Fully Secure Spatial Encryption under Simple Assumptions with Constant-Size Ciphertexts

In this paper, we propose two new spatial encryption (SE) schemes based on existing inner product encryption (IPE) schemes. Both of our SE schemes are fully secure under simple assumptions and in prime order bilinear groups. Moreover, one of our SE schemes has constant-size ciphertexts. Since SE implies hierarchical identity-based encryption (HIBE), we also obtain a fully secure HIBE scheme with constant-size ciphertexts under simple assumptions. Our second SE scheme is attribute-hiding (or anonymous). It has sizes of public parameters, secret keys and ciphertexts that are quadratically smaller than the currently known SE scheme with similar properties. As a side result, we show that negated SE is equivalent to non-zero IPE. This is somewhat interesting since the latter is known to be a special case of the former

Doubly Spatial Encryption from DBDH

Functional encryption is an emerging paradigm for public-key encryption which enables fine-grained control of access to encrypted data. Doubly-spatial encryption (DSE) captures all functionalities that we know how to realize via pairings-based assumptions, including (H)IBE, IPE, NIPE, CP-ABE and KP-ABE. In this paper, we propose a construction of DSE from the decisional bilinear Diffie-Hellman (DBDH) assumption. This also yields the first non-zero inner product encryption (NIPE) scheme based on DBDH. Quite surprisingly, we know how to realize NIPE and DSE from stronger assumptions in bilinear groups but not from the basic DBDH assumption. Along the way, we present a novel algebraic characterization of *NO* instances for the DSE functionality, which we use crucially in the proof of security

Efficient privacy preserving predicate encryption with fine-grained searchable capability for cloud storage

With the fast development in Cloud storage technologies and ever increasing use of Cloud data centres, data privacy and confidentiality has become a must. Indeed, Cloud data centres store each time more sensitive data such as personal data, organizational and enterprise data, transactional data, etc. However, achieving confidentiality with flexible searchable capability is a challenging issue. In this article, we show how to construct an efficient predicate encryption with fine-grained searchable capability. Predicate Encryption (PEPE) can achieve more sophisticated and flexible functionality compared with traditional public key encryption. We propose an efficient predicate encryption scheme by utilizing the dual system encryption technique, which can also be proved to be IND-AH-CPA (indistinguishable under chosen plain-text attack for attribute-hiding) secure without random oracle. We also carefully analyse the relationship between predicate encryption and searchable encryption. To that end, we introduce a new notion of Public-Key Encryption with Fine-grained Keyword Search (PEFKSPEFKS). Our results show that an IND-AH-CPA secure PE scheme can be used to construct an IND-PEFKS-CPA (indistinguishable under chosen plain-text attack for public-key encryption with fine-grained keyword search) secure PEFKSPEFKS scheme. A new transformation of PE-to-PEFKS is also proposed and used to construct an efficient PEFKSPEFKS scheme based on the transformation from the proposed PEPE scheme. Finally, we design a new framework for supporting privacy preserving predicate encryption with fine-grained searchable capability for Cloud storage. Compared to most prominent frameworks, our framework satisfies more features altogether and can serve as a basis for developing such frameworks for Cloud data centres.Peer ReviewedPostprint (author's final draft

Compact CCA2-secure Hierarchical Identity-Based Broadcast Encryption for Fuzzy-entity Data Sharing

With the advances of cloud computing, data sharing becomes easier for large-scale enterprises. When deploying privacy and security schemes in data sharing systems, fuzzy-entity data sharing, entity management, and efficiency must take into account, especially when the system is asked to share data with a large number of users in a tree-like structure. (Hierarchical) Identity-Based Encryption is a promising candidate to ensure fuzzy-entity data sharing functionalities while meeting the security requirement, but encounters efficiency difficulty in multi-user settings. This paper proposes a new primitive called Hierarchical Identity-Based Broadcast Encryption (HIBBE) to support multi-user data sharing mechanism. Similar to HIBE, HIBBE organizes users in a tree-like structure and users can delegate their decryption capability to their subordinates. Unlike HIBE merely allowing a single decryption path, HIBBE enables encryption to any subset of the users and only the intended users (and their supervisors) can decrypt. We define Ciphertext Indistinguishability against Adaptively Chosen-Identity-Vector-Set and Chosen-Ciphertext Attack (IND-CIVS-CCA2) for HIBBE, which capture the most powerful attacks in the real world. We achieve this goal in the standard model in two steps. We first construct an efficient HIBBE Scheme (HIBBES) against Adaptively Chosen-Identity-Vector-Set and Chosen-Plaintext Attack (IND-CIVS-CPA) in which the attacker is not allowed to query the decryption oracle. Then we convert it into an IND-CIVS-CCA2 scheme at only a marginal cost, i.e., merely adding one on-the-fly dummy user at the first depth of hierarchy in the basic scheme without requiring any other cryptographic primitives. Our CCA2-secure scheme natively allows public ciphertext validity test, which is a useful property when a CCA2-secure HIBBES is used to design advanced protocols and auditing mechanisms for HIBBE-based data sharing

Advances in Functional Encryption

Functional encryption is a novel paradigm for public-key encryption that enables both fine-grained access control and selective computation on encrypted data, as is necessary to protect big, complex data in the cloud. In this thesis, I provide a brief introduction to functional encryption, and an overview of my contributions to the area

New Fundamental Technologies in Data Mining

The progress of data mining technology and large public popularity establish a need for a comprehensive text on the subject. The series of books entitled by "Data Mining" address the need by presenting in-depth description of novel mining algorithms and many useful applications. In addition to understanding each section deeply, the two books present useful hints and strategies to solving problems in the following chapters. The contributing authors have highlighted many future research directions that will foster multi-disciplinary collaborations and hence will lead to significant development in the field of data mining

Electronic Voting: 6th International Joint Conference, E-Vote-ID 2021, Virtual Event, October 5–8, 2021: proceedings

This volume contains the papers presented at E-Vote-ID 2021, the Sixth International Joint Conference on Electronic Voting, held during October 5–8, 2021. Due to the extraordinary situation brought about by the COVID-19, the conference was held online for the second consecutive edition, instead of in the traditional venue in Bregenz, Austria. The E-Vote-ID conference is the result of the merger of the EVOTE and Vote-ID conferences, with first EVOTE conference taking place 17 years ago in Austria. Since that conference in 2004, over 1000 experts have attended the venue, including scholars, practitioners, authorities, electoral managers, vendors, and PhD students. The conference focuses on the most relevant debates on the development of electronic voting, from aspects relating to security and usability through to practical experiences and applications of voting systems, also including legal, social, or political aspects, amongst others, and has turned out to be an important global referent in relation to this issue

Sixth International Joint Conference on Electronic Voting E-Vote-ID 2021. 5-8 October 2021

This volume contains papers presented at E-Vote-ID 2021, the Sixth International Joint Conference on Electronic Voting, held during October 5-8, 2021. Due to the extraordinary situation provoked by Covid-19 Pandemic, the conference is held online for second consecutive edition, instead of in the traditional venue in Bregenz, Austria. E-Vote-ID Conference resulted from the merging of EVOTE and Vote-ID and counting up to 17 years since the _rst E-Vote conference in Austria. Since that conference in 2004, over 1000 experts have attended the venue, including scholars, practitioners, authorities, electoral managers, vendors, and PhD Students. The conference collected the most relevant debates on the development of Electronic Voting, from aspects relating to security and usability through to practical experiences and applications of voting systems, also including legal, social or political aspects, amongst others; turning out to be an important global referent in relation to this issue. Also, this year, the conference consisted of: · Security, Usability and Technical Issues Track · Administrative, Legal, Political and Social Issues Track · Election and Practical Experiences Track · PhD Colloquium, Poster and Demo Session on the day before the conference E-VOTE-ID 2021 received 49 submissions, being, each of them, reviewed by 3 to 5 program committee members, using a double blind review process. As a result, 27 papers were accepted for its presentation in the conference. The selected papers cover a wide range of topics connected with electronic voting, including experiences and revisions of the real uses of E-voting systems and corresponding processes in elections. We would also like to thank the German Informatics Society (Gesellschaft für Informatik) with its ECOM working group and KASTEL for their partnership over many years. Further we would like to thank the Swiss Federal Chancellery and the Regional Government of Vorarlberg for their kind support. EVote- ID 2021 conference is kindly supported through European Union's Horizon 2020 projects ECEPS (grant agreement 857622) and mGov4EU (grant agreement 959072). Special thanks go to the members of the international program committee for their hard work in reviewing, discussing, and shepherding papers. They ensured the high quality of these proceedings with their knowledge and experience

Interdependent Security and Compliance in Service Selection

Application development today is characterized by ever shorter release cycles and more frequent change requests. Hence development methods such as service composition are increasingly arousing interest as viable alternative approaches. While employing web services as building blocks rapidly reduces development times, it raises new challenges regarding security and compliance since their implementation remains a black box which usually cannot be controlled. Security in particular gets even more challenging since some applications require domainspecific security objectives such as location privacy. Another important aspect is that security objectives are in general no singletons but subject to interdependence. Hence this thesis addresses the question of how to consider interdependent security and compliance in service composition. Current approaches for service composition do neither consider interdependent security nor compliance. Selecting suiting services for a composition is a combinatorial problem which is known to be NP-hard. Often this problem is solved utilizing genetic algorithms in order to obtain near-optimal solutions in reasonable time. This is particularly the case if multiple objectives have to be optimized simultaneously such as price, runtime and data encryption strength. Security properties of compositions are usually verified using formal methods. However, none of the available methods supports interdependence effects or defining arbitrary security objectives. Similarly, no current approach ensures compliance of service compositions during service selection. Instead, compliance is verified afterwards which might necessitate repeating the selection process in case of a non-compliant solution. In this thesis, novel approaches for considering interdependent security and compliance in service composition are being presented and discussed. Since no formal methods exist covering interdependence effects for security, this aspect is covered in terms of a security assessment. An assessment method is developed which builds upon the notion of structural decomposition in order to assess the fulfillment of arbitrary security objectives in terms of a utility function. Interdependence effects are being modeled as dependencies between utility functions. In order to enable compliance-awareness, an approach is presented which checks compliance of compositions during service selection and marks non-compliant parts. This enables to repair the corresponding parts during the selection process by replacing the current services and hence avoids the necessity to repeat the selection process. It is demonstrated how to embed the presented approaches into a genetic algorithm in order to ease integration with existing approaches for service composition. The developed approaches are being compared to state-of-the-art genetic algorithms using simulations