A New Cryptosystem Based On Hidden Order Groups

Let $G_1$ be a cyclic multiplicative group of order $n$. It is known that the Diffie-Hellman problem is random self-reducible in $G_1$ with respect to a fixed generator $g$ if $\phi(n)$ is known. That is, given $g, g^x\in G_1$ and having oracle access to a `Diffie-Hellman Problem' solver with fixed generator $g$, it is possible to compute $g^{1/x} \in G_1$ in polynomial time (see theorem 3.2). On the other hand, it is not known if such a reduction exists when $\phi(n)$ is unknown (see conjuncture 3.1). We exploit this ``gap'' to construct a cryptosystem based on hidden order groups and present a practical implementation of a novel cryptographic primitive called an \emph{Oracle Strong Associative One-Way Function} (O-SAOWF). O-SAOWFs have applications in multiparty protocols. We demonstrate this by presenting a key agreement protocol for dynamic ad-hoc groups.Comment: removed examples for multiparty key agreement and join protocols, since they are redundan

Is TRIPS suffering from Big Giant’s Syndrome: Good Economics versus Self Interest?

The paper discusses TRIPS as a protection measure on knowledge and new technologies through property rights and analyses the Southern concern if protection of new technologies by means of TRIPS may mean that South can no longer imitate the North in implementing emerging technologies and concepts as was the case with Newly Industrialized Countries of Asia in 1980s. The paper shows that trade and research and development trends are highly skewed in favor of the North and this means that in any such international economic landscape, TRIPS may advantage the North and restrict the South from trading under a technologically aligned level playing field

Mode-locked dysprosium fiber laser: picosecond pulse generation from 2.97 to 3.30 {\mu}m

Mode-locked fiber laser technology to date has been limited to sub-3 {\mu}m wavelengths, despite significant application-driven demand for compact picosecond and femtosecond pulse sources at longer wavelengths. Erbium- and holmium-doped fluoride fiber lasers incorporating a saturable absorber are emerging as promising pulse sources for 2.7--2.9 {\mu}m, yet it remains a major challenge to extend this coverage. Here, we propose a new approach using dysprosium-doped fiber with frequency shifted feedback (FSF). Using a simple linear cavity with an acousto-optic tunable filter, we generate 33 ps pulses with up to 2.7 nJ energy and 330 nm tunability from 2.97 to 3.30 {\mu}m (3000--3400 cm^-1)---the first mode-locked fiber laser to cover this spectral region and the most broadly tunable pulsed fiber laser to date. Numerical simulations show excellent agreement with experiments and also offer new insights into the underlying dynamics of FSF pulse generation. This highlights the remarkable potential of both dysprosium as a gain material and FSF for versatile pulse generation, opening new opportunities for mid-IR laser development and practical applications outside the laboratory.Comment: Accepted for APL Photonics, 22nd August 201

Multilateral Versus Regional Trading Arrangements: Substitutes Or Compliments?

We summarise salient developments in the interaction of the multilateral trading system and multilateral trading agreements (MTAs) on the one hand and regional trading agreements (RTAs) on the other. We then consider the economic effects of RTAs, comparing customs unions with free trade agreements. We argue, contrary to much received wisdom, that either may produce more economic benefits than the other, depending on the specific context in which they are introduced. There follows a discussion of the political economy effects of RTAs. Some of these have unfavourable, some neutral and some favourable effects on the progress of further MTAs. We conclude that the case against RTAs as eroding the MTS and inhibiting further MTA negotiations, as expounded by such economists as Krueger and Bhagwati, is not well founded. There remain grounds for optimism that the process of competitive liberalisation in RTAs will lead eventually to further multilateral liberalisation.customs unions, free trade areas, multilateral agreements, multilateral trading system, regional agreements, rules of origin, scale economies, trade creation, trade diversion.

The challenge of reducing international trade and migration barriers

While barriers to trade in most goods and some services including capital flows have been reduced considerably over the past two decades, many remain. Such policies harm most the economies imposing them, but the worst of the merchandise barriers (in agriculture and textiles) are particularly harmful to the world's poorest people, as are barriers to worker migration across borders. This paper focuses on how costly those anti-poor trade policies are, and examines possible strategies to reduce remaining distortions. Two opportunities in particular are addressed: completing the Doha Development Agenda process at the World Trade Organization (WTO), and freeing up the international movement of workers. A review of the economic benefits and adjustment costs associated with these opportunities provides the foundation to undertake benefit/cost analysis required to rank this set of opportunities against those aimed at addressing the world's other key challenges as part of the Copenhagen Consensus project. The paper concludes with key caveats and suggests that taking up these opportunities could generate huge social benefit/cost ratios that are considerably higher than the direct economic ones quantified in this study, even without factoring in their contribution to alleviating several of the other challenges identified by that project, including malnutrition, disease, poor education and air pollution.Economic Theory&Research,Environmental Economics&Policies,Emerging Markets,Free Trade,Trade Policy