw new Exception("Invalid XML root: " + doc.Root.Name);
}
string product = doc.Root.Attribute("product").Value;
string expirationString = doc.Root.Attribute("expires").Value;
string signatureText = doc.Root.Attribute("signature").Value;
byte[] signature = Convert.FromBase64String(signatureText);
DateTime?expiration;
if (expirationString == "never")
{
expiration = null;
}
else
{
expiration = DateTime.Parse(expirationString);
}
LicenseInformation info = new LicenseInformation
{
Product = product,
Expiration = expiration
};
byte[] sourceBytes = GetSourceBytes(product, expiration);
info.IsValid = rsa.VerifyData(sourceBytes, CryptoConfig.MapNameToOID("SHA512"), signature);
return(info);
}
}
