Ronin Bridge

What happened

The Ronin bridge, which connected the Axie Infinity game's sidechain to Ethereum, was drained in March 2022 after attackers gained control of a majority of the small validator set whose signatures authorised withdrawals. Nothing was broken in the contract: the withdrawals were validly signed by the keys the system trusted. The loss was only discovered days later, when a user reported being unable to withdraw. US authorities subsequently attributed the theft to the North Korea-linked Lazarus Group.

What to take from it

A bridge is only as decentralised as its signer set. When a handful of keys can authorise every withdrawal, compromising those keys is the whole attack — and if nobody is watching the balance, it can take days for anyone to notice the money has gone.

Dates and figures are widely reported public estimates from coverage at the time, not KripZen's own audited data.