How Much Must a Private Mempool Hide? Exact Leakage Thresholds for Sandwich Attacks
How much information can secret transaction pools safely leak?
Researchers discovered exactly how much information about a pending trade can leak from a private transaction pool before attackers can profitably sandwich it. Even when a pool hides the full transaction size, knowing just the lower bound of that size—and the trade's direction—is enough for attackers to reliably profit, while the upper bound turns out to be irrelevant.
Private pools are sold as protection against sandwich attacks, but this work shows their privacy guarantees have hard limits. A pool operator now knows precisely what to hide and what can safely be revealed—information that could be baked into privacy layer designs to give traders genuine protection without making pools unnecessarily opaque.