Proof Of Retrievability Research Articles

Cumulus: Blockchain-Enabled Privacy Preserving Data Audit in Cloud

Data owners upload large files to cloud storage servers, but malicious servers may potentially tamper data. To check integrity of remote data, Proof of Retrievability (PoR) schemes were introduced. Existing PoR protocols assume that data owners and third-party auditors are honest and audit only the potentially malicious cloud server to check integrity of stored data. In this paper we consider a system where any party may attempt to cheat others and consider collusion cases. We design a protocol, Cumulus, that is secure under such adversarial assumptions and use blockchain smart contracts to act as mediator in case of dispute and payment settlement. We use state channels to reduce blockchain interactions in order to build a practical audit solution. The security of the protocol has been proven in Universal Composability (UC) framework. Finally, we illustrate several applications of our basic protocol and evaluate practicality of our approach via a prototype implementation for fairly selling large files over the Ethereum platform. We evaluate the prototype and show that our scheme has comparable performance.

A General Blockchain-Based Automatic Audit Scheme For Proofs Of Retrievability

Abstract Cloud storage has been widely used in remote data management, although correct storage of the outsourced file is still challenging in practice. Proofs of Retrievability (PoRs), a storage-oriented cryptographic tool, support integrity checking and efficient retrieval of the file. However, due to the lack of a fully credible oversight mechanism or a serious dependence on a trusted third party, most PoRs are incapable of achieving essential and straightforward trust between participants (i.e. the client and server). While blockchain shows promise in solving this trust issue, existing blockchain-based storage systems are scenario-constrained as they require private/permissioned or special-construct blockchains. Consequently, none of these systems provide robust and decentralized trustworthiness. We propose a general Blockchain-based Automatic Audit (BAA) scheme for PoR without limitations based on specific blockchain types. Specifically, we present BAA via stitching together a carefully designed or chosen array of sub-components such as storage proofs and Turing-complete smart contracts. We also integrate BAA with specific PoR models to prove its strong generality and availability. To our best knowledge, our proposal is the first blockchain-based approach that enhances traditional PoR models with both automatic audit and fair payment. The final analysis and implemented prototype on Ethereum demonstrate the utility of BAA.

Ensuring Data Integrity And Security In Diverse Cloud Environments To Prevent Duplicacy.

Data deduplication is a valuable technique for compressing and minimizing data duplication during data transfers, especially in cloud environments. By eliminating redundant data, it optimizes transmission capacity and reduces memory usage. To ensure the integrity of sensitive data, encryption is applied throughout the deduplication process. The SHA algorithm is commonly used for storing text data during deduplication. It generates security bits by padding the text and computes a hash consisting of hexadecimal, string, and integer data. Hash-based deduplication involves hashing the entire file and treating the hash values of text data as unique identifiers. This allows clients to identify duplicate data within the cloud. The Proof-of-Work (PoW) algorithm is widely utilized in blockchain networks like Bitcoin and Ethereum. Its primary function is to verify transactions through a process called mining. Miners engage in competition to solve complex mathematical problems, and the first one to find a solution is granted the right to add a new block to the blockchain. PoW relies on cryptographic hashing, such as the SHA-256 hashing function, to validate and secure transactions. On the other hand, the Proof of Retrievability (PoR) algorithm finds application in cloud computing systems. It serves as a consensus mechanism, ensuring that cloud storage providers store and retrieve data accurately. PoR enables cloud providers to demonstrate to consumers that their files can be fully recovered. This algorithm incorporates cryptographic proofs that validate the integrity and availability of the stored data. In cloud storage, deduplication is often implemented using the Memory mapping technique (MPT). This allows multiple data owners to store the same data in a single copy, enhancing storage efficiency. To maintain data security, encryption is applied both before and during the deduplication process, ensuring that sensitive information remains protected. In summary, data deduplication is a powerful method for compressing data, minimizing duplication, and optimizing transmission capacity. With encryption techniques and hash-based identification, it provides secure and efficient deduplication in cloud environments, while memory deduplication and MPT support further enhance performance and storage efficiency.

Proof of retrievability with flexible designated verification for cloud storage

With numerous applications in cloud storage, Proof of Retrievability (PoR) is an efficient solution for verification and retrieval of big data on a remote server. Existing PoR schemes can support two mutually exclusive verification modes, namely either private verifiability or public verifiability, depending on whether the outsourced data is verifiable by the data owner (user) only or by everyone. In order to allow the user to flexibly designate the capability of verification, we propose a novel framework for PoR schemes that enables fine-grained control of remote data verification for cloud storage. Our idea is enabling the user to dynamically release some tokens (verification keys) to one or more third parties (designated verifiers), such that only the user and the designated verifiers can verify and retrieve the outsourced data from the server. We formalize this notion as PoR with Flexible Designated Verification (PoR-FDV), and define an extended adversarial model for PoR-FDV based on Juel et al.'s PoR model. Under the new framework, we propose a generic, simple and elegant construction of PoR-FDV from public verifiable PoR and identity-based KEM/DEM, which then gives birth to a concrete and efficient PoR-FDV scheme. Compared to existing PoR schemes, PoR-FDV provides higher flexibility and scalability, as well as many useful features.

VeriDedup: A Verifiable Cloud Data Deduplication Scheme With Integrity and Duplication Proof

Data deduplication is a technique to eliminate duplicate data in order to save storage space and enlarge upload bandwidth, which has been applied by cloud storage systems. However, a cloud storage provider (CSP) may tamper user data or cheat users to pay unused storage for duplicate data that are only stored once. Although previous solutions adopt message-locked encryption along with Proof of Retrievability (PoR) to check the integrity of deduplicated encrypted data, they ignore proving the correctness of duplication check during data upload and require the same file to be derived into same verification tags, which suffers from brute-force attacks and restricts users from flexibly creating their own individual verification tags. In this paper, we propose a verifiable deduplication scheme called VeriDedup to address the above problems. It can guarantee the correctness of duplication check and support flexible tag generation for integrity check over encrypted data deduplication in an integrative way. Concretely, we propose a novel Tag-flexible Deduplication-supported Integrity Check Protocol (TDICP) based on Private Information Retrieval (PIR) by introducing a novel verification tag called <inline-formula><tex-math notation="LaTeX">${note\ set}$</tex-math></inline-formula> , which allows multiple users holding the same file to generate their individual verification tags and still supports tag deduplication at the CSP. Furthermore, we make the first attempt to guarantee the correctness of data duplication check by introducing a novel User Determined Duplication Check Protocol (UDDCP) based on Private Set Intersection (PSI), which can resist a CSP from providing a fake duplication check result to users. Security analysis shows the correctness and soundness of our scheme. Simulation studies based on real data show the efficacy and efficiency of our proposed scheme and its significant advantages over prior arts.

Proofs of retrievability with tag outsourcing based on Goppa codes

In cloud storage, because the data owner loses the physical control of the data, the data may be tampered with or deleted. Although, it has been proposed to adopt provable data possession (PDP) or proofs of retrievability (POR) mechanism to ensure the integrity of cloud storage data. However, at present, most PDP/POR schemes are based on traditional cryptographic mechanisms and cannot resist quantum computer attacks. For this reason, the first POR scheme based on coding mechanism (BC-POR) is proposed in this paper. The scheme is constructed based on the difficulty assumptions of 2-regular word syndrome decoding (2-RWSD) problem and Goppa code distinguishing problem. Moreover, considering the low computing power of lightweight users, this paper adopts an audit scheme that supports the outsourcing of data tag calculation on the client side, that is, the calculation of data tag generation is outsourced to a third-party institution for execution. First of all, this scheme can prevent third-party institution from obtaining the real content of the data in the process of calculation tags and realize the privacy protection of user data. Secondly, the scheme uses a FSB hash function to generate a decodable syndrome, and this algorithm does not require iterative operations during the tagging process, thereby reducing the computational overhead of the tag. Finally, the provable security method is used to prove the security of the proposed scheme, and the performance of the proposed audit scheme is evaluated to prove the effectiveness of the scheme.

Secure Virtual Machine Image Storage Process into a Trusted Zone-based Cloud Storage

The emerging trend of Cloud Computing inducts virtualization as the quintessence concept to offer to end users a large scale Infrastructure-as-a-Service (IaaS) paradigm. Virtualization leverages virtual environment instantiated from user namely Virtual Machine Images (VMI) where user has the ability to provision and manage its own operating system. Therefore, user VMI dynamic data privacy depends upon the supplied security policy by Cloud Service Provider (CSP) and cloud storage architecture which remains the most prominent cloud delivered services. This paper covers thoroughly a secure storage process of user VMI in a cloud zone-based storage based on Proof-of-Retrievability (PoR). The proposed security architecture ensures the elementary security triad CIA (Confidentiality, Integritty and availability). VMI data confidentiality comprises generation of encryption key pair based on Goppa Code and McEliece cryptosystem, thus, integrity and stored VMI dynamic data correctness have been ensured using public auditing privacy-preserving in cloud zone-based storage. a know practical Error-Correcting-Codes (ECC) in heuristic researches

Blockchain-Based Self-Auditing Scheme with Batch Verification for Decentralized Storage

Data owners outsource their data to remote storage providers without keeping local replicas to save their precious storage resources. However, the ownership and management of data are separated after outsourcing. How to ensure the integrity and recoverability of outsourced data becomes a significant problem. Provable Data Possession (PDP) and Proofs of Retrievability (POR) are two cryptographic protocols that enable users to verify the integrity of outsourced data. Nevertheless, the state-of-the-art PDP and POR schemes either need users to perform the complicated audit tasks by themselves or delegate these tasks to a Third-Party Auditor (TPA). Moreover, these schemes are constructed on a centralized storage framework which vulnerably suffers single-point-of-failure. In this paper, we propose a blockchain-based decentralized self-auditing scheme with batch verification. Firstly, data owners outsource their data to decentralized storage nodes, which can achieve self-auditing based on blockchain without TPA. Secondly, our scheme uses Pedersen-based polynomial commitment to significantly reduce the number of authenticators. Furthermore, we propose a batch verification algorithm, which can verify multiple proofs from different storage nodes to improve the verification efficiency. Finally, we analyze the security of our scheme and implement a gas-efficient system prototype using the smart contracts of the Ethereum Reposten test network. The results demonstrate that the scheme is practical.

Blockchain-based continuous data integrity checking protocol with zero-knowledge privacy protection

The cloud computing technology has emerged, developed, and matured in recent years, consequently commercializing remote outsourcing storage services. An increasing number of companies and individuals have chosen the cloud to store their data. However, accidents, such as cloud server downtime, cloud data loss, and accidental deletion, are serious issues for some applications that need to run around the clock. For some mission and business-critical applications, the continuous availability of outsourcing storage services is also necessary to protect users' outsourced data during downtime. Nevertheless, ensuring the continuous availability of data in public cloud data integrity auditing protocols leads to data privacy issues because auditors can obtain the data content of users by a sufficient number of storage proofs. Therefore, protecting data privacy is a burning issue. In addition, existing data integrity auditing schemes that rely on semi-trusted third-party auditors have several security problems, including single points of failure and performance bottlenecks. To deal with these issues, we propose herein a blockchain-based continuous data integrity checking protocol with zero-knowledge privacy protection. We realize a concrete construction by using a verifiable delay function with high efficiency and proof of retrievability, and prove the security of the proposal in a random oracle model. The proposed construction supports dynamic updates for the outsourced data. We also design smart contracts to ensure fairness among the parties involved. Finally, we implement the protocols, and the experimental results demonstrate the efficiency of the proposed protocol.

Consensus Mechanism of Blockchain Based on PoR with Data Deduplication

As the basis of cloud computing, distributed storage technology mainly studies how data centers store, organize and manage data. Blockchain has become the most secure solution for cloud storage due to its decentralization and immutability. Consensus mechanism is one of the core technologies of blockchain, which affects the transaction processing capability, security and scalability of blockchain. The current mainstream consensus algorithms such as Proof of Work, Proof of Stake, and Delegated Proof of Stake all have the problem of wasting resources. And with the explosive growth of data, cloud storage nodes store a large amount of redundant data, which inevitably increases storage overhead and computing cost. To this end, we propose to use the Proof of Retrievability with deduplication algorithm as the consensus mechanism of the blockchain system and design a blockchain consensus protocol suitable for distributed storage. First, the data integrity verification protocol in the scheme guarantees that storage nodes correctly store the data they promise to store. Second, the deduplication algorithm in the protocol can optimize data auditing, greatly reduce the need for data storage space, and improve the scalability of data transmission. In addition, the scheme uses ring signatures in the audit process to ensure user anonymity and data unlinkability, while providing highly reliable data storage, and ensuring data storage security through blockchain. Finally, we demonstrate the security of the proposed scheme and evaluate its performance. The evaluation results show that our scheme is efficient and scalable.

Password-Authenticated Proofs of Retrievability for Multiple Devices Checking Cloud Data

Password-Authenticated Proofs of Retrievability for Multiple Devices Checking Cloud Data

Provable Data Possession (PDP) and Proofs of Retrievability (POR) of Current Big User Data

A growing trend over the last few years is storage outsourcing, where the concept of third-party data warehousing has become more popular. This trend prompts several interesting privacy and security issues. One of the biggest concerns with third-party data storage providers is accountability. This article, critically reviews two schemas/algorithms that allow users to check the integrity and availability of their outsourced data on untrusted data stores (i.e., third-party data storages). The reviewed schemas are provable data possession (PDP) and proofs of retrievability (POR). Both are cryptographic protocols designed to provide clients the assurance that their data are secure on the untrusted data storages. Furthermore, a conceptual framework is proposed to mitigate the weaknesses of the current storage solutions.

BOSSA: A Decentralized System for Proofs of Data Retrievability and Replication

Proofs of retrievability and proofs of replication are two cryptographic tools that enable a remote server to prove that the users’ data has been correctly stored. Nevertheless, the literature either requires the users themselves to perform expensive verification jobs, or relies on a “fully trustworthy” third party auditor (TPA) to execute the public verification. In addition, none of existing solutions consider the underlying incentive issues behind a rational server who is motivated to collect users’ data but tries to evade the replication checking in order to save storage resources. In this article, we propose the first decentralized system for proofs of data retrievability and replication— ${\sf BOSSA}$ BOSSA , which is incentive-compatible for each party and realizes automated auditing atop off-the-shelf blockchain platforms. We deal with issues such as proof enforcements to catch malicious behaviors, new metrics to measure the contributions, and reward distributions to create a fair reciprocal environment. ${\sf BOSSA}$ BOSSA also incorporates privacy-enhancing techniques to prevent decentralized peers (including blockchain nodes) from inferring private information about the outsourced data. Security analysis is presented in the context of integrity, privacy, and reliability. We implement a prototype based on ${\sf BOSSA}$ BOSSA leveraging the smart contracts of Ethereum blockchain. Our extensive experimental evaluations demonstrate the practicality of our proposal.

Privacy-Preserving Proof of Storage for the Pay-As-You-Go Business Model

Proof of Storage (PoS) enables a cloud storage provider to prove that a client’s data is intact. However, existing PoS protocols are not designed for the pay-as-you-go business model in which payment is made based on both storage volume and duration. In this paper, we propose two PoS protocols suitable for the pay-as-you-go storage business model. The first is a time encapsulated Proof of Retrievability (PoR) protocol that ensures retrievability of the original file upon successful auditing by a client. Considering the large size of outsourced data, we then extend the protocol to a privacy-preserving public auditing protocol which allows a third party auditor to audit outsourced data on behalf of its clients without sacrificing the privacy of the data or the timestamp (i.e., time of storage). We formalize the definition, system model and security model of the proposed PoS system and prove the security of the proposed protocols by a sequence of games in the algebraic group model with a random oracle. We analyze the performance of the protocols both theoretically and experimentally and show that the protocols are practical.

Outsourcing Proofs of Retrievability

Proofs of Retrievability (POR) are cryptographic proofs that enable a cloud provider to prove that a user can retrieve his file in its entirety. POR need to be frequently executed by the user to ensure that their files stored in the cloud can be fully retrieved at any point in time. To conduct and verify POR, users need to be equipped with devices that have network access, and that can tolerate the (non-negligible) computational overhead incurred by the verification process. This clearly hinders the large-scale adoption of POR by cloud users, since many users increasingly rely on portable devices that have limited computational capacity, or might not always have network access. In this paper, we introduce the notion of outsourced proofs of retrievability (OPOR), in which users can task an external auditor to perform and verify POR with the cloud provider. We argue that the OPOR setting is subject to security risks that have not been covered by existing POR security models. To remedy that, we propose a formal framework and a security model for OPOR. We then propose a generic procedure for transforming a public POR into an OPOR and we show the security of the resulting OPOR in our proposed security model. We demonstrate the transformation on two different instantiations of public POR schemes due to Shacham and Waters (Asiacrypt'08)-one based on BLS signatures and one using RSA signatures. A shortcoming of this transformation is that the generated OPOR inherits the high computational overhead from the underlying public key cryptography. Consequently, we propose afterwards an OPOR that is build from a private POR by Shacham and Waters. We implement a prototype based on our solutions, and evaluate their performance in a realistic cloud setting. Our evaluation results show that our proposals minimize user effort, and incur negligible overhead on the auditor.

Verifiable Cloud Data Access: Design, Analysis, and Implementation

In this article, we consider the following cloud storage security problem: A user outsources his/her data to a cloud and later frequently updates the data by adding new data items and deleting existing ones. When the user requests an existing data item from the cloud, the cloud may claim that there is no such data item. This could happen due to cloud management issues, hardware/software failures, hackers, or economic incentives, such as saving cloud’s operation costs. The ability to confirm the data existence/nonexistence when accessing a data item on the dynamic outsourced cloud storage is referred to as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dynamic verifiable data access</i> (DVDA). Existing cloud security research works, including encrypted search and proof of storage (i.e., proof of retrievability and proof of data possession), are not sufficient for addressing dynamic verifiable data access. In this article, we present a solution for the dynamic verifiable data access problem. In order to support data dynamics and verifiability, we enhance a hash authentication tree that is build on top of a hash table with a new semantics. With the enhanced hash authentication tree, the proposed protocol supports adding/deleting data in the outsourced storage while satisfying data access verifiability requirement simultaneously. Our open-source experimental evaluation shows that it only takes less than 0.1 ms to verify a data access on a dataset with 400 items using communication cost around 1.7 KB.

Proofs of Physical Reliability for Cloud Storage Systems

Cloud service providers (CSPs) promise to reliably store repositories outsourced by clients. Unfortunately, once files have left the client's control, he has no means to verify their redundant storage. In this article, we develop Proof of Physical Reliability (PoPR) auditing mechanisms that prove that a CSP stores an outsourced repository across multiple physical storage nodes. A PoPR complements the existing proof-of-retrievability (PoR) and proof-of-data possession (PDP) methods that are concerned with file retrievability, but without any verification of the fault-tolerance to physical storage nodes failures. A PoPR goes beyond retrievability by verifying that a file is redundantly stored across multiple physical storage nodes according to a pre-agreed layout and can, therefore, survive node failures. The verification mechanism relies on a combination of storage integrity and timing tests on the simultaneous retrieval of a collection of file symbols from multiple storage nodes. Compared to the state-of-the-art, our approach accommodates CSPs with heterogeneous storage devices (hard disks, SSDs, etc.) and does not assume constant data processing nor network delays. Instead, it can operate under any delay variance, because it relies only on (loose) delay bounds. We analytically prove the security of our construction and experimentally validate its success in heterogeneous storage settings.

Efficient Proofs of Retrievability with Public Verifiability for Dynamic Cloud Storage

Cloud service providers offer various facilities to their clients. The clients with limited resources opt for some of these facilities. They can outsource their bulk data to the cloud server. The cloud server maintains these data in lieu of monetary benefits. However, a malicious cloud server might delete some of these data to save some space and offer this extra amount of storage to another client. Therefore, the client might not retrieve her file (or some portions of it) as often as needed. Proofs of retrievability (POR) provide an assurance to the client that the server is actually storing all of her data appropriately and they can be retrieved at any point of time. In a dynamic POR scheme, the client can update her data after she uploads them to the cloud server. Moreover, in publicly verifiable POR schemes, the client can delegate her auditing task to some third party specialized for this purpose. In this work, we exploit the homomorphic hashing technique to design a publicly verifiable dynamic POR scheme that is more efficient (in terms of bandwidth required between the client and the server) than the “state-of-the-art” publicly verifiable dynamic POR scheme. We also analyze security and performance of our scheme.

A novel zero knowledge proof of retrievability

Proof of retrievability is a cryptographic tool which interacts between the data user and the server, and the server proves to the data user the integrity of data which he will download. It is a crucial problem in outsourcing storage such as cloud computing. In this paper, a novel scheme called the zero knowledge proof of retrievability is proposed, which combines proof of retrievability and zero knowledge proof. It has lower computation and communication complexity and higher security than the previous schemes.

Secure Enterprise and Read Performance Enhancement in Data Deduplication for Secondary Storage

With the tremendous growth of available digital data, the use of Cloud Service Providers (CSPs) are gaining more popularity, since these types of services promise to provide convenient and efficient storage services to end-users by taking advantage of a new set of benefits and savings offered by cloud technologies in terms of computational, storage, bandwidth, and transmission costs. we propose solutions for different data types (text, image and video) for secure data de-duplication in cloud environments. Our schemes allow users to upload their data in a secure and efficient manner such that neither a semi-honest CSP nor a malicious user can access or compromise the security of the data. Moreover, we propose proof of storage protocols including Proof of Retrievability (POR) and Proof of Ownership (POW) so that users of cloud storage services are able to ensure that their data has been saved in the cloud without tampering or manipulation. Experimental results are provided to validate the effectiveness of the proposed schemes. proposes a method to improve the read performance by investigating the recently accessed chunks and their locality in the backup set (data stream). Based on this study of the distribution of chunks in the data stream, few chunks are identified that need to be accumulated and stored to serve the future read requests better. This identification and accumulation happen on cached chunks. By this a small degree of duplication of the de-duplicated data is introduced, but by later caching them together during the restore of the same data stream, the read performance is improved. Finally the read performance results obtained through experiments with trace datasets are presented and analyzed to evaluate the design.