hw6 - 1 single crash fault reliable channels under an...

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CSE4/586 (Spring 2009): Homework 6 Due by Apr 23 Thursday, in class. 1. (40 points) Consider the “synchronous agreement with crash faults” program we studied in Section 12.6. Modify this algorithm to design an early-stopping version of the algorithm that terminates within f 0 + 1 rounds, where f 0 , the actual number of crash faults, is less than f . Prove (argue for) the correctness of your algorithm. (Hint: Processes can track the other processes that failed, which is detectable by identi- fying the processes from which no message was received.) 2. (30 points) Prove or disprove whether the leader election problem (where all the nodes select the node with the highest id in the system as the leader) is solvable deterministically under
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Unformatted text preview: 1. single crash fault, reliable channels, under an asynchronous system model, 2. single crash fault, reliable channels, under synchronous system model, and 3. single crash fault, and undetectable message loss, under the synchronous model (Hint: Consider a reduction from the leader election problem to the consensus problem.) 3. (30 points) Consider a network of three processes labeled, Alice, Bob, and Eve. Eve is a Byzantine node unbeknownst to the other processes. 1. In the absence of authenticated signatures, construct a scenario where Eve can leave Alice perplexed about which process is Byzantine. 2. In the presence of authenticated signatures show how the above scenario is resolved. 1...
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