Symmetric Public-Key Encryption

Public-key encryption would seem to be inherently asymmetric. in that only messages sent to a user can be encrypted using his public key. We demonstrate that the use of interactive protocols for sending encrypted messages enables a symmetric use of public keys; we give cryptographic protocols for the following tasks: 1. Probabilistic encryption, using the same public key, both of messages that are sent to a particular user as well as of messages that the user sends to others, without compromising the key. We propose a public-key cryptosystem based on these protocols which has only one key, owned by a cryptographic server. 2. Authentication both of the sender and of the receiver of a probabilistically encrypted message. 3. Probabilistic encryption which is provably secure against both chosen-message and chosen-ciphertext attack

Enhancing Cryptographic Security by Partial Key Management

Cryptographic security can degrade over time due to attackers using more powerful hardware or more sophisticated software. To maintain security, cryptographic machinery is replaced or strengthened as and when weaknesses are found. However, updating certain cryptographic components is infeasible or expensive, resulting in updates that either don’t occur or are delayed. This disclosure describes techniques to enhance cryptographic security by updating portions of a cryptographic system when updating cryptographic parameters is only partially possible. Authenticating data (auth-data) sent by the un-updateable component during normal operation is used to deliver new and upgraded security parameters to secure communication. Security degradation resulting from the inability to effect an end-to-end update is limited to the immediate vicinity of the un-updateable component. The described techniques can be used to improve security of Internet-of-Things (IoT) device communication

Distributed Algorithms in Synchronous Broadcasting Networks

In this paper we consider a synchronous broadcasting network, a distributed computation model which represents communication networks that are used extensively in practice. This is the first work we know of that deals with this model in a theoretical context. The problem we consider is a basic problem of information sharing, the computation of the multiple identification function. That is, given a network of p processors, each of which contains an n-bit string of information, the question is how every processor can compute the subset of processors which have the same information as itself. The problem was suggested by Yao in his classical paper in communication complexity [17], as a generalization of the two-processor case studied in that paper. The immediate algorithm which solves this problem takes O(np) time (time = communication time in bits, which is our complexity measure). We present the following algorithms: - a. An algorithm which takes advantage of properties of strings, uses a very simple scheduling policy, and does not use arithmetic operations. (In fact, the processor can be a Turing machine). 'the algorithm's complexity is O(nlog2p+p). - b. An algorithm which uses a simulation of sorting networks by the distributed system. If t(p) is the depth of the sorting network of p processors, then our algorithm takes O( n t(p) + p) time. Using recent results on sorting networks we get an O(nlogp+p) (impractical) algorithm. The algorithm also uses addition and subtraction operations. -c. By letting the processor use modular arithmetic operations as well, we can use Yao's probabilistic version, modify our algorithms and get probabilistic algorithms (with small error) where logn replaces n in the complexity expressions. To prove lower bounds for the problem we use Yao's result to get an fl(n) bound, and we also show an fl(p) bound. We suggest open problems concerning new techniques for proving lower bounds in the presence of broadcasting, as well as other problems about efficient use of the model and comparisons between different models of distributed computation

Penetrating Spinal Cord Injury

Penetrating spinal cord injury (SCI) is a relatively rare entity affecting mainly young males and military personnel worldwide. These injuries are the source of permanent disabilities to the affected patient and family and have substantial social and economic concerns. This chapter is an overview of the common penetrating spinal cord injuries, their incidence worldwide, causes, primary evaluation, and treatment including medical treatment and late definitive surgical treatment. It also describes common complications and strategies preventing secondary and collateral damage and disability

Burn-Resistant, Strong Metal-Matrix Composites

Ceramic particulate fillers increase the specific strengths and burn resistances of metals: This is the conclusion drawn by researchers at Johnson Space Center's White Sands Test Facility. The researchers had theorized that the inclusion of ceramic particles in metal tools and other metal objects used in oxygen-rich atmospheres (e.g., in hyperbaric chambers and spacecraft) could reduce the risk of fire and the consequent injury or death of personnel. In such atmospheres, metal objects act as ignition sources, creating fire hazards. However, not all metals are equally hazardous: some are more burn-resistant than others are. It was the researchers purpose to identify a burn-resistant, high-specific-strength ceramic-particle/metal-matrix composite that could be used in oxygen-rich atmospheres. The researchers studied several metals. Nickel and cobalt alloys exhibit high burn resistances and are dense. The researchers next turned to ceramics, which they knew do not act as ignition sources. Unlike metals, ceramics are naturally burn-resistant. Unfortunately, they also exhibit low fracture toughnesses

Distributed Algorithms in Synchronous Broadcasting Networks

In this paper we consider a synchronous broadcasting network, a distributed computation model which represents communication networks that are used extensively in practice. This is the first work we know of that deals with this model in a theoretical context. The problem we consider is a basic problem of information sharing, the computation of the multiple identification function. That is, given a network of p processors, each of which contains an n-bit string of information, the question is how every processor can compute the subset of processors which have the same information as itself. The problem was suggested by Yao in his classical paper in communication complexity [17], as a generalization of the two-processor case studied in that paper. The immediate algorithm which solves this problem takes O(np) time (time = communication time in bits, which is our complexity measure). We present the following algorithms: - a. An algorithm which takes advantage of properties of strings, uses a very simple scheduling policy, and does not use arithmetic operations. (In fact, the processor can be a Turing machine). 'the algorithm's complexity is O(nlog2p+p). - b. An algorithm which uses a simulation of sorting networks by the distributed system. If t(p) is the depth of the sorting network of p processors, then our algorithm takes O( n t(p) + p) time. Using recent results on sorting networks we get an O(nlogp+p) (impractical) algorithm. The algorithm also uses addition and subtraction operations. -c. By letting the processor use modular arithmetic operations as well, we can use Yao's probabilistic version, modify our algorithms and get probabilistic algorithms (with small error) where logn replaces n in the complexity expressions. To prove lower bounds for the problem we use Yao's result to get an fl(n) bound, and we also show an fl(p) bound. We suggest open problems concerning new techniques for proving lower bounds in the presence of broadcasting, as well as other problems about efficient use of the model and comparisons between different models of distributed computation

A pitfall in the interpretation of plain abdnominal radiographs in neonatal intestinal perforation: a case report

<p>Abstract</p> <p>Introduction</p> <p>The recognition of neonatal intestinal perforation relies on identification of free gas in the peritoneum on plain abdominal radiographs and the associated clinical signs. The neonatal bowel takes several hours to fill with gas, potentially obscuring one of the radiological signs of bowel perforation in the neonate.</p> <p>Case presentation</p> <p>We describe the case of a male, Caucasian neonate, born prematurely at 35⁺²weeks of gestation, who was suspected before birth to be at risk of intestinal perforation, based on antenatal ultrasound signs of bowel obstruction. However, the diagnosis of intestinal perforation after birth was initially delayed because the first abdominal radiograph, requested by the neonatal team, was taken too early in the clinical progression of the neonate's condition. As a consequence, this delayed referral to the paediatric surgical team and definitive management.</p> <p>Conclusion</p> <p>This case illustrates how consideration of the timing of abdominal radiographs in suspected intestinal perforation in the neonate may avoid misinterpretation of radiographic signs, thereby avoiding delays in referral and treatment in the crucial first few hours of life.</p