SilentRelay

SilentRelay is an amateur secure messaging system, implemented in Java. It allows users to send and receive encryted messages securely. This repository contains the source code for both the server and the client components of the system.

Table of Contents

• Installation
• Architecture
• Model

Installation

Prerequisites

• Java Development Kit (JDK 17)

Clone the Repository

• git clone https://github.com/davidigandan/silentrelay.git

Generate Cryptographic Keys

javac RSAKeyGen.java
java RSAKeyGen <server>
java RSAKeyGen <clientID>

Start the server

javac Server.java
java server <port>

Start the client

javac Client.java
java client <host> <port> <uuid>

Architecture

• The server must be started up first. It listens for an incoming client connection. The server will NOT handle multiple client connections
• The server will store (in memory) user messages. Messages will be lost once the program stops.
• Both the server and the client will verify message signatures, encrypt them and decrypt them as the messages are transmitted.
• Messages are encrypted using RSA public-key cryptography
• Each message includes a digital signature

Model

sequenceDiagram
Alice -->> Server: Hello Bob, how are you?
Server-->>Bob: Hello Bob, how are you?
Bob -->> Server: I am good thanks!
Server -->> Alice: I am good thanks!
Note left of Server: The server has access to<br/> the private key server.prv <br/>as well as public keys <br/> from all potential recipients. 

Loading

Detailed Flowchart

graph LR
A[Alice] -- plaintext message --> X(encrypt with server.pub, timestamp, sign)
X --> ciphertext,signature --> D{Server} 
D --> H(Decrypt with server.prv)-->I(Verify signature)-->J(Store for Bob) -->D
B[Bob] --> C(hashedUserId) --> D
D--> E(ciphertext,signature) --> B[Bob] 

Loading