You can Encrypt and Decrypt string variable like QueryString etc by FormsAuthentication class. This class is Derived from System.Web.Security. This is a simple method to encryption and decryption. I think the code will definitely explain how it works. if anyone want detailed description just drop a comment i will reply ASAP.
First Initializes a new instance of FormsAuthenticationTicket class, this ticket is used to encrypt via FormsAuthentication.Encrypt(FormsAuthenticationTicket tk) method. FormsAuthentication.Encrypt method return encrypted string.
FormsAuthenticationTicket has three parameters.parameters are string name, bool isPersistent, and int timeout.The time, in minutes, for which the authentication ticket is valid. if isPersistent is true if the ticket will be stored in a persistent cookie (saved across browser sessions); otherwise, false. If the ticket is stored in the URL, this value is ignored.
private string Encrypt(string stringToEncrypt)
FormsAuthenticationTicket tk = new FormsAuthenticationTicket(stringToEncrypt, false, 600);
// returns encrypted string
private string Decrypt(string encryptedString)
FormsAuthenticationTicket tk= FormsAuthentication.Decrypt(encryptedString);