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Polygon PoS
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Choose token
Tether USD (USDT)
Ether (ETH)
USD Coin (USDC)
Wrapped BTC (WBTC)
Dai Stablecoin (DAI)
SAND (SAND)
Telcoin (TEL)
PYR Token (PYR)
PlayDapp Token (PLA)
ChainLink Token (LINK)
Wrapped liquid staked Ether 2.0 (wstETH)
Aave Token (AAVE)
Render Token (RNDR)
Graph Token (GRT)
Wootrade Network (WOO)Funds can be stolen if
- validators decide to mint more tokens than there are locked on Ethereum thus preventing some existing holders from being able to bring their funds back to Ethereum (CRITICAL),
- validators submit a fraudulent checkpoint allowing themselves to withdraw all locked funds (CRITICAL),
- destination token contract is maliciously upgraded (CRITICAL),
- a contract receives a malicious code upgrade. There is a 48 hours delay on code upgrades.
Users can be censored if
Principle of operation
This is a very typical Token Bridge that locks tokens in the escrow contracts on Ethereum and mints tokens on the Polygon network. When bridging back to Ethereum tokens are burned on Polygon and then released from the escrow on Ethereum.
Outbound transfers are externally verified, inbound require merkle proof
Validators on the Polygon network watch for events on Ethereum and when they see that tokens have been locked they mint new tokens on Polygon. Around every 30 minutes validators submit new Polygon state checkpoints to the Ethereum smart contracts. To withdraw tokens users need to present a merkle proof of a burn event that is verified against the checkpoints.
Users can be censored if validators on Polygon decide to not mint tokens after observing an event on Ethereum (CRITICAL).
Funds can be stolen if validators decide to mint more tokens than there are locked on Ethereum thus preventing some existing holders from being able to bring their funds back to Ethereum (CRITICAL).
Funds can be stolen if validators submit a fraudulent checkpoint allowing themselves to withdraw all locked funds (CRITICAL).
Destination tokens are upgradeable
Tokens transferred end up as wrapped ERC20 proxies, some of them are upgradable. The contract is named UChildERC20Proxy.
Funds can be stolen if destination token contract is maliciously upgraded (CRITICAL).
The system uses the following set of permissioned addresses:
Can propose and execute code upgrades via Timelock contract. This is a Gnosis Safe with 5 / 9 threshold.
Those are the participants of the PolygonMultisig.
The system consists of the following smart contracts:
Smart contract containing the logic for syncing the state of registered bridges.
Main contract to manage bridge tokens, deposits and withdrawals.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Contract storing Polygon sidechain checkpoints. Note that validity of these checkpoints is not verified, it is assumed to be valid if signed by 2/3 of the Polygon Validators.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Contract enforcing delay on code upgrades. The current delay is 2d.
Escrow contract for ETH. This contract stores the following tokens: ETH.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Escrow contract for ERC20 tokens. This contract can store any token.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Escrow contract for mintable ERC20 tokens.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Escrow contract for ERC20 tokens. This contract can store any token.
Escrow contract for ERC20 tokens that can be minted and burned.
Escrow contract for ERC721 tokens.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Escrow contract for ERC1155 tokens.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Escrow contract for mintable ERC1155 tokens.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Escrow contract for ERC1155 tokens.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Escrow contract for Unstoppable Domains NFTs.
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Value Locked is calculated based on these smart contracts and tokens:
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
Can be upgraded by: PolygonMultisig
Upgrade delay: 2d
The current deployment carries some associated risks:
Funds can be stolen if a contract receives a malicious code upgrade. There is a 48 hours delay on code upgrades.
