Multilevel Threshold Secret and Function Sharing based on the Chinese Remainder Theorem

A recent work of Harn and Fuyou presents the first multilevel (disjunctive) threshold secret sharing scheme based on the Chinese Remainder Theorem. In this work, we first show that the proposed method is not secure and also fails to work with a certain natural setting of the threshold values on compartments. We then propose a secure scheme that works for all threshold settings. In this scheme, we employ a refined version of Asmuth-Bloom secret sharing with a special and generic Asmuth-Bloom sequence called the {\it anchor sequence}. Based on this idea, we also propose the first multilevel conjunctive threshold secret sharing scheme based on the Chinese Remainder Theorem. Lastly, we discuss how the proposed schemes can be used for multilevel threshold function sharing by employing it in a threshold RSA cryptosystem as an example

Transaction Propagation on Permissionless Blockchains: Incentive and Routing Mechanisms

Existing permissionless blockchain solutions rely on peer-to-peer propagation mechanisms, where nodes in a network transfer transaction they received to their neighbors. Unfortunately, there is no explicit incentive for such transaction propagation. Therefore, existing propagation mechanisms will not be sustainable in a fully decentralized blockchain with rational nodes. In this work, we formally define the problem of incentivizing nodes for transaction propagation. We propose an incentive mechanism where each node involved in the propagation of a transaction receives a share of the transaction fee. We also show that our proposal is Sybil-proof. Furthermore, we combine the incentive mechanism with smart routing to reduce the communication and storage costs at the same time. The proposed routing mechanism reduces the redundant transaction propagation from the size of the network to a factor of average shortest path length. The routing mechanism is built upon a specific type of consensus protocol where the round leader who creates the transaction block is known in advance. Note that our routing mechanism is a generic one and can be adopted independently from the incentive mechanism.Comment: 2018 Crypto Valley Conference on Blockchain Technolog

Universal Soldier: Using Universal Adversarial Perturbations for Detecting Backdoor Attacks

Deep learning models achieve excellent performance in numerous machine learning tasks. Yet, they suffer from security-related issues such as adversarial examples and poisoning (backdoor) attacks. A deep learning model may be poisoned by training with backdoored data or by modifying inner network parameters. Then, a backdoored model performs as expected when receiving a clean input, but it misclassifies when receiving a backdoored input stamped with a pre-designed pattern called "trigger". Unfortunately, it is difficult to distinguish between clean and backdoored models without prior knowledge of the trigger. This paper proposes a backdoor detection method by utilizing a special type of adversarial attack, universal adversarial perturbation (UAP), and its similarities with a backdoor trigger. We observe an intuitive phenomenon: UAPs generated from backdoored models need fewer perturbations to mislead the model than UAPs from clean models. UAPs of backdoored models tend to exploit the shortcut from all classes to the target class, built by the backdoor trigger. We propose a novel method called Universal Soldier for Backdoor detection (USB) and reverse engineering potential backdoor triggers via UAPs. Experiments on 345 models trained on several datasets show that USB effectively detects the injected backdoor and provides comparable or better results than state-of-the-art methods

Get Me out of This Payment! Bailout: An HTLC Re-routing Protocol

The Lightning Network provides almost-instant payments to its parties. In addition to direct payments requiring a shared payment channel, parties can pay each other in the form of multi-hop payments via existing channels. Such multi-hop payments rely on a 2-phase commit protocol to achieve balance security; that is, no honest intermediary party loses her coins. Unfortunately, failures or attacks in this 2-phase commit protocol can lead to coins being committed (locked) in a payment for extended periods of time (in the order of days in the worst case). During these periods, parties cannot go offline without losing funds due to their existing commitments, even if they use watchtowers. Furthermore, they cannot use the locked funds for initiating or forwarding new payments, reducing their opportunities to use their coins and earn fees. We introduce Bailout, the first protocol that allows intermediary parties in a multi-hop payment to unlock their coins before the payment completes by re-routing the payment over an alternative path. We achieve this by creating a circular payment route starting from the intermediary party in the opposite direction of the original payment. Once the circular payment is locked, both payments are canceled for the intermediary party, which frees the coins of the corresponding channels. This way, we create an alternative route for the ongoing multi-hop payment without involving the sender or receiver. The parties on the alternative path are incentivized to participate through fees. We evaluate the utility of our protocol using a real-world Lightning Network snapshot. Bailouts may fail due to insufficient balance in alternative paths used for re-routing. We find that attempts of a node to bailout typically succeed with a probability of more than 94% if at least one alternative path exists

Jejunogastric Intussusception: A Rare Complication of Gastric Surgery

Jejunogastric intussusception is a rare complication of gastric surgery. It usually presents with severe epigastric pain, vomiting, and hematemesis. A history of gastric surgery can help in making an accurate and early diagnosis which calls forth an urgent surgical intervention. Only reduction or resection with revision of the previously performed anastomosis is the choice which is decided according to the operative findings. We present a case of JGI in a patient with a history of Billroth II operation diagnosed by computed tomography. At emergent laparotomy, an efferent loop type JGI was found. Due to necrosis, resection of the intussuscepted bowel with Roux-en-Y anastomosis was performed. Postoperative recovery was uneventful

Relation of leptin, adiponectin and insulin resistance to bone mineral density in type 2 diabetic postmenopausal women

Wstęp: Celem badania było porównanie zależności między stężeniami leptyny i adiponektyny oraz insulinoopornością a gęstością mineralną kości (BMD) u kobiet po menopauzie chorujących na cukrzycę typu 2 i u osób z niechorującej na cukrzycę grupy kontrolnej. Materiał i metody: Do badania zrekrutowano łącznie 76 kobiet po menopauzie, które podzielono na grupy obejmujące kobiety chorujące na cukrzycę typu 2 (n = 19) i bez cukrzycy (n = 19), u których wartość T score dla BMD kręgosłupa i/lub bliższego odcinka kości udowej wynosiło mniej niż -2 oraz chore na cukrzycę typu 2 (n = 20) i niechorujące na cukrzycę (n = 18) z prawidłowymi wartościami BMD (T score > -1). Kryteria wykluczenia obejmowały stosowanie leków przeciwosteoporotycznych, wiek ponad 65 lat, choroby lub terapie mogące wpływać na metabolizm kostny. U uczestniczek badania wykonano badania biochemiczne, oznaczono stężenia leptyny, adiponektyny i insuliny oraz oszacowano stopień insulinooporności HOMA. Wyniki: Nie zaobserwowano korelacji między niskimi wartościami BMD a stężeniami leptyny i adiponektyny oraz insulinoopornością. Stwierdzono jedynie odwrotną zależność między stężeniem leptyny a BMD kości udowej w obrębie trójkąta Warda. Wnioski: Konieczne są dalsze badania obejmujące dużą grupę chorych, aby ustalić wpływ stężeń leptyny i adiponektyny oraz insulinooporności na metabolizm kostny u chorych na cukrzycę typu 2. (Endokrynol Pol 2011; 62 (5): 429–435)Background: Our aim is to identify the relation of leptin, adiponectin and insulin resistance to bone mineral density (BMD) in type 2 diabetic postmenopausal women and compare it with that experienced by nondiabetics. Material and methods: Seventy six postmenopausal female patients were included in the study. Postmenopausal type 2 diabetic (n = 19) and nondiabetic patients (n = 19) with spine and/or hip BMD T score lower than -2 were included in the study, and postmenopausal type 2 diabetic (n = 20) and nondiabetic women (n = 18) with normal BMD (T score > –1) were selected as control groups. Those receiving therapy for osteoporosis, over the age of 65, those who had a disease and were taking a medication that could affect bone metabolism were excluded. Biochemical tests, as well as leptin, adiponectin and insulin levels, were measured and insulin resistance was calculated using the HOMA test. Results: There was no correlation between low BMD and leptin, adiponectin and insulin resistance. There was only a negative correlation between leptin and femur Ward’s triangle BMD. Conclusion: Further large-scale studies must to be performed in order to analyse the effects of leptin, adiponectin and insulin resistance on bone metabolism in type 2 diabetic patients. (Pol J Endocrinol 2011; 62 (5): 429–435

Case Report Lingual Thyroid Excision with Transoral Robotic Surgery

Ectopic thyroid gland may be detected at any place between foramen caecaum and normal thyroid localization due to inadequacy of the embryological migration of the thyroid gland. It has a prevalence varying between 1/10.000 and 1/100000 in the community. Usually follow-up without treatment is preferred except for obstructive symptoms, bleeding, and suspicion of malignity. Main symptoms are dysphagia, dysphonia, bleeding, dyspnea, and obstructive sleep apnea. In symptomatic cases, the first described method in surgical treatment is open approach since it is a region difficult to have access to. However, this approach has an increased risk of morbidity and postoperative complications. Transoral robotic surgery, which is a minimally invasive surgical procedure, has advantages such as larger three-dimensional point of view and ease of manipulation due to robotic instruments. In this report, a case at the age of 49 who presented to our clinic with obstructive symptoms increasing within the last year and was found to have lingual thyroid and underwent excision of ectopic thyroid tissue by da Vinci surgical system is presented

Case Report Jejunogastric Intussusception: A Rare Complication of Gastric Surgery

Jejunogastric intussusception is a rare complication of gastric surgery. It usually presents with severe epigastric pain, vomiting, and hematemesis. A history of gastric surgery can help in making an accurate and early diagnosis which calls forth an urgent surgical intervention. Only reduction or resection with revision of the previously performed anastomosis is the choice which is decided according to the operative findings. We present a case of JGI in a patient with a history of Billroth II operation diagnosed by computed tomography. At emergent laparotomy, an efferent loop type JGI was found. Due to necrosis, resection of the intussuscepted bowel with Roux-en-Y anastomosis was performed. Postoperative recovery was uneventful

A New Look at Blockchain Leader Election: Simple, Efficient, Sustainable and Post-Quantum

In this work, we study the blockchain leader election problem. The purpose of such protocols is to elect a leader who decides on the next block to be appended to the blockchain, for each block proposal round. Solutions to this problem are vital for the security of blockchain systems. We introduce an efficient blockchain leader election method with security based solely on standard assumptions for cryptographic hash functions (rather than public-key cryptographic assumptions) and that does not involve a racing condition as in Proof-of-Work based approaches. Thanks to the former feature, our solution provides the highest confidence in security, even in the post-quantum era. A particularly scalable application of our solution is in the Proof-of-Stake setting, and we investigate our solution in the Algorand blockchain system. We believe our leader election approach can be easily adapted to a range of other blockchain settings. At the core of Algorand\u27s leader election is a verifiable random function (VRF). Our approach is based on introducing a simpler primitive which still suffices for the blockchain leader election problem. In particular, we analyze the concrete requirements in an Algorand-like blockchain setting to accomplish leader election, which leads to the introduction of indexed VRF (iVRF). An iVRF satisfies modified uniqueness and pseudorandomness properties (versus a full-fledged VRF) that enable an efficient instantiation based on a hash function without requiring any complicated zero-knowledge proofs of correct PRF evaluation. We further extend iVRF to an authenticated iVRF with forward-security, which meets all the requirements to establish an Algorand-like consensus. Our solution is simple, flexible and incurs only a 32-byte additional overhead when combined with the current best solution to constructing a forward-secure signature (in the post-quantum setting). We implemented our (authenticated) iVRF proposal in C language on a standard computer and show that it significantly outperforms other quantum-safe VRF proposals in almost all metrics. Particularly, iVRF evaluation and verification can be executed in 0.02 ms, which is even faster than ECVRF used in Algorand