Biblio

In recent years, blockchain-based cryptocurren-cies have attracted much attention. Attacks targeting cryptocurrencies and related services directly profit an attacker if successful. Related studies have reported attacks targeting configuration-vulnerable nodes in Ethereum using a method called honeypots to observe malicious user attacks. They have analyzed 380 million observed requests and showed that attacks had to that point taken at least 4193 Ether. However, long-term observations using honeypots are difficult because the cost of maintaining honeypots is high. In this study, we analyze the behavior of malicious users using our honeypot system. More precisely, we clarify the pre-investigation that a malicious user performs before attacks. We show that the cost of maintaining a honeypot can be reduced. For example, honeypots need to belong in Ethereum's P2P network but not to the mainnet. Further, if they belong to the testnet, the cost of storage space can be reduced.

Cloud storage has been gaining in popularity as an on-line service for archiving, backup, and even primary storage of files. However, due to the data outsourcing, cloud storage also introduces new security challenges, which require a data audit and data repair service to ensure data availability and data integrity in the cloud. In this paper, we present the design and implementation of a network-coding-based Proof Of Retrievability scheme called ELAR, which achieves a lightweight data auditing and data repairing. In particular, we support direct repair mechanism in which the client can be free from the data repair process. Simultaneously, we also support the task of allowing a third party auditor (TPA), on behalf of the client, to verify the availability and integrity of the data stored in the cloud servers without the need of an asymmetric-key setting. The client is thus also free from the data audit process. TPA uses spot-checking which is a very efficient probabilistic method for checking a large amount of data. Extensive security and performance analysis show that the proposed scheme is highly efficient and provably secure.