mirror of
https://github.com/saymrwulf/curve25519-dalek-source.git
synced 2026-09-04 20:24:10 +00:00
Wrap the existing basepoint table as a BasepointTable
This commit is contained in:
Henry de Valence
parent
05fa1318b9
commit
640f40287f
2 changed files with 40 additions and 97 deletions
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@ -23,6 +23,7 @@ use field::FieldElement;
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use curve::ExtendedPoint;
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use curve::AffineNielsPoint;
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use curve::CompressedEdwardsY;
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use curve::BasepointTable;
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use scalar::Scalar;
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pub const d: FieldElement = FieldElement([
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@ -100,7 +101,7 @@ pub const BASE_CMPRSSD: CompressedEdwardsY =
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0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66]);
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/// Basepoint has y = 4/5.
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pub const BASEPOINT: ExtendedPoint = ExtendedPoint{
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pub const ED25519_BASEPOINT: ExtendedPoint = ExtendedPoint{
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X: FieldElement([-14297830, -7645148, 16144683, -16471763, 27570974, -2696100, -26142465, 8378389, 20764389, 8758491]),
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Y: FieldElement([-26843541, -6710886, 13421773, -13421773, 26843546, 6710886, -13421773, 13421773, -26843546, -6710886]),
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Z: FieldElement([1, 0, 0, 0, 0, 0, 0, 0, 0, 0]),
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@ -225,7 +226,7 @@ pub const bi: [AffineNielsPoint; 8] = [
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///
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/// The table is defined so `constants::base[i][j-1] = j*(16^2i)*B`,
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/// for `0 ≤ i < 32`, `1 ≤ j < 9`.
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pub const base: [[AffineNielsPoint; 8]; 32] = [
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pub const ED25519_BASEPOINT_TABLE: BasepointTable = BasepointTable([
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[
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AffineNielsPoint{
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y_plus_x: FieldElement([25967493, -14356035, 29566456, 3660896, -12694345, 4014787, 27544626, -11754271, -6079156, 2047605]),
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@ -1569,7 +1570,7 @@ pub const base: [[AffineNielsPoint; 8]; 32] = [
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y_minus_x: FieldElement([29701166, -14373934, -10878120, 9279288, -17568, 13127210, 21382910, 11042292, 25838796, 4642684]),
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xy2d: FieldElement([-20430234, 14955537, -24126347, 8124619, -5369288, -5990470, 30468147, -13900640, 18423289, 4177476]),
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},
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]];
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]]);
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#[cfg(test)]
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mod test {
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@ -1670,23 +1671,4 @@ mod test {
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let a_minus_d = &a - &constants::d;
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assert_eq!(a_minus_d, constants::a_minus_d);
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}
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/// Test the values in the lookup table of precomputed multiples
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/// of the basepoint.
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#[test]
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fn test_precomputed_basepoint_multiples() {
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let bp = constants::BASE_CMPRSSD.decompress().unwrap();
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let mut P = bp;
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for i in 0..32 {
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// P = (16^2)^i * B
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let mut jP = P.to_affine_niels();
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for j in 1..9 {
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// constants::base[i][j-1] is supposed to be
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// j * (16^2)^i * B
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assert_eq!(constants::base[i][j-1], jP);
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jP = (&P + &jP).to_extended().to_affine_niels();
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}
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P = P.mult_by_pow_2(8);
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}
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}
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}
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111
src/curve.rs
111
src/curve.rs
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@ -912,52 +912,11 @@ pub trait BasepointMult<S> {
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impl BasepointMult<Scalar> for ExtendedPoint {
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fn basepoint() -> ExtendedPoint {
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constants::BASEPOINT
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constants::ED25519_BASEPOINT
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}
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/// Construct an `ExtendedPoint` from a `Scalar`, `scalar`, by
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/// computing the multiple `aB` of the basepoint `B`.
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///
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/// Precondition: the scalar must be reduced.
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///
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/// The computation proceeds as follows, as described on page 13
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/// of the Ed25519 paper. Write the scalar `a` in radix 16 with
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/// coefficients in [-8,8), i.e.,
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///
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/// a = a_0 + a_1*16^1 + ... + a_63*16^63,
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///
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/// with -8 ≤ a_i < 8. Then
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///
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/// a*B = a_0*B + a_1*16^1*B + ... + a_63*16^63*B.
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///
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/// Grouping even and odd coefficients gives
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///
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/// a*B = a_0*16^0*B + a_2*16^2*B + ... + a_62*16^62*B
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/// + a_1*16^1*B + a_3*16^3*B + ... + a_63*16^63*B
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/// = (a_0*16^0*B + a_2*16^2*B + ... + a_62*16^62*B)
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/// + 16*(a_1*16^0*B + a_3*16^2*B + ... + a_63*16^62*B).
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///
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/// We then use the `select_precomputed_point` function, which
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/// takes `-8 ≤ x < 8` and `[16^2i * B, ..., 8 * 16^2i * B]`,
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/// and returns `x * 16^2i * B` in constant time.
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fn basepoint_mult(scalar: &Scalar) -> ExtendedPoint { //GeScalarMultBase
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let e = scalar.to_radix_16();
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let mut h = ExtendedPoint::identity();
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let mut t: CompletedPoint;
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for i in (0..64).filter(|x| x % 2 == 1) {
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t = &h + &select_precomputed_point(e[i], &constants::base[i/2]);
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h = t.to_extended();
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}
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h = h.mult_by_pow_2(4);
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for i in (0..64).filter(|x| x % 2 == 0) {
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t = &h + &select_precomputed_point(e[i], &constants::base[i/2]);
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h = t.to_extended();
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}
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h
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fn basepoint_mult(scalar: &Scalar) -> ExtendedPoint {
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constants::ED25519_BASEPOINT_TABLE.basepoint_mult(scalar)
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}
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}
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@ -1222,7 +1181,7 @@ mod test {
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/// Test Montgomery conversion against the X25519 basepoint.
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#[test]
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fn basepoint_to_montgomery() {
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assert_eq!(constants::BASEPOINT.compress_montgomery().unwrap(),
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assert_eq!(constants::ED25519_BASEPOINT.compress_montgomery().unwrap(),
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BASE_CMPRSSD_MONTY);
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}
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@ -1275,10 +1234,10 @@ mod test {
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.decompress().unwrap();
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// Test projective coordinates exactly since we know they should
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// only differ by a flipped sign.
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assert_eq!(minus_basepoint.X, -(&constants::BASEPOINT.X));
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assert_eq!(minus_basepoint.Y, constants::BASEPOINT.Y);
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assert_eq!(minus_basepoint.Z, constants::BASEPOINT.Z);
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assert_eq!(minus_basepoint.T, -(&constants::BASEPOINT.T));
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assert_eq!(minus_basepoint.X, -(&constants::ED25519_BASEPOINT.X));
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assert_eq!(minus_basepoint.Y, constants::ED25519_BASEPOINT.Y);
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assert_eq!(minus_basepoint.Z, constants::ED25519_BASEPOINT.Z);
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assert_eq!(minus_basepoint.T, -(&constants::ED25519_BASEPOINT.T));
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}
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/// Test that computing 1*basepoint gives the correct basepoint.
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@ -1293,7 +1252,7 @@ mod test {
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/// using basepoint + basepoint versus the 2*basepoint constant.
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#[test]
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fn basepoint_plus_basepoint_vs_basepoint2() {
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let bp = constants::BASEPOINT;
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let bp = constants::ED25519_BASEPOINT;
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let bp_added = &bp + &bp;
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assert_eq!(bp_added.compress_edwards(), BASE2_CMPRSSD);
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}
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@ -1302,7 +1261,7 @@ mod test {
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/// using the basepoint, basepoint2 constants
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#[test]
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fn basepoint_plus_basepoint_projective_niels_vs_basepoint2() {
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let bp = constants::BASEPOINT;
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let bp = constants::ED25519_BASEPOINT;
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let bp_added = (&bp + &bp.to_projective_niels()).to_extended();
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assert_eq!(bp_added.compress_edwards(), BASE2_CMPRSSD);
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}
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@ -1311,7 +1270,7 @@ mod test {
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/// using the basepoint, basepoint2 constants
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#[test]
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fn basepoint_plus_basepoint_affine_niels_vs_basepoint2() {
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let bp = constants::BASEPOINT;
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let bp = constants::ED25519_BASEPOINT;
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let bp_affine_niels = bp.to_affine_niels();
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let bp_added = (&bp + &bp_affine_niels).to_extended();
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assert_eq!(bp_added.compress_edwards(), BASE2_CMPRSSD);
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@ -1360,16 +1319,17 @@ mod test {
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/// Test precomputed basepoint mult
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#[test]
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fn test_precomputed_basepoint_mult() {
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let table = BasepointTable::create(&constants::BASEPOINT);
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let table = BasepointTable::create(&constants::ED25519_BASEPOINT);
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let aB_1 = ExtendedPoint::basepoint_mult(&A_SCALAR);
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let aB_2 = table.basepoint_mult(&A_SCALAR);
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assert_eq!(aB_1.compress(), aB_2.compress());
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assert_eq!(aB_1.compress_edwards(),
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aB_2.compress_edwards());
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}
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/// Test scalar_mult versus a known scalar multiple from ed25519.py
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#[test]
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fn scalar_mult_vs_ed25519py() {
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let aB = constants::BASEPOINT.scalar_mult(&A_SCALAR);
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let aB = constants::ED25519_BASEPOINT.scalar_mult(&A_SCALAR);
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assert_eq!(aB.compress_edwards(), A_TIMES_BASEPOINT);
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}
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@ -1384,7 +1344,7 @@ mod test {
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/// Test basepoint.double() versus the 2*basepoint constant.
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#[test]
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fn basepoint_double_vs_basepoint2() {
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assert_eq!(constants::BASEPOINT.double().compress_edwards(),
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assert_eq!(constants::ED25519_BASEPOINT.double().compress_edwards(),
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BASE2_CMPRSSD);
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}
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@ -1399,14 +1359,15 @@ mod test {
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/// Check that converting to projective and then back to extended round-trips.
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#[test]
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fn basepoint_projective_extended_round_trip() {
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assert_eq!(constants::BASEPOINT.to_projective().to_extended().compress_edwards(),
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assert_eq!(constants::ED25519_BASEPOINT
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.to_projective().to_extended().compress_edwards(),
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constants::BASE_CMPRSSD);
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}
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/// Test computing 16*basepoint vs mult_by_pow_2(4)
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#[test]
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fn basepoint16_vs_mult_by_pow_2_4() {
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let bp16 = constants::BASEPOINT.mult_by_pow_2(4);
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let bp16 = constants::ED25519_BASEPOINT.mult_by_pow_2(4);
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assert_eq!(bp16.compress_edwards(), BASE16_CMPRSSD);
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}
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@ -1415,7 +1376,7 @@ mod test {
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fn conditional_assign_for_affine_niels_point() {
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let id = AffineNielsPoint::identity();
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let mut p1 = AffineNielsPoint::identity();
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let bp = constants::BASEPOINT.to_affine_niels();
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let bp = constants::ED25519_BASEPOINT.to_affine_niels();
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p1.conditional_assign(&bp, 0);
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assert_eq!(p1, id);
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@ -1426,7 +1387,7 @@ mod test {
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#[test]
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fn is_small_order() {
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// The basepoint has large prime order
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assert!(constants::BASEPOINT.is_small_order() == false);
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assert!(constants::ED25519_BASEPOINT.is_small_order() == false);
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// constants::EIGHT_TORSION has all points of small order.
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for torsion_point in &constants::EIGHT_TORSION {
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assert!(torsion_point.is_small_order() == true);
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@ -1441,8 +1402,8 @@ mod test {
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#[test]
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fn is_identity() {
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assert!(ExtendedPoint::identity().is_identity() == true);
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assert!( constants::BASEPOINT.is_identity() == false);
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assert!( ExtendedPoint::identity().is_identity() == true);
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assert!(constants::ED25519_BASEPOINT.is_identity() == false);
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}
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}
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@ -1464,13 +1425,13 @@ mod bench {
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#[bench]
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fn scalar_mult(b: &mut Bencher) {
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let bp = constants::BASEPOINT;
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let bp = constants::ED25519_BASEPOINT;
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b.iter(|| bp.scalar_mult(&A_SCALAR));
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}
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#[bench]
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fn bench_select_precomputed_point(b: &mut Bencher) {
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b.iter(|| select_precomputed_point(0, &constants::base[12]));
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b.iter(|| select_precomputed_point(0, &constants::ED25519_BASEPOINT_TABLE.0[0]));
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}
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#[bench]
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@ -1481,53 +1442,53 @@ mod bench {
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#[bench]
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fn add_extended_and_cached_output_completed(b: &mut Bencher) {
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let p1 = constants::BASEPOINT;
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let p2 = constants::BASEPOINT.to_projective_niels();
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let p1 = constants::ED25519_BASEPOINT;
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let p2 = constants::ED25519_BASEPOINT.to_projective_niels();
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b.iter(|| &p1 + &p2);
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}
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#[bench]
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fn add_extended_and_cached_output_extended(b: &mut Bencher) {
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let p1 = constants::BASEPOINT;
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let p2 = constants::BASEPOINT.to_projective_niels();
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let p1 = constants::ED25519_BASEPOINT;
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let p2 = constants::ED25519_BASEPOINT.to_projective_niels();
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b.iter(|| (&p1 + &p2).to_extended());
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}
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#[bench]
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fn add_extended_and_precomputed_output_completed(b: &mut Bencher) {
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let p1 = constants::BASEPOINT;
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let p2 = select_precomputed_point(6, &constants::base[27]);
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let p1 = constants::ED25519_BASEPOINT;
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let p2 = constants::ED25519_BASEPOINT.to_affine_niels();
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b.iter(|| &p1 + &p2);
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}
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#[bench]
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fn add_extended_and_precomputed_output_extended(b: &mut Bencher) {
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let p1 = constants::BASEPOINT;
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let p2 = select_precomputed_point(6, &constants::base[27]);
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let p1 = constants::ED25519_BASEPOINT;
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let p2 = constants::ED25519_BASEPOINT.to_affine_niels();
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b.iter(|| (&p1 + &p2).to_extended());
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}
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#[bench]
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fn projective_double_output_completed(b: &mut Bencher) {
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let p1 = constants::BASEPOINT.to_projective();
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let p1 = constants::ED25519_BASEPOINT.to_projective();
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b.iter(|| p1.double() );
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}
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#[bench]
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fn extended_double_output_extended(b: &mut Bencher) {
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let p1 = constants::BASEPOINT;
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let p1 = constants::ED25519_BASEPOINT;
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b.iter(|| p1.double() );
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}
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#[bench]
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fn mult_by_cofactor(b: &mut Bencher) {
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let p1 = constants::BASEPOINT;
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let p1 = constants::ED25519_BASEPOINT;
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b.iter(|| p1.mult_by_cofactor() );
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}
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