Mrs XYZ, a 30-year-old woman, came with complaints of three and half months of amenorrhea. She was G2P1L1 with a previous LSCS done for cephalo pelvic disproportion (CPD). She had presented with symptoms of fatigue, malaise, weakness, and anemia and was referred to a hematologist in 1985. Her hemoglobin was 8 g %, Hematocrit 25 %, total count 75,000, Lymphoblast 88 %, and Platelet 1.6 lacs. Her...

In this thesis, we design randomized algorithms for classical problems in faulttolerant distributed computing in the full-information model. The full-information model is a strong adversarial model which imposes no restrictions on the computational power of the faulty players nor on the information available to them. Namely, the faulty players are infinitely powerful and are privy to all the co...

We introduce a new coordination problem in distributed computing that we call the population stability problem. A system of agents each with limited memory and communication, as well as the ability to replicate and self-destruct, is subjected to attacks by a worst-case adversary that can at a bounded rate (1) delete agents chosen arbitrarily and (2) insert additional agents with arbitrary initi...

Secure multi-party computation (MPC) has been thoroughly studied over the past decades. The vast majority of works assume a full communication pattern: every party exchanges messages with all the network participants over a complete network of point-to-point channels. This can be problematic in modern large scale networks, where the number of parties can be of the order of millions, as for exam...

Background: The association between conduction disturbances and atherosclerotic coronary artery disease has been investigated in a few small studies in the early 1970s and the study result was inconclusive. Thereafter some investigators found in their separate study that a group of patients with conduction disturbances that required permanent pacemaker who had coronary atherosclerotic disease t...

A threshold signature or decryption scheme is a distributed implementation of a cryptosystem, in which the secret key is secret-shared among a group of servers. These servers can then sign or decrypt messages by following a distributed protocol. The goal of a threshold scheme is to protect the secret key in a highly fault-tolerant way. Namely, the key remains secret, and correct signatures or d...

This paper considers two questions in cryptography. 1. Simultaneous Hardcore Bits. Let f be a one-way function. We say that a block of bits of x are simultaneously hard-core for f(x) if given f(x), they cannot be distinguished from a random string of the same length. Although there are many examples of (candidate) one-way functions with one hardcore bit (or even O(log n) simultaneously hardcore...

In this thesis we introduce and solve three privacy problems in Secure Database Access protocols: Database Privacy, the Data Replication Problem, and the Secure user Identity problem. Database Privacy is concerned with keeping the databases information secure from the user. The Data Replication problem (DRP) deals with a new security concern for databases that emanates from the need to replicat...

Acknowledgments This thesis is based on joint work with Professor Mihir Bellare and David Cash. I'd like to express gratitude for the time that we explored ideas together; you were wonderful to work with! A very special thank you to my Advisor, Professor Shafi Goldwasser, for such caring mentorship – it has been such a pleasure to work and to learn under you for my time at MIT. Finally, I'd lik...

The main results of this work are new public-key encryption schemes that, under the quadratic residuosity (QR) assumption (or Paillier’s decisional composite residuosity (DCR) assumption), achieve key-dependent message security as well as high resilience to secret key leakage and high resilience to the presence of auxiliary input information. In particular, under what we call the subgroup indis...