Recognition: 2 theorem links
· Lean TheoremDeterministic Hardness of Approximation For SVP in all Finite ell_p Norms
Pith reviewed 2026-05-13 21:11 UTC · model grok-4.3
The pith
Assuming NP lacks subexponential algorithms, approximating the shortest vector in lattices is hard to within 2^{(log n)^{1-o(1)}} in every finite l_p norm via deterministic reduction.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Under the assumption that NP is not contained in the intersection over delta greater than zero of DTIME of exp n to the delta, there is a deterministic reduction establishing that approximating the shortest vector to within 2 to the power of (log n) to the (1 minus o(1)) is hard for lattices of rank n in any finite l_p norm.
What carries the argument
A deterministic reduction from an NP-complete problem that produces lattices whose shortest-vector gap encodes the original instance, with the gap preserved under any chosen finite l_p norm.
If this is right
- Approximating shortest vectors remains hard even when the reduction itself must be deterministic and cannot use randomness.
- The same superpolynomial hardness factor applies simultaneously to every finite p-norm rather than requiring separate arguments.
- No subexponential algorithm can approximate SVP to the stated factor unless the assumption on NP fails.
- Exact SVP inherits deterministic hardness in the Euclidean norm as a special case of the approximation result.
Where Pith is reading between the lines
- If the hardness holds, lattice-based cryptographic primitives would retain security even when instantiated with non-Euclidean norms.
- The deterministic technique might extend to other lattice problems such as the closest vector problem under similar assumptions.
- A concrete next step would be to check whether the reduction can be made to work for p equal to infinity or for other geometric problems on lattices.
Load-bearing premise
NP does not admit algorithms that run in time exponential in any positive power of n less than 1.
What would settle it
Either a deterministic polynomial-time algorithm that approximates shortest vectors to within 2^{(log n)^{1-o(1)}} for some finite p, or a subexponential-time algorithm for an NP-complete problem.
Figures
read the original abstract
We show that, assuming NP $\not\subseteq$ $\cap_{\delta > 0}$DTIME$\left(\exp{n^\delta}\right)$, the shortest vector problem for lattices of rank $n$ in any finite $\ell_p$ norm is hard to approximate within a factor of $2^{(\log n)^{1 - o(1)}}$, via a deterministic reduction. Previously, for the Euclidean case $p=2$, even hardness of the exact shortest vector problem was not known under a deterministic reduction.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims that, assuming NP ⊈ ∩_{δ>0} DTIME(exp n^δ), the shortest vector problem for lattices of rank n in any finite ℓ_p norm is hard to approximate within a factor of 2^{(log n)^{1-o(1)}}, via a deterministic Karp reduction. This strengthens prior work by derandomizing randomized techniques through explicit constructions that preserve lattice rank and the target factor uniformly across all finite p, including the Euclidean case p=2 where even exact SVP hardness was previously unknown under deterministic reductions.
Significance. If the result holds, it is a significant contribution to the deterministic complexity of lattice problems. The deterministic reduction from a standard subexponential hardness assumption to GapSVP in every finite ℓ_p norm, achieved via explicit constructions without increasing rank or weakening the 2^{(log n)^{1-o(1)}} factor, provides a uniform treatment across norms and removes reliance on randomness. This is a clear technical strength that could support further derandomization results in the area.
minor comments (2)
- [Abstract] The abstract states the main claim clearly but could briefly note the explicit construction technique used for derandomization to give readers an immediate sense of the proof strategy.
- [Section 4] In the time-complexity accounting for the reduction, the precise dependence on the lattice rank n should be stated explicitly when bounding the overall running time under the subexponential assumption.
Simulated Author's Rebuttal
We thank the referee for the positive assessment of our work and the recommendation to accept. We are pleased that the uniform deterministic hardness result for GapSVP across all finite ℓ_p norms, including the Euclidean case, is viewed as a significant contribution.
Circularity Check
No significant circularity identified
full rationale
The paper establishes hardness of approximating the shortest vector problem (SVP) in any finite ℓ_p norm via a deterministic Karp reduction from a standard complexity assumption (NP ⊈ ∩_δ DTIME(exp n^δ)). The derivation chain consists of explicit derandomization constructions that preserve lattice rank n and the target approximation factor 2^(log n)^{1-o(1)} uniformly across p. No step reduces by construction to a fitted parameter, self-definition, or unverified self-citation chain; the source problem's hardness is external to the target SVP instance. The result is therefore self-contained against the stated assumption with no load-bearing circularity.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption NP is not contained in ∩_{δ>0} DTIME(exp n^δ)
Lean theorems connected to this paper
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IndisputableMonolith/Foundation/RealityFromDistinction.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We show that, assuming NP ⊈ ∩_{δ>0} DTIME(exp n^δ), the shortest vector problem for lattices of rank n in any finite ℓ_p norm is hard to approximate within a factor of 2^{(log n)^{1-o(1)}}, via a deterministic reduction.
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Our main technical contribution is a new type of tensor product, dubbed the Vandermonde fortified tensor product, which we apply to the matrix representation of a quasi-random PCP [Kho06].
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
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[2]
For all nonzero vectorsx∈Z M, we have∥xB∥ 0 ≥2h. In particular, case (1) enforces that the lattice vector is not only of small norm but also in{−1,0,1} N. Theorem 3.2 implies Theorem 3.1 via direct tensoring. Proof of Theorem 3.1 using Theorem 3.2.Fix any constantp≥1, and use the reduction from Theorem 3.2 to get an integer matrixB∈Z M×N , where1≤M≤exp ¶ ...
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[3]
There exists a nonzero vectorx ′ ∈Z M ′ such that∥x ′B′∥0 ≤h n1/log logn
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[4]
The first case also maintains thatx ′B′ ∈ {−1,0,1} N ′
For all nonzero vectorsx ′ ∈Z M ′ , we have∥x ′B′∥0 ≥2 n1/log logn hn1/log logn . The first case also maintains thatx ′B′ ∈ {−1,0,1} N ′ . For all finitep≥1, theℓ p norm of an integer vectorw ′ havingxnonzero entries is at leastx 1/p, and this is realized with equality when the entries ofw ′ are in{−1,0,1}. So cases (1) and (2) from above have the followi...
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[5]
There exists a nonzero vectorx ′ ∈Z M ′ such that∥x ′B′∥p ≤h ′
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[6]
For all nonzero vectorsx ′ ∈Z M ′ , we have∥x ′B′∥p >2 n1/log logn /p−1h′. All that remains is to lower bound the multiplicative gapγ= 2 n1/log logn /p−1 in terms of the rankM ′. Claim 3.3.Letp≥1be any constant, letMbe a parameter such that1≤M≤exp ¶ 2O(√logn(log logn) O(1)) © , and letM ′ = exp ¶ n1/log logn logM © . Then 2n1/log logn /p−1 ≥exp ¶ Ω Ä (log...
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[8]
As shorthand, we refer to the problem as(N, M, d, r, α, β)-QRDH
Every vertex subsetV ′ ⊆Vfully contains at most(|V ′|/N)dM+βMhyperedges. As shorthand, we refer to the problem as(N, M, d, r, α, β)-QRDH. We refer torandαas thecompleteness parameters, andβas thesoundness parameter. 10We assume without loss of generality thath≥2and henceh ′ ≥2; otherwise the problem is trivial. 12 Tensor Products and Indicator Matrices.We...
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[9]
LetQ=P ⊗q be theq-fold tensor product ofPwith itself. 13
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[10]
Define a collectionSofqM q−1 subsets of[M] q: S= n {(e1, . . . , eℓ−1, e′ ℓ, eℓ+1, . . . , eq) :e ′ ℓ ∈[M]}:ℓ∈[q]ande 1, . . . , eℓ−1, eℓ+1, . . . , eq ∈[M] o . That is, each set inSis constructed by choosing a designated coordinateℓ, fixing the valuese 1, . . . , eℓ−1, eℓ+1, . . . , eq of all other coordinates, and allowing the designated coordinate to v...
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[11]
Index the firstM q rows ofVusing distinct elements of[M] q
Letabe a prime satisfyingM q < a <3M q,11 and letVbe an(a, M/t)reduced Vandermonde matrix. Index the firstM q rows ofVusing distinct elements of[M] q. Now for eachS∈ S, define anM q ×M/tinteger matrixA (S) as follows. For alle∈[M] q, ife∈Sthen setA (S) e =V e, and otherwise setA (S) =0 M/t
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[12]
The(t, q)-VF tensor product ofPisT= A∥Q
Denote the horizontal concatenation of allA (S) matrices asA∈Z M q×qM q/t. The(t, q)-VF tensor product ofPisT= A∥Q . The synergy between VF tensor products and instances of QRDH is formalized below. Roughly speak- ing, VF tensor products allow us to amplify the gap between cases (1) and (2) in the QRDH problem, without creating spurious vertex subsets in ...
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[13]
DenoteH’s indicator matrix asP∈ {0,1} M×N , and letT= A∥Q be the(t, q)-VF tensor product ofP
(Expansion) Every vertex subsetV ′ ⊆Vfully contains at most(|V ′|/N)dM+βMhyperedges. DenoteH’s indicator matrix asP∈ {0,1} M×N , and letT= A∥Q be the(t, q)-VF tensor product ofP. The following holds for all vectorsx∈Z M q such thatxA=0, and all parametersδ∈[0,1]. LetE ′ be the subset of[M] q containing all indices for the nonzero entries ofx. If|E ′|> M q...
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[14]
DenoteH’s indicator matrix asP∈ {0,1} M×N
(Expansion) Every vertex subsetV ′ ⊆Vfully contains at most(|V ′|/N)dM+βMhyperedges. DenoteH’s indicator matrix asP∈ {0,1} M×N . For all positive integersq, for all(t, q)-legal subsetsE ′ ⊆[M] q, and for all parametersδ∈[0,1], the following holds. If|E ′|> M qδd (1−βt)q , then|N (q) P (E′)|> N qδ. Proof.We give a proof by induction on the tensoring expone...
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[15]
There exists a nonzero vectorx∈Z M such that∥xB∥ 0 ≤h,and additionallyxB∈ {−1,0,1} N
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[16]
For reference, we also re-state the QRDH problem
For all nonzero vectorsx∈Z M, we have∥xB∥ 0 ≥2h. For reference, we also re-state the QRDH problem. 21 Problem 4, Restated.Given a hypergraphH= (V, E)of aritydwith|V|=Nand|E|=M, along with a parameterr≥1and parametersα, β∈[0,1], distinguish between the following two cases:
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[18]
As shorthand, we refer to the problem as(N, M, d, r, α, β)-QRDH
Every vertex subsetV ′ ⊆Vfully contains at most(|V ′|/N)dM+βMhyperedges. As shorthand, we refer to the problem as(N, M, d, r, α, β)-QRDH. We refer torandαas thecompleteness parameters, andβas thesoundness parameter. We show in Section 6 that a modification of Khot’s quasi-random PCP [Kho06], combined with tools from a paper by Khot and Saket [KS16], gives...
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[19]
LetT= A∥Q be the(t, q)-VF tensor product ofP. Notice thatAis an integer matrix withM q rows andqM q/tcolumns, andQis an integer matrix withM q rows andN q columns. All entries of Aare nonnegative and less than3M q, andQis a 0/1 matrix
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[20]
Index the firstM q rows ofVusing distinct elements of[M] q
LetV∈Z M q×w be an(a, w)reduced Vandermonde matrix, whereais a prime satisfyingM q < a < 3M q. Index the firstM q rows ofVusing distinct elements of[M] q. For eachv∈[N] q, we construct a matrixR (v) ∈Z M q×w usingQas follows: • For eache∈[M] q, do: –IfQ e,v = 0, then setR (v) e =0 w. –Otherwise, setR (v) e =V e. Now letRbe the horizontal concatenation of ...
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[21]
LetW∈Z M q×h/n be an(a, h/n)reduced Vandermonde matrix, whereais a prime satisfying M q < a <3M q
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[22]
LetC= A∥R∥W ∈Z M q×(qM q/t+N qw+h/n)
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[23]
For convenience, denote the number of rows inBas M ′ and the number of columns inBasN ′
Construct the basis matrixBby horizontally concatenating2hcopies ofC, and then horizontally appending a singleM q ×M q identity matrix. For convenience, denote the number of rows inBas M ′ and the number of columns inBasN ′. 23 Relating Back to Theorem 3.2.By our choice of parameters, the time to constructBisexp ¶ 2O(√logn(log logn) O(1)) © , and all step...
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[24]
There exists a vertex subsetV ′ ⊆Vof size at mostN/rthat fully contains at leastα(1/r) d−1M hyperedges
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[25]
As shorthand, we refer to the problem as(N, M, d, r, α, β)-QRDH
Every vertex subsetV ′ ⊆Vfully contains at most(|V ′|/N)dM+βMhyperedges. As shorthand, we refer to the problem as(N, M, d, r, α, β)-QRDH. We refer torandαas thecompleteness parameters, andβas thesoundness parameter. Theorem 5.1, Restated.There is a deterministicexp ¶ 2O(√lognlog 4 logn) © time reduction from SAT in- stances of sizento N= exp ¶ 2O(√lognlog...
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[26]
We denote usingΠthe set of all proof locations
The proof for the verifier is of size2 O(nε). We denote usingΠthe set of all proof locations
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[27]
The verifier usesO(n ε)random bits to choose a subsetQ⊆Πof proof locations, where|Q|=d
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[28]
Suppose the starting SAT instance was satisfiable. Then there exists a subsetΠ ′ ⊆Πof at most half the locations in the proof such that Pr Q [Q⊆Π ′]≥(1−O(1/d))·(1/2) d−1
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[29]
Then for all subsetsΠ ′ ⊆Πof at most half the locations in the proof, Pr Q [Q⊆Π ′]≤(1/2) d + 1/220d
Suppose the starting SAT instance was unsatisfiable. Then for all subsetsΠ ′ ⊆Πof at most half the locations in the proof, Pr Q [Q⊆Π ′]≤(1/2) d + 1/220d. 29 Notice that thequery patternof the verifier is what changes depending on whether the starting SAT instance was satisfiable or not. This is why we do not specify the alphabet for the proof. Also notice...
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[30]
Suppose the starting SAT instance was unsatisfiable. Then for allζ∈[0,1]and for all subsetsΠ ′ containing aζfraction of the locations in the proof, we have Pr Q [Q⊆Π ′]≤ζ d + 1/220d. To interpret Theorem 6.1 in terms of QRDH, construct a hypergraphHas follows. Execute the2 O(nε) time (deterministic) algorithm to construct the PCP verifier. For every proof...
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[31]
Suppose that the starting SAT instance was satisfiable. Then there exists a subsetΠ ′ of exactly half the vertices inHsuch that a(1−O(1/d))·(1/2) d−1 fraction of the hyperedges inHhave all of their endpoints inΠ ′
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[32]
Suppose that the starting SAT instance was unsatisfiable. Then for allζ∈[0,1]and for all subsets Π′ containing aζfraction of the vertices inH, the fraction of hyperedges inHthat have all of their endpoints inΠ ′ is at mostζ d + 1/220d. We can thus re-interpret Theorem 6.1 as: Theorem 6.2([Kho06]).For everyε >0, there is a deterministic2 O(nε) time reducti...
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[33]
There exists a nonzero vectorx∈F M such thatxGhas relative weight at mostα
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[34]
For all nonzero vectorsx∈F M,xGhas relative weight at leastβ. As shorthand, we refer to the problem as(F, N, M, α, β)-GapMDC. We assume that all rows ofGare linearly independent; otherwise the problem is trivial. NP hardness of the exact minimum distance of code problem was first shown by Vardy [Var02]. Constant factor hardness of approximation was then p...
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[35]
Horizontally concatenate the columnsc (v1), . . . ,c(vr) to get a matrixC∈F M×r . 32
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[36]
LetV∈F r×w be a Vandermonde matrix; such a matrix exists because|F|> w≥rby assumption
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[37]
The final matrixG ′ is the horizontal concatenation of allG (v1,...,vr) formed as above
LetG (v1,...,vr) =CV. The final matrixG ′ is the horizontal concatenation of allG (v1,...,vr) formed as above. The number of rows inG ′ is equal to the number of rows inG, soG ′ is of heightMas required. The number of columnsN ′ inG ′ iswtimes the number of length-rwalks in the graphG; because the graph isO((1/δ) O(1))-regular, we havew≤N ′ ≤O(N w(1/δ) O(...
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[38]
In other words,A (ℓ) is the tensor product of the previous matrixG (ℓ−1) with the starting matrixG
LetA (ℓ) =G (ℓ−1) ⊗G. In other words,A (ℓ) is the tensor product of the previous matrixG (ℓ−1) with the starting matrixG. 35
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[39]
Invoke the algorithm from Lemma 6.10 on matrixA (ℓ) with parametersδ, r,andw; by our choice of f(β),Fis large enough to apply the lemma. The resulting matrix isG (ℓ). Our final GapMDC instance will be with respect to the matrixG (L). We know that the starting matrixGis of sizen O(1), and that the width ofG (ℓ) is only a constant factor larger than the wid...
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[40]
Each constraintC∈ Cis of the formC= (p (1), . . . ,p(k), H), wherep (1), . . . ,p(k) ∈F m are points andH⊆F k is a linear subspace
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[41]
Anassignment polynomialffor the HomAlgCSP is a polynomialf:F m →F
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[42]
We say that a constraintC∈ Cissatisfiedby the assignment polynomialfiff the vectorf(p (1))∥. . .∥f(p (k)) is orthogonal toH. 37 The goal is to find anonzeroassignment polynomialfof degree at mostdsatisfying the maximum number of constraints. More precisely, we reduce to a gap version of the problem: Problem 7(GapAlgCSP).Given a Homogeneous Algebraic CSP w...
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[43]
There exists a nonzero assignment polynomial of degree at mostdsatisfying at least anαfraction of the constraints
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[44]
Notice that a gap is present intworegards
Every nonzero assignment polynomial of degree at most1000dsatisfies at most aβfraction of the constraints. Notice that a gap is present intworegards. First, we want the assignment polynomial in case (1) to satisfy a larger fraction of constraints than any possible assignment polynomial in case (2). Additionally, we want case (2) to hold even for assignmen...
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1, 2 [Zam14] Ram Zamir.Lattice coding for signals and networks: A structured coding approach to quanti- zation, modulation, and multiuser information theory. Cambridge University Press, 2014. 1 42 A Proof of Claim 3.3 Recall the statement of the claim: Claim 3.3, Restated.Letp≥1be any constant, letMbe a parameter such that1≤M≤ exp ¶ 2O(√logn(log logn) O(1...
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discussion (0)
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