Variação sazonal na riqueza e na abundância de pequenos mamíferos, na estrutura da floresta e na disponibilidade de artrópodes em fragmentos florestais no Mato Grosso, Brasil

We captured small mammals in eight forest fragments (43 a 1.411 ha.) during the dry and wet seasons, in southwest Mato Grosso, Brazil, and investigated the variation in small mammal richness and abundance, as well as in forest structure variables (litter volume and canopy openness) and arthropod availability, between the two seasons. Sampling was carried out during the wet season between 2002 and 2003 and in the dry season of 2003. In each fragment, we used Sherman, Tomahawk, snap, and pitfall traps during 10 consecutive days per season, totaling 17,600 trap x nights. In total, we obtained 379 captures of 20 species, seven of marsupials and 13 of rodents. Overall capture success was 2.2% (1.6% during the wet season and 2.7% during the dry season). Total richness, richness of rodents, richness of marsupials, total abundance and abundance of rodents did not varied significantly between seasons. However, marsupial abundance was significantly lower in the dry season, when rainfall is high. Litter volume was significantly higher during the dry season, while arthropod availability was significantly higher during the wet season. Therefore, higher food availability during the wet season may have made trap baits less attractive. In general, the observed variations between dry and wet seasons are in accordance with patterns described in other studies

ROTIV: RFID Ownership Transfer with Issuer Verification

RFID tags travel between partner sites in a supply chain. For privacy reasons, each partner “owns” the tags present at his site, i.e., the owner is the only entity able to authenticate his tags. However, when passing tags on to the next partner in the supply chain, ownership of the old partner is “transferred” to the new partner. In this paper, we propose ROTIV, a protocol that allows for secure ownership transfer against some malicious owners. Furthermore, ROTIV offers issuer verification to prevent malicious partners from injecting fake tags not originally issued by some trusted party. As part of ownership, ROTIV provides a constant-time, privacy-preserving authentication. ROTIV’s main idea is to combine an HMAC-based authentication with tag key and state updates during ownership transfer. To assure privacy, ROTIV implements tag state re-encryption techniques and key update techniques, performed on the reader. ROTIV is designed for lightweight tags – tags are only required to evaluate a hash function

New privacy results on synchronized RFID authentication protocols against tag tracing

Many RFID authentication protocols with randomized tag response have been proposed to avoid simple tag tracing. These protocols are symmetric in common due to the lack of computational power to perform expensive asymmetric cryptography calculations in low-cost tags. Protocols with constantly changing tag key have also been proposed to avoid more advanced tag tracing attacks. With both the symmetric and constant changing properties, tag and reader re-synchronization is unavoidable as the key of a tag can be made desynchronized with the reader due to offline attacks or incomplete protocol runs. In this paper, our contribution is to classify these synchronized RFID authentication protocols into different types and then examine their highest achievable levels of privacy protections using the privacy model proposed by Vaudenay in Asiacrypt 2007 and later extended by Ng et al. in ESORICS 2008. Our new privacy results show the separation between weak privacy and narrow-forward privacy in these protocols, which effectively fills themissing relationship of these two privacy levels in Vaudenay’s paper and answer the question raised by Paise and Vaudenay in ASIACCS 2008 on why they cannot find a candidate protocol that can achieve both privacy levels at the same time. We also show that forward privacy is impossible with these synchronized protocols