An analysis of acceptance policies for blockchain transactions

The standard acceptance policy for a cryptocurrency transaction at most exchanges is to wait until the transaction is placed in the blockchain and followed by a certain number of blocks. However, as noted by Sompolinsky and Zohar [16], the amount of time for blocks to arrive should also be taken into account as it affects the probability of double spending. Specifically, they propose a dynamic policy for transaction acceptance that depends on both the number of confirmations and the amount of time since transaction broadcast. In this work we study the implications of using such a policy compared with the standard option that ignores block timing information. Using an exact expression for the probability of double spend, via numerical results, we analyze time to transaction acceptance (performance) as well as the time and cost to perform a double spend attack (security). We show that while expected time required for transaction acceptance is improved using a dynamic policy, the time and cost to perform a double spend attack for a particular transaction is reduced.First author draf

Revealing the unseen: how to expose cloud usage while protecting user privacy

Cloud users have little visibility into the performance characteristics and utilization of the physical machines underpinning the virtualized cloud resources they use. This uncertainty forces users and researchers to reverse engineer the inner workings of cloud systems in order to understand and optimize the conditions their applications operate. At Massachusetts Open Cloud (MOC), as a public cloud operator, we'd like to expose the utilization of our physical infrastructure to stop this wasteful effort. Mindful that such exposure can be used maliciously for gaining insight into other user's workloads, in this position paper we argue for the need for an approach that balances openness of the cloud overall with privacy for each tenant inside of it. We believe that this approach can be instantiated via a novel combination of several security and privacy technologies. We discuss the potential benefits, implications of transparency for cloud systems and users, and technical challenges/possibilities.Accepted manuscrip

EasyUC: using EasyCrypt to mechanize proofs of universally composable security

We present a methodology for using the EasyCrypt proof assistant (originally designed for mechanizing the generation of proofs of game-based security of cryptographic schemes and protocols) to mechanize proofs of security of cryptographic protocols within the universally composable (UC) security framework. This allows, for the first time, the mechanization and formal verification of the entire sequence of steps needed for proving simulation-based security in a modular way: Specifying a protocol and the desired ideal functionality; Constructing a simulator and demonstrating its validity, via reduction to hard computational problems; Invoking the universal composition operation and demonstrating that it indeed preserves security. We demonstrate our methodology on a simple example: stating and proving the security of secure message communication via a one-time pad, where the key comes from a Diffie-Hellman key-exchange, assuming ideally authenticated communication. We first put together EasyCrypt-verified proofs that: (a) the Diffie-Hellman protocol UC-realizes an ideal key-exchange functionality, assuming hardness of the Decisional Diffie-Hellman problem, and (b) one-time-pad encryption, with a key obtained using ideal key-exchange, UC-realizes an ideal secure-communication functionality. We then mechanically combine the two proofs into an EasyCrypt-verified proof that the composed protocol realizes the same ideal secure-communication functionality. Although formulating a methodology that is both sound and workable has proven to be a complex task, we are hopeful that it will prove to be the basis for mechanized UC security analyses for significantly more complex protocols and tasks.Accepted manuscrip

An Exploration of the Role of Principal Inertia Components in Information Theory

The principal inertia components of the joint distribution of two random variables $X$ and $Y$ are inherently connected to how an observation of $Y$ is statistically related to a hidden variable $X$. In this paper, we explore this connection within an information theoretic framework. We show that, under certain symmetry conditions, the principal inertia components play an important role in estimating one-bit functions of $X$, namely $f(X)$, given an observation of $Y$. In particular, the principal inertia components bear an interpretation as filter coefficients in the linear transformation of $p_{f(X)|X}$ into $p_{f(X)|Y}$. This interpretation naturally leads to the conjecture that the mutual information between $f(X)$ and $Y$ is maximized when all the principal inertia components have equal value. We also study the role of the principal inertia components in the Markov chain $B\rightarrow X\rightarrow Y\rightarrow \widehat{B}$, where $B$ and $\widehat{B}$ are binary random variables. We illustrate our results for the setting where $X$ and $Y$ are binary strings and $Y$ is the result of sending $X$ through an additive noise binary channel.Comment: Submitted to the 2014 IEEE Information Theory Workshop (ITW

Guidelines for parents on homeschooling deaf children

Many families have turned their family room into classrooms. In 1993, homeschooling became legal in all 50 states, when the number of students staying at home for schooling tripled. This trend continues today because parents want to retain control over the education and socialization of their children. Homeschooling refers to education of school-age children with their parents\u27 guiding, directing, and monitoring them. It replaces full-time attendance at a traditional school. Parents express various reasons for educating their children at home; individualization, family time, strong academic, moral, and religious foundations. The problem with homeschooling, for parents of deaf children, is the lack of informational pamphlets to provide information and guide parents to educate their deaf children successfully. How can parents learn to guide their deaf children in their home without instructions on homeschooling? Where they find resources or materials they can use in homeschooling? Parents might have interrogations on homeschooling. Creating a pamphlet with guidelines for parents homeschooling their deaf children is suggested as a possible solution. These will help prepare parents in educating their deaf children in their home. Parents need to be aware of all aspects of children\u27s life illustrating social, academics, and other issues

Bio-electrochemical systems for the remediation of metal-ion effluents

PhD ThesisThe roots of this study stem from the applied sciences of microbiology and electrochemistry to form the exciting new field of bio-electrochemistry. Our aim here being the application of bioelectrochemical processes for social and environmental value in toxic metal ion remediation and recovery from the discharge of aqueous mine and industrial effluents. This within a broader vision of reducing the present burden caused by industrial and mining anthropogenic activity on the planet we inhabit. These processes we have explored within a green chemistry philosophy with the application of chemical engineering principles. Our aims being (i) to further the scientific state of art and (ii) conceptualize the feasible engineering of novel metal remediation strategies, with the lucrative application of bacterial cells as green “nanofactories” and recovery of metallic biogenic nanoparticles with application in the ever growing field of nanotechnology. The proof of principle has been evaluated with a systematic study of Au3+, Co2+ and Fe3+ metallic cationic species (Co < 500 ppm) dissolved in acidic (pH < 3) aqueous electrolytes and their removal by microbiological (chapter 3) and bioelectrochemical (chapter 4) processes. Electrochemical remediation as described by electronation charge transfer at an electrified interface for various potentials causes the electrodeposition of metal ions upon electrode surfaces and hence separation by phase transformation. Of note, base cations such Co2+ and Fe3+ co-deposited with the evolution of hydrogen gas could be applied as electron donors for chemolithotrophic bacteria as part of dissimilatory respiration. Microbial biosorption of metal ions by means of ionized groups located on the outer membrane of the outer lipopolysaccharide leaf of gram negative bacteria, with some evidence of bio-reduction via dissimilatory and redox resistance mechanisms, with biogenic nanoparticles produced as a consequence. Bio-electrochemistry formed by the collaboration of these two processes where electroactive bacteria such as that of the Shewanella genus are known to respire by the application of cathodic currents directly via bio-nanowires or indirectly using in-situ electron mediators or in-situ hydrogen production. The effects of bacteria on electronation thermodynamics were investigated in chapter 4 with observed positive shifts in reversible potentials (Er) for AuCl3- electrodeposition