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mrwulf
6fe31be80d
Transpile the Scalar52 limb backend (backend::serial::u64::scalar
add/sub/mul/square/montgomery_*) from Rust to Lean via Charon/Aeneas,
scoped at the function level to the iterator-free arithmetic core.
- verification/extract-scalar.sh: function-level Charon/Aeneas extraction.
This fork (v4.1.3) inlines a local `black_box` (a volatile read used as an
optimization barrier) inside Scalar52::sub; charon cannot translate the
`&raw const` it lowers to, so it is marked --opaque and modeled below.
- verification/gen/CurveScalar/{Types,Funs}.lean: transpiled model (27 defs)
- verification/gen/CurveScalar/FunsExternal.lean: hand-written model of
Scalar52::sub::black_box as the identity on u64 (a volatile read returns
the value written; the qualifier is only an optimization barrier).
TypesExternal.lean is decl-free — this fork pulls in no external types
(unlike v5 dalek, which routes sub through subtle::Choice).
- verification/Proofs/ScalarDenote.lean: semantic foundation — Scalar52
denotation into ℤ/ℓℤ, limb-bound invariant, and L_val (the transpiled
constants::L denotes exactly the group order ℓ, kernel-checked).
- verification/check-scalar.sh: guarded compile of the gen modules plus the
denotation foundation.
check-scalar.sh passes: gen compiles; denotation + L = ℓ proven.
add/sub/mul remain in progress.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
28 lines
1.4 KiB
Text
28 lines
1.4 KiB
Text
-- Hand-written external function models for the Scalar52 arithmetic extraction.
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-- This fork (curve25519-dalek v4.1.3) implements Scalar52::sub's constant-time
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-- conditional add directly with a local `black_box` optimization barrier rather
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-- than routing through subtle::ConditionallySelectable (as the v5 dalek does).
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-- The sole external item is that `black_box`.
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import Aeneas
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import CurveScalar.Types
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open Aeneas Aeneas.Std Result ControlFlow Error
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set_option linter.dupNamespace false
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set_option linter.hashCommand false
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set_option linter.unusedVariables false
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set_option maxHeartbeats 1000000
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set_option maxRecDepth 2048
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open curve25519_dalek
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/-- [curve25519_dalek::backend::serial::u64::scalar::{curve25519_dalek::backend::serial::u64::scalar::Scalar52}::sub::black_box]:
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Source: 'curve25519-dalek/src/backend/serial/u64/scalar.rs', lines 179:8-183:9
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MODEL (faithful): the Rust body is
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`unsafe { core::ptr::read_volatile(&value) }`
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— a volatile read of the `u64` `value` living on the stack. The `volatile`
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qualifier only forbids the compiler from eliding/reordering the read (an
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optimization barrier to keep the constant-time path branch-free); the VALUE
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read back is exactly the value written, so semantically this is the identity
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on `u64`. -/
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def backend.serial.u64.scalar.Scalar52.sub.black_box
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(value : Std.U64) : Result Std.U64 :=
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ok value
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