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Push last bit of Point functionality into impls. (I hope.)

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This commit is contained in:
Adam Wick
2019-05-26 16:06:37 -07:00
parent 7f2b509640
commit 4ce8797da2
4 changed files with 124 additions and 120 deletions
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40
src/ed25519/constants.rs
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@@ -10,7 +10,7 @@ pub struct Precomp {
impl Precomp
{
pub fn new() -> Precomp
fn new() -> Precomp
{
Precomp {
yplusx: FieldElement::new(),
@@ -44,8 +44,46 @@ impl Precomp
self.yminusx.cmov(&u.yminusx, b);
self.xy2d.cmov(&u.xy2d, b);
}
pub fn table_select(pos: i32, b: i8) -> Precomp
{
let mut minust = Precomp::new();
let mut res = Precomp::zero();
let bnegative = negative(b);
let babs = b - (((-(bnegative as i8)) & b) << 1);
res.cmov(&K25519_PRECOMP[pos as usize][0], equal(babs, 1));
res.cmov(&K25519_PRECOMP[pos as usize][1], equal(babs, 2));
res.cmov(&K25519_PRECOMP[pos as usize][2], equal(babs, 3));
res.cmov(&K25519_PRECOMP[pos as usize][3], equal(babs, 4));
res.cmov(&K25519_PRECOMP[pos as usize][4], equal(babs, 5));
res.cmov(&K25519_PRECOMP[pos as usize][5], equal(babs, 6));
res.cmov(&K25519_PRECOMP[pos as usize][6], equal(babs, 7));
res.cmov(&K25519_PRECOMP[pos as usize][7], equal(babs, 8));
minust.yplusx.overwrite_with(&res.yminusx);
minust.yminusx.overwrite_with(&res.yplusx);
minust.xy2d = -&res.xy2d;
res.cmov(&minust, bnegative != 0);
res
}
}
fn equal(b: i8, c: i8) -> bool
{
let ub = b;
let uc = c;
let x = ub ^ uc; /* 0: yes; 1..255: no */
(x == 0)
}
fn negative(b: i8) -> u8
{
let mut x = b as u32;
x >>= 31; /* 1: yes; 0: no */
x as u8
}
/* k25519Precomp[i][j] = (j+1)*256^i*B */
pub const K25519_PRECOMP: [[Precomp; 8]; 32] = [
[

2
src/ed25519/mod.rs
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@@ -149,7 +149,7 @@ impl ED25519Public {
a.invert();
let h_digest = eddsa_digest(signature_r, &self.public, msg);
let h = digest_scalar(&h_digest);
let r = ge_double_scalarmult_vartime(&h, &a, &signature_s);
let r = Point2::double_scalarmult_vartime(&h, &a, &signature_s);
let r_check = r.encode();
signature_r.to_vec() == r_check
}

194
src/ed25519/point.rs
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@@ -488,43 +488,6 @@ fn addsub() {
});
}
fn equal(b: i8, c: i8) -> bool
{
let ub = b;
let uc = c;
let x = ub ^ uc; /* 0: yes; 1..255: no */
(x == 0)
}
fn negative(b: i8) -> u8
{
let mut x = b as u32;
x >>= 31; /* 1: yes; 0: no */
x as u8
}
fn table_select(pos: i32, b: i8) -> Precomp
{
let mut minust = Precomp::new();
let mut res = Precomp::zero();
let bnegative = negative(b);
let babs = b - (((-(bnegative as i8)) & b) << 1);
res.cmov(&K25519_PRECOMP[pos as usize][0], equal(babs, 1));
res.cmov(&K25519_PRECOMP[pos as usize][1], equal(babs, 2));
res.cmov(&K25519_PRECOMP[pos as usize][2], equal(babs, 3));
res.cmov(&K25519_PRECOMP[pos as usize][3], equal(babs, 4));
res.cmov(&K25519_PRECOMP[pos as usize][4], equal(babs, 5));
res.cmov(&K25519_PRECOMP[pos as usize][5], equal(babs, 6));
res.cmov(&K25519_PRECOMP[pos as usize][6], equal(babs, 7));
res.cmov(&K25519_PRECOMP[pos as usize][7], equal(babs, 8));
minust.yplusx.overwrite_with(&res.yminusx);
minust.yminusx.overwrite_with(&res.yplusx);
minust.xy2d = -&res.xy2d;
res.cmov(&minust, bnegative != 0);
res
}
impl Point {
/* h = a * B
* where a = a[0]+256*a[1]+...+256^31 a[31]
@@ -557,7 +520,7 @@ impl Point {
let mut h = Point::zero();
for i in &[1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47,49,51,53,55,57,59,61,63] {
t = table_select(*i / 2, e[*i as usize]);
t = Precomp::table_select(*i / 2, e[*i as usize]);
r = &h + &t;
h = Point::from(&r);
}
@@ -572,7 +535,7 @@ impl Point {
h = Point::from(&r);
for i in &[0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,60,62] {
t = table_select(*i / 2, e[*i as usize]);
t = Precomp::table_select(*i / 2, e[*i as usize]);
r = &h + &t;
h = Point::from(&r);
}
@@ -646,89 +609,92 @@ fn helper_slide() {
});
}
/* r = a * A + b * B
* where a = a[0]+256*a[1]+...+256^31 a[31].
* and b = b[0]+256*b[1]+...+256^31 b[31].
* B is the Ed25519 base point (x,4/5) with x positive. */
#[allow(non_snake_case)]
pub fn ge_double_scalarmult_vartime(a: &[u8], A: &Point, b: &[u8]) -> Point2
impl Point2
{
let mut aslide: [i8; 256] = [0; 256];
let mut bslide: [i8; 256] = [0; 256];
#[allow(non_snake_case)]
let mut Ai: [Cached; 8] = [Cached::new(), Cached::new(), Cached::new(), Cached::new(),
Cached::new(), Cached::new(), Cached::new(), Cached::new()];
/* r = a * A + b * B
* where a = a[0]+256*a[1]+...+256^31 a[31].
* and b = b[0]+256*b[1]+...+256^31 b[31].
* B is the Ed25519 base point (x,4/5) with x positive. */
#[allow(non_snake_case)]
pub fn double_scalarmult_vartime(a: &[u8], A: &Point, b: &[u8]) -> Point2
{
let mut aslide: [i8; 256] = [0; 256];
let mut bslide: [i8; 256] = [0; 256];
#[allow(non_snake_case)]
let mut Ai: [Cached; 8] = [Cached::new(), Cached::new(), Cached::new(), Cached::new(),
Cached::new(), Cached::new(), Cached::new(), Cached::new()];
#[allow(non_snake_case)]
slide(&mut aslide, &a);
slide(&mut bslide, &b);
slide(&mut aslide, &a);
slide(&mut bslide, &b);
Ai[0] = Cached::from(A);
let mut t = A.double();
let A2 = Point::from(&t);
t = &A2 + &Ai[0];
let mut u = Point::from(&t);
Ai[1] = Cached::from(&u);
t = &A2 + &Ai[1];
u = Point::from(&t);
Ai[2] = Cached::from(&u);
t = &A2 + &Ai[2];
u = Point::from(&t);
Ai[3] = Cached::from(&u);
t = &A2 + &Ai[3];
u = Point::from(&t);
Ai[4] = Cached::from(&u);
t = &A2 + &Ai[4];
u = Point::from(&t);
Ai[5] = Cached::from(&u);
t = &A2 + &Ai[5];
u = Point::from(&t);
Ai[6] = Cached::from(&u);
t = &A2 + &Ai[6];
u = Point::from(&t);
Ai[7] = Cached::from(&u);
Ai[0] = Cached::from(A);
let mut t = A.double();
let A2 = Point::from(&t);
t = &A2 + &Ai[0];
let mut u = Point::from(&t);
Ai[1] = Cached::from(&u);
t = &A2 + &Ai[1];
u = Point::from(&t);
Ai[2] = Cached::from(&u);
t = &A2 + &Ai[2];
u = Point::from(&t);
Ai[3] = Cached::from(&u);
t = &A2 + &Ai[3];
u = Point::from(&t);
Ai[4] = Cached::from(&u);
t = &A2 + &Ai[4];
u = Point::from(&t);
Ai[5] = Cached::from(&u);
t = &A2 + &Ai[5];
u = Point::from(&t);
Ai[6] = Cached::from(&u);
t = &A2 + &Ai[6];
u = Point::from(&t);
Ai[7] = Cached::from(&u);
let mut r = Point2::zero();
let mut r = Point2::zero();
let mut i: i32 = 255;
loop {
if (aslide[i as usize] != 0) || (bslide[i as usize] != 0) {
break;
let mut i: i32 = 255;
loop {
if (aslide[i as usize] != 0) || (bslide[i as usize] != 0) {
break;
}
i -= 1;
if i < 0 {
break;
}
}
i -= 1;
if i < 0 {
break;
while i >= 0 {
t = r.double();
if aslide[i as usize] > 0 {
u = Point::from(&t);
let idx = (aslide[i as usize] / 2) as usize;
t = &u + &Ai[idx]
} else if aslide[i as usize] < 0 {
u = Point::from(&t);
let idx = ((-aslide[i as usize]) / 2) as usize;
t = &u - &Ai[idx];
}
if bslide[i as usize] > 0 {
u = Point::from(&t);
let idx = (bslide[i as usize] / 2) as usize;
t = &u + &BI[idx];
} else if bslide[i as usize] < 0 {
u = Point::from(&t);
let idx = ((-bslide[i as usize]) / 2) as usize;
t = &u - &BI[idx];
}
r = Point2::from(&t);
i -= 1;
}
r
}
while i >= 0 {
t = r.double();
if aslide[i as usize] > 0 {
u = Point::from(&t);
let idx = (aslide[i as usize] / 2) as usize;
t = &u + &Ai[idx]
} else if aslide[i as usize] < 0 {
u = Point::from(&t);
let idx = ((-aslide[i as usize]) / 2) as usize;
t = &u - &Ai[idx];
}
if bslide[i as usize] > 0 {
u = Point::from(&t);
let idx = (bslide[i as usize] / 2) as usize;
t = &u + &BI[idx];
} else if bslide[i as usize] < 0 {
u = Point::from(&t);
let idx = ((-bslide[i as usize]) / 2) as usize;
t = &u - &BI[idx];
}
r = Point2::from(&t);
i -= 1;
}
r
}
#[cfg(test)]
@@ -744,7 +710,7 @@ fn double_scalarmult() {
assert!(!nega && !negb && !negc && !negd);
let b = Point::load_test_value(bbytes);
let d = Point2::load_test_value(dbytes);
let mine = ge_double_scalarmult_vartime(&abytes, &b, &cbytes);
let mine = Point2::double_scalarmult_vartime(&abytes, &b, &cbytes);
assert_eq!(mine, d);
});
}

0
src/ed25519/scalars.rs Normal file
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