[DigitalToday reporter Yoonseo Lee] Former Ripple Chief Technology Officer David Schwartz said it would be difficult to sustain a practical attack on the XRP Ledger's design to prevent frontrunning and sandwich attacks, even for a state-backed attacker.

On June 30 (local time), blockchain outlet The Crypto Basic reported that Schwartz said even if an attack occurs, the network can respond by increasing the cost of attacking.

At the center of the debate is an XRPL transaction reservation structure previously proposed by Schwartz. The plan aims to reduce frontrunning and sandwich attacks that could occur during payments and offer crossing. An X (formerly Twitter) user, however, said defenses against denial-of-service (DoS) attacks were insufficient and that a well-funded, state-backed actor could keep pressuring the network.

Schwartz did not accept that argument. He wrote, "If that happens, you raise the cost," adding that the attack would either stop or amount to "a huge financial gift" from state-backed forces to XRP holders. As the attack continues, more fees accumulate on the network, he said, meaning the burden of the costs is concentrated on the attacker rather than users.

He also said the fee-increase mechanism does not need to be a fixed value. Schwartz proposed allowing related parameters to be adjusted through XRPL's existing voting process. Validators could change the value that determines how quickly the reservation fee rises, which he said would curb abuse without imposing unnecessary costs on ordinary users.

He also questioned the assumption that a state-backed attacker would keep spending vast sums against a network that maintains its current level of security. Schwartz said, "It's very strange to worry that such actors would want to give thousands of dollars per hour to XRP holders without even being able to make XRPL more vulnerable to frontrunning and sandwich attacks than it is now."

Schwartz's original proposal focuses on introducing a new "reserved transaction" structure. He proposed a 'ReservedTxns' ledger object and a 'TxnReserve' transaction type. Users can pay at least twice the standard transaction fee to secure a transaction slot to be executed on a future ledger. The reservation is valid up to 16 ledger intervals ahead, and initially a maximum of 32 reserved transaction slots are allocated per ledger.

The operating method also differs from the existing transaction flow. After a user reserves a slot, the actual transaction is not propagated until the consensus process for the immediately preceding ledger is effectively complete. Under this structure, it is difficult for an attacker to preview a transaction and insert a competing transaction ahead of it. At the ledger execution stage, reserved transactions are processed before normal transactions and are removed from the reservation list immediately after processing, preserving the intended order.

Schwartz acknowledged limitations as well. If an attacker reserves all slots across multiple future ledgers, other users may be unable to use this protective mechanism. To prevent that, he suggested gradually raising the reservation fee as remaining slots shrink. As an example, he cited starting fee increases once 16 of 32 slots are filled and raising the fee linearly to as much as three times the base reservation fee when 30 slots are filled.

He said if demand rises further, the reservation limit itself could be increased from 32 to 64. That would require an attacker to pay several times more than ordinary users to keep occupying all slots. Schwartz said if an attacker continues spending anyway, the fees would ultimately go to the XRP Ledger ecosystem and XRP holders.

The discussion is also tied to what cost structure XRPL will adopt to reduce abuse of transaction ordering. How to strike a balance between the effectiveness of protective measures and the burden on ordinary users is expected to be a point of contention going forward.

I think that's fine. If that happens, we can just raise the cost of the attack and it would either stop or be, in effect, a huge financial gift from state actors to XRP holders. One simple change to my proposal if you're concerned about this. Make the fee escalation…