Matrix Factorization Techniques for Recommender Systems

This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

A systematic literature review of blockchain-based applications: Current status, classification and open issues

The sharp increase in the number of smartphones on the market, with the Android platform posed to becoming a market leader makes the need for malware analysis on this platform an urgent issue.In this paper we capitalize on earlier approaches for dynamic analysis of application behavior as a means for detecting malware in the Android platform. The detector is embedded in a overall framework for collection of traces from an unlimited number of real users based on crowdsourcing. Our framework has been demonstrated by analyzing the data collected in the central server using two types of data sets: those from artificial malware created for test purposes, and those from real malware found in the wild. The method is shown to be an effective means of isolating the malware and alerting the users of a downloaded malware. This shows the potential for avoiding the spreading of a detected malware to a larger community.

/pdf/crowdroid-behavior-based-malware-detection-system-for-x2tq6w9qk1.pdf

Crowdroid: behavior-based malware detection system for Android

我的台灣, 看見心靈的故鄉 =2009林磐聳藝術與設計展

Hash functions using stream ciphers as components perform fast on a variety of platforms. However, the security and the design policy of stream-cipher-based hash functions (SCHs) have not yet been studied sufficiently. In this paper, we analyze its design criteria based on a ideal function of SCHs. First, we show that attacks against a stream cipher can also be threats against SCHs. Then we discuss the security on each phase of SCH; message injection, blank rounds, and hash generation with this function. Finally we derive the necessary conditions on the stream cipher function for an SCH to be secure.

On a construction of stream-cipher-based hash functions

A key issue for an organization that is responsible for disaster and emergency management becomes how to gather reliable and useful information during a major disaster. We consider an information-gathering platform for large-scale disasters and emergencies based on mobile terminals. A simple solution to realize an information-gathering system is to construct a server where information is uploaded and published. However, such a centralized approach is not flexible nor is it robust. For example, it is very hard to find an appropriate system to which the user can upload information during a disaster, and the centralized server may be down because of overload or has been physically destroyed. We must consider a distributed and dynamic architecture for the system. Security and privacy issues are another concern that should be addressed for providing information from user's mobile terminals. We focus on a design of a privacy preserving data upload mechanism for the information-gathering system. We design the mechanism that accommodates privacy requirements and present a feasibility analysis of the mechanism.

On Designing Privacy-Aware Data Upload Mechanism -- Towards Information-Gathering System for Disasters

In Time-Specific Signatures (TSS) parameterized by an integer \(T\in \mathbb {N}\), a signer with a secret-key associated with a numerical value \(t\in [0,T-1]\) can anonymously, i.e., without revealing t, sign a message under a numerical range [L, R] such that \(0\le L \le t\le R\le T-1\). A direct application of TSS is anonymous questionnaire, where each user associated with a numerical value such as age, date, salary, geographical position (represented by longitude and latitude), etc., can anonymously fill in a questionnaire in an efficient manner.

Time-Specific Signatures

Abstract Privacy risks of collaborative filtering (CF) have been widely studied. The current state-of-theart inference attack on user behaviors (e.g., ratings/purchases on sensitive items) for CF is by Calandrino et al. (S&P, 2011). They showed that if an adversary obtained a moderate amount of user’s public behavior before some time T, she can infer user’s private behavior after time T. However, the existence of an attack that infers user’s private behavior before T remains open. In this paper, we propose the first inference attack that reveals past private user behaviors. Our attack departs from previous techniques and is based on model inversion (MI). In particular, we propose the first MI attack on factorization-based CF systems by leveraging data poisoning by Li et al. (NIPS, 2016) in a novel way. We inject malicious users into the CF system so that adversarialy chosen “decoy” items are linked with user’s private behaviors. We also show how to weaken the assumption made by Li et al. on the information available to the adversary from the whole rating matrix to only the item profile and how to create malicious ratings effectively. We validate the effectiveness of our inference algorithm using two real-world datasets.

https://sciendo.com/pdf/10.2478/popets-2020-0052

Exposing Private User Behaviors of Collaborative Filtering via Model Inversion Techniques

In Time-Specific Encryption (TSE) [Paterson&Quaglia, SCN’10] system, each secret-key (resp. ciphertext) is associated with a time period t ∈ [0,T − 1] (resp. a time interval [L,R] where L,R ∈ [0,T − 1]). A ciphertext under [L,R] is correctly decrypted by any secret-key for any time t included in the interval, i.e., t ∈ [L,R]. TSE’s generic construction from identity-based encryption (IBE) (resp. hierarchical IBE (HIBE)) from which we obtain a concrete TSE scheme with secret-keys of size O(log T )|g| (resp. O(log T )|g|) and ciphertexts of size O(log T )|g| (resp. O(1)|g|) has been proposed in [Paterson&Quaglia, SCN’10] (resp. [Kasamatsu et al., SCN’12]), where |g| denotes bit length of an element in a bilinear groupG. In this paper, we propose another TSE’s generic construction from wildcarded identity-based encryption (WIBE). Differently from the original WIBE ([Abdalla et al., ICALP’06]), we consider WIBE w/o (hierarchical) key-delegatability. By instantiating the TSE’s generic construction, we obtain the first concrete scheme with constant size secret-keys secure under a standard (static) assumption. Specifically, it has secret-keys of size O(1)|g| and ciphertexts of size O(log T )|g|, and achieves security under the decisional bilinear Diffie-Hellman (DBDH) assumption.

Shinsaku Kiyomoto

Papers

On a construction of stream-cipher-based hash functions

On Designing Privacy-Aware Data Upload Mechanism -- Towards Information-Gathering System for Disasters

Time-Specific Signatures

Exposing Private User Behaviors of Collaborative Filtering via Model Inversion Techniques

Time-Specific Encryption with Constant-Size Secret-Keys Secure under Standard Assumption.