We present a new distributed model of probabilistically checkable proofs (PCP). A satisfying assignment x ∈ {0, 1} n to a CNF formula ϕ is shared between two parties, where Alice knows x 1 , . . . , x n/2 , Bob knows x n/2+1 , . . . , x n , and both parties know ϕ. The goal is to have Alice and Bob jointly write a PCP that x satisfies ϕ, while exchanging little or no information. Unfortunately, this model as-is does not allow for nontrivial query complexity. Instead, we focus on a non-deterministic variant, where the players are helped by Merlin, a third party who knows all of x.Using our framework, we obtain, for the first time, PCP-like reductions from the Strong Exponential Time Hypothesis (SETH) to approximation problems in P. In particular, under SETH we show that there are no truly-subquadratic approximation algorithms for Bichromatic Maximum Inner Product over {0, 1}-vectors, Bichromatic LCS Closest Pair over permutations, Approximate Regular Expression Matching, and Diameter in Product Metric. All our inapproximability factors are nearly-tight. In particular, for the first two problems we obtain nearly-polynomial factors of 2 (log n) 1−o(1) ; only (1 + o(1))-factor lower bounds (under SETH) were known before.1 SETH is a pessimistic version of P = NP, stating that for every ε > 0 there is a k such that k-SAT cannot be solved in O((2 − ε) n ) time.2 See the end of this section for a discussion of "bichromatic" vs "monochromatic" closest pair problems. 3 In SODA'17, two entire sessions were dedicated to algorithms for similarity search.