Blockchain sharding is a promising approach to enhancing scalability by partitioning the network into smaller, parallel shards. However, existing sharding blockchains that rely on Byzantine fault tolerance protocols require large shard sizes to meet strict security thresholds, limiting scalability, while relaxing security parameters can lead to liveness and safety violations. In this work, we present Camael, a secure sharding blockchain that achieves corrupted-shard tolerance through effective detection and processing mechanisms for both liveness and safety violations. Specifically, fake liveness violations forged by malicious nodes are accurately detected via a two-phase reporting and confirmation mechanism, while concealed safety violations are efficiently identified using a lightweight snapshot mechanism. Furthermore, a state determination process ensures overall system consistency. Malicious nodes are precisely identified through a conviction mechanism, which enables the replacement of the targeted nodes and the reconfiguration of the shards. Notably, Camael ensures security while preserving a global fault tolerance of 1/3 and tolerating corrupted shards, with each shard accommodating up to 2/3 malicious nodes. Extensive experiments conducted on 2000 AWS EC2 nodes across 4 regions demonstrate that Camael improves throughput by 3.56 times compared to the baseline (Kronos, NDSS'25), achieving a throughput of 109.3 ktx/sec, while the violation processing requires only 1.64 sec.

Due to the promising scalability property, sharding technology has gained widespread attention. It improves the transaction throughput of blockchain systems but also introduces cross-shard transactions. Current two-phase commit (2PC) protocols process different cross-shard transactions sequentially, resulting in significant system overhead and low throughput. Besides, current sharding blockchains rely on Byzantine fault tolerance (BFT) as a black box, lacking specific designs to efficiently handle cross-shard proposals. Moreover, cross-shard communication complexity is high, and transaction processing parallelism is low. In this paper, we first propose P-2PC, a general framework to process cross-shard transactions of different phases in a pipelined way, suitable for most sharding blockchains. Further, we design Cherubim with improved quadruple 2PC, 4P-2PC. By combining P-2PC with an intra-shard pipelined BFT, 4P-2PC achieves both intra-shard and cross-shard pipelined processing. Combined with a newly designed batch processing method, each shard processes 4 transaction batches simultaneously through 1 round of calculation and communication, compared to 4 rounds in previous work. In particular, Cherubim seamlessly integrates a multi-signature algorithm supporting further aggregation, reducing communication complexity. Furthermore, we evaluate our work through theoretical analysis and implementation, proving that Cherubim has a communication complexity linear to the node number. We also propose horizontal and vertical consensus parallelism degrees to evaluate the parallelism ability. Compared to the state-of-the-art solutions, the evaluation demonstrates that Cherubim achieves a transaction throughput improvement of at least 2.28×.