Secure two-party quantum evaluation of unitaries against specious adversaries

We describe how any two-party quantum computation, specified by a unitary which simultaneously acts on the registers of both parties, can be privately implemented against a quantum version of classical semi-honest adversaries that we call specious. Our construction requires two ideal functionalities to garantee privacy: a private SWAP between registers held by the two parties and a classical private AND-box equivalent to oblivious transfer. If the unitary to be evaluated is in the Clifford group then only one call to SWAP is required for privacy. On the other hand, any unitary not in the Clifford requires one call to an AND-box per R-gate in the circuit. Since SWAP is itself in the Clifford group, this functionality is universal for the private evaluation of any unitary in that group. SWAP can be built from a classical bit commitment scheme or an AND-box but an AND-box cannot be constructed from SWAP. It follows that unitaries in the Clifford group are to some extent the easy ones. We also show that SWAP cannot be implemented privately in the bare model

General paradigm for distilling classical key from quantum states

We develop a formalism for distilling a classical key from a quantum state in a systematic way, expanding on our previous work on secure key from bound entanglement [K. Horodecki et. al., Phys. Rev. Lett. 94 (2005)]. More detailed proofs, discussion and examples are provided of the main results. Namely, we demonstrate that all quantum cryptographic protocols can be recast in a way which looks like entanglement theory, with the only change being that instead of distilling EPR pairs, the parties distill private states. The form of these general private states are given, and we show that there are a number of useful ways of expressing them. Some of the private states can be approximated by certain states which are bound entangled. Thus distillable entanglement is not a requirement for a private key. We find that such bound entangled states are useful for a cryptographic primitive we call a controlled private quantum channel. We also find a general class of states which have negative partial transpose (are NPT), but which appear to be bound entangled. The relative entropy distance is shown to be an upper bound on the rate of key. This allows us to compute the exact value of distillable key for a certain class of private states.Comment: 41 pages, ReVTeX4, improved version, resubmitted to IEE

Competition and mergers in networks with call externalities

This paper considers a model of two interconnected networks with different qualities. There are call externalities in the sense that consumers value calls they send and receive. Networks compete in two part tariffs. We show that call externalities create private incentives for each competitor to charge low access prices. This result moderates the risk of tacit collusion when competitors can freely negotiate their access charges. We also analyze the case of a merger between the two networks and give conditions under which the merger can be welfare improving.

Competition and mergers in networks with call externalities

This paper considers a model of two interconnected networks with different qualities. There are call externalities in the sense that consumers value calls they send and receive. Networks compete in two part tariffs. We show that call externalities create private incentives for each competitor to charge low access prices. This result moderates the risk of tacit collusion when competitors can freely negotiate their access charges. We also analyze the case of a merger between the two networks and give conditions under which the merger can be welfare improving.call externalities; interconnection; mergers; telecommunications

Ethical reconstruction of citizenship: A proposal between the intimate self and the public sphere

When, in societies today, civic commitment decreases, there is a call for the need to strengthen citizenship education, identified uniquely with its public dimension and, on the other hand, the requirement for character education has been advocated, which is a cultivator of the most strictly private dimension. Setting out from the recognition of the new social conditions, mediated by the phenomenon of globalisation and of the place that people have in these new contexts, we ask ourselves about the new profile which the construction of citizenship must adopt. We endeavor to show that the moral dimension is the core of reconsidering the link between the private and the public, so it would currently be meaningless to propose an education of citizenship exclusively focused on its public dimensio

Internet Giants as Quasi-Governmental Actors and the Limits of Contractual Consent

Although the government’s data-mining program relied heavily on information and technology that the government received from private companies, relatively little of the public outrage generated by Edward Snowden’s revelations was directed at those private companies. We argue that the mystique of the Internet giants and the myth of contractual consent combine to mute criticisms that otherwise might be directed at the real data-mining masterminds. As a result, consumers are deemed to have consented to the use of their private information in ways that they would not agree to had they known the purposes to which their information would be put and the entities – including the federal government – with whom their information would be shared. We also call into question the distinction between governmental actors and private actors in this realm, as the Internet giants increasingly exploit contractual mechanisms to operate with quasi-governmental powers in their relations with consumers. As regulators and policymakers focus on how to better protect consumer data, we propose that solutions that rely upon consumer permission adopt a more exacting and limited concept of the consent required before private entities may collect or make use of consumer’s information where such uses touch upon privacy interests

Intra-backbone and Inter-backbone Peering Among Internet Service Providers

We consider a model with two backbones and a finite number of Internet Service Providers (ISPs) connected to the backbones. ISPs decide on private peering agreements, comparing the benefits of private peering to costs. Intra-backbone peering refers to peering between ISPs connected to the same backbone, whereas inter-backbone peering refers to peering between ISPs connected to different backbones. We formulate the model as a two-stage game. In the first stage, ISPs decide on peering agreements. In the second stage they compete in prices a la Bertrand. We examine the effects of peering on profits of ISPs. Peering affects profits through two channels - reduction of backbone congestion which we call the symmetric effect and ability to send traffic bypassing or circumventing congested backbones which we call the asymmetric effect. The first has a negative or ambiguous effect while the second has a generally positive effect on firm profits. The two often act against each other making the net effect ambiguous. We also conduct simulations to determine pairwise stable peering configurations in a six-provider model and find that there is a paucity of inter-backbone peering in asymmetric settings.Peering, Networks

Intra-backbone and Inter-backbone Peering Among Internet Service Providers

We consider a model with two backbones and a finite number of Internet Service Providers (ISPs) connected to the backbones. ISPs decide on private peering agreements, comparing the benefits of private peering to costs. Intra-backbone peering refers to peering between ISPs connected to the same backbone, whereas inter-backbone peering refers to peering between ISPs connected to different backbones. We formulate the model as a two-stage game. In the first stage, ISPs decide on peering agreements. In the second stage they compete in prices a la Bertrand. We examine the effects of peering on profits of ISPs. Peering affects profits through two channels - reduction of backbone congestion which we call the symmetric effect and ability to send traffic bypassing or circumventing congested backbones which we call the asymmetric effect. The first has a negative or ambiguous effect while the second has a generally positive effect on firm profits. The two often act against each other making the net effect ambiguous. We also conduct simulations to determine pairwise stable peering configurations in a six-provider model and find that there is a paucity of inter-backbone peering in asymmetric settings.Peering, Networks