P versus NP: does Boolean satisfiability have a polynomial-time algorithm?
The anchor: difficulty, application value and leverage are 100 by definition and no other problem reaches 100 on any scale. It is the central open problem of complexity theory, shielded by three formal barriers (relativization, natural proofs, algebrization); a constructive P = NP would upend deployed cryptography and optimisation, and thousands of results across complexity, cryptography and algorithms are stated conditionally on P ≠ NP or on stronger hypotheses.
The problem
If a solution to a puzzle is easy to check, is it also easy to find? Nobody knows.
- 1Some puzzles are easy to check
- 2Are they also easy to solve?
- 3SAT stands for thousands of puzzles
- 4No proof; known methods blocked
- 5Answer reshapes security and optimisation
Statement. is the class of yes/no problems a deterministic computer solves in time polynomial in the input length. is the class of problems where a yes answer has a short certificate that can be checked in polynomial time. For example, for a logical formula, a satisfying assignment is a certificate. Clearly . asks whether they are equal.
Built from
earlier problems → this oneThe problems this one is built from: progress or tools it needs (builds on), special cases that come first (generalizes), and weaker results on the way (implies). On the right, what builds on it.
- Start with
- P versus NP: does Boolean satisfiability have a polynomial-time algorithm?This problem
- Then
- Strong Exponential Time Hypothesis: no (2−ε)ⁿ-time algorithm for k-SAT as k → ∞Complexity Theory · D88
Path to understanding
foundations → problemThe research entries this problem rests on, in the order to read them. Each links to its explainer.
- Start with
- Step 2
- Computational complexity theoryTheory · host
- Then
- P versus NP: does Boolean satisfiability have a polynomial-time algorithm?The problem
State of the art
No proof in either direction. Most experts believe . Three barriers explain why standard techniques fail: relativization (Baker, Gill, Solovay, 1975), natural proofs (Razborov and Rudich, 1994) and algebrization (Aaronson and Wigderson, 2008). The best unconditional results are far weaker: only linear lower bounds on general Boolean circuit size are known for explicit functions in , and Williams (2011) proved that does not have polynomial-size circuits. Geometric complexity theory (Mulmuley and Sohoni) proposes an algebraic-geometric route to related lower bounds, but no separation has come from it. Related time–space progress, such as Williams's 2025 simulation of time in space , concerns versus -type questions, not P versus NP. P versus NP is not among the claims in the batch of AI-generated manuscripts released by OpenAI on 6 October 2026 (Aaronson: "P≠NP isn't there").
Realistic applications
If were shown with a practical algorithm, most deployed public-key cryptography would fail, and optimisation, verification, scheduling and machine learning would change at scale; this outcome is considered very unlikely, and a proof of with an impractical algorithm (for example with a huge exponent) would have far less effect. A proof of would change no deployed system by itself, since cryptography needs average-case hardness and one-way functions, which does not provide. Its value would be in the techniques (new lower-bound methods) and in settling whether the search for efficient exact algorithms for -complete problems is futile.
What counts as solved
A proof of or in the standard formalisation above, accepted by the complexity-theory community after scrutiny. The Clay Institute requires publication in a qualifying outlet, at least two years to have passed since publication, and general acceptance in the mathematics community.
How it gets verified
Lean proofA formal proof checked by Lean 4 / Mathlib.
Statement: ComplexityTheory.P_ne_NP : P ≠ NP in Millennium/PvsNP.lean (Formal Conjectures pinned at commit e754a78 (17 October 2026)). The classes are defined in the corpus file Computability/Complexity.lean on top of Mathlib's polynomial-time Turing machines (TM2ComputableInPolyTime) over bit-string encodings, with NP as languages whose witnesses of polynomial length are checked by a polynomial-time relation (Arora–Barak, Definition 2.1). A resolution in either direction is accepted when a Lean proof of P_ne_NP or of its negation compiles against the pinned corpus and passes Comparator with only the three standard axioms; because the machine-level definitions belong to the corpus, a complexity theorist must also confirm that they match the textbook classes. No proof technique is known that avoids relativization, natural proofs and algebrization, so a formal proof is far off, and Clay's own rules (publication and two years of acceptance) still govern the prize.
Claims under verification
+ add a claimNo claimed results on the Verification board for this problem yet.
Where the work is
Resolution needs proof techniques that do not yet exist; all three known barriers are about methods, not computation. Computer search for small circuits says nothing about asymptotics.
Bottlenecks
ranked by votes- #1TheoryRelativization, natural proofs and algebrization
Diagonalization relativizes (Baker–Gill–Solovay). Most combinatorial circuit lower-bound methods are natural proofs, which would break pseudorandom functions (Razborov–Rudich). Arithmetization-based methods algebrize (Aaronson–Wigderson). A separation must evade all three at once, and no technique is known to.
Community grades
Sign in to add your own grade.
Connected problems
Progress
- Jun 8, 2011NEXP ⊄ ACC⁰source
Ryan Williams proved that NEXP lacks polynomial-size ACC⁰ circuits by turning faster satisfiability algorithms into lower bounds (CCC 2011; JACM 2014; day approximate).
- May 23, 1994Natural proofs barriersource
Razborov and Rudich showed that 'natural' circuit-lower-bound arguments would break strong pseudorandom generators (STOC 1994; JCSS 1997; day of the STOC presentation approximate).
- Dec 1, 1975Relativization barriersource
Baker, Gill and Solovay gave oracles under which P = NP and others under which P ≠ NP, so relativizing proofs cannot settle the question.
- May 3, 1971The problem is formulatedsource
Cook's STOC 1971 paper introduced NP-completeness and posed the question; Levin obtained equivalent results independently (published 1973).