Oblivious Random Access Machine (ORAM) is a kind of cryptographic primitive that allows a client to access its private data from the server without disclosing the access pattern. To deal with consecutive requested blocks at a time efficiently, range ORAM (rORAM) is presented. In the previous rORAM scheme, the locality, namely, the number of discontinuous seeks to complete a request, is reduced to O(log2 N), nevertheless, the bandwidth cost is increased to the poly-logarithmic level. Hence, there exists an open question, that is, whether rORAM can be constructed with the same bandwidth efficiency as a regular ORAM, that is, O(log N)-block? In this paper, we propose a new rORAM scheme, called L2-rORAM. In our scheme, a compatible superblock technique is proposed, and it is combined together with an eviction technique for range blocks, so that it avoids duplication of multiple copies and extra dummy access. As a result, it obtains O(log N)-block bandwidth cost, which affirmatively answers the above open question. Meanwhile, the data locality is reduced to O(log N). In addition, the client storage is maintained at the small level of O(log N)-block, and the server storage is maintained at the unexpanded level of O(N)-block. Finally, experimental results show that the average response time of our L2-rORAM is reduced by one order of magnitude over the state-of-the-art rORAM scheme.

Cloud storage attracts a lot of clients to join the paradise. For a high data availability, some clients require their files to be replicated and stored on multiple servers. Because clients are generally charged based on the redundancy level required by them, it is critical for clients to obtain convincing evidence that all replicas are stored correctly and are updated to the up-to-date version. In this article, we propose a dynamic proof of data possession and replication (DPDPR) scheme, which is proved to be secure in the defined security model. Our scheme shares a single authenticated tree across multiple replicas, which reduces the tree's storage cost significantly. Our scheme allows for batch verification for multiple challenged leaves and can verify multiple replicas in a single batch way, which considerably save bandwidth and computation resources during audit process. We also evaluate the DPDPR's performance and compare it with the most related scheme. The evaluation results show that our scheme saves almost 66 percent tree's storage cost for three replicas, and obtains almost 60 and 80 percent efficiency improvements in terms of the overall bandwidth and computation costs, respectively, when three replicas are checked and each challenged with 460 blocks.

Abstract For a high level of data availability and reliability, a common strategy for cloud service providers is to rely on replication, i.e. storing several replicas onto different servers. To provide cloud users with a strong guarantee that all replicas required by them are actually stored, many multi-replica integrity auditing schemes were proposed. However, most existing solutions are not resource economical since users need to create and upload replicas of their files by themselves. A multi-replica solution called Mirror is presented to overcome the problems, but we find that it is vulnerable to storage saving attack, by which a dishonest provider can considerably save storage costs compared to the costs of storing all the replicas honestly—while still can pass any challenge successfully. In addition, we also find that Mirror is easily subject to substitution attack and forgery attack, which pose new security risks for cloud users. To address the problems, we propose some simple yet effective countermeasures and an improved proofs of retrievability and replication scheme, which can resist the aforesaid attacks and maintain the advantages of Mirror, such as economical bandwidth and efficient verification. Experimental results show that our scheme exhibits comparable performance with Mirror while achieving high security.

Abstract Location-based services have attracted much attention in both academia and industry. However, protecting user’s privacy while providing accurate service for users remains challenging. In most of the existing research works, a semi-trusted proxy is employed to act on behalf of a user to minimize the computation and communication costs of the user. However, user privacy, e.g. location privacy, cannot be protected against the proxy. In this paper, we design a new blind filter protocol where a user can employ a semi-trusted proxy to determine whether a point of interest is within a circular area centered at the user’s location. During the protocol, neither the proxy nor the location-based service provider can obtain the location of the user and the query results. Moreover, each type of query is controlled by an access tree and only the users whose attributes satisfy this access tree can complete the specific type of query. Security analysis and efficiency experiments validate that the proposed protocol is secure and efficient in terms of the computation and communication overhead.

Replication is a fundamental solution for the cloud service provider (CSP) to guarantee data availability. To provide users with convincing evidence that the copies required by them are all stored correctly, a number of multi-copy integrity auditing schemes were presented. Recently, Barsoum and Hasan proposed a map-based provable multi-copy dynamic data possession scheme (IEEE Transactions on Information Forensics and Security, vol. 10, no. 3, pp. 485-497, 2015), which was claimed to be secure and can ensure that the CSP possesses all copies required by the contract. However, in this letter, we show that the scheme is easily subject to a copy-summation attack and a single-copy attack, by which a cheating CSP only needs to invest a storage cost of a single copy-while can still pass the verifier's challenge at all times. Therefore, the scheme is no longer secure in this case. Furthermore, we propose some simple but effective countermeasures and give a repaired scheme which is free from the above two attacks.

In the cloud, for achieving access control and keeping data confidential, the data owners could adopt attribute-based encryption to encrypt the stored data. Users with limited computing power are however more likely to delegate the mask of the decryption task to the cloud servers to reduce the computing cost. As a result, attribute-based encryption with delegation emerges. Still, there are caveats and questions remaining in the previous relevant works. For instance, during the delegation, the cloud servers could tamper or replace the delegated ciphertext and respond a forged computing result with malicious intent. They may also cheat the eligible users by responding them that they are ineligible for the purpose of cost saving. Furthermore, during the encryption, the access policies may not be flexible enough as well. Since policy for general circuits enables to achieve the strongest form of access control, a construction for realizing circuit ciphertext-policy attribute-based hybrid encryption with verifiable delegation has been considered in our work. In such a system, combined with verifiable computation and encrypt-then-mac mechanism, the data confidentiality, the fine-grained access control and the correctness of the delegated computing results are well guaranteed at the same time. Besides, our scheme achieves security against chosen-plaintext attacks under the k-multilinear Decisional Diffie-Hellman assumption. Moreover, an extensive simulation campaign confirms the feasibility and efficiency of the proposed solution.

Among the existing identity-based authenticated key agreement ID-AKA protocols, there are only a few of them that can resist to leakage of ephemeral secret keys, which is about the protection of the session secret key after the ephemeral secret keys of users are compromised. However, all these ID-AKA protocols with leakage of ephemeral secret keys resistance require expensive bilinear pairing operations. In this paper, we present a pairing-free ID-AKA protocol with ephemeral secrets leakage resistance. We also provide a full proof of its security in the extended Canetti-Krawczyk model, which not only can capture resistance to leakage of ephemeral secret keys but also can capture other basic security properties such as master key forward security and key compromise impersonation resistance. Compared with the existing ID-AKA protocols, our scheme is a good trade-off between security and efficiency. Copyright © 2015 John Wiley & Sons, Ltd.

The ability to easily deploy parallel computations on the Cloud is becoming ever more important. The first uniform mechanism for checkpointing a network of virtual machines is described. This is important for the parallel versions of common productivity software. Potential examples of parallelism include Simulink for MATLAB, parallel R for the R statistical modelling language, parallel blast.py for the BLAST bioinformatics software, IPython.parallel for Python, and GNU parallel for parallel shells. The checkpoint mechanism is implemented as a plugin in the DMTCP checkpoint-restart package. It operates on KVM/QEMU, and has also been adapted to Lguest and pure user-space QEMU. The plugin is surprisingly compact, comprising just 400 lines of code to checkpoint a single virtual machine, and 200 lines of code for a plugin to support saving and restoring network state. Incremental checkpoints of the associated virtual filesystem are accommodated through the Btrfs filesystem. Experiments demonstrate checkpoint times of a fraction of a second by using forked checkpointing, mmap-based restart, and incremental Btrfs-based snapshots.

In cloud storage environment, clients no longer have physical possession of their data, it indicates that their data may be leaked maliciously by cloud provider. To avoid the security risks, we propose a privacy preserving keyword searching scheme whose encryption procedure needs no pairing operation. Our scheme allows users to encrypt their data before uploading to the cloud, and retrieve them by searching the encrypted keywords, besides it enables the cloud service provider to participate in decipherment which reduces the computational overhead of the client's decryption. Performance analysis shows our new scheme is more efficient and more adaptable to the cloud environment than the existing schemes. In addition, the new scheme is proved to be semantically secure in the random oracle model.

This paper describes two preliminary experiments concerned with the construction of a robot head. The initial design and research is aimed at producing a system with two cameras and two microphones on a system capable of operating with the same degrees of freedom and reflex times as its biological counterpart. Whilst the primary goal of the project is develop an anthropomorphic system with the sensory reflex capabilities of a human head, the system will also contain some non-anthropomorphic components. The most obvious of the non-anthropomorphic components is a spatially and temporally programmable light source. Some preliminary results are presented. use this information to direct autonomous behaviour (Brooks, 1989) but these reflexes have not been coupled