Finite key size analysis of two-way quantum cryptography

Quantum cryptographic protocols solve the longstanding problem of distributing a shared secret string to two distant users by typically making use of one-way quantum channel. However, alternative protocols exploiting two-way quantum channel have been proposed for the same goal and with potential advantages. Here we overview a security proof for two-way quantum key distribution protocols, against the most general eavesdropping attack, that utilize an entropic uncertainty relation. Then, by resorting to the `smooth' version of involved entropies, we extend such a proof to the case of finite key size. The results will be compared to those available for one-way protocols showing some advantages

Cultivating Extension Communities of Practice

This study empirically describes and analyzes the characteristics and functionality of the ―Communities of Practice (CoPs)‖ used within eXtension, a new initiative of the Cooperative Extension (CE) system. It also endeavors to lay the foundation for empirical analysis of CoP processes, which to date have been explained almost exclusively using qualitative case study methods. Land-grant universities were founded on the ideals that higher education should be accessible to all, that the university should teach liberal and practical subjects and should share the college\u27s knowledge with people throughout their states. eXtension is an educational partnership of more than 70 land-grant universities. Its reported purpose is to help Americans improve their lives with access to timely, objective, research-based information and educational opportunities accessed through http://www.extension.org . This Web resource is customized with links to state land-grant university CE Web sites. This mixed-method, action research project applied to the virtual environment describes the extent to which people who became part of an eXtension Communities of Practice (XCoPs) reported that they engaged in purposeful cycles of continuous inquiry in dialog, decision, action, and evaluation (DDAE) and the attainment of eXtension‘s goals. An Internet survey obtained descriptive data of members‘ participation within the eight pioneer XCoPs to assess the extent to which each XCoP engaged in the DDAE cycles of inquiry. Analysis of the survey data resulted in the categorization of low-, medium-, and high-level functioning XCoPs. Members of three pioneer XCoPs representing each category (low, medium, high collaboration) participated in online interviews that revealed how CE‘s reward structure, XCoP membership composition, and leader/member skill sets impact XCoP performance in meeting eXtension goals. Two sets of ―best practices‖ for eXtension initiative staff and XCoPs emerge from the discussion of triangulated data