All proofs
Project-declaredLean 4.31.0 · mathlib@fabf563a7c95

Mk reverse eq galois Autₛ mul

ArkLib.Lattices.CyclotomicModulus.mk_reverse_eq_galoisAutₛ_mul

Plain-language statement

The reverse identity. In S = Z_q[X]/(X^{2^α}+1), the conjugation σ_{-1} (here the semantic automorphism galoisAutₛ of exponent conjExp = 2^{α+1}-1) and the polynomial reversal are related by mk(reverse p) = σ_{-1}(mk p) · (mk X)^{deg p}. This is the concrete handle behind "σ_{-1} swaps the two factors": since (mk X)^{deg p} is a unit, `σ...

Exact Lean statement

theorem mk_reverse_eq_galoisAutₛ_mul (α : ℕ) (p : (ZMod q)[X]) :
    Ideal.Quotient.mk (powTwoCyclotomic (R := ZMod q) α).modIdeal p.reverse
      = galoisAutₛ α (conjExp α) (conjExp_odd α)
          (Ideal.Quotient.mk (powTwoCyclotomic (R := ZMod q) α).modIdeal p)
        * (Ideal.Quotient.mk (powTwoCyclotomic (R := ZMod q) α).modIdeal X) ^ p.natDegree

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
theorem mk_reverse_eq_galoisAutₛ_mul (α : ) (p : (ZMod q)[X]) :    Ideal.Quotient.mk (powTwoCyclotomic (R := ZMod q) α).modIdeal p.reverse      = galoisAutₛ α (conjExp α) (conjExp_odd α)          (Ideal.Quotient.mk (powTwoCyclotomic (R := ZMod q) α).modIdeal p)        * (Ideal.Quotient.mk (powTwoCyclotomic (R := ZMod q) α).modIdeal X) ^ p.natDegree := by  set mk := Ideal.Quotient.mk (powTwoCyclotomic (R := ZMod q) α).modIdeal with hmkdef  set x : (powTwoCyclotomic (R := ZMod q) α).CyclotomicRing := mk X with hxdef  have hx2d : x ^ (2 ^+ 1)) = 1 := by rw [hxdef,  map_pow]; exact mk_X_pow_conductor_eq_one α  have hcx : x ^ (conjExp α) * x = 1 := by    rw [ pow_succ, conjExp, Nat.sub_add_cancel Nat.one_le_two_pow, hx2d]  letI invx : Invertible x := x ^ (conjExp α), hcx, by rw [mul_comm]; exact hcx  set i : ZMod q →+* (powTwoCyclotomic (R := ZMod q) α).CyclotomicRing := mk.comp C with hidef  have heval_mk :  r : (ZMod q)[X], eval₂ i x r = mk r := by    have hext : (Polynomial.evalRingHom i x) = mk := by      apply Polynomial.ringHom_ext      · intro a        simp only [Polynomial.coe_evalRingHom, eval₂_C, hidef, RingHom.comp_apply]      · simp only [Polynomial.coe_evalRingHom, eval₂_X, hxdef]    intro r; rw [ hext]; rfl  have hxc : mk (X ^ (conjExp α)) = ⅟x := by rw [map_pow]; rfl  have hsigma : galoisAutₛ α (conjExp α) (conjExp_odd α) (mk p) = eval₂ i (⅟x) p := by    rw [galoisAutₛ_mk, Polynomial.aeval_def, Polynomial.algebraMap_eq, Polynomial.hom_eval₂,       hidef, hxc]  have hrev := Polynomial.eval₂_reverse_mul_pow i (⅟x) p  rw [invOf_invOf, heval_mk,  hsigma] at hrev  rw [ hrev, mul_assoc,  mul_pow, invOf_mul_self, one_pow, mul_one]
Project
ArkLib
License
Apache-2.0
Commit
fad5cbf80877
Source
ArkLib/Data/Lattices/CyclotomicRing/Subfield/Field.lean:63-88

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