Statically Aggregate Verifiable Random Functions and Application to E-Lottery

Cohen, Goldwasser, and Vaikuntanathan (TCC’15) introduced the concept of aggregate pseudo-random functions (PRFs), which allow efficiently computing the aggregate of PRF values over exponential-sized sets. In this paper, we explore the aggregation augmentation on verifiable random function (VRFs), introduced by Micali, Rabin and Vadhan (FOCS’99), as well as its application to e-lottery schemes. We introduce the notion of static aggregate verifiable random functions (Agg-VRFs), which perform aggregation for VRFs in a static setting. Our contributions can be summarized as follows: (1) we define static aggregate VRFs, which allow the efficient aggregation of VRF values and the corresponding proofs over super-polynomially large sets; (2) we present a static Agg-VRF construction over bit-fixing sets with respect to product aggregation based on the q-decisional Diffie–Hellman exponent assumption; (3) we test the performance of our static Agg-VRFs instantiation in comparison to a standard (non-aggregate) VRF in terms of costing time for the aggregation and verification processes, which shows that Agg-VRFs lower considerably the timing of verification of big sets; and (4) by employing Agg-VRFs, we propose an improved e-lottery scheme based on the framework of Chow et al.’s VRF-based e-lottery proposal (ICCSA’05). We evaluate the performance of Chow et al.’s e-lottery scheme and our improved scheme, and the latter shows a significant improvement in the efficiency of generating the winning number and the player verification.

An Information Theoretically Secure E-Lottery Scheme Based on Symmetric Bivariate Polynomials

E-lottery schemes have attracted much interest from both industry and academia recently, because they are not only useful to raise funds for charity institutions, but also can be used as the major building blocks to design micro-payment systems. In the literature, a number of e-lottery schemes have been introduced over the last two decades. However, most of these schemes rely on some computational assumptions. In this paper, we introduce a novel e-lottery scheme that achieves information theoretical security. Our proposed scheme is designed using symmetric bivariate polynomials, and it satisfies the required security properties, such as correctness, unpredictability, verifiability, and robustness. Moreover, the winning number is generated in a distributed fashion, so that no trusted third party needs to be involved and the danger of a single point of failure is minimized.

An Improved LambdaMART Algorithm Based on the Matthew Effect

Matthew effect is a desirable phenomenon for a ranking model in search engines and recommendation systems. However, most of algorithms of learning to rank (LTR) do not pay attention to Matthew effect. LambdaMART is a well-known LTR algorithm that can be further optimized based on Matthew effect. Inspired by Matthew effect, we distinguish queries with different effectiveness and then assign a higher weight to a query with higher effectiveness. We improve the gradient in the LambdaMART algorithm to optimize the queries with high effectiveness, that is, to highlight the Matthew effect of the produced ranking models. In addition, we propose strategies of evaluating a ranking model and dynamically decreasing the learning rate to both strengthen the Matthew effect of ranking models and improve the effectiveness of ranking models. We use Gini coefficient, mean-variance, quantity statistics, and winning number to measure the performances of the ranking models. Experimental results on multiple benchmark datasets show that the ranking models produced by our improved LambdaMART algorithm can exhibit a stronger Matthew effect and achieve higher effectiveness compared to the original one and other state-of-the-art LTR algorithms.

Managing Risk in Numbers Games

This chapter applies Benford's law to study how players choose numbers in fixed-odds number lottery games. Empirical data suggests that not all players choose numbers with equal probability in lottery games. Some of them tend to bet on (smaller) numbers that are closely related to events around them (e.g., birthdays, anniversaries, addresses, etc.). In a fixed-odds lottery game, this small-number phenomenon imposes a serious risk on the game operator of a big payout if a very popular number is chosen as the winning number. The chapter quantifies this phenomenon and develops a choice model incorporating a modified Benford's law for lottery players to capture the magnitude of the small-number phenomenon observed in the empirical data.

SUKUK MUDHARABAH SEBAGAI INSTRUMEN KEUANGAN ISLAM IDEAL KONTEMPORER

The year 2012 and 2013 can be regarded as the mudaraba sukuk revival since winning number and the value as compared to previous years. Indonesian mudaraba sukuk attract Islamic financial worlds' attention, because he was the first Indonesian sukuk while abroad is more aitively issuing ijara sukuk. In addition, it is identified that the Indonesia mudaraba sukuk is very attractive to investors and seem to be consistent and honest, but why ultimately mudaraba sukuk like abandoned? Actually, the more appropriate format for sukuk is mudhrabah while it is difficult to be applied in Islamic banking. Indonesia mudaraba sukuk application is quite phenomenal because it provides a very high return even once reached 24.3%, the highest return compared to all the world's sukuk and more Islamic and even more consistent in many ways. However, according to the application in general, mudaraba sukuk is still not consistent in terms of Shariah compliance, such as providing income and principal guarantees. Further, the fluctuation phenomenon of use of fixed return sukuk type and floating return in Indonesia is quite interesting to obseroe the high returns associated with these and also with the market desire to implement the shariah compliant sukuk. The authors analyze the problem in this paper qualitatively from two perspectives, namely through sharia compliance perspective and the perspective of investment effectiveness. Key words: mudaraba, sukuk, Islamic financial, Islamic banking