Based on feedback, research, and further development, we have made some updates to the BoLD AIP. Key highlights include:
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Reducing the challenge levels from 4 to 3 and reducing the challenge bond sizes by ~43% without compromising on security! This means that previously, it would cost 1000+100+10 ETH to fight off 1 challenge, but now it will only cost 555+79 ETH! These new numbers were carefully selected using the formulas and specifications in the whitepaper - optimizing for security (resource exhaustion ratio) and the worse-case scenario of elevated, sustained L1 gas costs during an attack. The top level assertion bond of 3600 ETH remains unchanged because it acts as a deterrent to open a challenge and spam the protocol to begin with.
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A “defender’s bounty” of 1% of confiscated bonds has been added to incentivize honest parties to defend Arbitrum One in the event of a challenge. This 1% would only go to defenders who put up bonds to defeat malicious actors during a challenge. Since confiscated funds will be sent to the ArbitrumDAO treasury, a DAO vote would be required to pay out this reward though because confiscated funds (by default) go to the DAO.
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An upper bound on L1 gas cost reimbursements to defenders has been added and is proposed to be 100% of confiscated bonds during a challenge. Honest parties should always be made whole when defending Arbitrum.
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Challenge bonds are now automatically refunded in-protocol once a sub-challenge assertion has been confirmed by the protocol!