New public blockchain protocol based on sharding and aggregate signatures

Existing blockchains, especially public blockchains, face the challenges of scalability which means the processing capacity will not get better with the addition of nodes, making it somewhat infeasible for mobile computing applications. Some improved technologies are known to speed up processing capacity by shrinking the consensus group, increasing the block capacity and/or shortening the block interval. Even these solutions are met with major problems such as storage limitations and weak security. To face the realistic application scenarios for blockchain technology in the mobile realm, we propose a new public blockchain designed based on sharding, aggregate signature and cryptographic sortition which we call SAC. In SAC, the transaction rate increases with the number of shards while the length of the consensus signature is a constant. Meanwhile, in SAC, the assignment of consensus representatives is controlled by a verifiable random function, which can effectively solve the problem of centralized consensus. In addition, this paper analyzes the performance of SAC to give adequate comparison with other sharding technologies while also giving a rational security analysis. Our experimental results clearly show the potential applicability of this novel blockchain protocol to in mobile computation.

Cryptanalysis of a Certificateless Aggregate Signature Scheme for Healthcare Wireless Sensor Network

Certificateless aggregate signatures aggregate n signatures from n different users into one signature. Therefore, a verifier can judge whether all signatures are valid by verifying once. With this advantage, certificateless aggregate signatures are widely used in the environment of limited computing resources. Recently, a novel certificateless aggregate signature scheme was proposed by Kumar et al. This scheme’s security was claimed to be secure against two types of attackers under the random oracle model. In this paper, we indicate that their scheme is unable to achieve this security goal. We show an attack algorithm that the second type of attacker could forge a valid signature under an identity without the private key of the target user. Moreover, we demonstrate that the second type of attacker could forge a valid aggregate signature.