Save an encrypted person class

EduNetworkBuilder/PersonClass.cs

@@ -7,6 +7,8 @@ using System.Xml;
 using System.IO;
 using System.Windows.Forms;
 using System.Drawing;
+using System.Security.Cryptography;
+using System.Security.Cryptography.Xml;
 
 namespace EduNetworkBuilder
 {
@@ -30,7 +32,7 @@ namespace EduNetworkBuilder
         /// </summary>
         public string FullName = "";  
 
-        List<string> Passwords = new List<string>();
+        string Password = "";
 
         string PasswordHint = "";
         /// <summary>
@@ -79,22 +81,9 @@ namespace EduNetworkBuilder
         }
 
 
-        public string Password(int index = 0)
-        {
-            if (Passwords.Count == 0) return "";
-            if (index < 0) return "";
-            if (index >= Passwords.Count) return "";
-            return Passwords[index];
-        }
-
         public void ChangePassword(string NewPassword)
         {
-            Passwords.Insert(0, NewPassword);
+            Password = NewPassword;
-            int maxPWs = 1;
-            if (isAdmin)
-                maxPWs = 10; //Admins store the last 10 passwords. If the admin changed his PW, we still need to decrypt the student's files
-            for (int a = Passwords.Count - 1; a >= maxPWs; a--)
-                Passwords.RemoveAt(a); //Remove all but the one password
         }
 
         #region Load and Save 
@@ -149,7 +138,7 @@ namespace EduNetworkBuilder
                             ChangePassAtFirstLogin = changepw;
                             break;
                         case "password":
-                            Passwords.Add(Individual.InnerText);
+                            Password = Individual.InnerText;
                             break;
                         case "settings":
                             UserSettings = NB.Deserialize<NBSettings>(Individual.InnerText);
@@ -198,7 +187,12 @@ namespace EduNetworkBuilder
                 writer.WriteEndElement();
                 writer.WriteEndDocument();
             }
-            doc.Save(filename);
+            if(TryToEncrypt(doc) != null)
+                doc.Save(filename);
+            else
+            {
+                //We should blow up gracefully.  Not sure why we failed.
+            }
         }
 
 
@@ -222,8 +216,7 @@ namespace EduNetworkBuilder
             string settingsstring = NB.SerializeObject<NBSettings>(UserSettings);
             writer.WriteElementString("Settings", settingsstring);
 
-            foreach(string One in Passwords)
+            writer.WriteElementString("Password", Password);
-                writer.WriteElementString("Password", One);
             foreach (PersonClass PC in Students)
                 PC.Save(writer, true); //Save as a student entry
             //Save all the devices
@@ -233,6 +226,43 @@ namespace EduNetworkBuilder
             }
             writer.WriteEndElement();
         }
+
+        private XmlDocument TryToEncrypt(XmlDocument What)
+        {
+            string UserPassword = UserName + Password;
+            if (UserPassword == "") return null; //This should never happen
+            string salt = TrippleDESDocumentEncryption.GenSalt(NB.GetRandom());
+
+            TripleDES tDESkey = TrippleDESDocumentEncryption.GenKey(UserPassword, salt);
+            TrippleDESDocumentEncryption xmlTDES = new TrippleDESDocumentEncryption(What, tDESkey);
+
+            try
+            {
+                // Encrypt the "user" element.
+                xmlTDES.Encrypt("User");
+                //make the entries for the key
+                XmlNode tNode = xmlTDES.Doc.CreateElement("EncryptedKey");
+                tNode.InnerText = UserPassword;
+                XmlElement inputElement = xmlTDES.Doc.GetElementsByTagName("EncryptedData")[0] as XmlElement;
+                xmlTDES.Doc.DocumentElement.InsertAfter(tNode, inputElement);
+
+                //add the salt
+                tNode = xmlTDES.Doc.CreateElement("Salt");
+                tNode.InnerText = salt;
+                xmlTDES.Doc.DocumentElement.InsertAfter(tNode, inputElement);
+
+                //encrypt the user key with the admin key
+                xmlTDES.SetKey(AltPassword, salt);
+                xmlTDES.Encrypt("EncryptedKey");
+
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e.Message);
+                return null;
+            }
+            return xmlTDES.Doc;
+        }
         #endregion
 
         public bool AddHomework(SchoolworkClass ToAdd)