The eruption of a pandemic, such as COVID-19, can cause an unprecedented global crisis. Contact tracing, as a pillar of communicable disease control in public health for decades, has shown its effectiveness on pandemic control. Despite intensive research on contact tracing, existing schemes are vulnerable to attacks and can hardly simultaneously meet the requirements of data integrity and user privacy. The design of a privacy-preserving contact tracing framework to ensure the integrity of the tracing procedure has not been sufficiently studied and remains a challenge. In this paper, we propose P2B-Trace, a privacy-preserving contact tracing initiative based on blockchain. First, we design a decentralized architecture with blockchain to record an authenticated data structure of the user's contact records, which prevents the user from intentionally modifying his local records afterward. Second, we develop a zero-knowledge proximity verification scheme to further verify the user's proximity claim while protecting user privacy. We implement P2B-Trace and conduct experiments to evaluate the cost of privacy-preserving tracing integrity verification. The evaluation results demonstrate the effectiveness of our proposed system.

P2B-Trace: Privacy-Preserving Blockchain-based Contact Tracing to Combat Pandemics

The Notarial Office(NO), working on providing various essential certificates, still relies on manual handling and requires paper materials from other government departments. That brings lots of inconvenience. The Notarial Office rejects non-local paper materials for their lower credibility in the local place and then cannot provide cross-borders services. It also easily cause sensitive information leakage as copies of paper materials have been stored. In this case, a blockchain-based system is suitable to address challenges in this scenario because of its advantages (e.g, decentralized, immutability, transparency, auditability). We implemented this system on top of the Hyperledger Fabric. Moreover, we replace manual operations with smart contracts, set extra ledgers to off-load different types of transactions and provide encryption for private information when needed. In the end, we get an expected result. That is, the modification outperformed the unmodified network in experiments.

/pdf/the-notarial-office-in-e-government-a-blockchain-based-1jx1400oq4.pdf

The Notarial Office in E-government: A Blockchain-Based Solution

Sharding has been considered as a prominent approach to enhance the limited performance of blockchain. However, most sharding systems leverage a non-cooperative design, which lowers the fault tolerance resilience due to the decreased mining power as the consensus execution is limited to each separated shard. To this end, we present Benzene, a novel sharding system that enhances the performance by cooperation-based sharding while defending the per-shard security. First, we establish a double-chain architecture for function decoupling. This architecture separates transaction-recording functions from consensus-execution functions, thereby enabling the cross-shard cooperation during consensus execution while preserving the concurrency nature of sharding. Second, we design a cross-shard block verification mechanism leveraging Trusted Execution Environment (TEE), via which miners can verify blocks from other shards during the cooperation process with the minimized overheads. Finally, we design a voting-based consensus protocol for cross-shard cooperation. Transactions in each shard are confirmed by all shards that simultaneously cast votes, consequently achieving an enhanced fault tolerance and lowering the confirmation latency. We implement Benzene and conduct both prototype experiments and large-scale simulations to evaluate the performance of Benzene. Results show that Benzene achieves superior performance than existing sharding/non-sharding blockchain protocols. In particular, Benzene achieves a linearly-improved throughput with the increased number of shards (e.g., 32,370 transactions per second with 50 shards) and maintains a lower confirmation latency than Bitcoin (with more than 50 shards). Meanwhile, Benzene maintains a fixed fault tolerance at 1/3 even with the increased number of shards. 

Benzene: Scaling Blockchain With Cooperation-Based Sharding

Sharding has been considered as a prominent approach to enhance the limited performance of blockchain. However, most sharding systems leverage a non-cooperative design, which lowers the fault tolerance resilience due to the decreased mining power as the consensus execution is limited to each separated shard. To this end, we present Benzene, a novel sharding system that enhances the performance by cooperation-based sharding while defending the per-shard security. First, we establish a double-chain architecture for function decoupling. This architecture separates transaction-recording functions from consensus-execution functions, thereby enabling the cross-shard cooperation during consensus execution while preserving the concurrency nature of sharding. Second, we design a cross-shard block verification mechanism leveraging Trusted Execution Environment (TEE), via which miners can verify blocks from other shards during the cooperation process with the minimized overheads. Finally, we design a voting-based consensus protocol for cross-shard cooperation. Transactions in each shard are confirmed by all shards that simultaneously cast votes, consequently achieving an enhanced fault tolerance and lowering the confirmation latency. We implement Benzene and conduct both prototype experiments and large-scale simulations to evaluate the performance of Benzene. Results show that Benzene achieves superior performance than existing sharding/non-sharding blockchain protocols. In particular, Benzene achieves a linearly-improved throughput with the increased number of shards (e.g., 32,370 transactions per second with 50 shards) and maintains a lower confirmation latency than Bitcoin (with more than 50 shards). Meanwhile, Benzene maintains a fixed fault tolerance at 1/3 even with the increased number of shards.

The development of Industrial Internet of Things (IIoT) provides massive abundant data resources for trading and mining. However, the existing data trading schemes achieve data usage control at the cost of high latency, thereby resulting in poor service quality as the values of IIoT data degrade over time. This article proposes a monitor-based usage control model to enforce data usage policies on the user side, which eliminates frequent interactions between owners and users. Based on that, a data trading scheme with efficient usage control for IIoT (called DTSI) is devised, which utilizes blockchain smart contract and software guard extensions (SGX) to enable owners to fully control users’ identities and operations at minimal overhead. Security analysis shows that DTSI effectively prevents data abuse and ensures the fair exchange of data. Meanwhile, extensive experiments are conducted on the DTSI prototype comparing with the state-of-the-art schemes with real-world IIoT datasets, which demonstrates the efficiency of DTSI. 

A Data Trading Scheme With Efficient Data Usage Control for Industrial IoT

Confidentiality is an indispensable requirement in financial applications of blockchain technology, and supporting it along with high performance and friendly programmability is technically challenging. In this paper, we present a system design called CONFIDE to support on-chain confidentiality by leveraging Trust Execution Environment (TEE). CONFIDE's secure data transmission protocol and data encryption protocol, together with a highly efficient virtual machine run in TEE, guarantee the confidentiality in the life cycle of a transaction from end to end. CONFIDE proposes a secure data model along with an application-driven secure protocol to guarantee data confidentiality and integrity. Its smart contract language extension offers users the flexibility to define complex confidentiality models. CONFIDE is implemented as a plugin module to Antfin Blockchain's proprietary platform, and can be plugged into other blockchain platforms as well with its universal interface design. Nowadays, CONFIDE is supporting millions of commercial transactions daily on consortium blockchain running financial applications including supply chain finance, ABS, commodity provenance, and cold-chain logistics.

Confidentiality Support over Financial Grade Consortium Blockchain

Implementations of the specification include receiving, by a smart contract service provider including a trusted computation execution environment (TEE) from a client associated with a target blockchain network, a request for operating cross-chain data of one or more blockchain networks different from the target blockchain, wherein the smart contract service provider is off the target blockchain network; sending, by the smart contract service provider to a data visiting service provider, a request for the cross-chain data; receiving, by the smart contract service provider, the cross-chain data from the data visiting service provider; generating, by the TEE, a result using the cross-chain data; and returning, by the smart contract service provider, the result to the client.

Off-chain smart contract service based on trusted execution environment

One or more embodiments of the invention provide a blockchain-based data authorization method and device. The blockchain-based data authorization method can comprise the steps that a blockchain node receives a data acquisition transaction submitted by a data user, and the data acquisition transaction is used for requesting to acquire target data held by a data owner; and the blockchain node executes a data authorization smart contract called by the data acquisition transaction, and the data authorization smart contract is used for issuing an authorization token to the data user when it is confirmed that the data user is authorized, wherein the authorization token is used for indicating the privacy computing platform to acquire the target data after being provided to the privacy computing platform by the data user, and returning the target data and/or an operation result obtained by executing preset operation on the target data to the data user.

Blockchain-based data authorization method and device

One or more embodiments of the present specification provide a data storage and acquisition method and device based on a block chain. The method and apparatus are applied to a block chain comprising a storage party node device and an acquisition party node device. Wherein an intelligent contract for data storage and reading is deployed on the block chain; the event evidence storage method based on the block chain comprises the following steps: the evidence storage party node equipment sends a first target transaction to the block chain, wherein the first target transaction comprises target event data to be stored; calling the smart contract, executing data storage logic declared by the smart contract, and storing the target event data to the smart contract; and generating a storage identification image at least based on the identification of the smart contract.

Data storage and acquisition method and device based on block chain

One or more embodiments of the invention provide a data authorization method and device based on block chain, and the method can comprise the steps that a block chain node receives an authentication transaction submitted by a privacy computing platform, and the authentication transaction is used for inquiring whether a data user obtains authorization for target data held by a data owner or not; and the block chain node executes the data authorization smart contract called by the authentication transaction, wherein the data authorization intelligent contract is used for sending the data authorization information to the data user when confirming that the data user obtains authorization, and providing an authorization token for the privacy computing platform to indicate the privacy computing platform to acquire the target data, and sending the target data and/or an operation result obtained by performing preset operation on the target data to the data user.

Data authorization method and device based on block chain

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