mirror of
https://github.com/saymrwulf/curve25519-dalek-source.git
synced 2026-09-04 20:24:10 +00:00
make diff_sum maskable
This commit is contained in:
Henry de Valence
parent
89753e7274
commit
80813e81b1
2 changed files with 68 additions and 85 deletions
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@ -229,7 +229,7 @@ impl<'a, 'b> Add<&'b ExtendedPoint> for &'a ExtendedPoint {
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}
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// set t0 = (Y1-X1 Y1+X1 Y2-X2 Y2+X2) = (S0 S1 S2 S3)
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t0.diff_sum();
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t0.diff_sum(0xff);
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// set t1 = (S0 S1 Z1 T1)
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// set t0 = (S2 S3 Z2 T2)
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@ -250,7 +250,7 @@ impl<'a, 'b> Add<&'b ExtendedPoint> for &'a ExtendedPoint {
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t2.swap_CD();
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// set t2 = (S9-S8 S9+S8 S10+S11 S10-S11) = (S12 S13 S15 S14)
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t2.diff_sum();
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t2.diff_sum(0xff);
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let c0 = u32x8::new(0,4,2,6,4,0,6,2); // (ABCD) -> (ACCA)
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let c1 = u32x8::new(5,1,7,3,5,1,7,3); // (ABCD) -> (DBDB)
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@ -19,13 +19,15 @@ use stdsimd::simd::{u32x8, i32x8, u64x4};
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use backend::u64::field::FieldElement64;
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pub(crate) static P_TIMES_2: FieldElement32x4 = FieldElement32x4([
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u32x8::new(134217690, 134217690, 67108862, 67108862, 134217690, 134217690, 67108862, 67108862),
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u32x8::new(134217726, 134217726, 67108862, 67108862, 134217726, 134217726, 67108862, 67108862),
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u32x8::new(134217726, 134217726, 67108862, 67108862, 134217726, 134217726, 67108862, 67108862),
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u32x8::new(134217726, 134217726, 67108862, 67108862, 134217726, 134217726, 67108862, 67108862),
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u32x8::new(134217726, 134217726, 67108862, 67108862, 134217726, 134217726, 67108862, 67108862)
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]);
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pub(crate) static P_TIMES_2_LO: u32x8 =
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u32x8::new(67108845 << 1, 67108845 << 1, 33554431 << 1, 33554431 << 1, 67108845 << 1, 67108845 << 1, 33554431 << 1, 33554431 << 1);
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pub(crate) static P_TIMES_2_HI: u32x8 =
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u32x8::new(67108863 << 1, 67108863 << 1, 33554431 << 1, 33554431 << 1, 67108863 << 1, 67108863 << 1, 33554431 << 1, 33554431 << 1);
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pub(crate) static P_TIMES_16_LO: u32x8 =
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u32x8::new(67108845 << 4, 67108845 << 4, 33554431 << 4, 33554431 << 4, 67108845 << 4, 67108845 << 4, 33554431 << 4, 33554431 << 4);
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pub(crate) static P_TIMES_16_HI: u32x8 =
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u32x8::new(67108863 << 4, 67108863 << 4, 33554431 << 4, 33554431 << 4, 67108863 << 4, 67108863 << 4, 33554431 << 4, 33554431 << 4);
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pub(crate) static P_TIMES_2_MASKED: FieldElement32x4 = FieldElement32x4([
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u32x8::new( 0, 134217690, 0, 67108862, 134217690, 0, 67108862, 0),
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@ -112,12 +114,14 @@ impl FieldElement32x4 {
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/// Negate variables in lanes where mask is set
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/// XXX fix up api
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pub fn mask_negate(&mut self, mask: u8) {
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let mask = mask as i32;
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unsafe {
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use stdsimd::vendor::_mm256_blend_epi32;
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for i in 0..5 {
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let negated = P_TIMES_2.0[i] - self.0[i];
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self.0[i] = _mm256_blend_epi32(self.0[i].into(), negated.into(), mask as i32).into();
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}
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self.0[0] = _mm256_blend_epi32(self.0[0].into(), (P_TIMES_16_LO - self.0[0]).into(), mask).into();
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self.0[1] = _mm256_blend_epi32(self.0[1].into(), (P_TIMES_16_HI - self.0[1]).into(), mask).into();
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self.0[2] = _mm256_blend_epi32(self.0[2].into(), (P_TIMES_16_HI - self.0[2]).into(), mask).into();
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self.0[3] = _mm256_blend_epi32(self.0[3].into(), (P_TIMES_16_HI - self.0[3]).into(), mask).into();
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self.0[4] = _mm256_blend_epi32(self.0[4].into(), (P_TIMES_16_HI - self.0[4]).into(), mask).into();
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}
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self.reduce32();
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}
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@ -134,78 +138,47 @@ impl FieldElement32x4 {
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}
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}
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/// Given `self = (A,B,C,D)`, set `self = (B - A, B + A, D - C, D + C)`.
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pub fn diff_sum(&mut self) {
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/// (v0 v1 v2 v3 v4 v5 v6 v7) -> (v1 v0 v3 v2 v5 v4 v7 v6)
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#[inline(always)]
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fn alternate_32bit_lanes(v: u32x8) -> u32x8 {
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unsafe {
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use stdsimd::vendor::_mm256_shuffle_epi32;
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_mm256_shuffle_epi32(v.as_i32x8(), 0b10_11_00_01).as_u32x8()
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}
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/// Given `self = (A,B,C,D)`, set `self = (B - A, B + A, D - C, D + C)` according to `mask`.
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pub fn diff_sum(&mut self, mask: u8) {
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let mask = mask as i32;
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unsafe {
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use stdsimd::vendor::{_mm256_shuffle_epi32, _mm256_blend_epi32};
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let x01 = self.0[0];
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let x01_shuf = _mm256_shuffle_epi32(x01.as_i32x8(), 0b10_11_00_01).as_u32x8();
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let v1 = (x01_shuf + P_TIMES_2_LO) - x01;
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let v2 = x01_shuf + x01;
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let diffsum01 = _mm256_blend_epi32(v1.into(), v2.into(), 0b10101010).as_u32x8();
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self.0[0] = _mm256_blend_epi32(x01.into(), diffsum01.into(), mask).into();
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let x23 = self.0[1];
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let x23_shuf = _mm256_shuffle_epi32(x23.as_i32x8(), 0b10_11_00_01).as_u32x8();
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let v1 = (x23_shuf + P_TIMES_2_HI) - x23;
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let v2 = x23_shuf + x23;
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let diffsum23 = _mm256_blend_epi32(v1.into(), v2.into(), 0b10101010).as_u32x8();
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self.0[1] = _mm256_blend_epi32(x23.into(), diffsum23.into(), mask).into();
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let x45 = self.0[2];
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let x45_shuf = _mm256_shuffle_epi32(x45.as_i32x8(), 0b10_11_00_01).as_u32x8();
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let v1 = (x45_shuf + P_TIMES_2_HI) - x45;
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let v2 = x45_shuf + x45;
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let diffsum45 = _mm256_blend_epi32(v1.into(), v2.into(), 0b10101010).as_u32x8();
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self.0[2] = _mm256_blend_epi32(x45.into(), diffsum45.into(), mask).into();
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let x67 = self.0[3];
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let x67_shuf = _mm256_shuffle_epi32(x67.as_i32x8(), 0b10_11_00_01).as_u32x8();
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let v1 = (x67_shuf + P_TIMES_2_HI) - x67;
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let v2 = x67_shuf + x67;
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let diffsum67 = _mm256_blend_epi32(v1.into(), v2.into(), 0b10101010).as_u32x8();
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self.0[3] = _mm256_blend_epi32(x67.into(), diffsum67.into(), mask).into();
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let x89 = self.0[4];
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let x89_shuf = _mm256_shuffle_epi32(x89.as_i32x8(), 0b10_11_00_01).as_u32x8();
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let v1 = (x89_shuf + P_TIMES_2_HI) - x89;
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let v2 = x89_shuf + x89;
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let diffsum89 = _mm256_blend_epi32(v1.into(), v2.into(), 0b10101010).as_u32x8();
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self.0[4] = _mm256_blend_epi32(x89.into(), diffsum89.into(), mask).into();
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}
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/// (v0 XX v2 XX v4 XX v6 XX)
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/// (XX v1 XX v3 XX v5 XX v7) -> (v0 v1 v2 v3 v4 v5 v6 v7)
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#[inline(always)]
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fn blend_alternating_32bit_lanes(v1: u32x8, v2: u32x8) -> u32x8 {
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unsafe {
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use stdsimd::vendor::_mm256_blend_epi32;
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_mm256_blend_epi32(v1.into(), v2.into(), 0b10101010).as_u32x8()
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}
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}
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for i in 0..5 {
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let x = self.0[i];
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let p = P_TIMES_2.0[i] ;
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let x_shuf = alternate_32bit_lanes(x);
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let diff = (x_shuf + p) - x;
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let sum = x + x_shuf;
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let diff_sum = blend_alternating_32bit_lanes(diff, sum);
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self.0[i] = diff_sum;
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}
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}
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// Given `self = (A,B,C,D)`, compute `(B + A, B - A, D + C, D - C)`.
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pub fn sum_diff(&self) -> FieldElement32x4 {
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/// (v0 v1 v2 v3 v4 v5 v6 v7) -> (v1 v0 v3 v2 v5 v4 v7 v6)
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#[inline(always)]
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#[allow(dead_code)] // XXX
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fn alternate_32bit_lanes(v: u32x8) -> u32x8 {
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unsafe {
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use stdsimd::vendor::_mm256_shuffle_epi32;
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_mm256_shuffle_epi32(v.as_i32x8(), 0b10_11_00_01).as_u32x8()
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}
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}
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/// (v0 XX v2 XX v4 XX v6 XX)
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/// (XX v1 XX v3 XX v5 XX v7) -> (v0 v1 v2 v3 v4 v5 v6 v7)
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#[inline(always)]
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#[allow(dead_code)] // XXX
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fn blend_alternating_32bit_lanes(v1: u32x8, v2: u32x8) -> u32x8 {
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unsafe {
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use stdsimd::vendor::_mm256_blend_epi32;
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_mm256_blend_epi32(v1.into(), v2.into(), 0b10101010).as_u32x8()
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}
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}
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let mut out = [u32x8::splat(0); 5];
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for i in 0..5 {
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let x = self.0[i];
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let p = P_TIMES_2.0[i];
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let x_shuf = alternate_32bit_lanes(x);
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let sum = x + x_shuf;
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let diff = (x + p) - x_shuf;
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let sum_diff = blend_alternating_32bit_lanes(sum, diff);
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out[i] = sum_diff;
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}
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FieldElement32x4(out)
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}
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/// Let `self` \\(= (A, B, C, D) \\).
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@ -590,7 +563,7 @@ mod test {
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let x3 = FieldElement64([10300, 10301, 10302, 10303, 10304]);
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let mut vec = FieldElement32x4::new(&x0, &x1, &x2, &x3);
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vec.diff_sum();
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vec.diff_sum(0xff);
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let result = vec.split();
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@ -598,6 +571,16 @@ mod test {
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assert_eq!(result[1], &x1 + &x0);
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assert_eq!(result[2], &x3 - &x2);
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assert_eq!(result[3], &x3 + &x2);
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let mut vec = FieldElement32x4::new(&x0, &x1, &x2, &x3);
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vec.diff_sum(0b01011111); // leave D unchanged
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let result = vec.split();
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assert_eq!(result[0], &x1 - &x0);
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assert_eq!(result[1], &x1 + &x0);
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assert_eq!(result[2], &x3 - &x2);
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assert_eq!(result[3], x3);
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}
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#[test]
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