A Blockchain Approach to Messaging Applications

Authors: Sherif Abdekarim, Yotam Golan, Brooke Ryan

CS 295, Blockchain Systems

UC Irvine Winter 2022

Professor Faisal Nawab

About

This is the repository for the code associated with the paper A Blockchain Approach to Messaging Applications. It is a low-cost, minimalistic messaging application that runs on the Ethereum Virtual Machine. It was written in Solidity, which is a language designed for writing smart contracts for Ethereum-based applications.

This application was developed as a course project for CS 295 Blockchain Systems at UC Irvine under the guidance of Professor Faisal Nawab.

messaging_app.sol contains the main code for the project. It contains the smart contracts for storage, the central contract, the sender, and receiver contracts.

messaging_app_optimizations.sol contains code created for preliminary experiments regarding cost optimizations.

Deployment

Note: The instructions provided here deploy the application to an Ethereum testing environment.

The following instructions delineate how to deploy all four of the Smart Contracts of the code provided in the paper. For some of the contracts, such as Sender and Receiver, there are multiple ways to instantiate a new user in the system. The outline below is just one of the ways.

1. Open messaging_app.sol in the Ethereum Remix IDE.
2. Navigate to the compiler tab and compile messaging_app.sol.

3. Navigate to the Deploy and Run Transactions Tab. Set the Environment to JavaScript VM (London or Berlin).

5. Select the Storage smart contract from the Contract configuration. Press Deploy.
   1. Ensure that the Storage contract is now listed as a Deployed Contract.

6. Next, select centralContract from the Contract dropdown menu. Paste the memory address from the Storage smart contract into the storage_address parameter, then press transact.

   1. Ensure that centralContract is listed under Deployed Contracts.

7. Next, we will deploy the Sender smart contract. Select Sender from the Contract dropdown menu. Paste the centralContract memory address into the smart_contract_address parameter, and then paste the encryption public key into the public_key_ parameter. (Ensure that the key is surrounded by quotation marks, since it is a string parameter.) Then press Transact. Ensure that the sender smart contract is listed under Deployed Contracts.

8. Finally, we will deploy the Receiver smart contract. Select Receiver from the Contract dropdown menu. Paste the centralContract memory address into the smart_contract_address parameter, and then paste the encryption public key into the public_key_ parameter. (Ensure that the key is surrounded by quotation marks, since it is a string parameter.) Then press Transact. Ensure that the Receiver smart contract is listed under Deployed Contracts.

Sending and Receiving Messages

Register Sender and Receiver Public Key to Central Contract

We now need to officially register the Sender and Receiver contracts to the central contract. To do this, simply call create_user from the respective Sender and Receiver contracts under the list of Deployed Contracts. Now that the main contracts have been deployed, we can send and receive messages between the existing users in the system.

Sending Messages

1. First, under the deployed Sender contract, we will call the get_public_key function. Paste in the memory address from the Receiver contract. Press transact, and observe the response in the console.

2. Then, on your own local machine, use the obtained public key to encrypt the message.
3. Paste the receiver's memory address into the receiver parameter, and paste the encrypted message into the message parameter. Press transact.

Receiving Messages

1. Now, transact the get_message function on the Receiver deployed contract. Observe the response in the console. Use the private key to decrypt the message.