Proof of Concept Single Node Bridge

[TorstenStueber]

Step 1

Deposit

• create the off-chain worker
  • see, e.g., the Tutorial
  • don't use a stream but poll horizon server
  • off-chain worker should only be called once (don't poll twice)
• create new transaction type
  • feeless transaction that can only be submitted by that node (the one bridge node)
  • needs to mint new funds and create the asset (requires usage of assets pallet)
  • as first step it's fine to use a hard coded account

Withdrawal

• use some off-chain worker (maybe same as the one for deposit?)
  • inspect the black has just been finalized
  • check if funds have been sent to some (fixed) burning address
  • create, sign, submit a Stellar transaction to release funds from escrow account
  • just transfer to a fixed use account

Step 2

Nice to have (step 2): actually support different user accounts instead of hard-coded accounts

The same but for Deposit:

• use the decoded account id (as Ed25519 public key) of the Stellar account for idenfying the Pendulum account
  • account might need to be created
  • then transfer funds Withdrawal
  • same

[gonzamontiel]

A comment on this:

feeless transaction that can only be submitted by that node (the one bridge node)

Apparently we can submit feeless transactions from an off chain worker, called unsigned transactions. But we have to be very careful at validating this kind of transactions for avoiding DDOS and spamming the network (as stated here). Anyway, this won't truly affect the PoC.

[andywer]

we have to be very careful at validating this kind of transactions

It will be relatively easy to validate after the POC phase: The node will add some kind of signature to the transaction and such a transaction is valid if it contains a signature of an escrow account signer.

Small additional concern (after the POC): To enable non-relaying nodes to verify who is currently escrow co-signer, every change to the multi-sig setup of the escrow account will need to be synced to the Pendulum chain as well by the relayers. Those sync transactions need to be co-signed just as deposits & withdrawals. Non-relaying nodes can then verify the validity of relayer-co-signed transactions.

[TorstenStueber]

Closed. Completed as part of ticket #30 .