Whenever Portal locks tokens on one blockchain -> Synthesis mints tokens on another blockchain.
Whenever Synthesis burns tokens on one blockchain -> Portal releases tokens on another blockchain.
Let's take a closer look at the BridgeV2 contract.
An instance of the BridgeV2 contract is deployed on each blockchain supported by Symbiosis and acts as a proxy between relayers and Portal/Synthesis contracts.
BridgeV2 accepts calls from:
The Portal/Synthesis contracts locked on the same blockchain
When BridgeV2 is invoked by these contracts, it issues an Oracle request (an event in terms of smart contracts) that contains all the necessary data and instructions to accomplish the operation on the corresponding destination blockchain.
Relayers: transactions signed with an MPC key, the MPC address for this key is stored in the BridgeV2 contract. When BridgeV2 is invoked by such a transaction, the instructions from the transaction calldata get executed on the blockchain.
Scheme 1 below shows the BridgeV2 routine during cross-chain operations:
About relayers. The Symbiosis relayers network is an off-chain part of the Symbiosis protocol. The main purpose of the network is to provide fast, accurate, and secure transfer of information about cross-chain operations conducted via the Symbiosis protocol. See Relayers network for more details.