Skip to content
This repository was archived by the owner on Apr 23, 2023. It is now read-only.

Security considerations

Jump to bottom
Fabian Sauter edited this page Jul 9, 2018 · 2 revisions

User authentication

We support user authentication with username and password.

DoS protection

To prevent DoS attacks we make sure the send Client-Hello-Handshake message is always larger than the Server-Hello-Handshake message. We fill up the Client-Hello-Handshake message with random bits so it is always 1000 bits long.

Multi-way handshake

For the key-exchange we use the Diffie-Hellman key-exchange.

Client				  Server
  |	ClientStartConnection	    |
  | ------------------------------> | Client calculates and sends P, G to the server.
  |				    | 
  |	onServerReceive             |
  | <------------------------------ | Server calculates it's shared key, public key and sends it's
  |				    | public key to client.
  |				    | Sets secureConnection to true.
  |	onClientReceive		    |
  | ------------------------------> | Client calculates it's shared key.
  |                                 | Sets secure connection to true.

Diffie-Hellman algorithm relies on discrete logarithm problem. It is very hard for computers to solve discrete logarithm thus it is a good candidate against brute force attacks. This implementation works like this:

  • Client and server have to have the common values P and G. P is a prime number and G is the primitive root of that number. As connections are initiated by client, both P and G is calculated by client. Before sending P and G, client generates a private key and calculates it's public key. P , G and client's public key are sent to server by the client at the beginning of the connection.

  • Server receives P , G , and client's public key. It selects a private key for itself and calculates it own public key. At this calculation, server also successfully calculates the shared key that the encryption will be based on.

  • Client receives server's public key and calculates the shared key. At this point both server and the client have the same shared key which has never transmitted through insecure channels.

  • Exposed API of Encrypt and Decrypt uses that shared key to encrypt and decrypt messages.

More info can be found at: Wiki Link

Encryption

We encrypt all messages with a asymmetric encryption (Implementation). Because we forgot to enable the encryption again, all messages get send unencrypted.

Man-in-the-Middle attacks

We are vulnerable against Man-in-the-Middle attacks. We do not use any server authentication mechanisms at the moment (e.g. certificates).

Clone this wiki locally