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P robabilistically C heckable P roofs. Guy Kindler The Hebrew University. Proofs – why?. Proofs problems all around… Math : Homework Identity: passwords suck Credit cards: chip (zero knowledge) Smartness!! Cloud computation Sensitive computation (fission decay) Etc…. What is a proof.
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ProbabilisticallyCheckableProofs Guy Kindler The Hebrew University
Proofs – why? Proofs problems all around… • Math : Homework • Identity: passwords suck • Credit cards: chip (zero knowledge) • Smartness!! • Cloud computation • Sensitive computation (fission decay) • Etc…
What is a proof • Euclid: argument based on axioms • Acommittee decides (Fourier 1825) • Frege System (1880) • Some paradoxes • Hilbert’s program (1900) • Godel: completeness, incompleteness (1930) • Turing: machine verifiable(1936) • Machine-generate (1976)
Turing Machine • Theoretical computer (1936) • Has inputs and outputs TM Input Output
Example: Traveling Salesman • All cities traversable, length < X • US: 13509 cities • Given proof: easy to verify • Finding route: virtually impossible!
Applications • Verify mathematics • Check homework • Check long Proofs (four color theorem) Proof TM Statement Accept/Reject
Checking Faster • Cook-Levin Theorem (70’s) • Each checker reads 3 letters! • Problem: reliability Proof TM Check 1 Statement, k Check 2 Check 3
Fixing Reliability Problem Proof TM Check 1 Statement, k Check 2 Check 3 Check 4 Check 5 Check 6 Check 6 Check 6 Check 6
Fixing Reliability Problem Correct Proof TM Check 1 Statement, k Check 2 Check 3 Check 4 Check 5 Check 6 Check 7 Check 8 Check 9
Fixing Reliability Problem Correct Proof TM Check 1 Statement, k Check 2 Check 3 Check 4 Check 5 Check 6 Check 7 Check 8 Check 9
Fixing Reliability Problem Proof TM Check 1 Wrong Statement Check 2 Check 3 Check 4 Check 5 Check 6 Check 7 Check 8 Check 9
Fixing Reliability Problem Proof TM Check 1 Wrong Statement Check 2 Check 3 Check 4 PCP Theorem [1992]! Check 5 Check 6 Check 7 Check 8 Check 9
Probabilistic Checking Proof TM Check 1 Wrong Statement Check 2 Check 3 Check 4 Choose few checkers randomly!! Check 5 Check 6 Check 7 Check 8 Check 9
Probabilistic Checking Proof TM Wrong Statement Check 2 Choose few checkers randomly!! Check 5 Check 8
Computation in Cloud Life the universe and everything? Prove! 42 Check 1,3,8,9 Proof
Problems • Constructing checkers takes time • Proof is long. • Many other real-life constraints. • But work is still in progress!