Sky Mavis, the developers of the popular play-for-profit (P2E) non-fungible token (NFT) game, has announced that the Ronin Bridge is back online three months after it was hacked for more than $600 million.
The Ronin Bridge is an Ethereum sidechain built for Axie Infinity, which enables users to move assets between the Ethereum sidechain and the mainnet.
On March 29, 173,600 Ether (ETH) and $25.5 million (USDC) were drained from the bridge after hackers gained access to private verification keys. The hack was valued at over $620 million at the time.
According to an announcement Tuesday from the Sky Mavis team, the Ronin Bridge is back online after three audits (one internal, two external), a new design and full compensation for stolen user assets:
“All Ronin Network, WETH, and USDC users owned by Ronin Network users are now fully backed by 1:1 ETH and USDC on Ethereum, as promised. All users are made complete.”
In total, Sky Mavis has now repaid 117,600 ETH and $25.5 million by providing ETH liquidity to support ETH (wETH) users on the Ronin network.
In April, about 46,000 of this ETH was already redeemed after Binance offered a bridge to the exchange so that users could exchange it for ETH. Liquidity was drawn from the Axie Infinity Balance and founders funds to support the move. Binance also led a $150 million funding round to help Sky Mavis repay Axie Infinity users.
The remaining 56,000 of the total stolen ETH belongs to Axie DAO Treasury and will remain unsecured as Sky Mavis is “working with law enforcement to recover the funds.”
As part of the design of the revamped bridge, Sky Mavis has updated its smart contract software to enable validators to set daily withdrawal limits, with the initial amount set at $50 million at this point. The team also introduced a circuit breaker system that divides the monetary value of withdrawals into three levels.
Level 1 is for withdrawals under $1 million and requires 70% of validators to sign, and Level 2 is for amounts over $1 million and requires 90% of validator signatures. Level 3 is for withdrawals over $10 million and requires a 90% validator checkout, a small transaction fee, and a seven-day review process:
“The design of the new bridge incorporates the circuit breaker system as a contingency plan that increases the security of the bridge by stopping large suspicious withdrawals.”
Sky Mavis admitted in an autopsy report in late April that its lack of decentralization made the Ronin Bridge vulnerable to hacking. At the time, it only had nine nodes for verification, and employees had access to four of them.
After immediately raising the knot count to 11, Sky Mavis set its intentions to increase the number to 21 within three months of the autopsy, with a long-term goal of exceeding 100 knots total.
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However, the team did not provide an update on the number of validator nodes the Ronin Network now has in the latest announcement.
Axie Infinity saw its monthly NFT sales volume rise in 2022, with data from CryptoSlam showing that the game went from generating $126.4 million in January to just $2.8 million in June.