Abstract-In order to protect privacy, Radio Frequency Identification (RFID) systems employ Privacy-Preserving Authentication (PPA) to allow valid readers to explicitly authenticate their dominated tags without leaking private information. Typically, an RF tag sends an encrypted message to the reader, then the reader searches for the key that can decrypt the cipher to identify the tag. Due to the large-scale deployment of today's RFID systems, the key search scheme for any PPA requires a short response time. Previous designs construct balance-tree based key management structures to accelerate the search speed to O(logN), where N is the number of tags. Being efficient, such approaches are vulnerable to compromising attacks. By capturing a small number of tags, compromising attackers are able to identify other tags that have not been corrupted. To address this issue, we propose an AntiCompromising authenticaTION protocol, ACTION, which employs a novel sparse tree architecture, such that the key of every tag is independent from one another. The advantages of this design include: 1) resilience to the compromising attack, 2) reduction of key storage for tags from O(logN) to O(1), which is significant for resource critical tag devices, and 3) high search efficiency, which is O(logN), as good as the best in the previous designs.

BACKGROUND Pancreatic lipomas are thought to be very rare. Lipomas are usually easy to identify on imaging, particularly via computed tomography (CT). But sometimes it’s quite difficult to distinguish a lipoma from a well-liposarcoma without histologic result. CASE SUMMARY Here, we present a case of pancreatic lipoma in a 59-year-old female. She was asymptomatic and had no medical history of note. CT and magnetic resonance imaging revealed a mass like well-differentiated liposarcoma in the pancreatic head, positron emission tomography/CT showed a low fluorodeoxyglucose uptake and laboratory tests revealed elevated transaminase and carbohydrate antigen-199 levels. Finally, the patient underwent a pancreaticoduodenectomy. Histologically, mature adipocytes were noted in the bulk of the tumor. Accordingly, the pathologic diagnosis of the pancreatic neoplasm was lipoma. To our knowledge, this case is the first example of a suspected well-differentiated liposarcoma that was actually a pancreatic lipoma. We also highlight the radiological features distinguishing a pancreatic lipoma from a pancreatic liposarcoma and briefly review the literature. CONCLUSION Pancreatic lipomas show no obvious gender bias and most commonly occur in the head of the pancreas, of which the maximum diameters are often less than 5 cm, and small, asymptomatic non-compressed lipomas require follow-up only. Surgical excision should be considered when the tumor has compressed important tissues or is difficult to distinguish from a liposarcoma, the choice of surgery depends on the intraoperative presentation.

Although anonymizing Peer-to-Peer (P2P) networks often means extra cost in terms of transfer efficiency, many systems try to mask the identities of their users for privacy consideration. By comparison and analysis of existing approaches, we investigate the properties of unstructured P2P anonymity, and summarize current attack models on these designs. Most of these approaches are path-based, which require peers to pre-construct anonymous paths before transmission, thus suffering significant overhead and poor reliability. We also discuss the open problems in this field and propose several future research directions.

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