Towards an interpreter for efficient encrypted computation

Fully homomorphic encryption (FHE) techniques are capable of performing encrypted computation on Boolean circuits, i.e., the user specifies encrypted inputs to the program, and the server computes on the encrypted inputs. Applying these techniques to general programs with recursive procedures and data-dependent loops has not been a focus of attention. In this paper, we take a first step toward building an interpreter that, given programs with complex control flow, schedules efficient code suitable for the application of FHE schemes. We first describe how programs written in a small Turing-complete instruction set can be executed with encrypted data and point out inefficiencies in this methodology. We then provide examples of scheduling (a) the greatest common divisor (GCD) problem using Euclid's algorithm and (b) the 3-Satisfiability (3SAT) problem using a recursive backtracking algorithm into path-levelized FHE computations. We describe how path levelization reduces control flow ambiguity and improves encrypted computation efficiency. Using these techniques and data-dependent loops as a starting point, we then build support for hierarchical programs made up of phases, where each phase corresponds to a fixed point computation that can be used to further improve the efficiency of encrypted computation. In our setting, the adversary learns an estimate of the number of steps required to complete the computation, which we show is the least amount of leakage possible

Ideal Tightly Couple (t,m,n) Secret Sharing

As a fundamental cryptographic tool, (t,n)-threshold secret sharing ((t,n)-SS) divides a secret among n shareholders and requires at least t, (t<=n), of them to reconstruct the secret. Ideal (t,n)-SSs are most desirable in security and efficiency among basic (t,n)-SSs. However, an adversary, even without any valid share, may mount Illegal Participant (IP) attack or t/2-Private Channel Cracking (t/2-PCC) attack to obtain the secret in most (t,n)-SSs.To secure ideal (t,n)-SSs against the 2 attacks, 1) the paper introduces the notion of Ideal Tightly cOupled (t,m,n) Secret Sharing (or (t,m,n)-ITOSS ) to thwart IP attack without Verifiable SS; (t,m,n)-ITOSS binds all m, (m>=t), participants into a tightly coupled group and requires all participants to be legal shareholders before recovering the secret. 2) As an example, the paper presents a polynomial-based (t,m,n)-ITOSS scheme, in which the proposed k-round Random Number Selection (RNS) guarantees that adversaries have to crack at least symmetrical private channels among participants before obtaining the secret. Therefore, k-round RNS enhances the robustness of (t,m,n)-ITOSS against t/2-PCC attack to the utmost. 3) The paper finally presents a generalized method of converting an ideal (t,n)-SS into a (t,m,n)-ITOSS, which helps an ideal (t,n)-SS substantially improve the robustness against the above 2 attacks

Solutions and Tools for Secure Communication in Wireless Sensor Networks

Secure communication is considered a vital requirement in Wireless Sensor Network (WSN) applications. Such a requirement embraces different aspects, including confidentiality, integrity and authenticity of exchanged information, proper management of security material, and effective prevention and reaction against security threats and attacks. However, WSNs are mainly composed of resource-constrained devices. That is, network nodes feature reduced capabilities, especially in terms of memory storage, computing power, transmission rate, and energy availability. As a consequence, assuring secure communication in WSNs results to be more difficult than in other kinds of network. In fact, trading effectiveness of adopted solutions with their efficiency becomes far more important. In addition, specific device classes or technologies may require to design ad hoc security solutions. Also, it is necessary to efficiently manage security material, and dynamically cope with changes of security requirements. Finally, security threats and countermeasures have to be carefully considered since from the network design phase. This Ph.D. dissertion considers secure communication in WSNs, and provides the following contributions. First, we provide a performance evaluation of IEEE 802.15.4 security services. Then, we focus on the ZigBee technology and its security services, and propose possible solutions to some deficiencies and inefficiencies. Second, we present HISS, a highly scalable and efficient key management scheme, able to contrast collusion attacks while displaying a graceful degradation of performance. Third, we present STaR, a software component for WSNs that secures multiple traffic flows at the same time. It is transparent to the application, and provides runtime reconfigurability, thus coping with dynamic changes of security requirements. Finally, we describe ASF, our attack simulation framework for WSNs. Such a tool helps network designers to quantitatively evaluate effects of security attacks, produce an attack ranking based on their severity, and thus select the most appropriate countermeasures

A Survey on the Path Computation Element (PCE) Architecture

Quality of Service-enabled applications and services rely on Traffic Engineering-based (TE) Label Switched Paths (LSP) established in core networks and controlled by the GMPLS control plane. Path computation process is crucial to achieve the desired TE objective. Its actual effectiveness depends on a number of factors. Mechanisms utilized to update topology and TE information, as well as the latency between path computation and resource reservation, which is typically distributed, may affect path computation efficiency. Moreover, TE visibility is limited in many network scenarios, such as multi-layer, multi-domain and multi-carrier networks, and it may negatively impact resource utilization. The Internet Engineering Task Force (IETF) has promoted the Path Computation Element (PCE) architecture, proposing a dedicated network entity devoted to path computation process. The PCE represents a flexible instrument to overcome visibility and distributed provisioning inefficiencies. Communications between path computation clients (PCC) and PCEs, realized through the PCE Protocol (PCEP), also enable inter-PCE communications offering an attractive way to perform TE-based path computation among cooperating PCEs in multi-layer/domain scenarios, while preserving scalability and confidentiality. This survey presents the state-of-the-art on the PCE architecture for GMPLS-controlled networks carried out by research and standardization community. In this work, packet (i.e., MPLS-TE and MPLS-TP) and wavelength/spectrum (i.e., WSON and SSON) switching capabilities are the considered technological platforms, in which the PCE is shown to achieve a number of evident benefits

Fiscal federalism in big developing countries: China and India

In South and East Asian countries a highly centralized government prevails, although recently some trends are moving toward a greater degree of decentralization. Also the two giants China and India, which cannot rely on a merely centralized Government, have experienced a greater or lesser degree of fiscal unionism. As to China the local government system provides four levels: provincial level; city level; county level; township level. Intergovernmental fiscal relations were revamped by the 1994 reform that established a new tax sharing system and gave local governments more control over the administration of local taxes but no significant degree of tax autonomy and no substantial expenditure assignments. The local financial revenue mainly derives from local taxes, shared taxes, and nontax revenue. As to India, the federal system is quite complex. The center-states relations are envisaged in the Constitution also for the financial aspects: two constitutional amendments adopted in 1992 made India one of the most politically decentralized countries among developing ones. However, the implementation of the decentralization program is still lagging: till now India seems to have considered decentralization mainly in terms of the local election system, without the transfer of all functions provided for devolution to local bodies. Only India set up a different system of local bodies in rural and urban areas with different expenditure responsibilities and financing powers. On the contrary, China has a unitary fiscal system. In India it is necessary to redesign the transfer system to improve accountability, incentives and equity, whereas in China, the fiscal revenue sharing schemes limit intergovernmental budget transfers. Finally, the rule of hard budget constraint in China is faced by all levels of government, while in India sub-national governments face soft budget constraint.

Indian Federalism, Economic Reform and Globalization

In this paper we examine several dimensions of economic reform in India, in the context of the country’s federal system and of globalization, i.e., we explicitly recognize that the national government has subnational governments below it, and that all these layers of government simultaneously interact with foreign governments and corporations in a global economy. We examine two groups of reforms, the first involving redrawing of state-market boundaries, and the second concerned with reconfiguring federal institutions themselves. The first group includes financial sector reforms, assignment of regulatory powers, infrastructure reform and development, and privatization. We note the progress made in financial sector reform but also the problems caused for the financial sector as a whole by state and central fiscal deficits. We discuss the extreme problems of the power sector, and the important federal dimensions that make reform more difficult there. We also highlight the regional concentration of FDI in India’s more liberalized economy. The second group of reforms includes tax reforms, reform of center-state fiscal transfer mechanisms, and local government reforms. To some degree, these reforms in federal governance hold the key to opening the door to further reform elsewhere, by reducing the fiscal burden placed on the private sector by government deficits. We acknowledge the political economy aspects of reform of governance, and discuss possibilities for politically acceptable packages of fiscal reforms, such as combinations of changes in tax assignment that would be acceptable to the center as well as the state governments. We also discuss the possibility that growing regional inequalities might require the intergovernmental transfer system to be more efficient and effective in its objectives.