Audit logs serve as a critical component in the enterprise business systems that are used for auditing, storing, and tracking changes made to the data. However, audit logs are vulnerable to a series of attacks, which enable adversaries to tamper data and corresponding audit logs. In this paper, we present BlockAudit: a scalable and tamper-proof system that leverages the design properties of audit logs and security guarantees of blockchains to enable secure and trustworthy audit logs. Towards that, we construct the design schema of BlockAudit, and outline its operational procedures. We implement our design on Hyperledger and evaluate its performance in terms of latency, network size, and payload size. Our results show that conventional audit logs can seamlessly transition into BlockAudit to achieve higher security, integrity, and fault tolerance.
Blockchain and Audit Logs Sutton and Samvi @cite_17 proposed a blockchain-based approach that stores the integrity proof digest to the Bitcoin blockchain. Castaldo al @cite_20 proposed a logging system to facilitate the exchange of electronic health data across multiple countries in Europe. Cucrull al @cite_2 proposed a system that uses blockchains to enhances the security of the immutable logs. Log integrity proofs are published in the blockchain, and provide non-repudiation security properties resilient to log truncation and log regeneration. In contrast, BlockAudit generates audit logs by extending the existing ORM (nHibernate), which is localized to ORM and other layers of business applicaiton are not effected. This makes it straightforward for existing application to user BlockAudit .
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Several applications require robust and tamper-proof logging systems, e.g. electronic voting or bank information systems. At Scytl we use a technology, called immutable logs, that we deploy in our electronic voting solutions. This technology ensures the integrity, authenticity and non-repudiation of the generated logs, thus in case of any event the auditors can use them to investigate the issue. As a security recommendation it is advisable to store and or replicate the information logged in a location where the logger has no writing or modification permissions. Otherwise, if the logger gets compromised, the data previously generated could be truncated or altered using the same private keys. This approach is costly and does not protect against collusion between the logger and the entities that hold the replicated data. In order to tackle these issues, in this article we present a proposal and implementation to immutabilize integrity proofs of the secure logs within the Bitcoin’s blockchain. Due to the properties of the proposal, the integrity of the immutabilized logs is guaranteed without performing log data replication and even in case the logger gets latterly compromised. Privacy audit logs are used to capture the actions of participants in a data sharing environment in order for auditors to check compliance with privacy policies. However, collusion may occur between the auditors and participants to obfuscate actions that should be recorded in the audit logs. In this paper, we propose a Linked Data based method of utilizing blockchain technology to create tamper-proof audit logs that provide proof of log manipulation and non-repudiation. We also provide experimental validation of the scalability of our solution using an existing Linked Data privacy audit log model. We present Catena, an efficiently-verifiable Bitcoinwitnessing scheme. Catena enables any number of thin clients, such as mobile phones, to efficiently agree on a log of application-specific statements managed by an adversarial server. Catenaimplements a log as an OP_RETURN transaction chain andprevents forks in the log by leveraging Bitcoin's security againstdouble spends. Specifically, if a log server wants to equivocate ithas to double spend a Bitcoin transaction output. Thus, Catenalogs are as hard to fork as the Bitcoin blockchain: an adversarywithout a large fraction of the network's computational powercannot fork Bitcoin and thus cannot fork a Catena log either. However, different from previous Bitcoin-based work, Catenadecreases the bandwidth requirements of log auditors from 90GB to only tens of megabytes. More precisely, our clients onlyneed to download all Bitcoin block headers (currently less than35 MB) and a small, 600-byte proof for each statement in a block. We implement Catena in Java using the bitcoinj library and use itto extend CONIKS, a recent key transparency scheme, to witnessits public-key directory in the Bitcoin blockchain where it can beefficiently verified by auditors. We show that Catena can securemany systems today, such as public-key directories, Tor directoryservers and software transparency schemes. Many real-world applications run on untrusted servers or are run on servers that are subject to strong insider attacks. Although we cannot prevent an untrusted server from modifying or deleting data, with tamper-evident data structures, we can discover when this has occurred. If an untrusted server knows that a particular reply will not be checked for correctness, it is free to lie. Auditing for correctness is thus a frequent but overlooked operation. In my thesis, I present and evaluate new efficient data structures for tamper-evident logging and tamper-evident storage of changing data on untrusted servers, focussing on the costs of the entire system. The first data structure is a new tamper-evident log design. I propose new semantics of tamper-evident logs in terms of the auditing process, required to detect misbehavior. To accomplish efficient auditing, I describe and benchmark a new tree-based data structure that can generate such proofs with logarithmic size and space, significantly improving over previous linear constructions while also offering a flexible query mechanism with authenticated results. The remaining data structures are designs for a persistent authenticated dictionary (PAD) that allows users to send lookup requests to an untrusted server and get authenticated answers, signed by a trusted author, for both the current and historical versions of the dataset. Improving on prior constructions that require logarithmic storage and time, I present new classes of efficient PAD algorithms offering constant-sized authenticated answers or constant storage per update. I implement 21 different versions of PAD algorithms and perform a comprehensive evaluation using contemporary cloud-computing prices for computing and bandwidth to determine the most monetarily cost-effective designs.