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69 lines
2.5 KiB
69 lines
2.5 KiB
dtmc
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// probability of forwarding
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const double PF = 0.8;
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const double notPF = .2; // must be 1-PF
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// probability that a crowd member is bad
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const double badC = .167;
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// probability that a crowd member is good
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const double goodC = 0.833;
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// Total number of protocol runs to analyze
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const int TotalRuns = 5;
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// size of the crowd
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const int CrowdSize = 5;
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module crowds
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// protocol phase
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phase: [0..4] init 0;
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// crowd member good (or bad)
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good: bool init false;
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// number of protocol runs
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runCount: [0..TotalRuns] init 0;
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// observe_i is the number of times the attacker observed crowd member i
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observe0: [0..TotalRuns] init 0;
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observe1: [0..TotalRuns] init 0;
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observe2: [0..TotalRuns] init 0;
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observe3: [0..TotalRuns] init 0;
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observe4: [0..TotalRuns] init 0;
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// the last seen crowd member
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lastSeen: [0..CrowdSize - 1] init 0;
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// get the protocol started
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[] phase=0 & runCount<TotalRuns -> 1: (phase'=1) & (runCount'=runCount+1) & (lastSeen'=0);
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// decide whether crowd member is good or bad according to given probabilities
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[] phase=1 -> goodC : (phase'=2) & (good'=true) + badC : (phase'=2) & (good'=false);
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// if the current member is a good member, update the last seen index (chosen uniformly)
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[] phase=2 & good -> 1/5 : (lastSeen'=0) & (phase'=3) + 1/5 : (lastSeen'=1) & (phase'=3) + 1/5 : (lastSeen'=2) & (phase'=3) + 1/5 : (lastSeen'=3) & (phase'=3) + 1/5 : (lastSeen'=4) & (phase'=3);
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// if the current member is a bad member, record the most recently seen index
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[] phase=2 & !good & lastSeen=0 & observe0 < TotalRuns -> 1: (observe0'=observe0+1) & (phase'=4);
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[] phase=2 & !good & lastSeen=1 & observe1 < TotalRuns -> 1: (observe1'=observe1+1) & (phase'=4);
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[] phase=2 & !good & lastSeen=2 & observe2 < TotalRuns -> 1: (observe2'=observe2+1) & (phase'=4);
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[] phase=2 & !good & lastSeen=3 & observe3 < TotalRuns -> 1: (observe3'=observe3+1) & (phase'=4);
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[] phase=2 & !good & lastSeen=4 & observe4 < TotalRuns -> 1: (observe4'=observe4+1) & (phase'=4);
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// good crowd members forward with probability PF and deliver otherwise
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[] phase=3 -> PF : (phase'=1) + notPF : (phase'=4);
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// deliver the message and start over
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[] phase=4 -> 1: (phase'=0);
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endmodule
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label "observe0Greater1" = observe0>1;
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label "observe1Greater1" = observe1>1;
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label "observe2Greater1" = observe2>1;
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label "observe3Greater1" = observe3>1;
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label "observe4Greater1" = observe4>1;
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label "observeIGreater1" = observe1>1|observe2>1|observe3>1|observe4>1;
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label "observeOnlyTrueSender" = observe0>1&observe1<=1 & observe2<=1 & observe3<=1 & observe4<=1;
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