Mitigating the One-Use Restriction in Attribute-Based Encryption

We present a key-policy attribute-based encryption scheme that is adaptively secure under a static assumption and is not directly affected by an attribute one-use restriction. Our construction improves upon the only other such scheme (Takashima \u2717) by mitigating its downside of a ciphertext size that is dependent on the maximum size of any supported attribute set

Privacy-preserving targeted advertising scheme for IPTV using the cloud

In this paper, we present a privacy-preserving scheme for targeted advertising via the Internet Protocol TV (IPTV). The scheme uses a communication model involving a collection of viewers/subscribers, a content provider (IPTV), an advertiser, and a cloud server. To provide high quality directed advertising service, the advertiser can utilize not only demographic information of subscribers, but also their watching habits. The latter includes watching history, preferences for IPTV content and watching rate, which are published on the cloud server periodically (e.g. weekly) along with anonymized demographics. Since the published data may leak sensitive information about subscribers, it is safeguarded using cryptographic techniques in addition to the anonymization of demographics. The techniques used by the advertiser, which can be manifested in its queries to the cloud, are considered (trade) secrets and therefore are protected as well. The cloud is oblivious to the published data, the queries of the advertiser as well as its own responses to these queries. Only a legitimate advertiser, endorsed with a so-called {\em trapdoor} by the IPTV, can query the cloud and utilize the query results. The performance of the proposed scheme is evaluated with experiments, which show that the scheme is suitable for practical usage

Bridging policy, regulation and practice? A techno-legal analysis of three types of data in the GDPR

The paper aims to determine how the General Data Protection Regulation (GDPR) could be read in harmony with Article 29 Working Party’s Opinion on anonymisation techniques. To this end, based on an interdisciplinary methodology, a common terminology to capture the novel elements enshrined in the GDPR is built, and, a series of key concepts (i.e. sanitisation techniques, contextual controls, local linkability, global linkability, domain linkability) followed by a set of definitions for three types of data emerging from the GDPR are introduced. Importantly, two initial assumptions are made: 1) the notion of identifiability (i.e. being identified or identifiable) is used consistently across the GDPR (e.g. Article 4 and Recital 26); 2) the Opinion on Anonymisation Techniques is still good guidance as regards the classification of re-identification risks and the description of sanitisation techniques. It is suggested that even if these two premises seem to lead to an over-restrictive approach, this holds true as long as contextual controls are not combined with sanitisation techniques. Yet, contextual controls have been conceived as complementary to sanitisation techniques by the drafters of the GDPR. The paper concludes that the GDPR is compatible with a risk-based approach when contextual controls are combined with sanitisation techniques

Protecting Public OSN Posts from Unintended Access

The design of secure and usable access schemes to personal data represent a major challenge of online social networks (OSNs). State of the art requires prior interaction to grant access. Sharing with users who are not subscribed or previously have not been accepted as contacts in any case is only possible via public posts, which can easily be abused by automatic harvesting for user profiling, targeted spearphishing, or spamming. Moreover, users are restricted to the access rules defined by the provider, which may be overly restrictive, cumbersome to define, or insufficiently fine-grained. We suggest a complementary approach that can be easily deployed in addition to existing access control schemes, does not require any interaction, and includes even public, unsubscribed users. It exploits the fact that different social circles of a user share different experiences and hence encrypts arbitrary posts. Hence arbitrary posts are encrypted, such that only users with sufficient knowledge about the owner can decrypt. Assembling only well-established cryptographic primitives, we prove that the security of our scheme is determined by the entropy of the required knowledge. We consequently analyze the efficiency of an informed dictionary attack and assess the entropy to be on par with common passwords. A fully functional implementation is used for performance evaluations, and available for download on the Web

A Secured Proxy-Based Data Sharing Module in IoT Environments Using Blockchain

Access and utilization of data are central to the cloud computing paradigm. With the advent of the Internet of Things (IoT), the tendency of data sharing on the cloud has seen enormous growth. With data sharing comes numerous security and privacy issues. In the process of ensuring data confidentiality and fine-grained access control to data in the cloud, several studies have proposed Attribute-Based Encryption (ABE) schemes, with Key Policy-ABE (KP-ABE) being the prominent one. Recent works have however suggested that the confidentiality of data is violated through collusion attacks between a revoked user and the cloud server. We present a secured and efficient Proxy Re-Encryption (PRE) scheme that incorporates an Inner-Product Encryption (IPE) scheme in which decryption of data is possible if the inner product of the private key, associated with a set of attributes specified by the data owner, and the associated ciphertext is equal to zero 0 . We utilize a blockchain network whose processing node acts as the proxy server and performs re-encryption on the data. In ensuring data confidentiality and preventing collusion attacks, the data are divided into two, with one part stored on the blockchain network and the other part stored on the cloud. Our approach also achieves fine-grained access control