//does encryption and decryption and returns a filled testResult
private TestResult process(String message)
{
TestResult testResult = new TestResult();
//encryption
stopWatch.Start();
byte[] plainMessageBytes = Encoding.UTF8.GetBytes(message); //convert message to byte array
Tuple <byte[], byte[]> res = CryptoUtility.AESEncrypt(plainMessageBytes, AESKey); //encrypts data
//extract results
byte[] encMessageBytes = res.Item1; //gets encrypted bytes from tuple
byte[] IV = res.Item2; //gets initialisation vector from tuple
stopWatch.Stop();
testResult.encryptionTime = (int)stopWatch.ElapsedMilliseconds; //store time taken
testResult.totalLength = encMessageBytes.Length; //store length of encrypted message
//decryption//
stopWatch.Reset();
stopWatch.Start();
//passes back encrypted message, key and initialisation vector to decrypt it
string decryptedMessage = CryptoUtility.AESDecrypt(encMessageBytes, AESKey, IV);
stopWatch.Stop();
testResult.decryptionTime = (int)stopWatch.ElapsedMilliseconds;
//check that nothing went wrong
if (0 != String.Compare(decryptedMessage, message))
{
throw new Exception("something ain't right");
}
testResult.totalTime = testResult.encryptionTime + testResult.decryptionTime; //adds up total time
return(testResult);
}
//reads contact info from database and creates Contact objects
private void loadContacts()
{
contactsList.Clear(); //empty list, if reading from database might as well reload everything
SQLiteDataReader reader = db.retrieve("SELECT * FROM Users"); //gets all user records
//if(reader.HasRows) //if any data was read from the DB
Contact contact; //temporary contact object to add to list
while (reader.Read()) //iterate over each tuple returned from the database
{
int ID = Convert.ToInt32((long)reader["userID"]); //sqlite handles primary key field as int64
byte[] encUsername = (byte[])reader["username"];
byte[] encIPAddress = (byte[])reader["IPAddress"];
byte[] IV = (byte[])reader["IV"]; //initialisation vector encUsername and ecnIPAddress were encrypted with
byte[] masterKey = Globals.getMasterKey(); //decrypts and gets master key
string username = CryptoUtility.AESDecrypt(encUsername, masterKey, IV); //decrypt username
string IPAddress = CryptoUtility.AESDecrypt(encIPAddress, masterKey, IV); //decrypt IPAddress
contact = new Contact(ID, username, IPAddress); //puts contact info into object
contactsList.Add(contact);
}
}
//this method tests the creation of a random AES key, then using it encrypt and decrypt a message
public void testRandomKeyEncryption()
{
string data = "hello, good morning, I hope all is well. blahblahblahblahblah";
byte[] dataBytes = Encoding.UTF8.GetBytes(data); //convert data to bytes
byte[] keyBytes = CryptoUtility.GenerateAESRandomKey(); //gets randomly generated
//tuple contains encrypted bytes plus initialisation vector needed to decrypt it
Tuple <byte[], byte[]> enc = CryptoUtility.AESEncrypt(dataBytes, keyBytes); //encypts and gets encrypted bytes + IV
byte[] encBytes = enc.Item1; //encrypted bytes
byte[] IV = enc.Item2; //Instantiation vector
string decryptedString = CryptoUtility.AESDecrypt(encBytes, keyBytes, IV);
Assert.AreEqual <string>(data, decryptedString); //compare original data to the decrypted string
}
/// <summary>
/// Takes a contact and returns a list containg all messages exchanged between local and contact.
/// </summary>
/// <param name="contact">Contace for which to get history of exchanges messages</param>
/// <returns>List of messages associated with the provided contact</returns>
public List <Message> getMessageHistory(Contact contact)
{
List <Message> messages = new List <Message>();
Message message; //temp var to hold messages before being put into list
//for <contactID> select every message, initialisation vector to decrypt the message, the ID of the key it's encrypted with, and bool if it was sent or received
SQLiteDataReader reader = db.retrieve($"SELECT sent, message, IV, keyID FROM Messages WHERE (conversationID = \"{contact.ID}\")");
//API BUG - SELECT with explicit fields fails ONLY when the fields are in brackets, lord knows why
while (reader.Read()) //iterate over all existing records
{
bool sent = (bool)reader["sent"]; //extract if message was sent or received
byte[] encMessageBytes = (byte[])reader["message"]; //extract message
byte[] messageIV = (byte[])reader["IV"]; //extract initialisation vector for message
int keyID = Convert.ToInt32((long)reader["keyID"]); //extract ID of key that encrypted message. sqlite handles forien keys to primary keys as int64.
byte[] messageKey = keyManager.getKey(keyID); //gets plain key from manager (must be discarded once done with)
//passes encrypted message bytes, plain key and IV to CryptoUtility and gets decrypted message in return
string messageString = CryptoUtility.AESDecrypt(encMessageBytes, messageKey, messageIV);
messageKey = null; //garbage collect key bytes
int senderID;
int targetID;
if (sent) //message was sent by local
{
senderID = 0;
targetID = contact.ID;
}
else //message was sent by contact
{
senderID = contact.ID;
targetID = 0;
}
message = new Message(messageString, senderID, targetID); //create the message object
messages.Add(message); //store it in list
}
return(messages);
}
/// <summary>
/// AES 解密(高级加密标准，是下一代的加密算法标准，速度快，安全级别高，目前 AES 标准的一个实现是 Rijndael 算法)
/// </summary>
/// <param name="decryptString">待解密密文</param>
/// <param name="decryptKey">解密密钥</param>
/// <returns></returns>
public static string AESDecrypt(this string decryptString, string decryptKey)
{
return(CryptoUtility.AESDecrypt(decryptString, decryptKey));
}