🤖 AI Summary
This work addresses the vulnerability in trusted execution environment (TEE)-based smart contract networks where encrypted transaction data still leaks sender–receiver linkability through storage access patterns. To mitigate this, the authors propose two novel structures: a Delayed Write Buffer and a Bitwise-Trie of Bucketed Entries. Leveraging the asymmetric update semantics and delay tolerance inherent in token transfers, these mechanisms decouple transaction execution from the receiver’s storage access. Combined with constant-size queries, randomized settlement, and privacy-preserving push notifications, the approach constructs a receiver anonymity set while maintaining high performance. The resulting system effectively resists both storage access pattern leakage and flooding attacks, achieving real-time private token transfers with probabilistic anonymity guarantees.
📝 Abstract
Trusted execution environment (TEE) based confidential smart contract networks promise privacy but remain vulnerable to storage access pattern attacks that can link senders and recipients in token transfers. When contracts update recipient balances during transfers, the unique storage keys accessed reveal transaction relationships even when data is encrypted. This paper introduces two novel data structures to address this vulnerability: the Delayed Write Buffer (DWB) and the Bitwise-Trie of Bucketed Entries (BTBE). The DWB delays recipient balance updates by buffering pending transfers and randomly settling entries, breaking the direct correlation between transfer execution and recipient storage access. The BTBE further enhances privacy by grouping addresses into constant-sized buckets, preventing flooding attacks and creating anonymity sets for balance queries. Additionally, we present a private notification system enabling real-time, privacy-preserving push notifications for confidential contracts. Our domain-specific approach leverages the unique characteristics of token transfers -- asymmetric balance updates and tolerance for delayed settlement -- to achieve practical performance with probabilistic anonymity guarantees.