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Move fe_frombytes into FieldElement.

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This commit is contained in:
Adam Wick
2019-05-20 21:17:53 -07:00
parent b42902e6ab
commit 8bca480e47
2 changed files with 62 additions and 70 deletions
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81
src/ed25519/fe.rs
View File

@@ -45,6 +45,37 @@ impl FieldElement
{ {
self.value.copy_from_slice(&other.value); self.value.copy_from_slice(&other.value);
} }
pub fn from_bytes(s: &[u8]) -> FieldElement
{
/* Ignores top bit of h. */
let mut h0 = load4(s) as i64;
let mut h1 = (load3(&s[4..]) << 6) as i64;
let mut h2 = (load3(&s[7..]) << 5) as i64;
let mut h3 = (load3(&s[10..]) << 3) as i64;
let mut h4 = (load3(&s[13..]) << 2) as i64;
let mut h5 = load4(&s[16..]) as i64;
let mut h6 = (load3(&s[20..]) << 7) as i64;
let mut h7 = (load3(&s[23..]) << 5) as i64;
let mut h8 = (load3(&s[26..]) << 4) as i64;
let mut h9 = ((load3(&s[29..]) & 8388607) << 2) as i64;
let carry9 = h9 + (1 << 24); h0 += (carry9 >> 25) * 19; h9 -= carry9 & KTOP_39BITS;
let carry1 = h1 + (1 << 24); h2 += carry1 >> 25; h1 -= carry1 & KTOP_39BITS;
let carry3 = h3 + (1 << 24); h4 += carry3 >> 25; h3 -= carry3 & KTOP_39BITS;
let carry5 = h5 + (1 << 24); h6 += carry5 >> 25; h5 -= carry5 & KTOP_39BITS;
let carry7 = h7 + (1 << 24); h8 += carry7 >> 25; h7 -= carry7 & KTOP_39BITS;
let carry0 = h0 + (1 << 25); h1 += carry0 >> 26; h0 -= carry0 & KTOP_38BITS;
let carry2 = h2 + (1 << 25); h3 += carry2 >> 26; h2 -= carry2 & KTOP_38BITS;
let carry4 = h4 + (1 << 25); h5 += carry4 >> 26; h4 -= carry4 & KTOP_38BITS;
let carry6 = h6 + (1 << 25); h7 += carry6 >> 26; h6 -= carry6 & KTOP_38BITS;
let carry8 = h8 + (1 << 25); h9 += carry8 >> 26; h8 -= carry8 & KTOP_38BITS;
FieldElement{ value: [h0 as i32, h1 as i32, h2 as i32, h3 as i32,
h4 as i32, h5 as i32, h6 as i32, h7 as i32,
h8 as i32, h9 as i32] }
}
} }
pub const KBOTTOM_25BITS : i64 = 0x1ffffffi64; pub const KBOTTOM_25BITS : i64 = 0x1ffffffi64;
@@ -80,44 +111,6 @@ fn loads() {
}); });
} }
pub fn fe_frombytes(h: &mut FieldElement, s: &[u8])
{
/* Ignores top bit of h. */
let mut h0 = load4(s) as i64;
let mut h1 = (load3(&s[4..]) << 6) as i64;
let mut h2 = (load3(&s[7..]) << 5) as i64;
let mut h3 = (load3(&s[10..]) << 3) as i64;
let mut h4 = (load3(&s[13..]) << 2) as i64;
let mut h5 = load4(&s[16..]) as i64;
let mut h6 = (load3(&s[20..]) << 7) as i64;
let mut h7 = (load3(&s[23..]) << 5) as i64;
let mut h8 = (load3(&s[26..]) << 4) as i64;
let mut h9 = ((load3(&s[29..]) & 8388607) << 2) as i64;
let carry9 = h9 + (1 << 24); h0 += (carry9 >> 25) * 19; h9 -= carry9 & KTOP_39BITS;
let carry1 = h1 + (1 << 24); h2 += carry1 >> 25; h1 -= carry1 & KTOP_39BITS;
let carry3 = h3 + (1 << 24); h4 += carry3 >> 25; h3 -= carry3 & KTOP_39BITS;
let carry5 = h5 + (1 << 24); h6 += carry5 >> 25; h5 -= carry5 & KTOP_39BITS;
let carry7 = h7 + (1 << 24); h8 += carry7 >> 25; h7 -= carry7 & KTOP_39BITS;
let carry0 = h0 + (1 << 25); h1 += carry0 >> 26; h0 -= carry0 & KTOP_38BITS;
let carry2 = h2 + (1 << 25); h3 += carry2 >> 26; h2 -= carry2 & KTOP_38BITS;
let carry4 = h4 + (1 << 25); h5 += carry4 >> 26; h4 -= carry4 & KTOP_38BITS;
let carry6 = h6 + (1 << 25); h7 += carry6 >> 26; h6 -= carry6 & KTOP_38BITS;
let carry8 = h8 + (1 << 25); h9 += carry8 >> 26; h8 -= carry8 & KTOP_38BITS;
h.value[0] = h0 as i32;
h.value[1] = h1 as i32;
h.value[2] = h2 as i32;
h.value[3] = h3 as i32;
h.value[4] = h4 as i32;
h.value[5] = h5 as i32;
h.value[6] = h6 as i32;
h.value[7] = h7 as i32;
h.value[8] = h8 as i32;
h.value[9] = h9 as i32;
}
pub fn fe_tobytes(s: &mut [u8], h: &FieldElement) pub fn fe_tobytes(s: &mut [u8], h: &FieldElement)
{ {
assert!(s.len() >= 32); assert!(s.len() >= 32);
@@ -206,9 +199,8 @@ fn from_to_bytes() {
let (negb, bbytes) = case.get("b").unwrap(); let (negb, bbytes) = case.get("b").unwrap();
assert!(!nega && !negb); assert!(!nega && !negb);
let mut e = FieldElement::new(); let e = FieldElement::from_bytes(abytes);
let mut target = FieldElement::new(); let mut target = FieldElement::new();
fe_frombytes(&mut e, abytes);
let mut cursor = Cursor::new(bbytes); let mut cursor = Cursor::new(bbytes);
cursor.read_i32_into::<NativeEndian>(&mut target.value).unwrap(); cursor.read_i32_into::<NativeEndian>(&mut target.value).unwrap();
assert_eq!(e, target, "from bytes"); assert_eq!(e, target, "from bytes");
@@ -231,9 +223,9 @@ impl Arbitrary for ValidFieldElement {
let mut bytes = [0; 32]; let mut bytes = [0; 32];
g.fill_bytes(&mut bytes); g.fill_bytes(&mut bytes);
curve25519_scalar_mask(&mut bytes); curve25519_scalar_mask(&mut bytes);
let mut res = ValidFieldElement{ values: FieldElement::new() }; ValidFieldElement{
fe_frombytes(&mut res.values, &bytes); values: FieldElement::from_bytes(&bytes)
res }
} }
} }
@@ -253,8 +245,7 @@ quickcheck! {
fn from_to_bytes_roundtrip(e: ValidFieldElement) -> bool { fn from_to_bytes_roundtrip(e: ValidFieldElement) -> bool {
let mut bytes = [0; 32]; let mut bytes = [0; 32];
fe_tobytes(&mut bytes, &e.values); fe_tobytes(&mut bytes, &e.values);
let mut trans = FieldElement::new(); let trans = FieldElement::from_bytes(&bytes);
fe_frombytes(&mut trans, &bytes);
trans == e.values trans == e.values
} }
} }

51
src/ed25519/point.rs
View File

@@ -39,7 +39,6 @@ impl Point {
/// statically timed, so don't use it if that's important to you. /// statically timed, so don't use it if that's important to you.
pub fn from_bytes(s: &[u8]) -> Option<Point> pub fn from_bytes(s: &[u8]) -> Option<Point>
{ {
let mut h = Point::new();
let mut u = FieldElement::new(); let mut u = FieldElement::new();
let mut v = FieldElement::new(); let mut v = FieldElement::new();
let mut v3 = FieldElement::new(); let mut v3 = FieldElement::new();
@@ -47,32 +46,33 @@ impl Point {
let mut check = FieldElement::new(); let mut check = FieldElement::new();
let mut temp; let mut temp;
fe_frombytes(&mut h.y, s); let hy = FieldElement::from_bytes(s);
h.z.overwrite_with(&FieldElement::one()); let hz = FieldElement::one();
fe_square(&mut u, &h.y); fe_square(&mut u, &hy);
fe_mul(&mut v, &u, &D); fe_mul(&mut v, &u, &D);
temp = u.clone(); temp = u.clone();
fe_sub(&mut u, &temp, &h.z); /* u = y^2-1 */ fe_sub(&mut u, &temp, &hz); /* u = y^2-1 */
temp = v.clone(); temp = v.clone();
fe_add(&mut v, &temp, &h.z); /* v = dy^2+1 */ fe_add(&mut v, &temp, &hz); /* v = dy^2+1 */
fe_square(&mut v3, &v); fe_square(&mut v3, &v);
temp = v3.clone(); temp = v3.clone();
fe_mul(&mut v3, &temp, &v); /* v3 = v^3 */ fe_mul(&mut v3, &temp, &v); /* v3 = v^3 */
fe_square(&mut h.x, &v3); let mut hx = FieldElement::zero();
temp = h.x.clone(); fe_square(&mut hx, &v3);
fe_mul(&mut h.x, &temp, &v); temp = hx.clone();
temp = h.x.clone(); fe_mul(&mut hx, &temp, &v);
fe_mul(&mut h.x, &temp, &u); /* x = uv^7 */ temp = hx.clone();
fe_mul(&mut hx, &temp, &u); /* x = uv^7 */
temp = h.x.clone(); temp = hx.clone();
fe_pow22523(&mut h.x, &temp); /* x = (uv^7)^((q-5)/8) */ fe_pow22523(&mut hx, &temp); /* x = (uv^7)^((q-5)/8) */
temp = h.x.clone(); temp = hx.clone();
fe_mul(&mut h.x, &temp, &v3); fe_mul(&mut hx, &temp, &v3);
temp = h.x.clone(); temp = hx.clone();
fe_mul(&mut h.x, &temp, &u); /* x = uv^3(uv^7)^((q-5)/8) */ fe_mul(&mut hx, &temp, &u); /* x = uv^3(uv^7)^((q-5)/8) */
fe_square(&mut vxx, &h.x); fe_square(&mut vxx, &hx);
temp = vxx.clone(); temp = vxx.clone();
fe_mul(&mut vxx, &temp, &v); fe_mul(&mut vxx, &temp, &v);
fe_sub(&mut check, &vxx, &u); /* vx^2-u */ fe_sub(&mut check, &vxx, &u); /* vx^2-u */
@@ -81,17 +81,18 @@ impl Point {
if fe_isnonzero(&check) { if fe_isnonzero(&check) {
return None; return None;
} }
temp = h.x.clone(); temp = hx.clone();
fe_mul(&mut h.x, &temp, &SQRTM1); fe_mul(&mut hx, &temp, &SQRTM1);
} }
if fe_isnegative(&h.x) != ((s[31] >> 7) == 1) { if fe_isnegative(&hx) != ((s[31] >> 7) == 1) {
temp = h.x.clone(); temp = hx.clone();
fe_neg(&mut h.x, &temp); fe_neg(&mut hx, &temp);
} }
fe_mul(&mut h.t, &h.x, &h.y); let mut ht = FieldElement::zero();
return Some(h); fe_mul(&mut ht, &hx, &hy);
return Some(Point{ x: hx, y: hy, z: hz, t: ht });
} }
pub fn encode_to(&self, target: &mut [u8]) pub fn encode_to(&self, target: &mut [u8])