Cody McGrath 
After Sky Mavis put in place a circuit breaker system and daily withdrawal limits, the Ronin bridge to Axie Infinity is back up with a new look.
Sky Mavis, the developers of the popular play-to-earn (P2E) NFT game Axie Infinity, have revealed that the Ronin bridge is now operational again, three months after it was hacked for more than $600 million.
The Ronin bridge is an Ethereum sidechain created for Axie Infinity that allows users to move assets between the sidechain and the Ethereum mainnet.
On March 29, hackers gained access to private validator keys and emptied 173,600 Ether (ETH) and 25.5 million USD Coin (USDC) from the bridge. At the time, the hack was worth more than $620 million.
The Ronin bridge is back up, according to a June 28 release from the Sky Mavis team, after three audits (one internal, two external), a fresh design, and complete restitution for consumers’ stolen money.
“All wETH and USDC owned by Ronin Network users are now fully backed 1:1 by ETH and USDC on Ethereum, as promised. All users’ have been made whole.”
Sky Mavis has already repaid 117,600 ETH and 25.5 million USDC in total by providing ETH liquidity to back users’ wrapped ETH (wETH) on the Ronin network.
Around 46,000 of that ETH had previously been reimbursed in April after Binance added a bridge to its exchange so that users could exchange wETH for ETH. To support the move, liquidity was drawn from the Axie Infinity balance and the founders’ cash. Binance also leads a $150 million round of funding to assist Sky Mavis in repaying Axie Infinity users.
The remaining 56,000 ETH belonging to the Axie DAO Treasury will remain uncollateralized as Sky Mavis “works with law enforcement to reclaim the cash.”
Sky Mavis has updated the smart contract software as part of the redesigned bridge design, allowing validators to establish daily withdrawal limitations, with the starting amount set at $50 million at this time. In addition, the team implemented a circuit breaker mechanism that divides the monetary worth of withdrawals into three layers.
Tier 1 requires 70 percent of validators to sign off on withdrawals less than $1 million, while Tier 2 requires 90 percent of validators to sign off on withdrawals higher than $1 million. Tier 3 withdrawals exceed $10 million and necessitate a 90 percent validator sign-off, a minor transaction charge, and a seven-day review period.
“The new bridge design includes a circuit-breaker system as a contingency plan which increases the security of the bridge by halting large suspicious withdrawals.”
Sky Mavis revealed in a postmortem study released in late April that the Ronin bridge was vulnerable to the breach because of a lack of decentralization. It had just nine validator nodes at the moment, with staff having access to four of them.
Sky Mavis announced her plan to increase the number of nodes to 21 within three months of the postmortem with the long-term objective of surpassing 100 total nodes.
In the recent announcement, the company did not provide an update on how many validators nodes the Ronin network now has.
Axie Infinity’s monthly NFT sales volume dropped substantially in 2022, according to CryptoSlam data, dropping from $126.4 million in January to $2.8 million in June.