Verifiability is the backbone of most ledger systems to realize credible authentication. However, existing permissioned blockchains and centralized ledger databases lack rigorous verifiability to authenticate all facts (i.e., what-when-who validation). Besides, they suffer from high verification cost to a continually growing immutable storage. In this paper, we introduce verification principles behind LedgerDB, a centralized ledger database that achieves both strong external auditability and fast verification. We coin a novel concept called Dasein Verification that composes of three validation factors what-when-who to formalize ledger auditing. Regarding what, LedgerDB devises fam (fractal accumulating model) to accelerate existence verification, and CM-Tree for efficient lineage verification. Veri-fiable data mutations are also supported. For when, we discuss attacks on existing time pegging protocols that compromise the authenticity of timestamps, and propose a time notary protocol to resolve those threats. Evaluations show that fam and CM- Tree significantly outperform traditional approaches. Compared to Hyperledger Fabric, LedgerDB achieves 23x higher verification throughput with 500 x lower latency in notarization applications, and 3 x higher throughput with 300 x lower latency in lineage tracking applications. As a public-cloud ledger service, the end-to-end verification latencies of LedgerDB are on average 50 x and 1000x lower than that of QLDB in the above applications, respectively.

The emergence of Blockchain has attracted widespread attention. However, we observe that in practice, many applications on permissioned blockchains do not benefit from the decentralized architecture. When decentralized architecture is used but not required, system performance is often restricted, resulting in low throughput, high latency, and significant storage overhead. Hence, we propose LedgerDB on Alibaba Cloud, which is a centralized ledger database with tamper-evidence and non-repudiation features similar to blockchain, and provides strong auditability. LedgerDB has much higher throughput compared to blockchains. It offers stronger auditability by adopting a TSA two-way peg protocol, which prevents malicious behaviors from both users and service providers. LedgerDB supports verifiable data removals demanded by many real-world applications, which are able to remove obsolete records for storage saving and hide records for regulatory purpose, without compromising its verifiability. Experimental evaluation shows that LedgerDB's throughput is 80X higher than state-of-the-art permissioned blockchain (i.e., Hyperledger Fabric). Many blockchain customers (e.g., IP protection and supply chain) on Alibaba Cloud have switched to LedgerDB for its high throughput, low latency, strong auditability, and ease of use.