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https://github.com/saymrwulf/risc0-ed25519-verified.git
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29 lines
1.4 KiB
Text
29 lines
1.4 KiB
Text
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-- 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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