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M2: Confidential Balances Contract

This is the final deliverables of pLIBRA Milestone 2. It implements a confidential Balances-like token contract where the balances are hidden to everyone except the owner.

The Balances module is a confidential contract on Phala Network. The contract execution happens inside TEE (Trusted Execution Environment, a hardware enclave) to keep the internal state secret.

Only the authorized commands and queries are executed. So the unauthorized balance queries are rejected.

Build the demo

The frontend is deployed here: https://webui.phala.network/

To play with Phala Network, you also need to deploy the rest of the components. We made a Docker image for easy deployment:

  1. Clone plibra-grant-docker

    git clone https://github.com/Phala-Network/plibra-grant-docker

  2. Build

    cd plibra-grant-docker
sudo docker build -t phala:test .

  3. Run and publish the API port to 8080.

    sudo docker run -p 8080:8080 phala:test

Enter the Substrate websocket RPC endpoint in Settings tab. If you published the port to 8080, use http://localhost:8080/ws.

Enter Phala Demo M2 tab. If you are using the default port 8080, the status bar should look like the screenshot above. By default the pRuntime endpoint is http://localhost:8080/tee-api/. It can be changed by clicking the setting button (first from left).

Once the pRuntime is connected, it shows "connected: (latency)". It should also say "initialized: yes", indicating a bridge between between the chain the pRuntime has already been established.

Transfer

To transfer some token, please select an identity as the sender first. In the screenshot we are transferring 1000 tokens from Alice to Bob.

At beginning, Alice is the only person with token. So we should transfer some tokens from Alice to another person. Otherwise the transaction is not going to be executed because of insufficient funds.

Check balance

After transferring 1000 tokens from Alice to Bob, we can check Alice's remaining balance by FreeBalance query. So 24 tokens remain.

The query is performed by the selected identity (Alice in the screenshot). So if you query Bob's balance, it should show 1000 as well.

However, as by the design, only the owner can see his balance. FreeBalance for Bob button always queries Bob's balance. So if you choose another identity other than Bob, you will get a NotAuthorized error as shown in the screenshot above. This is the unique feature provided of confidential contracts.

Finally, TotalIssuance shows the total token issuance. It doesn't require any authentication.

Ecdh Test

All the communication between the client and the confidential contract is end-to-end encrypted. The encryption is based on ECDH key agreement. In this section it shows the agreed secret. (It's only shown in the demo for testing purpose. It will be removed in production.)

See also

Demo:

  • M2: Confidential Balances Contract

Deep dive:

Projects: