mirror of
https://github.com/saymrwulf/anza-ed25519-verified.git
synced 2026-09-04 20:24:06 +00:00
mrwulf
4c331378fc
The complete non_adjacent_form(5) verification (four stages):
- `Proofs/DsmNafLoadSpec.lean` (generated) — the LE byte-to-word load.
- `Proofs/DsmNafMath.lean` — the digit loop's arithmetic core: window-read
lemmas (single/cross-word), the exact ZZ invariant steps (Nat.mod_mul
telescope), the carry-kill argument from V < 2^253, and the exit theorem.
- `Proofs/DsmNafLoopSpec.lean` — the w=5 digit loop by induction on the
remaining-bits measure: per-step 64-bit window read (4-way word split),
digit write via hcast/wrapping_sub (exact value window - 32*carry',
oddness, |d| < 16), invariant carried through even/odd steps.
- `Proofs/DsmNafSpec.lean` — the public spec: both entry masserts
DISCHARGED; the digits satisfy the NAF conditions and
sum naf[k]*2^k = V EXACTLY (integers, no modular slack)
for any scalar whose LE byte value V is below 2^253.
And the campaign's brick 4, `Proofs/DsmMulSpec.lean`:
- `run_basepoint` — the transpiled ED25519_BASEPOINT_POINT is the standard
base point: valid extended coordinates (X*Y = Z*T) and the curve equation,
kernel-checked via denominator-free 121666-scaled witnesses. Includes the
generic witness lemmas fp_mul_eq_of_witness / onCurve_of_witness.
- `vartime_double_base_mul_spec` — THE PHASE-1 COMPUTATIONAL SPEC of
vartime_double_base::mul: for canonical scalars and a valid on-curve A,
the result is valid, on-curve, and denotes
dsmFold (naf a) (naf b) (edPt A) edBasePt edId 256
with both digit arrays proven exact NAF encodings. Phase 2 (group
semantics [a]A + [b]B) requires Edwards associativity — deferred and
documented; nothing assumes it.
Also: removed a vestigial pre-re-extraction axiom stub
(backend.serial.scalar_mul.vartime_double_base.mul) from FunsExternal —
a root-level leftover that shadowed the real namespaced definition during
name resolution in proof files. Never referenced by any certificate (the
#print-axioms audit guards against that); deleted for hygiene.
CERTS += naf_load_spec, naf_exit, naf_digit_loop_spec,
non_adjacent_form_spec, run_basepoint, vartime_double_base_mul_spec —
each audited to exactly [propext, Classical.choice, Quot.sound].
Full check.sh green.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
418 lines
19 KiB
Text
418 lines
19 KiB
Text
/- ──────────────────────────────────────────────────────────────────────────────
|
||
Proofs/DsmNafLoopSpec.lean — NAF campaign, stage 3: the w=5 digit loop,
|
||
by induction on the remaining-bits measure (no unrolling).
|
||
|
||
State (naf, pos, carry); exact ℤ invariant (DsmNafMath):
|
||
carry ≤ 1 ∧ (carry = 1 → pos ≤ 254) ∧ digits ≥ pos all zero ∧
|
||
digit conditions ∧ nafSum naf 256 + carry·2^pos = V mod 2^pos.
|
||
One symbolic body-walk per induction step:
|
||
· `naf_bitbuf_spec` — the (single|cross)-word 64-bit read at bit pos,
|
||
4-way split on the word index, closed by naf_window_single/cross.
|
||
· `naf_update_spec` — the odd-digit write: hcast / wrapping_sub digit,
|
||
new carry ∈ {0,1}, exact digit value window − 32·carry′, oddness and
|
||
|d| < 16 (the strict lower bound needs the window's oddness).
|
||
· even step: pos+1 via naf_even_step / naf_carry_even;
|
||
odd step: pos+5 via nafSum_set / naf_odd_step / naf_carry_odd.
|
||
Exit (pos ≥ 256): naf_exit — the carry is provably dead and
|
||
nafSum naf 256 = V exactly (V < 2^253: canonical scalars, which is
|
||
what the mul call sites provide).
|
||
────────────────────────────────────────────────────────────────────────────── -/
|
||
import Proofs.DsmNafMath
|
||
open Aeneas Aeneas.Std Result ControlFlow
|
||
open curve25519
|
||
|
||
set_option maxHeartbeats 8000000
|
||
set_option linter.unusedSimpArgs false
|
||
set_option maxRecDepth 8000
|
||
|
||
namespace CurveFieldProofs
|
||
|
||
open Aeneas.Std.WP
|
||
|
||
/-! ### Digit-array set plumbing -/
|
||
|
||
/-- Entries away from the written index are unchanged. -/
|
||
theorem nafDigit_set_ne (naf naf' : Std.Array Std.I8 256#usize) (pos : ℕ)
|
||
(d : Std.I8) (hset : (↑naf' : List Std.I8) = (↑naf : List Std.I8).set pos d)
|
||
(k : ℕ) (hk : k < 256) (hne : k ≠ pos) :
|
||
nafDigit naf' k = nafDigit naf k := by
|
||
have hlen : (↑naf : List Std.I8).length = 256 := by scalar_tac
|
||
unfold nafDigit
|
||
rw [hset, getElem!_pos ((↑naf : List Std.I8).set pos d) k
|
||
(by rw [List.length_set]; omega),
|
||
List.getElem_set_ne (by omega),
|
||
← getElem!_pos (↑naf : List Std.I8) k (by omega)]
|
||
|
||
/-- The written entry holds the new digit. -/
|
||
theorem nafDigit_set_eq (naf naf' : Std.Array Std.I8 256#usize) (pos : ℕ)
|
||
(d : Std.I8) (hpos : pos < 256)
|
||
(hset : (↑naf' : List Std.I8) = (↑naf : List Std.I8).set pos d) :
|
||
nafDigit naf' pos = d.val := by
|
||
have hlen : (↑naf : List Std.I8).length = 256 := by scalar_tac
|
||
unfold nafDigit
|
||
rw [hset, getElem!_pos ((↑naf : List Std.I8).set pos d) pos
|
||
(by rw [List.length_set]; omega),
|
||
List.getElem_set_self]
|
||
|
||
/-! ### The 64-bit window read and the digit write -/
|
||
|
||
/-- The 64-bit buffer read of the digit loop at bit position pos: its masked
|
||
value is the 5-bit window of V at pos. Four word cases (the fifth word is
|
||
the zero pad), each closed by naf_window_single (bit_idx < 59) or
|
||
naf_window_cross. -/
|
||
theorem naf_bitbuf_spec
|
||
(x_u64 : Std.Array Std.U64 5#usize) (v0 v1 v2 v3 : Std.U64) (V : ℕ)
|
||
(hx : (↑x_u64 : List Std.U64) = [v0, v1, v2, v3, 0#u64])
|
||
(hVdef : V = v0.val + 2^64 * (v1.val + 2^64 * (v2.val + 2^64 * (v3.val + 2^64 * 0))))
|
||
(u bidx : Usize) (pos : ℕ) (hposv : pos < 256)
|
||
(hu : u.val = pos / 64) (hbidx : bidx.val = pos % 64) :
|
||
(if bidx < 59#usize
|
||
then do
|
||
let i1 ← Array.index_usize x_u64 u
|
||
i1 >>> bidx
|
||
else
|
||
do
|
||
let i1 ← Array.index_usize x_u64 u
|
||
let i2 ← i1 >>> bidx
|
||
let i3 ← 1#usize + u
|
||
let i4 ← Array.index_usize x_u64 i3
|
||
let i5 ← 64#usize - bidx
|
||
let i6 ← i4 <<< i5
|
||
ok (i2 ||| i6))
|
||
⦃ buf => buf.val % 32 = (V / 2^pos) % 32 ⦄ := by
|
||
have hb0 : v0.val < 2^64 := by scalar_tac
|
||
have hb1 : v1.val < 2^64 := by scalar_tac
|
||
have hb2 : v2.val < 2^64 := by scalar_tac
|
||
have hb3 : v3.val < 2^64 := by scalar_tac
|
||
have hulen : u.val < 4 := by clear * - hu hposv; omega
|
||
have hsz : (U64.size : ℕ) = 2^64 := by scalar_tac
|
||
split
|
||
· -- single-word read
|
||
rename_i hblt
|
||
have hbv : pos % 64 < 59 := by
|
||
have h := hbidx ▸ (show bidx.val < 59 by clear * - hblt; scalar_tac)
|
||
omega
|
||
step as ⟨w, hw⟩
|
||
step as ⟨buf, hbuf⟩
|
||
rcases (show pos / 64 = 0 ∨ pos / 64 = 1 ∨ pos / 64 = 2 ∨ pos / 64 = 3 by omega)
|
||
with hc | hc | hc | hc
|
||
· have huv : u.val = 0 := by omega
|
||
simp only [hx, huv] at hw
|
||
simp at hw
|
||
rw [hbuf, hw, hbidx, Nat.shiftRight_eq_div_pow]
|
||
have hd : V = 0 + 2^0 * (v0.val + 2^64 * (v1.val + 2^64 * (v2.val + 2^64 * (v3.val + 2^64 * 0)))) := by
|
||
rw [hVdef]; try ring
|
||
have h := naf_window_single V (0) v0.val (v1.val + 2^64 * (v2.val + 2^64 * (v3.val + 2^64 * 0))) 0 (pos % 64)
|
||
hd (by norm_num) (by omega)
|
||
rw [show (0 : ℕ) + pos % 64 = pos from by omega] at h
|
||
exact h
|
||
· have huv : u.val = 1 := by omega
|
||
simp only [hx, huv] at hw
|
||
simp at hw
|
||
rw [hbuf, hw, hbidx, Nat.shiftRight_eq_div_pow]
|
||
have hd : V = v0.val + 2^64 * (v1.val + 2^64 * (v2.val + 2^64 * (v3.val + 2^64 * 0))) := by
|
||
rw [hVdef]; try ring
|
||
have h := naf_window_single V (v0.val) v1.val (v2.val + 2^64 * (v3.val + 2^64 * 0)) 64 (pos % 64)
|
||
hd (by omega) (by omega)
|
||
rw [show (64 : ℕ) + pos % 64 = pos from by omega] at h
|
||
exact h
|
||
· have huv : u.val = 2 := by omega
|
||
simp only [hx, huv] at hw
|
||
simp at hw
|
||
rw [hbuf, hw, hbidx, Nat.shiftRight_eq_div_pow]
|
||
have hd : V = v0.val + 2^64 * v1.val + 2^128 * (v2.val + 2^64 * (v3.val + 2^64 * 0)) := by
|
||
rw [hVdef]; try ring
|
||
have h := naf_window_single V (v0.val + 2^64 * v1.val) v2.val (v3.val + 2^64 * 0) 128 (pos % 64)
|
||
hd (by omega) (by omega)
|
||
rw [show (128 : ℕ) + pos % 64 = pos from by omega] at h
|
||
exact h
|
||
· have huv : u.val = 3 := by omega
|
||
simp only [hx, huv] at hw
|
||
simp at hw
|
||
rw [hbuf, hw, hbidx, Nat.shiftRight_eq_div_pow]
|
||
have hd : V = v0.val + 2^64 * v1.val + 2^128 * v2.val + 2^192 * (v3.val + 2^64 * (0)) := by
|
||
rw [hVdef]; try ring
|
||
have h := naf_window_single V (v0.val + 2^64 * v1.val + 2^128 * v2.val) v3.val (0) 192 (pos % 64)
|
||
hd (by omega) (by omega)
|
||
rw [show (192 : ℕ) + pos % 64 = pos from by omega] at h
|
||
exact h
|
||
· -- cross-word read
|
||
rename_i hbge
|
||
have hbv : 59 ≤ pos % 64 := by
|
||
have h : ¬ (bidx.val < 59) := by clear * - hbge; scalar_tac
|
||
omega
|
||
step as ⟨w, hw⟩
|
||
step as ⟨i2, hi2⟩
|
||
step as ⟨i3, hi3⟩
|
||
step as ⟨w', hw'⟩
|
||
step as ⟨i5, hi5⟩
|
||
step as ⟨i6, hi6⟩
|
||
try simp only [spec_ok]
|
||
rcases (show pos / 64 = 0 ∨ pos / 64 = 1 ∨ pos / 64 = 2 ∨ pos / 64 = 3 by omega)
|
||
with hc | hc | hc | hc
|
||
· have huv : u.val = 0 := by omega
|
||
have hi3v : i3.val = 1 := by clear * - hi3 huv; omega
|
||
simp only [hx, huv] at hw
|
||
simp at hw
|
||
simp only [hx, hi3v] at hw'
|
||
simp at hw'
|
||
rw [UScalar.val_or, hi2, hi6, hi5, hbidx, hw, hw', hsz,
|
||
Nat.shiftRight_eq_div_pow]
|
||
have hd : V = 0 + 2^0 * (v0.val + 2^64 * (v1.val + 2^64 * (v2.val + 2^64 * (v3.val + 2^64 * 0)))) := by
|
||
rw [hVdef]; try simp; try ring
|
||
have h := naf_window_cross V (0) v0.val (v1.val) (v2.val + 2^64 * (v3.val + 2^64 * 0)) 0 (pos % 64)
|
||
hd (by norm_num) (by omega) (by omega)
|
||
rw [show (0 : ℕ) + pos % 64 = pos from by omega] at h
|
||
exact h
|
||
· have huv : u.val = 1 := by omega
|
||
have hi3v : i3.val = 2 := by clear * - hi3 huv; omega
|
||
simp only [hx, huv] at hw
|
||
simp at hw
|
||
simp only [hx, hi3v] at hw'
|
||
simp at hw'
|
||
rw [UScalar.val_or, hi2, hi6, hi5, hbidx, hw, hw', hsz,
|
||
Nat.shiftRight_eq_div_pow]
|
||
have hd : V = v0.val + 2^64 * (v1.val + 2^64 * (v2.val + 2^64 * (v3.val + 2^64 * 0))) := by
|
||
rw [hVdef]; try simp; try ring
|
||
have h := naf_window_cross V (v0.val) v1.val (v2.val) (v3.val + 2^64 * 0) 64 (pos % 64)
|
||
hd (by omega) (by omega) (by omega)
|
||
rw [show (64 : ℕ) + pos % 64 = pos from by omega] at h
|
||
exact h
|
||
· have huv : u.val = 2 := by omega
|
||
have hi3v : i3.val = 3 := by clear * - hi3 huv; omega
|
||
simp only [hx, huv] at hw
|
||
simp at hw
|
||
simp only [hx, hi3v] at hw'
|
||
simp at hw'
|
||
rw [UScalar.val_or, hi2, hi6, hi5, hbidx, hw, hw', hsz,
|
||
Nat.shiftRight_eq_div_pow]
|
||
have hd : V = v0.val + 2^64 * v1.val + 2^128 * (v2.val + 2^64 * (v3.val + 2^64 * (0))) := by
|
||
rw [hVdef]; try simp; try ring
|
||
have h := naf_window_cross V (v0.val + 2^64 * v1.val) v2.val (v3.val) (0) 128 (pos % 64)
|
||
hd (by omega) (by omega) (by omega)
|
||
rw [show (128 : ℕ) + pos % 64 = pos from by omega] at h
|
||
exact h
|
||
· have huv : u.val = 3 := by omega
|
||
have hi3v : i3.val = 4 := by clear * - hi3 huv; omega
|
||
simp only [hx, huv] at hw
|
||
simp at hw
|
||
simp only [hx, hi3v] at hw'
|
||
simp at hw'
|
||
rw [UScalar.val_or, hi2, hi6, hi5, hbidx, hw, hw', hsz,
|
||
Nat.shiftRight_eq_div_pow]
|
||
have hd : V = v0.val + 2^64 * v1.val + 2^128 * v2.val + 2^192 * (v3.val + 2^64 * ((0#u64).val + 2^64 * (0))) := by
|
||
rw [hVdef]; try simp; try ring
|
||
have h := naf_window_cross V (v0.val + 2^64 * v1.val + 2^128 * v2.val) v3.val ((0#u64).val) (0) 192 (pos % 64)
|
||
hd (by omega) (by omega) (by omega)
|
||
rw [show (192 : ℕ) + pos % 64 = pos from by omega] at h
|
||
exact h
|
||
|
||
/-- The odd-digit write: hcast (or hcast + wrapping_sub) produces the digit
|
||
window − 32·carry′ with carry′ the ≥16 indicator; the digit is odd with
|
||
|d| < 16, and the entry is written at pos. -/
|
||
theorem naf_update_spec (naf : Std.Array Std.I8 256#usize) (pos : Usize) (window : Std.U64)
|
||
(hpos : pos.val < 256) (hwle : window.val ≤ 32) (hwodd : window.val % 2 = 1) :
|
||
(if window < 16#u64
|
||
then do
|
||
let i4 ← lift (UScalar.hcast .I8 window)
|
||
let a ← Array.update naf pos i4
|
||
ok (a, 0#u64)
|
||
else
|
||
do
|
||
let i4 ← lift (UScalar.hcast .I8 window)
|
||
let i5 ← lift (UScalar.hcast .I8 32#u64)
|
||
let i6 ← lift (core.num.I8.wrapping_sub i4 i5)
|
||
let a ← Array.update naf pos i6
|
||
ok (a, 1#u64))
|
||
⦃ p => ∃ d : Std.I8, (↑p.1 : List Std.I8) = (↑naf : List Std.I8).set pos.val d ∧
|
||
p.2.val ≤ 1 ∧
|
||
(d.val : ℤ) = (window.val : ℤ) - 32 * (p.2.val : ℤ) ∧
|
||
d.val % 2 = 1 ∧ -16 < d.val ∧ d.val < 16 ∧
|
||
((window.val < 16 ∧ p.2.val = 0) ∨ (16 ≤ window.val ∧ p.2.val = 1)) ⦄ := by
|
||
split
|
||
· rename_i hlt
|
||
have hltv : window.val < 16 := by clear * - hlt; scalar_tac
|
||
step with (UScalar.hcast_inBounds_spec .I8 window
|
||
(by clear * - hltv; scalar_tac)) as ⟨d, hd⟩
|
||
step as ⟨a, ha⟩
|
||
try simp only [spec_ok]
|
||
refine ⟨d, by rw [ha, Array.set_val_eq], by simp, by simp [hd], ?_, ?_, ?_,
|
||
Or.inl ⟨hltv, by simp⟩⟩
|
||
· rw [hd]; clear * - hwodd; omega
|
||
· rw [hd]; push_cast; omega
|
||
· rw [hd]; clear * - hltv; omega
|
||
· rename_i hge
|
||
have hgev : 16 ≤ window.val := by clear * - hge; scalar_tac
|
||
step with (UScalar.hcast_inBounds_spec .I8 window
|
||
(by clear * - hwle; scalar_tac)) as ⟨d0, hd0⟩
|
||
step with (UScalar.hcast_inBounds_spec .I8 32#u64
|
||
(by scalar_tac)) as ⟨t32, ht32⟩
|
||
step as ⟨d, hd⟩
|
||
step as ⟨a, ha⟩
|
||
try simp only [spec_ok]
|
||
have hdv : (d.val : ℤ) = (window.val : ℤ) - 32 := by
|
||
rw [hd]
|
||
simp only [core.num.I8.wrapping_sub_val_eq, hd0, ht32]
|
||
have hb := Aeneas.Arith.Int.bmod_pow2_eq_of_inBounds' 8 ((window.val : ℤ) - 32)
|
||
(by norm_num) (by clear * - ; push_cast; omega)
|
||
(by clear * - hwle; push_cast; omega)
|
||
push_cast at hb ⊢
|
||
convert hb using 2 <;> norm_num
|
||
refine ⟨d, by rw [ha, Array.set_val_eq], by simp, by simp [hdv], ?_, ?_, ?_,
|
||
Or.inr ⟨hgev, by simp⟩⟩
|
||
· rw [hdv]; clear * - hwodd hgev; omega
|
||
· rw [hdv]; clear * - hgev hwodd; push_cast; omega
|
||
· rw [hdv]; clear * - hwle; omega
|
||
|
||
|
||
/-! ### The digit loop -/
|
||
|
||
/-- **The w=5 NAF digit loop**, by induction on the remaining-bits measure.
|
||
From any state satisfying the invariant, the loop returns a digit array
|
||
with the NAF digit conditions and exact value V. -/
|
||
theorem naf_digit_loop_spec
|
||
(x_u64 : Std.Array Std.U64 5#usize) (v0 v1 v2 v3 : Std.U64) (V : ℕ)
|
||
(hx : (↑x_u64 : List Std.U64) = [v0, v1, v2, v3, 0#u64])
|
||
(hVdef : V = v0.val + 2^64 * (v1.val + 2^64 * (v2.val + 2^64 * (v3.val + 2^64 * 0))))
|
||
(hV : V < 2^253) (m : ℕ) :
|
||
∀ (naf : Std.Array Std.I8 256#usize) (pos : Usize) (carry : Std.U64),
|
||
256 - pos.val ≤ m →
|
||
carry.val ≤ 1 →
|
||
(carry.val = 1 → pos.val ≤ 254) →
|
||
(∀ k, pos.val ≤ k → k < 256 → nafDigit naf k = 0) →
|
||
(∀ k, k < 256 → (nafDigit naf k = 0 ∨ nafDigit naf k % 2 = 1) ∧
|
||
-16 < nafDigit naf k ∧ nafDigit naf k < 16) →
|
||
nafSum naf 256 + carry.val * 2^pos.val = ((V % 2^pos.val : ℕ) : ℤ) →
|
||
scalar.Scalar.non_adjacent_form_loop1 5#usize naf x_u64 32#u64 31#u64 pos carry
|
||
⦃ res => NafDigits res ∧ nafSum res 256 = (V : ℤ) ⦄ := by
|
||
induction m with
|
||
| zero =>
|
||
intro naf pos carry hm hc hcp hzero hdig hinv
|
||
unfold scalar.Scalar.non_adjacent_form_loop1
|
||
apply loop_step
|
||
simp only [scalar.Scalar.non_adjacent_form_loop1.body]
|
||
have hguard : ¬ (pos < 256#usize) := by clear * - hm; scalar_tac
|
||
rw [if_neg hguard]
|
||
try simp only [spec_ok]
|
||
exact ⟨hdig, naf_exit V pos.val carry.val _ hV (by clear * - hm; omega) hc hcp hinv⟩
|
||
| succ m ih =>
|
||
intro naf pos carry hm hc hcp hzero hdig hinv
|
||
unfold scalar.Scalar.non_adjacent_form_loop1
|
||
apply loop_step
|
||
simp only [scalar.Scalar.non_adjacent_form_loop1.body]
|
||
by_cases hguard : pos < 256#usize
|
||
swap
|
||
· -- exit branch (measure slack)
|
||
rw [if_neg hguard]
|
||
try simp only [spec_ok]
|
||
have hge : 256 ≤ pos.val := by clear * - hguard; scalar_tac
|
||
exact ⟨hdig, naf_exit V pos.val carry.val _ hV hge hc hcp hinv⟩
|
||
· rw [if_pos hguard]
|
||
have hposv : pos.val < 256 := by clear * - hguard; scalar_tac
|
||
-- u64_idx ← pos / 64 ; bit_idx ← pos % 64 ; i ← 64 − 5
|
||
step as ⟨u, hu⟩
|
||
step as ⟨bidx, hbidx⟩
|
||
step as ⟨i59, hi59⟩
|
||
have hi59v : i59 = 59#usize := by clear * - hi59; scalar_tac
|
||
rw [hi59v]
|
||
-- bit_buf: the 5-bit window of V at pos
|
||
step with (naf_bitbuf_spec x_u64 v0 v1 v2 v3 V hx hVdef u bidx pos.val
|
||
hposv hu hbidx) as ⟨buf, hbuf⟩
|
||
-- i1 ← buf &&& 31 : the masked window
|
||
step as ⟨msk, hmsk⟩
|
||
have hmskv : msk.val = (V / 2^pos.val) % 32 := by
|
||
rw [hmsk, UScalar.val_and]
|
||
rw [show (31#u64).val = 2^5 - 1 by scalar_tac,
|
||
Nat.and_two_pow_sub_one_eq_mod]
|
||
rw [show (2:ℕ)^5 = 32 from by norm_num]
|
||
exact hbuf
|
||
-- window ← carry + msk
|
||
step as ⟨win, hwin⟩
|
||
have hwinv : win.val = carry.val + (V / 2^pos.val) % 32 := by
|
||
rw [hwin, hmskv]
|
||
have hwle : win.val ≤ 32 := by clear * - hwinv hc; omega
|
||
-- i2 ← win &&& 1 : the parity bit
|
||
step as ⟨par, hpar⟩
|
||
have hparv : par.val = win.val % 2 := by
|
||
rw [hpar, UScalar.val_and]
|
||
rw [show (1#u64).val = 2^1 - 1 by scalar_tac,
|
||
Nat.and_two_pow_sub_one_eq_mod]
|
||
try norm_num
|
||
split
|
||
· -- EVEN window: digit 0, pos+1, carry unchanged
|
||
rename_i hz
|
||
have heven : (carry.val + (V / 2^pos.val) % 32) % 2 = 0 := by
|
||
have h : par.val = 0 := by rw [hz]; simp
|
||
rw [← hwinv, ← hparv]
|
||
exact h
|
||
step as ⟨pos1, hpos1⟩
|
||
have hpos1v : pos1.val = pos.val + 1 := by clear * - hpos1; omega
|
||
try simp only [spec_ok]
|
||
apply ih naf pos1 carry (by clear * - hm hpos1v; omega) hc
|
||
(fun h1 => by have := naf_carry_even V pos.val carry.val hV hc heven h1
|
||
clear * - this hpos1v; omega)
|
||
(fun k hk1 hk2 => hzero k (by clear * - hk1 hpos1v; omega) hk2)
|
||
hdig
|
||
(by rw [hpos1v]
|
||
exact naf_even_step V pos.val carry.val _ hc hinv heven)
|
||
· -- ODD window: write digit, pos+5, carry from the ≥16 test
|
||
rename_i hnz
|
||
have hwodd : win.val % 2 = 1 := by
|
||
have h : par.val ≠ 0 := by
|
||
clear * - hnz
|
||
intro h
|
||
exact hnz (by scalar_tac)
|
||
clear * - h hparv
|
||
omega
|
||
-- i3 ← 32 / 2 (= 16)
|
||
step as ⟨h16, hh16⟩
|
||
have hh16v : h16 = 16#u64 := by clear * - hh16; scalar_tac
|
||
rw [hh16v]
|
||
-- the digit write (both branches of the < 16 test)
|
||
step with (naf_update_spec naf pos win hposv hwle hwodd) as
|
||
⟨d, naf1, carry1, hset, hc1, hdval, hdodd, hdlo, hdhi, hcase⟩
|
||
-- pos1 ← pos + 5
|
||
step as ⟨pos1, hpos1⟩
|
||
have hpos1v : pos1.val = pos.val + 5 := by clear * - hpos1; scalar_tac
|
||
try simp only [spec_ok]
|
||
-- the digit facts at the written index and away from it
|
||
have holdz : nafDigit naf pos.val = 0 :=
|
||
hzero pos.val (le_refl _) hposv
|
||
have hsum1 : nafSum naf1 256 = nafSum naf 256 + d.val * 2^pos.val :=
|
||
nafSum_set naf naf1 pos.val d hposv holdz hset
|
||
have hdig1 : ∀ k, k < 256 → nafDigit naf1 k =
|
||
if k = pos.val then d.val else nafDigit naf k := by
|
||
intro k hk
|
||
by_cases h : k = pos.val
|
||
· subst h
|
||
rw [nafDigit_set_eq naf naf1 pos.val d hk hset, if_pos rfl]
|
||
· rw [nafDigit_set_ne naf naf1 pos.val d hset k hk h, if_neg h]
|
||
-- the window as a ℕ fact for the step lemmas
|
||
have hwcase : (carry.val + (V / 2^pos.val) % 32 < 16 ∧ carry1.val = 0) ∨
|
||
(16 ≤ carry.val + (V / 2^pos.val) % 32 ∧ carry1.val = 1) := by
|
||
rw [← hwinv]
|
||
exact hcase
|
||
apply ih naf1 pos1 carry1 (by clear * - hm hpos1v; omega) hc1
|
||
(fun h1 => by
|
||
have := naf_carry_odd V pos.val carry.val carry1.val hV hc hwcase h1
|
||
clear * - this hpos1v; omega)
|
||
(fun k hk1 hk2 => by
|
||
rw [hdig1 k hk2, if_neg (by clear * - hk1 hpos1v hposv; omega)]
|
||
exact hzero k (by clear * - hk1 hpos1v; omega) hk2)
|
||
(fun k hk => by
|
||
rw [hdig1 k hk]
|
||
by_cases h : k = pos.val
|
||
· rw [if_pos h]
|
||
exact ⟨Or.inr hdodd, hdlo, hdhi⟩
|
||
· rw [if_neg h]
|
||
exact hdig k hk)
|
||
(by rw [hpos1v, hsum1]
|
||
have hd' : (d.val : ℤ) = (carry.val : ℤ) +
|
||
((V / 2^pos.val) % 32 : ℕ) - 32 * carry1.val := by
|
||
rw [hdval, hwinv]
|
||
push_cast
|
||
ring
|
||
exact naf_odd_step V pos.val carry.val carry1.val _ d.val hinv hd')
|
||
|
||
|
||
end CurveFieldProofs
|