public void CheckServerEncryption_RM()
{
GenerateClientSessionKeys(out _, out var encryptedSessionKeys);
List <byte[]> decryptedSessionKeys = new List <byte[]>();
foreach (string key in encryptedSessionKeys)
{
decryptedSessionKeys.Add(ServerEncryption.RsaDecryptCipher(key));
}
Assert.That(decryptedSessionKeys.Count > 0);
for (int i = 0; i < decryptedSessionKeys.Count; i++)
{
string plainText = GenerateRandomString(36);
Assert.That(plainText.Length == 36);
// Encrypt and prepare the message.
string cipher = ServerEncryption.EncryptPlainText(plainText, decryptedSessionKeys[i], out string initialisationVector).ToHexString();
string message = $"{initialisationVector}{cipher}";
// Decrypt the message [ClientDecryption_RM]
byte[] initialisationVectorBytes = ClientEncryption.ParseIvFromMessage(message);
byte[] cipherBytes = ClientEncryption.ParseCipherFromMessage(message);
string decipher = ClientEncryption.DecryptCipher(cipherBytes, decryptedSessionKeys[i], initialisationVectorBytes);
Assert.AreEqual(plainText, decipher);
}
}
public void CheckServerDecryption_RSA()
{
GenerateClientSessionKeys(out var unencryptedSessionKeys, out var encryptedSessionKeys);
List <byte[]> decryptedSessionKeys = new List <byte[]>();
Assert.That(encryptedSessionKeys.Count > 0);
foreach (string key in encryptedSessionKeys)
{
decryptedSessionKeys.Add(ServerEncryption.RsaDecryptCipher(key));
}
Assert.AreEqual(encryptedSessionKeys.Count, decryptedSessionKeys.Count);
// Ensuring that there is equivalence between unencrypted and decrypted session keys.
for (int i = 0; i < decryptedSessionKeys.Count; i++)
{
Assert.AreEqual(decryptedSessionKeys[i].ToHexString(), unencryptedSessionKeys[i]);
}
}
public static void Main(string[] args)
{
// T0
// -- CLIENT --
// Simulating a client-server relationship, the first step required is for the client to
// generate a session key and encrypt it by virtue of the server's public key.
// (Because the encryption libraries are static, this first step is automatically completed.)
string sessionKey = ClientEncryption.RsaEncryptCipher().ToHexString();
Console.WriteLine($"Client session key is: {sessionKey}");
// At this point, the client sends this session key to the server.
// -- END CLIENT --
// T1
// -- SERVER --
// Once the server receives this session key, it must decrypt it by virtue of its private key.
// Now actual messages can be sent.
byte[] decryptedSessionKey = ServerEncryption.RsaDecryptCipher(sessionKey);
Console.WriteLine($"Client session key length is: {decryptedSessionKey.Length}");
// -- END SERVER --
while (true)
{
// T2
// At this stage, your program will send whatever information to the server or client.
Console.WriteLine("Please enter some plain text: ");
string plainText = Console.ReadLine();
// T3
// -- CLIENT --
// Now the session key can be itself used for encryption.
// Hex string is convenient for sending data because its characters are wide-spread.
string initialisationVector = ClientEncryption.InitialisationVector;
Console.WriteLine($"The current initialisation vector is: {initialisationVector}");
// Encrypt the plain text.
string cipher = ClientEncryption.EncryptPlainText(plainText, sessionKey.ToByteArray()).ToHexString();
Console.WriteLine($"Your plain text ({plainText}) encrypted is: {cipher}");
// Then send the cipher to the server.
// Remember to send the initialisation vector, if using it, along with the message, like so:
string message = $"{initialisationVector}{cipher}";
Console.WriteLine($"The complete message (IV and cipher) is: {message}");
// -- END CLIENT --
// T4
// -- SERVER --
// The server then receives an encrypted (hex) string. However, it first needs to organise the
// information before decrypting it, by discerning the IV and cipher (i.e., the actual message).
// Of course, this step is not necessary if you decide not to utilise initialisation vectors.
byte[] initialisationVectorBytes = ServerEncryption.ParseIvFromMessage(message);
Console.WriteLine($"The length of the initialisation vector is: {initialisationVectorBytes.Length}");
byte[] decipherBytes = ServerEncryption.ParseCipherFromMessage(message);
Console.WriteLine($"The length of the (de)cipher is: {decipherBytes.Length}");
// All that is remaining to do is to decrypt the cipher.
string decipher = ServerEncryption.DecryptCipher(decipherBytes, decryptedSessionKey, initialisationVectorBytes);
Console.WriteLine($"The deciphered message is: {decipher}");
// Decryption complete.
// -- END SERVER --
}
}