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During the last years many RFID authentication protocols have been proposed with major or minor success (van Deursen and Radomirović (2008)). Juels (2004) introduced a different and novel problem that aims to evidence that two tags have been simultaneously scanned. He called this kind of evidence a yoking-proof that is supposed to be verifiable offline. Then, some authors suggested the generalization of the proof for a larger number of tags. In this paper, we review the literature published in this research topic and show the security flaws of the proposed protocols, named RFID groupingproofs generally. More precisely, we cryptanalyze five of the most recent schemes and we also show how our techniques can be applied to older proposals. We provide some guidelines that should be followed to design secure protocols and preclude past errors. Finally, we present a yoking-proof for low-cost RFID tags, named Kazahaya, that conforms to the proposed guidelines. Keywords:RFID; Grouping-proof; Security; Privacy, Cryptanalysis * Corresponding author Email addresses: P.PerisLopez@tudelft.nl (Pedro Peris-Lopez), Preprint submitted to Journal of Network and Computer Applications March 25, 2010A c c e p t e d m a n u s c r i p t

Use of the internet as a trade platform has resulted in a shift in the illegal wildlife trade. Increased scrutiny of illegal wildlife trade has led to concerns that online trade of wildlife will move onto the dark web. To provide a baseline of illegal wildlife trade on the dark web, we downloaded and archived 9852 items (individual posts) from the dark web, then searched these based on a list of 121 keywords associated with illegal online wildlife trade, including 30 keywords associated with illegally traded elephant ivory on the surface web. Results were compared with items known to be illegally traded on the dark web, specifically cannabis, cocaine, and heroin, to compare the extent of the trade. Of these 121 keywords, 4 resulted in hits, of which only one was potentially linked to illegal wildlife trade. This sole case was the sale and discussion of Echinopsis pachanoi (San Pedro cactus), which has hallucinogenic properties. This negligible level of activity related to the illegal trade of wildlife on the dark web relative to the open and increasing trade on the surface web may indicate a lack of successful enforcement against illegal wildlife trade on the surface web.

The design of ultralightweight authentication protocols that conform to low-cost tag requirements is imperative. This paper analyses the most important proposals (except for those based in hard problems such as the HB [1-3] family) in the area [4-6] and identifies the common weaknesses that have left all of them open to various attacks [7-11]. Finally, we present Gossamer, a new protocol inspired by the recently published SASI scheme [13], that was lately also the subject of a disclosure attack by Hernandez-Castro et al. [14]. Specifically, this new protocol is designed to avoid the problems of the past, and we examine in some deep its security and performance.

Low-cost Radio Frequency Identification (RFID) tags affixed to consumer items as smart labels are emerging as one of the most pervasive computing technology in history. This can have huge security implications. The present article surveys the most important technical security challenges of RFID systems. We first provide a brief summary of the most relevant standards related to this technology. Next, we present an overview about the state of the art on RFID security, addressing both the functional aspects and the security risks and threats associated to its use. Finally, we analyze the main security solutions proposed until date.

h i g h l i g h t s • A methodology to detect discussion communities on vaccination is proposed. • Vaccine opinions in twitter can affect the decision-making about vaccination. • The most relevant and influential users are identified analysing the communities. • The collective sentiment on vaccination has been studied for the detected groups. • Results provide useful information to improve immunization strategies.