Axie Infinity Restarts Ronin Bridge Months After $625M Exploit

Axie Infinity’s Ronin bridge has been restarted three months after a sophisticated exploit saw some $625 million worth of cryptocurrencies stolen from the protocol, the developers said Tuesday.

The bridge was restarted after an internal audit and external audits by blockchain security firms Verichains and Certik. All user funds are fully backed on a 1:1 basis by the new bridge and users have been made whole, developers said.

The new bridge design includes a circuit-breaker system as a contingency plan to increase the security of the bridge by halting large, suspicious withdrawals, developers said.

Bridges are protocols that enables an exchange of information, cryptocurrency or assets such as non-fungible tokens (NFT) from one blockchain network to another. The Ronin bridge allows funds to flow between Ethereum and the Ronin blockchain.

The March exploit affected Ronin validator nodes for Sky Mavis, the publisher of the popular Axie Infinity game, and the Axie DAO, with attackers stealing some 173,600 ether (ETH) and 25.5 million in USDC. An attacker “used hacked private keys in order to forge fake withdrawals” from the Ronin bridge across two transactions, according to a blog posted at the time.

Ronin took corrective measures at the time, such as reducing token emissions, to prevent the collapse of the Axie Infinity ecosystem. The moves did little to save prices of Axie’s native AXS tokens amid a broader market decline, with prices down 90% since their lifetime highs in November.

"We're glad to put this behind us and push onwards with shipping more games in the Axie Universe and on the Ronin Network," Sky Mavis CEO Aleksander Larsen wrote in an email to CoinDesk.

UPDATE (June 29, 08:14 UTC): Adds Sky Mavis CEO in last paragraph.