Play with pDiem

The pdiem full stack includes:

  • A local Diem testnet: diem, diem-cli
  • A Phala Network local testnet with the pdiem contract: phala-node, phala-pruntime, phala-phost
  • A relayer to connect the both networks: pdiem-relayer

With the pdiem full stack running, we are going to send some Diem transactions to the pdiem deposit account, and check if the pdiem contract has received it.

Create Diem accounts

Start the diem-cli from the same directory by:

docker-compose run --rm --entrypoint /bin/bash -- diem-cli ./diem-cli.sh

Then run the following commands to prepare the accounts:

# Create two accounts
diem% account create
diem% account create
# Mint some funds
diem% account mint 0 100 XUS
diem% account mint 1 100 XUS

The diem-cli tool is a light wallet connecting to the diem node via RPC. It can be used to manage accounts, transfer tokens, and query the blockchain. In the above steps, we created two accounts (indexed by 0 & 1), and mint some test XUS token to the account.

Among them, the account 0 is a special account that hard-coded in the pdiem-m3 demo contract as the deposit address. Usually diem-cli generates random accounts. But in the pdiem-m3 demo, the seed to generate the wallets is pinned with a special file client.mnemonic so that everytime it generates the same hard-coded account.

Simple diem-to-pdiem transfer

Simple transfer refers to the transfer between the admin address (account 0, hardcoded in the pdiem-m3 contract).

To send Diem assets to pdiem, just transfer it to the admin address (account 0) in diem-cli. For example, we can send 10 XUS to account 0 like this:

diem% transfer 1 0 10 XUS

And that’s all!

Behind the scene, pdiem-relayer picked up the deposit transaction, sent a regular Substrate extrinsic to the pdiem confidential contract on Phala to sync the transaction. After the validation of the incoming transaction and the proof, the pdiem contract will accept it. Usually it takes 30 seconds for the relayer to pick up the transaction, and relay to pdiem side.

Balances in pdiem

./phala-console.sh pdiem-balances

Verified transactions

All the transactiosn received by pdiem contract are validated against the latest Diem ledger state, which is protected by a PoS-like consensus. The validated transactions are stored inside the pdiem contract storage, and can be checked by anyone:

./phala-console.sh pdiem-tx

Prepare subaccounts for two-way transfer

pdiem-m3 uses Diem’s subaccount feature to create deposit accounts. Any user can create its Diem deposit subaccount by sending a NewAccount command:

./phala-console.sh pdiem-new-account 0 '//Bob'

The above command will send Command::NewAccount to the pdiem contract from Substrate account “Bob”. You can create as many accounts as you want. It takes 2-3 blocks to process the command.

The first argument of pdiem-new-account is the sequence id of the new account transaction on Diem. Similar to the other blockchains, Diem also requires every transaction has incremented sequence id. So when creating another new subaccount, run ./phala-console.sh pdiem-new-account 1 '//Charlie'.

Then you can get a full list of the Diem accounts by a query:

./phala-console.sh pdiem-balances

As shown in the screenshot, Bob just created its deposit Diem address 4DB6A10FCEB765C55ADC3751474AE8D1.

Deposit (diem → pdiem)

Get your deposit address from the last step. And now you can deposit some XUS on the Diem side in diem-cli:

diem% transfer 0x57c76da2e144c0357336ace2f3f8ac9b 0x4DB6A10FCEB765C55ADC3751474AE8D1 10 XUS
The transfer command in diem-cli takes the source account and the destination account as the first two arguments. It accepts either two account references (e.g. 0 for account 0 in the local wallet), or two hex-encoded addresses. In the example above, 0x57c76da2e144c0357336ace2f3f8ac9b is account 1 and 0x4DB6A10FCEB765C55ADC3751474AE8D1 is Bob’s the deposit subaccount.

The corss-chain transfer takes around 4-6 blocks to complete. Check the balance by:

./phala-console.sh pdiem-balances

In this example, Bob’s Diem account will get 10 XUS, which is 10000000 under the free field in the pdiem-balances outputs (6 decimals).

Withdraw (pdiem → diem)

You can withdraw assets from pdiem back to diem by pdiem-withdraw:

./phala-console.sh pdiem-withdraw 4DB6A10FCEB765C55ADC3751474AE8D1 '10 XUS' '//Bob'

In the command above the arguments are:

  • 4DB6A10FCEB765C55ADC3751474AE8D1: The Diem address to withdraw
  • '10 XUS': The amount of the assets
  • '//Bob': The SURI of the Substrate account private key to withdraw

The pdiem-withdraw command sends a Command::TransferXUS transaction to the pdiem contract via the Phala blockchain. The contract then creates a Diem transaction from the subaccount to the withdrawal target, sign it, and push it to a queue. Once the pdiem-relayer noticed new transactions in the queue, it relays them to the Diem blockchain.

The withdrawal transactions are queued until it gets confirmed on Diem. When confirmed, the outgoing transactions are observed by the pdiem-relayer, and an evidence is sent back to the pdiem contract. Finally the pdiem contract will confirm the withdrawal transactions are executed.

You can check your pdiem balance at any point:

./phala-console.sh pdiem-balances

You can still see the withdrawal amount under the “locked” balances until transaction is confimed on Diem. The above screenshot has two sides. The left side shows the withdrawal funds was locked and pending confirmation, while the right side shows the locked funds were removed because the outgoing tx is confirmed. Finally the sequence under the deposit account was incremented to 1.

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