Revisit the Concept of PEKS: Problems and a Possible Solution

Since Boneh et al. propose the concept, non-interactive\ud Public-key Encryption with Keyword Search (PEKS) has attracted lots of attention from cryptographers. Non-interactive PEKS enables a third party to test whether or not a tag, generated by the message sender, and a trapdoor, generated by the receiver, contain the same keyword without revealing further information. In this paper we investigate a non-interactive PEKS application proposed by Boneh et al. and show our observations, especially that privacy is\ud not protected against a curious server. We propose the notion of interactive PEKS, which, in contrast to non-interactive PEKS, requires the tag to be generated interactively by the message sender and the receiver. For this new primitive, we identify two types of adversaries, namely a curious user and a curious server, and provide\ud security formulations for the desirable properties. We propose a construction for interactive PEKS and prove its security in the proposed security model

Public Key Encryption Supporting Plaintext Equality Test and User-Specified Authorization

In this paper we investigate a category of public key encryption schemes which supports plaintext equality test and user-specified authorization. With this new primitive, two users, who possess their own public/private key pairs, can issue token(s) to a proxy to authorize it to perform plaintext equality test from their ciphertexts. We provide a formal formulation for this primitive, and present a construction with provable security in our security model. To mitigate the risks against the semi-trusted proxies, we enhance the proposed cryptosystem by integrating the concept of computational client puzzles. As a showcase, we construct a secure personal health record application based on this primitive

On Using Encryption Techniques to Enhance Sticky Policies Enforcement

How to enforce privacy policies to protect sensitive personal data has become an urgent research topic for security researchers, as very little has been done in this field apart from some ad hoc research efforts. The sticky policy paradigm, proposed by Karjoth, Schunter, and Waidner, provides very useful inspiration on how we can protect sensitive personal data, but the enforcement is very weak. In this paper we provide an overview of the state of the art in enforcing sticky policies, especially the concept of sticky policy enforcement using encryption techniques including Public-Key Encryption (PKE), Identity-Based Encryption (IBE), Attribute-Based Encryption (ABE), and Proxy Re-Encryption (PRE). We provide detailed comparison results on the (dis)advantages of these enforcement mechanisms. As a result of the analysis, we provide a general framework for enhancing sticky policy enforcement using Type-based PRE (TPRE), which is an extension of general PRE

On Non-Parallelizable Deterministic Client Puzzle Scheme with Batch Verification Modes

A (computational) client puzzle scheme enables a client to prove to a server that a certain amount of computing resources (CPU cycles and/or Memory look-ups) has been dedicated to solve a puzzle. Researchers have identified a number of potential applications, such as constructing timed cryptography, fighting junk emails, and protecting critical infrastructure from DoS attacks. In this paper, we first revisit this concept and formally define two properties, namely deterministic computation and parallel computation resistance. Our analysis show that both properties are crucial for the effectiveness of client puzzle schemes in most application scenarios. We prove that the RSW client puzzle scheme, which is based on the repeated squaring technique, achieves both properties. Secondly, we introduce two batch verification modes for the RSW client puzzle scheme in order to improve the verification efficiency of the server, and investigate three methods for handling errors in batch verifications. Lastly, we show that client puzzle schemes can be integrated with reputation systems to further improve the effectiveness in practice

On the inability of existing security models to cope with data mobility in dynamic organizations

Modeling tools play an important role in identifying threats in traditional\ud IT systems, where the physical infrastructure and roles are assumed\ud to be static. In dynamic organizations, the mobility of data outside the\ud organizational perimeter causes an increased level of threats such as the\ud loss of confidential data and the loss of reputation. We show that current\ud modeling tools are not powerful enough to help the designer identify the\ud emerging threats due to mobility of data and change of roles, because they\ud do not include the mobility of IT systems nor the organizational dynamics\ud in the security model. Researchers have proposed security models that\ud particularly focus on data mobility and the dynamics of modern organizations,\ud such as frequent role changes of a person. We show that none\ud of the current security models simultaneously considers the data mobility\ud and organizational dynamics to a satisfactory extent. As a result, none\ud of the current security models effectively identifies the potential security\ud threats caused by data mobility in a dynamic organization

From Ephemerizer to Timed-Ephemerizer: Achieve Assured Lifecycle Enforcement for Sensitive Data

The concept of Ephemerizer, proposed by Perlman, is a cryptographic primitive for assured data deletion. With an Ephemerizer protocol, data in persistent storage devices will always be encrypted simultaneously using an ephemeral public key of the Ephemerizer (an entity which will publish a set of ephemeral public keys and periodically delete the expired ones) and the long-term public key of a user. An Ephemerizer protocol enables the user to securely decrypt the encrypted data without leaking any information to the Ephemerizer. So far, no security model has ever been proposed for this primitive and existing protocols have not been studied formally. Not surprisingly, we show that some existing Ephemerizer protocols possess security vulnerabilities. In this paper, we introduce the notion of Timed-Ephemerizer, which can be regarded as a hybrid primitive by combining Ephemerizer and Timed-Release Encryption. Compared with an Ephemerizer protocol, a Timed-Ephemerizer protocol further guarantees that data will only be released after a pre-defined disclosure time. Moreover, we propose a security model for Timed-Ephemerizer and formalize relevant security properties. We also propose a new Timed-Ephemerizer protocol and prove its security in the security model

Sedenion algebra for three lepton/quark generations and its relations to SU(5)

In this work, we analyze two models beyond the Standard Models descriptions that make ad hoc hypotheses of three point-like lepton and quark generations without explanations of their physical origins. Instead of using the same Dirac equation involving four anti-commutative matrices for all such structure-less elementary particles, we consider in the first model the use of sixteen direct-product matrices of quaternions that are related to Diracs gamma matrices. This associative direct-product matrix model could not generate three fermion generations satisfying Einsteins mass-energy relation. We show that sedenion algebra contains five distinct quaternion sub-algebras and three octonion sub-algebras but with a common intersecting quaternion algebra. This model naturally leads to precisely three generations as each of the non-associative octonion sub-algebra leads to one fermion generation. Moreover, we demonstrate the use of basic sedenion.Comment: 19 pages, 5 figure

A unified sedenion model for the origins of three generations of charged and neutral leptons, flavor mixing, mass oscillations and small masses of neutrinos

We present a unified model without the need for an ad hoc Standard Model hypothesis; we explain why there are three generations of charged and neutral leptons, why neutrinos have a vanishingly small mass, and why flavor-mixing emerges and mass oscillations occur. We show that the sedenion algebra contains three types of non-associative octonion algebra, with each corresponding to a generation of leptons. By incorporating extra degrees of freedom, the generalized higher dimensional Dirac equation accounts for the internal structural dynamics. This study sheds light on the intrinsic physical properties of three generations of charged leptons and neutrinos and their distinctive spacetime structures.Comment: 22 pages, 6 figure