All proofs
Project-declaredLean 4.31.0 · mathlib@fabf563a7c95

Interpolate degree ge of no data

KZG.CommitmentScheme.interpolate_degree_ge_of_no_data

Plain-language statement

If no degree-n coefficient vector fits the data, interpolation has degree at least n + 1.

Exact Lean statement

lemma interpolate_degree_ge_of_no_data {n L : ℕ} (S : Finset (Fin L))
    {queryOf responseOf : Fin L → ZMod p}
    (hquery : Set.InjOn queryOf ↑S)
    (hNoData : ¬ ∃ d : Fin (n + 1) → ZMod p,
      ∀ i ∈ S, (CPolynomial.ofFn d).eval (queryOf i) = responseOf i) :
    (↑(n + 1) : WithBot ℕ) ≤
      (CLagrange.interpolate S queryOf responseOf).degree

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
lemma interpolate_degree_ge_of_no_data {n L : } (S : Finset (Fin L))    {queryOf responseOf : Fin L  ZMod p}    (hquery : Set.InjOn queryOf ↑S)    (hNoData : ¬  d : Fin (n + 1)  ZMod p,       i  S, (CPolynomial.ofFn d).eval (queryOf i) = responseOf i) :    (↑(n + 1) : WithBot )       (CLagrange.interpolate S queryOf responseOf).degree := by  by_contra hlt  push Not at hlt  set Q : Polynomial (ZMod p) :=    Lagrange.interpolate S queryOf responseOf with hQ_def  have hQdeg_lt : Q.degree < (↑(n + 1) : WithBot ) := by    have h := hlt    rw [show        (CLagrange.interpolate S          queryOf responseOf).degree          = Q.degree from by          rw [hQ_def,  CLagrange.cinterpolate_eq_interpolate,  degree_toPoly]] at h    exact h  have hQ_mem : Q  Polynomial.degreeLT (ZMod p) (n + 1) :=    Polynomial.mem_degreeLT.mpr hQdeg_lt  apply hNoData  refine Polynomial.degreeLTEquiv (ZMod p) (n + 1) Q, hQ_mem, ?_  intro i hi  have hQ_eval : Q.eval (queryOf i) = responseOf i := by    rw [hQ_def]    exact Lagrange.eval_interpolate_at_node responseOf      hquery hi  have hQ_sum :      Q.eval (queryOf i) =        ∑ k : Fin (n + 1),          Polynomial.degreeLTEquiv (ZMod p) (n + 1) Q, hQ_mem k *            (queryOf i) ^ (k : ) :=    Polynomial.eval_eq_sum_degreeLTEquiv hQ_mem (queryOf i)  set d : Fin (n + 1)  ZMod p :=    Polynomial.degreeLTEquiv (ZMod p) (n + 1) Q, hQ_mem with hd_def  let P_C : CPolynomial (ZMod p) :=    (CompPoly.CPolynomial.Raw.mk (Array.ofFn d)).trim,      CompPoly.CPolynomial.Raw.Trim.isCanonical_trim _  change CPolynomial.eval (queryOf i) P_C = responseOf i  rw [eval_toPoly]  have hPC_eq : P_C.toPoly = Q := by    apply Polynomial.ext    intro k    rw [ coeff_toPoly]    change ((CompPoly.CPolynomial.Raw.mk (Array.ofFn d)).trim).coeff k = Q.coeff k    rw [CompPoly.CPolynomial.Raw.Trim.coeff_eq_coeff]    change (Array.ofFn d).getD k 0 = Q.coeff k    rw [Array.getD_eq_getD_getElem?, Array.getElem?_ofFn]    by_cases hk : k < n + 1    · simp [hk, hd_def, Polynomial.degreeLTEquiv]    · push Not at hk      simp only [hk.not_gt, dite_false, Option.getD_none]      symm      exact Polynomial.coeff_eq_zero_of_degree_lt        (lt_of_lt_of_le hQdeg_lt (by exact_mod_cast hk))  rw [hPC_eq]  exact hQ_eval
Project
ArkLib
License
Apache-2.0
Commit
fad5cbf80877
Source
ArkLib/Commitments/Functional/KZG/FunctionBinding/DegreeConflict.lean:87-144

Reuse this declaration

Bring the exact result into your workflow

The import identifies the source module. Your project still needs the pinned package dependency shown on this page.

What this badge means

This completion status comes from the project or community source. It has not yet been represented here as an independent rebuild and axiom audit.

Continue in this project

Related declarations

Project-declaredLean 4.31.0

Affine gaps lifted to interleaved codes

affine_gaps_lifted_to_interleaved_codes

Project documentation

This lemma proves the final algebraic step in the DG25 Theorem 3.1 proof. It shows that if R > e + 1, then e * (R / (R - 1)) < e + 1. The intuition is that the fraction R / (R - 1) is always greater than 1, but as R gets larger, it gets closer to 1. The hypothesis R > e + 1 provides a strong enough bound to ensure the product e * (fraction) do...

cryptographyproof systemscoding theory

Source project: ArkLib

Person-level attribution pending.

View proof record
Project-declaredLean 4.31.0

Gadget Decompose coeff

ArkLib.Lattices.Ajtai.gadgetDecompose_coeff

Plain-language statement

The k-th coefficient (k < deg φ) of a gadget-decomposition block is exactly the corresponding digit of the corresponding input coefficient.

cryptographyproof systemscoding theory

Source project: ArkLib

Person-level attribution pending.

View proof record
Project-declaredLean 4.31.0

Gadget Decompose lawful

ArkLib.Lattices.Ajtai.gadgetDecompose_lawful

Plain-language statement

The base-b gadget decomposition is a lawful gadget decomposition.

cryptographyproof systemscoding theory

Source project: ArkLib

Person-level attribution pending.

View proof record