Prasant Gopal

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In the <i>unconditionally reliable message transmission</i> (URMT) problem, two non-faulty players, the <i>sender</i> <b>S</b> and the <i>receiver</i> <b>R</b> are part of a synchronous network modeled as a directed graph. <b>S</b> has a message that he wishes to send to <b>R</b>; the challenge is to design a protocol such that after exchanging messages as(More)
Pease et al. introduced the problem of Byzantine Generals (BGP) to study the effects of Byzantine faults in distributed protocols for reliable broadcast. It is well known that BGP among n players tolerating up to t faults is (efficiently) possible if and only if n > 3t. To overcome this severe limitation, Pease et al. introduced a variant of BGP,(More)
Three decades ago, Pease et al. introduced the problem of Byzantine Agreement [PSL80] where nodes need to maintain a consistent view of the world in spite of the challenge posed by Byzantine faults. Subsequently, it is well known that Byzantine agreement over a completely connected synchronous graph of n nodes tolerating up to t faults is (efficiently)(More)
We consider the problem of probabilistic reliable communication (PRC) over directed networks: Over a synchronous directed network <i>N</i>} = (<i>P</i>,<i>E</i>) where <i>P</i> is the set of vertices and <i>E</i> denotes the set of arcs/edges in the network, the sender <b>S</b> &#8712; <i>P</i> wishes to send a message <i>m</i> to the receiver <b>R</b>(More)
Kshitij Rescue Team participated in RoboCup Rescue competition for the first time in 2005 at Osaka, Japan and obtained the 3rd position. In this paper, we briefly discuss the high level strategies used by our team in the major aspects of rescue like fire extinguishing, civilian rescue, blockade removal and exploration. Some of our approaches are scalable(More)
The problem of Authenticated Byzantine Generals (ABG) aims to simulate a virtual reliable broadcast channel from the General to all the players via a protocol over a real (point-to-point) network in the presence of faults. We propose a new model to study the self-composition of ABG protocols. The central dogma of our approach can be phrased as follows:(More)
An ID-based cryptographic scheme enables the user to public keys without exchanging public key certificates. In these schemes, users can generate their public and private keys using their identity. The positive application of bilinear pairings over elliptic curves makes the system easy and efficient in providing security. In this paper, we propose an(More)
Consider a player who diligently executes (only) the delegated protocol but the adversary steals some private information from him. Should such a player be considered faulty? In a stand alone execution model, the answer can be either yes or no depending on the context/settings. However, with respect to composition of protocols, we show that the answer has(More)
Global consistency or Byzantine Agreement (BA) and reliable point-to-point communication are two of the most important and well-studied problems in distributed computing. Informally, BA is about maintaining a consistent view of the world among all the non-faulty players in the presence of faults. In a synchronous network over <i>n</i> nodes of which up to(More)
We consider the problem of probabilistic reliable communication (PRC) over synchronous networks modeled as directed graphs in the presence of a Byzantine adversary when players’ knowledge of the network topology is not complete. We show that possibility of PRC is extremely sensitive to the changes in players’ knowledge of the topology. This is in complete(More)