mirror of
https://github.com/saymrwulf/curve25519-dalek-source.git
synced 2026-09-06 20:41:14 +00:00
f1d2b5182b
This begins to attempt to restructure the source tree so that the common parts are common and the different parts are different. The backend is now split into two parts: - serial (containing the implementation using serial formulas and mixed-model arithmetic). - vector (containing the implementation using parallel formulas and single-model arithmetic). The serial scalar_mul tree is now under backend::serial::scalar_mul. The avx2 scalar_mul tree is now under backend::avx2::scalar_mul.
60 lines
1.5 KiB
Rust
60 lines
1.5 KiB
Rust
// -*- mode: rust; -*-
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//
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// This file is part of curve25519-dalek.
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// Copyright (c) 2016-2018 Isis Lovecruft, Henry de Valence
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// See LICENSE for licensing information.
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//
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// Authors:
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// - Isis Agora Lovecruft <isis@patternsinthevoid.net>
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// - Henry de Valence <hdevalence@hdevalence.ca>
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#![allow(non_snake_case)]
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use backend::vector::BASEPOINT_ODD_LOOKUP_TABLE;
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use backend::vector::{CachedPoint, ExtendedPoint};
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use edwards::EdwardsPoint;
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use scalar::Scalar;
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use traits::Identity;
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use window::NafLookupTable5;
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/// Compute \\(aA + bB\\) in variable time, where \\(B\\) is the Ed25519 basepoint.
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pub fn mul(a: &Scalar, A: &EdwardsPoint, b: &Scalar) -> EdwardsPoint {
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let a_naf = a.non_adjacent_form(5);
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let b_naf = b.non_adjacent_form(8);
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// Find starting index
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let mut i: usize = 255;
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for j in (0..255).rev() {
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i = j;
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if a_naf[i] != 0 || b_naf[i] != 0 {
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break;
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}
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}
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let table_A = NafLookupTable5::<CachedPoint>::from(A);
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let table_B = &BASEPOINT_ODD_LOOKUP_TABLE;
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let mut Q = ExtendedPoint::identity();
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loop {
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Q = Q.double();
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if a_naf[i] > 0 {
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Q = &Q + &table_A.select(a_naf[i] as usize);
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} else if a_naf[i] < 0 {
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Q = &Q - &table_A.select(-a_naf[i] as usize);
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}
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if b_naf[i] > 0 {
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Q = &Q + &table_B.select(b_naf[i] as usize);
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} else if b_naf[i] < 0 {
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Q = &Q - &table_B.select(-b_naf[i] as usize);
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}
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if i == 0 {
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break;
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}
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i -= 1;
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}
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Q.into()
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}
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