From d1599410ee7817150ba63012cc92a5133162392a Mon Sep 17 00:00:00 2001 From: Henry de Valence Date: Fri, 23 Dec 2016 17:50:24 -0800 Subject: [PATCH] Rename CompressedPoint -> CompressedEdwardsY This allows other compression formats (e.g., CompressedMontgomeryX). --- src/curve.rs | 73 ++++++++++++++++++++++++++-------------------------- 1 file changed, 37 insertions(+), 36 deletions(-) diff --git a/src/curve.rs b/src/curve.rs index 971cdb5..17cc9ac 100644 --- a/src/curve.rs +++ b/src/curve.rs @@ -91,33 +91,34 @@ use util::bytes_equal_ct; // Compressed points // ------------------------------------------------------------------------ -/// An affine point `(x,y)` on the curve is determined by the -/// `y`-coordinate and the sign of `x`, marshalled into a 32-byte array. +/// In "Edwards y" format, the point `(x,y)` on the curve is +/// determined by the `y`-coordinate and the sign of `x`, marshalled +/// into a 32-byte array. /// -/// The first 255 bits of a CompressedPoint represent the +/// The first 255 bits of a CompressedEdwardsY represent the /// y-coordinate. The high bit of the 32nd byte gives the sign of `x`. #[derive(Copy, Clone)] -pub struct CompressedPoint(pub [u8; 32]); +pub struct CompressedEdwardsY(pub [u8; 32]); -impl Debug for CompressedPoint { +impl Debug for CompressedEdwardsY { fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result { - write!(f, "CompressedPoint: {:?}", &self.0[..]) + write!(f, "CompressedEdwardsY: {:?}", &self.0[..]) } } -impl Eq for CompressedPoint {} -impl PartialEq for CompressedPoint { - /// Determine if this `CompressedPoint` is equal to another. +impl Eq for CompressedEdwardsY {} +impl PartialEq for CompressedEdwardsY { + /// Determine if this `CompressedEdwardsY` is equal to another. /// /// # Warning /// /// This function is NOT constant time. - fn eq(&self, other: &CompressedPoint) -> bool { + fn eq(&self, other: &CompressedEdwardsY) -> bool { return self.0 == other.0; } } -impl Index for CompressedPoint { +impl Index for CompressedEdwardsY { type Output = u8; fn index<'a>(&'a self, _index: usize) -> &'a u8 { @@ -126,8 +127,8 @@ impl Index for CompressedPoint { } } -impl CompressedPoint { - /// View this `CompressedPoint` as an array of bytes. +impl CompressedEdwardsY { + /// View this `CompressedEdwardsY` as an array of bytes. pub fn to_bytes(&self) -> [u8;32] { self.0 } @@ -332,8 +333,8 @@ impl ProjectivePoint { } } - /// Convert this point to a `CompressedPoint` - pub fn compress(&self) -> CompressedPoint { + /// Convert this point to a `CompressedEdwardsY` + pub fn compress(&self) -> CompressedEdwardsY { let recip = self.Z.invert(); let x = &self.X * &recip; let y = &self.Y * &recip; @@ -341,7 +342,7 @@ impl ProjectivePoint { s = y.to_bytes(); s[31] ^= (x.is_negative() << 7) as u8; - CompressedPoint(s) + CompressedEdwardsY(s) } } @@ -368,8 +369,8 @@ impl ExtendedPoint { } } - /// Convert this point to a `CompressedPoint` - pub fn compress(&self) -> CompressedPoint { + /// Compress this point to `CompressedEdwardsY` format + pub fn compress(&self) -> CompressedEdwardsY { self.to_projective().compress() } } @@ -814,11 +815,11 @@ mod test { /// /// Generated with Sage: these are the bytes of 4/5 in 𝔽_p. The /// sign bit is 0 since the basepoint has x chosen to be positive. - static BASE_CMPRSSD: CompressedPoint = - CompressedPoint([0x58, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, - 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, - 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, - 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66]); + static BASE_CMPRSSD: CompressedEdwardsY = + CompressedEdwardsY([0x58, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, + 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, + 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, + 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66]); /// X coordinate of the basepoint. /// = 15112221349535400772501151409588531511454012693041857206046113283949847762202 @@ -826,17 +827,17 @@ mod test { [0x1a, 0xd5, 0x25, 0x8f, 0x60, 0x2d, 0x56, 0xc9, 0xb2, 0xa7, 0x25, 0x95, 0x60, 0xc7, 0x2c, 0x69, 0x5c, 0xdc, 0xd6, 0xfd, 0x31, 0xe2, 0xa4, 0xc0, 0xfe, 0x53, 0x6e, 0xcd, 0xd3, 0x36, 0x69, 0x21]; - static BASE2_CMPRSSD: CompressedPoint = - CompressedPoint([0xc9, 0xa3, 0xf8, 0x6a, 0xae, 0x46, 0x5f, 0xe, - 0x56, 0x51, 0x38, 0x64, 0x51, 0x0f, 0x39, 0x97, - 0x56, 0x1f, 0xa2, 0xc9, 0xe8, 0x5e, 0xa2, 0x1d, - 0xc2, 0x29, 0x23, 0x09, 0xf3, 0xcd, 0x60, 0x22]); + static BASE2_CMPRSSD: CompressedEdwardsY = + CompressedEdwardsY([0xc9, 0xa3, 0xf8, 0x6a, 0xae, 0x46, 0x5f, 0xe, + 0x56, 0x51, 0x38, 0x64, 0x51, 0x0f, 0x39, 0x97, + 0x56, 0x1f, 0xa2, 0xc9, 0xe8, 0x5e, 0xa2, 0x1d, + 0xc2, 0x29, 0x23, 0x09, 0xf3, 0xcd, 0x60, 0x22]); - static BASE16_CMPRSSD: CompressedPoint = - CompressedPoint([0xeb, 0x27, 0x67, 0xc1, 0x37, 0xab, 0x7a, 0xd8, - 0x27, 0x9c, 0x07, 0x8e, 0xff, 0x11, 0x6a, 0xb0, - 0x78, 0x6e, 0xad, 0x3a, 0x2e, 0x0f, 0x98, 0x9f, - 0x72, 0xc3, 0x7f, 0x82, 0xf2, 0x96, 0x96, 0x70]); + static BASE16_CMPRSSD: CompressedEdwardsY = + CompressedEdwardsY([0xeb, 0x27, 0x67, 0xc1, 0x37, 0xab, 0x7a, 0xd8, + 0x27, 0x9c, 0x07, 0x8e, 0xff, 0x11, 0x6a, 0xb0, + 0x78, 0x6e, 0xad, 0x3a, 0x2e, 0x0f, 0x98, 0x9f, + 0x72, 0xc3, 0x7f, 0x82, 0xf2, 0x96, 0x96, 0x70]); /// 4493907448824000747700850167940867464579944529806937181821189941592931634714 static A_SCALAR: Scalar = Scalar([ @@ -853,14 +854,14 @@ mod test { 0x56, 0xa7, 0xd4, 0xaa, 0xb8, 0x60, 0x8a, 0x05]); /// A_SCALAR * basepoint, computed with ed25519.py - static A_TIMES_BASEPOINT: CompressedPoint = CompressedPoint([ + static A_TIMES_BASEPOINT: CompressedEdwardsY = CompressedEdwardsY([ 0xea, 0x27, 0xe2, 0x60, 0x53, 0xdf, 0x1b, 0x59, 0x56, 0xf1, 0x4d, 0x5d, 0xec, 0x3c, 0x34, 0xc3, 0x84, 0xa2, 0x69, 0xb7, 0x4c, 0xc3, 0x80, 0x3e, 0xa8, 0xe2, 0xe7, 0xc9, 0x42, 0x5e, 0x40, 0xa5]); /// A_SCALAR * (A_TIMES_BASEPOINT) + B_SCALAR * BASEPOINT - static DOUBLE_SCALAR_MULT_RESULT: CompressedPoint = CompressedPoint([ + static DOUBLE_SCALAR_MULT_RESULT: CompressedEdwardsY = CompressedEdwardsY([ 0x7d, 0xfd, 0x6c, 0x45, 0xaf, 0x6d, 0x6e, 0x0e, 0xba, 0x20, 0x37, 0x1a, 0x23, 0x64, 0x59, 0xc4, 0xc0, 0x46, 0x83, 0x43, 0xde, 0x70, 0x4b, 0x85, @@ -886,7 +887,7 @@ mod test { let mut m_bp_bytes: [u8;32] = BASE_CMPRSSD.to_bytes().clone(); // Set the high bit of the last byte to flip the sign m_bp_bytes[31] |= 1 << 7; - let m_bp = CompressedPoint(m_bp_bytes).decompress().unwrap(); + let m_bp = CompressedEdwardsY(m_bp_bytes).decompress().unwrap(); let bp = BASE_CMPRSSD.decompress().unwrap(); assert_eq!(m_bp.X, -(&bp.X)); assert_eq!(m_bp.Y, bp.Y);