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Oneway Functions Debdeep Mukhopadhyay IIT Kharagpur Strong Oneway  Informally  easy to Oneway Functions Debdeep Mukhopadhyay IIT Kharagpur Strong Oneway  Informally  easy to

Oneway Functions Debdeep Mukhopadhyay IIT Kharagpur Strong Oneway Informally easy to - PDF document

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Oneway Functions Debdeep Mukhopadhyay IIT Kharagpur Strong Oneway Informally easy to - PPT Presentation

The problem is easy when one of the inputs is even probability of the event34 and is hence non negligible thus there is a nonnegligible fraction of the inputs for which fx is easy to invert these functions are not captured by our rather restrict ID: 12108

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1 One-way FunctionsDebdeep MukhopadhyayIIT Kharagpur •Informally, –easy to compute–f can be inverted only with a negligible 2 Strong One-way {0,1}A function f:{0,1}{0,1} is (t,)-one way if f is computable in poly(n) time and for all adversaries A running in time bounded by t(n):Pr[(())(())]()Afxffxn •Consider the problem of finding non-trivial factors.•The problem is easy when one of the –probability of the event=3/4 and is hence non-negligible.–thus there is a non-negligible fraction of the –these functions are not captured by our rather 5 The first step x{0,1}Suppose there is a PPT algorithm A:Pr[(())(())]'(),Pr[{0,1};((...))((...))]Thus A takes ... as input and outputs ..., such that () for aimmAgxggxpmnorxAgxxggxxyyzzfzy←∈> ll with probability� : To construct A' that uses A to invert with probability 1- (that is violate the weakone-wayness of )Goalf Adversary A’ A' repeats the following procedure 2() times:Procedure IFor i=1 to m let y for all ji, pick x{0,1} and let y() let z...(...) if f(z), output z elsnmpn f zAyy≠==e output fail