On the Gold Standard for Security of Universal Steganography

While symmetric-key steganography is quite well understood both in the information-theoretic and in the computational setting, many fundamental questions about its public-key counterpart resist persistent attempts to solve them. The computational model for public-key steganography was proposed by von Ahn and Hopper in EUROCRYPT 2004. At TCC 2005, Backes and Cachin gave the first universal public-key stegosystem - i.e. one that works on all channels - achieving security against replayable chosen-covertext attacks (SS-RCCA) and asked whether security against non-replayable chosen-covertext attacks (SS-CCA) is achievable. Later, Hopper (ICALP 2005) provided such a stegosystem for every efficiently sampleable channel, but did not achieve universality. He posed the question whether universality and SS-CCA-security can be achieved simultaneously. No progress on this question has been achieved since more than a decade. In our work we solve Hopper's problem in a somehow complete manner: As our main positive result we design an SS-CCA-secure stegosystem that works for every memoryless channel. On the other hand, we prove that this result is the best possible in the context of universal steganography. We provide a family of 0-memoryless channels - where the already sent documents have only marginal influence on the current distribution - and prove that no SS-CCA-secure steganography for this family exists in the standard non-look-ahead model.Comment: EUROCRYPT 2018, llncs styl

BCG treatment of malignant pleural effusions in the rat.

Intrapleurally injected cells of an ascitic rat tumour produced intrapleural effusions and solid pleural deposits. BCG, or its methanol extraction residue (MER) injected into the pleural space, suppressed tumour development and prolonged survival. Treatment was effective if given a few days before or after tumour injection. In contrast, active specific immunotherapy by repeated s.c. injection of viable or radiation-attenuated tumour cells in admixture with BCG was unsuccessful, and did not improve the response to intrapleural BCG treatment

Extension of Lake Whatcom phosphorus ban: environmental impact assessment

Lake Whatcom is the main source of drinking water for over 96,000 people in Whatcom County including 82,000 residents of the City of Bellingham. Unfortunately, Lake Whatcom is currently listed under the Washington State Department of Ecology\u27s 303D list as an impaired water body due to lack of dissolved oxygen. The main cause of low oxygen levels in the lake is excess phosphorus. Phosphorus is a nutrient necessary for all plant life. However, when too much of it enters aquatic systems, it can cause an imbalance in the aquatic ecosystem. In the past, phosphorus that was used in fertilizers and detergents has entered Lake Whatcom watershed through stormwater runoff. Phosphorus in the lake has contributed to an increase in algal blooms. If these blooms are allowed to continue to grow in the lake, they will have a negative impact on drinking water quality, aesthetics, public services and utilities, recreation in Lake Whatcom, energy and natural resources, as well as quality of life for fish and other wildlife. This environmental impact assessment offers two alternatives to the no-action option regarding phosphorus in the watershed. The first alternative (original ban) would be to return to the original 2005 ordinance restricting the use of phosphorus. This was a control ordinance on commercial fertilizers labeled as containing more than 0% phosphorus by weight. It was based on an honor system, and not enforced. There were also educational materials provided to people living in the watershed on how phosphorus affects the lake, with low phosphorus fertilizers for people to use. The use of phosphorus on first year planting is still allowed within the watershed under the original ban alternative. Additionally, many private land owners could still bring in other materials containing phosphorus such as composts, mulches, etc. The second alternative is the new ordinance that was recently passed by the City Council in January 2011. This new ban limits the use of fertilizers, mulches, wood chips, composts, and other products containing phosphorus for all land uses (with the exception of forestry) within the Lake Whatcom watershed. It also requires retail to post signage notifying customers of the prohibited uses of soil amendments containing over 0% phosphorus on landscaping and horticultural applications. There is already an adequate amount of phosphorus in the soil for plants to grow, and added nutrients are not actually necessary. If no action is taken to limit the amount of added phosphorus coming into the watershed, stormwater runoff will continue to carry more nutrients into the lake, degrading the quality of the water