Query String Encryption

Hi

i am encrypt my  query string using from Authentication. my code is pasted below. is this method is good or not.

please help me to find out.

  public static string Encrypt(string encryptQuery)
    {
        FormsAuthenticationTicket tk = 
                   new FormsAuthenticationTicket(encryptQuery, false, 30);
        return FormsAuthentication.Encrypt(tk);
    }

i get encripted string using this method  like photos.aspx?aid=3306F85765AA9E9CA5F41AA0269BE6F13F6DCD51<br />EE419DF1E4C711CE22671B617C396C1DEC67089FEE19616FC1D1E808ED<br />C9287A8A10213D40D51F900363A243 

and working properly without any errors.

But i don't know is this a correct method to encrypt. 

thank you all, i think my method also a correct answer  to encrypt and decrypt string 

 public static string Decrypt(string decritptext)
    {
        FormsAuthenticationTicket tk = FormsAuthentication.Decrypt(decritptext);
        return tk.Name.ToString();
    }

this is my method to decrypt.