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boringssl/ssl/test/runner/ed25519/internal/edwards25519/edwards25519.go
David Benjamin ca4971cbae Sync bundled bits of golang.org/x/crypto. 
We no longer need to fork them. This is in preparation for pulling it
via Go modules, but probably need to figure out the network issue first.
Slightly bad manners for CI to do that.

Change-Id: Ic258264f3c3559817d5e4921e4ad3282e94d05fe
Reviewed-on: https://boringssl-review.googlesource.com/31904
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-09-17 23:14:35 +00:00

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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package edwards25519
import "encoding/binary"
// This code is a port of the public domain, “ref10” implementation of ed25519
// from SUPERCOP.
// FieldElement represents an element of the field GF(2^255 - 19). An element
// t, entries t[0]...t[9], represents the integer t[0]+2^26 t[1]+2^51 t[2]+2^77
// t[3]+2^102 t[4]+...+2^230 t[9]. Bounds on each t[i] vary depending on
// context.
type FieldElement [10]int32
var zero FieldElement
func FeZero(fe *FieldElement) {
copy(fe[:], zero[:])
}
func FeOne(fe *FieldElement) {
FeZero(fe)
fe[0] = 1
}
func FeAdd(dst, a, b *FieldElement) {
dst[0] = a[0] + b[0]
dst[1] = a[1] + b[1]
dst[2] = a[2] + b[2]
dst[3] = a[3] + b[3]
dst[4] = a[4] + b[4]
dst[5] = a[5] + b[5]
dst[6] = a[6] + b[6]
dst[7] = a[7] + b[7]
dst[8] = a[8] + b[8]
dst[9] = a[9] + b[9]
}
func FeSub(dst, a, b *FieldElement) {
dst[0] = a[0] - b[0]
dst[1] = a[1] - b[1]
dst[2] = a[2] - b[2]
dst[3] = a[3] - b[3]
dst[4] = a[4] - b[4]
dst[5] = a[5] - b[5]
dst[6] = a[6] - b[6]
dst[7] = a[7] - b[7]
dst[8] = a[8] - b[8]
dst[9] = a[9] - b[9]
}
func FeCopy(dst, src *FieldElement) {
copy(dst[:], src[:])
}
// Replace (f,g) with (g,g) if b == 1;
// replace (f,g) with (f,g) if b == 0.
//
// Preconditions: b in {0,1}.
func FeCMove(f, g *FieldElement, b int32) {
b = -b
f[0] ^= b & (f[0] ^ g[0])
f[1] ^= b & (f[1] ^ g[1])
f[2] ^= b & (f[2] ^ g[2])
f[3] ^= b & (f[3] ^ g[3])
f[4] ^= b & (f[4] ^ g[4])
f[5] ^= b & (f[5] ^ g[5])
f[6] ^= b & (f[6] ^ g[6])
f[7] ^= b & (f[7] ^ g[7])
f[8] ^= b & (f[8] ^ g[8])
f[9] ^= b & (f[9] ^ g[9])
}
func load3(in []byte) int64 {
var r int64
r = int64(in[0])
r |= int64(in[1]) << 8
r |= int64(in[2]) << 16
return r
}
func load4(in []byte) int64 {
var r int64
r = int64(in[0])
r |= int64(in[1]) << 8
r |= int64(in[2]) << 16
r |= int64(in[3]) << 24
return r
}
func FeFromBytes(dst *FieldElement, src *[32]byte) {
h0 := load4(src[:])
h1 := load3(src[4:]) << 6
h2 := load3(src[7:]) << 5
h3 := load3(src[10:]) << 3
h4 := load3(src[13:]) << 2
h5 := load4(src[16:])
h6 := load3(src[20:]) << 7
h7 := load3(src[23:]) << 5
h8 := load3(src[26:]) << 4
h9 := (load3(src[29:]) & 8388607) << 2
FeCombine(dst, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9)
}
// FeToBytes marshals h to s.
// Preconditions:
// |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
//
// Write p=2^255-19; q=floor(h/p).
// Basic claim: q = floor(2^(-255)(h + 19 2^(-25)h9 + 2^(-1))).
//
// Proof:
// Have |h|<=p so |q|<=1 so |19^2 2^(-255) q|<1/4.
// Also have |h-2^230 h9|<2^230 so |19 2^(-255)(h-2^230 h9)|<1/4.
//
// Write y=2^(-1)-19^2 2^(-255)q-19 2^(-255)(h-2^230 h9).
// Then 0<y<1.
//
// Write r=h-pq.
// Have 0<=r<=p-1=2^255-20.
// Thus 0<=r+19(2^-255)r<r+19(2^-255)2^255<=2^255-1.
//
// Write x=r+19(2^-255)r+y.
// Then 0<x<2^255 so floor(2^(-255)x) = 0 so floor(q+2^(-255)x) = q.
//
// Have q+2^(-255)x = 2^(-255)(h + 19 2^(-25) h9 + 2^(-1))
// so floor(2^(-255)(h + 19 2^(-25) h9 + 2^(-1))) = q.
func FeToBytes(s *[32]byte, h *FieldElement) {
var carry [10]int32
q := (19*h[9] + (1 << 24)) >> 25
q = (h[0] + q) >> 26
q = (h[1] + q) >> 25
q = (h[2] + q) >> 26
q = (h[3] + q) >> 25
q = (h[4] + q) >> 26
q = (h[5] + q) >> 25
q = (h[6] + q) >> 26
q = (h[7] + q) >> 25
q = (h[8] + q) >> 26
q = (h[9] + q) >> 25
// Goal: Output h-(2^255-19)q, which is between 0 and 2^255-20.
h[0] += 19 * q
// Goal: Output h-2^255 q, which is between 0 and 2^255-20.
carry[0] = h[0] >> 26
h[1] += carry[0]
h[0] -= carry[0] << 26
carry[1] = h[1] >> 25
h[2] += carry[1]
h[1] -= carry[1] << 25
carry[2] = h[2] >> 26
h[3] += carry[2]
h[2] -= carry[2] << 26
carry[3] = h[3] >> 25
h[4] += carry[3]
h[3] -= carry[3] << 25
carry[4] = h[4] >> 26
h[5] += carry[4]
h[4] -= carry[4] << 26
carry[5] = h[5] >> 25
h[6] += carry[5]
h[5] -= carry[5] << 25
carry[6] = h[6] >> 26
h[7] += carry[6]
h[6] -= carry[6] << 26
carry[7] = h[7] >> 25
h[8] += carry[7]
h[7] -= carry[7] << 25
carry[8] = h[8] >> 26
h[9] += carry[8]
h[8] -= carry[8] << 26
carry[9] = h[9] >> 25
h[9] -= carry[9] << 25
// h10 = carry9
// Goal: Output h[0]+...+2^255 h10-2^255 q, which is between 0 and 2^255-20.
// Have h[0]+...+2^230 h[9] between 0 and 2^255-1;
// evidently 2^255 h10-2^255 q = 0.
// Goal: Output h[0]+...+2^230 h[9].
s[0] = byte(h[0] >> 0)
s[1] = byte(h[0] >> 8)
s[2] = byte(h[0] >> 16)
s[3] = byte((h[0] >> 24) | (h[1] << 2))
s[4] = byte(h[1] >> 6)
s[5] = byte(h[1] >> 14)
s[6] = byte((h[1] >> 22) | (h[2] << 3))
s[7] = byte(h[2] >> 5)
s[8] = byte(h[2] >> 13)
s[9] = byte((h[2] >> 21) | (h[3] << 5))
s[10] = byte(h[3] >> 3)
s[11] = byte(h[3] >> 11)
s[12] = byte((h[3] >> 19) | (h[4] << 6))
s[13] = byte(h[4] >> 2)
s[14] = byte(h[4] >> 10)
s[15] = byte(h[4] >> 18)
s[16] = byte(h[5] >> 0)
s[17] = byte(h[5] >> 8)
s[18] = byte(h[5] >> 16)
s[19] = byte((h[5] >> 24) | (h[6] << 1))
s[20] = byte(h[6] >> 7)
s[21] = byte(h[6] >> 15)
s[22] = byte((h[6] >> 23) | (h[7] << 3))
s[23] = byte(h[7] >> 5)
s[24] = byte(h[7] >> 13)
s[25] = byte((h[7] >> 21) | (h[8] << 4))
s[26] = byte(h[8] >> 4)
s[27] = byte(h[8] >> 12)
s[28] = byte((h[8] >> 20) | (h[9] << 6))
s[29] = byte(h[9] >> 2)
s[30] = byte(h[9] >> 10)
s[31] = byte(h[9] >> 18)
}
func FeIsNegative(f *FieldElement) byte {
var s [32]byte
FeToBytes(&s, f)
return s[0] & 1
}
func FeIsNonZero(f *FieldElement) int32 {
var s [32]byte
FeToBytes(&s, f)
var x uint8
for _, b := range s {
x |= b
}
x |= x >> 4
x |= x >> 2
x |= x >> 1
return int32(x & 1)
}
// FeNeg sets h = -f
//
// Preconditions:
// |f| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
//
// Postconditions:
// |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
func FeNeg(h, f *FieldElement) {
h[0] = -f[0]
h[1] = -f[1]
h[2] = -f[2]
h[3] = -f[3]
h[4] = -f[4]
h[5] = -f[5]
h[6] = -f[6]
h[7] = -f[7]
h[8] = -f[8]
h[9] = -f[9]
}
func FeCombine(h *FieldElement, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9 int64) {
var c0, c1, c2, c3, c4, c5, c6, c7, c8, c9 int64
/*
|h0| <= (1.1*1.1*2^52*(1+19+19+19+19)+1.1*1.1*2^50*(38+38+38+38+38))
i.e. |h0| <= 1.2*2^59; narrower ranges for h2, h4, h6, h8
|h1| <= (1.1*1.1*2^51*(1+1+19+19+19+19+19+19+19+19))
i.e. |h1| <= 1.5*2^58; narrower ranges for h3, h5, h7, h9
*/
c0 = (h0 + (1 << 25)) >> 26
h1 += c0
h0 -= c0 << 26
c4 = (h4 + (1 << 25)) >> 26
h5 += c4
h4 -= c4 << 26
/* |h0| <= 2^25 */
/* |h4| <= 2^25 */
/* |h1| <= 1.51*2^58 */
/* |h5| <= 1.51*2^58 */
c1 = (h1 + (1 << 24)) >> 25
h2 += c1
h1 -= c1 << 25
c5 = (h5 + (1 << 24)) >> 25
h6 += c5
h5 -= c5 << 25
/* |h1| <= 2^24; from now on fits into int32 */
/* |h5| <= 2^24; from now on fits into int32 */
/* |h2| <= 1.21*2^59 */
/* |h6| <= 1.21*2^59 */
c2 = (h2 + (1 << 25)) >> 26
h3 += c2
h2 -= c2 << 26
c6 = (h6 + (1 << 25)) >> 26
h7 += c6
h6 -= c6 << 26
/* |h2| <= 2^25; from now on fits into int32 unchanged */
/* |h6| <= 2^25; from now on fits into int32 unchanged */
/* |h3| <= 1.51*2^58 */
/* |h7| <= 1.51*2^58 */
c3 = (h3 + (1 << 24)) >> 25
h4 += c3
h3 -= c3 << 25
c7 = (h7 + (1 << 24)) >> 25
h8 += c7
h7 -= c7 << 25
/* |h3| <= 2^24; from now on fits into int32 unchanged */
/* |h7| <= 2^24; from now on fits into int32 unchanged */
/* |h4| <= 1.52*2^33 */
/* |h8| <= 1.52*2^33 */
c4 = (h4 + (1 << 25)) >> 26
h5 += c4
h4 -= c4 << 26
c8 = (h8 + (1 << 25)) >> 26
h9 += c8
h8 -= c8 << 26
/* |h4| <= 2^25; from now on fits into int32 unchanged */
/* |h8| <= 2^25; from now on fits into int32 unchanged */
/* |h5| <= 1.01*2^24 */
/* |h9| <= 1.51*2^58 */
c9 = (h9 + (1 << 24)) >> 25
h0 += c9 * 19
h9 -= c9 << 25
/* |h9| <= 2^24; from now on fits into int32 unchanged */
/* |h0| <= 1.8*2^37 */
c0 = (h0 + (1 << 25)) >> 26
h1 += c0
h0 -= c0 << 26
/* |h0| <= 2^25; from now on fits into int32 unchanged */
/* |h1| <= 1.01*2^24 */
h[0] = int32(h0)
h[1] = int32(h1)
h[2] = int32(h2)
h[3] = int32(h3)
h[4] = int32(h4)
h[5] = int32(h5)
h[6] = int32(h6)
h[7] = int32(h7)
h[8] = int32(h8)
h[9] = int32(h9)
}
// FeMul calculates h = f * g
// Can overlap h with f or g.
//
// Preconditions:
// |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
// |g| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
//
// Postconditions:
// |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
//
// Notes on implementation strategy:
//
// Using schoolbook multiplication.
// Karatsuba would save a little in some cost models.
//
// Most multiplications by 2 and 19 are 32-bit precomputations;
// cheaper than 64-bit postcomputations.
//
// There is one remaining multiplication by 19 in the carry chain;
// one *19 precomputation can be merged into this,
// but the resulting data flow is considerably less clean.
//
// There are 12 carries below.
// 10 of them are 2-way parallelizable and vectorizable.
// Can get away with 11 carries, but then data flow is much deeper.
//
// With tighter constraints on inputs, can squeeze carries into int32.
func FeMul(h, f, g *FieldElement) {
f0 := int64(f[0])
f1 := int64(f[1])
f2 := int64(f[2])
f3 := int64(f[3])
f4 := int64(f[4])
f5 := int64(f[5])
f6 := int64(f[6])
f7 := int64(f[7])
f8 := int64(f[8])
f9 := int64(f[9])
f1_2 := int64(2 * f[1])
f3_2 := int64(2 * f[3])
f5_2 := int64(2 * f[5])
f7_2 := int64(2 * f[7])
f9_2 := int64(2 * f[9])
g0 := int64(g[0])
g1 := int64(g[1])
g2 := int64(g[2])
g3 := int64(g[3])
g4 := int64(g[4])
g5 := int64(g[5])
g6 := int64(g[6])
g7 := int64(g[7])
g8 := int64(g[8])
g9 := int64(g[9])
g1_19 := int64(19 * g[1]) /* 1.4*2^29 */
g2_19 := int64(19 * g[2]) /* 1.4*2^30; still ok */
g3_19 := int64(19 * g[3])
g4_19 := int64(19 * g[4])
g5_19 := int64(19 * g[5])
g6_19 := int64(19 * g[6])
g7_19 := int64(19 * g[7])
g8_19 := int64(19 * g[8])
g9_19 := int64(19 * g[9])
h0 := f0*g0 + f1_2*g9_19 + f2*g8_19 + f3_2*g7_19 + f4*g6_19 + f5_2*g5_19 + f6*g4_19 + f7_2*g3_19 + f8*g2_19 + f9_2*g1_19
h1 := f0*g1 + f1*g0 + f2*g9_19 + f3*g8_19 + f4*g7_19 + f5*g6_19 + f6*g5_19 + f7*g4_19 + f8*g3_19 + f9*g2_19
h2 := f0*g2 + f1_2*g1 + f2*g0 + f3_2*g9_19 + f4*g8_19 + f5_2*g7_19 + f6*g6_19 + f7_2*g5_19 + f8*g4_19 + f9_2*g3_19
h3 := f0*g3 + f1*g2 + f2*g1 + f3*g0 + f4*g9_19 + f5*g8_19 + f6*g7_19 + f7*g6_19 + f8*g5_19 + f9*g4_19
h4 := f0*g4 + f1_2*g3 + f2*g2 + f3_2*g1 + f4*g0 + f5_2*g9_19 + f6*g8_19 + f7_2*g7_19 + f8*g6_19 + f9_2*g5_19
h5 := f0*g5 + f1*g4 + f2*g3 + f3*g2 + f4*g1 + f5*g0 + f6*g9_19 + f7*g8_19 + f8*g7_19 + f9*g6_19
h6 := f0*g6 + f1_2*g5 + f2*g4 + f3_2*g3 + f4*g2 + f5_2*g1 + f6*g0 + f7_2*g9_19 + f8*g8_19 + f9_2*g7_19
h7 := f0*g7 + f1*g6 + f2*g5 + f3*g4 + f4*g3 + f5*g2 + f6*g1 + f7*g0 + f8*g9_19 + f9*g8_19
h8 := f0*g8 + f1_2*g7 + f2*g6 + f3_2*g5 + f4*g4 + f5_2*g3 + f6*g2 + f7_2*g1 + f8*g0 + f9_2*g9_19
h9 := f0*g9 + f1*g8 + f2*g7 + f3*g6 + f4*g5 + f5*g4 + f6*g3 + f7*g2 + f8*g1 + f9*g0
FeCombine(h, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9)
}
func feSquare(f *FieldElement) (h0, h1, h2, h3, h4, h5, h6, h7, h8, h9 int64) {
f0 := int64(f[0])
f1 := int64(f[1])
f2 := int64(f[2])
f3 := int64(f[3])
f4 := int64(f[4])
f5 := int64(f[5])
f6 := int64(f[6])
f7 := int64(f[7])
f8 := int64(f[8])
f9 := int64(f[9])
f0_2 := int64(2 * f[0])
f1_2 := int64(2 * f[1])
f2_2 := int64(2 * f[2])
f3_2 := int64(2 * f[3])
f4_2 := int64(2 * f[4])
f5_2 := int64(2 * f[5])
f6_2 := int64(2 * f[6])
f7_2 := int64(2 * f[7])
f5_38 := 38 * f5 // 1.31*2^30
f6_19 := 19 * f6 // 1.31*2^30
f7_38 := 38 * f7 // 1.31*2^30
f8_19 := 19 * f8 // 1.31*2^30
f9_38 := 38 * f9 // 1.31*2^30
h0 = f0*f0 + f1_2*f9_38 + f2_2*f8_19 + f3_2*f7_38 + f4_2*f6_19 + f5*f5_38
h1 = f0_2*f1 + f2*f9_38 + f3_2*f8_19 + f4*f7_38 + f5_2*f6_19
h2 = f0_2*f2 + f1_2*f1 + f3_2*f9_38 + f4_2*f8_19 + f5_2*f7_38 + f6*f6_19
h3 = f0_2*f3 + f1_2*f2 + f4*f9_38 + f5_2*f8_19 + f6*f7_38
h4 = f0_2*f4 + f1_2*f3_2 + f2*f2 + f5_2*f9_38 + f6_2*f8_19 + f7*f7_38
h5 = f0_2*f5 + f1_2*f4 + f2_2*f3 + f6*f9_38 + f7_2*f8_19
h6 = f0_2*f6 + f1_2*f5_2 + f2_2*f4 + f3_2*f3 + f7_2*f9_38 + f8*f8_19
h7 = f0_2*f7 + f1_2*f6 + f2_2*f5 + f3_2*f4 + f8*f9_38
h8 = f0_2*f8 + f1_2*f7_2 + f2_2*f6 + f3_2*f5_2 + f4*f4 + f9*f9_38
h9 = f0_2*f9 + f1_2*f8 + f2_2*f7 + f3_2*f6 + f4_2*f5
return
}
// FeSquare calculates h = f*f. Can overlap h with f.
//
// Preconditions:
// |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
//
// Postconditions:
// |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
func FeSquare(h, f *FieldElement) {
h0, h1, h2, h3, h4, h5, h6, h7, h8, h9 := feSquare(f)
FeCombine(h, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9)
}
// FeSquare2 sets h = 2 * f * f
//
// Can overlap h with f.
//
// Preconditions:
// |f| bounded by 1.65*2^26,1.65*2^25,1.65*2^26,1.65*2^25,etc.
//
// Postconditions:
// |h| bounded by 1.01*2^25,1.01*2^24,1.01*2^25,1.01*2^24,etc.
// See fe_mul.c for discussion of implementation strategy.
func FeSquare2(h, f *FieldElement) {
h0, h1, h2, h3, h4, h5, h6, h7, h8, h9 := feSquare(f)
h0 += h0
h1 += h1
h2 += h2
h3 += h3
h4 += h4
h5 += h5
h6 += h6
h7 += h7
h8 += h8
h9 += h9
FeCombine(h, h0, h1, h2, h3, h4, h5, h6, h7, h8, h9)
}
func FeInvert(out, z *FieldElement) {
var t0, t1, t2, t3 FieldElement
var i int
FeSquare(&t0, z) // 2^1
FeSquare(&t1, &t0) // 2^2
for i = 1; i < 2; i++ { // 2^3
FeSquare(&t1, &t1)
}
FeMul(&t1, z, &t1) // 2^3 + 2^0
FeMul(&t0, &t0, &t1) // 2^3 + 2^1 + 2^0
FeSquare(&t2, &t0) // 2^4 + 2^2 + 2^1
FeMul(&t1, &t1, &t2) // 2^4 + 2^3 + 2^2 + 2^1 + 2^0
FeSquare(&t2, &t1) // 5,4,3,2,1
for i = 1; i < 5; i++ { // 9,8,7,6,5
FeSquare(&t2, &t2)
}
FeMul(&t1, &t2, &t1) // 9,8,7,6,5,4,3,2,1,0
FeSquare(&t2, &t1) // 10..1
for i = 1; i < 10; i++ { // 19..10
FeSquare(&t2, &t2)
}
FeMul(&t2, &t2, &t1) // 19..0
FeSquare(&t3, &t2) // 20..1
for i = 1; i < 20; i++ { // 39..20
FeSquare(&t3, &t3)
}
FeMul(&t2, &t3, &t2) // 39..0
FeSquare(&t2, &t2) // 40..1
for i = 1; i < 10; i++ { // 49..10
FeSquare(&t2, &t2)
}
FeMul(&t1, &t2, &t1) // 49..0
FeSquare(&t2, &t1) // 50..1
for i = 1; i < 50; i++ { // 99..50
FeSquare(&t2, &t2)
}
FeMul(&t2, &t2, &t1) // 99..0
FeSquare(&t3, &t2) // 100..1
for i = 1; i < 100; i++ { // 199..100
FeSquare(&t3, &t3)
}
FeMul(&t2, &t3, &t2) // 199..0
FeSquare(&t2, &t2) // 200..1
for i = 1; i < 50; i++ { // 249..50
FeSquare(&t2, &t2)
}
FeMul(&t1, &t2, &t1) // 249..0
FeSquare(&t1, &t1) // 250..1
for i = 1; i < 5; i++ { // 254..5
FeSquare(&t1, &t1)
}
FeMul(out, &t1, &t0) // 254..5,3,1,0
}
func fePow22523(out, z *FieldElement) {
var t0, t1, t2 FieldElement
var i int
FeSquare(&t0, z)
for i = 1; i < 1; i++ {
FeSquare(&t0, &t0)
}
FeSquare(&t1, &t0)
for i = 1; i < 2; i++ {
FeSquare(&t1, &t1)
}
FeMul(&t1, z, &t1)
FeMul(&t0, &t0, &t1)
FeSquare(&t0, &t0)
for i = 1; i < 1; i++ {
FeSquare(&t0, &t0)
}
FeMul(&t0, &t1, &t0)
FeSquare(&t1, &t0)
for i = 1; i < 5; i++ {
FeSquare(&t1, &t1)
}
FeMul(&t0, &t1, &t0)
FeSquare(&t1, &t0)
for i = 1; i < 10; i++ {
FeSquare(&t1, &t1)
}
FeMul(&t1, &t1, &t0)
FeSquare(&t2, &t1)
for i = 1; i < 20; i++ {
FeSquare(&t2, &t2)
}
FeMul(&t1, &t2, &t1)
FeSquare(&t1, &t1)
for i = 1; i < 10; i++ {
FeSquare(&t1, &t1)
}
FeMul(&t0, &t1, &t0)
FeSquare(&t1, &t0)
for i = 1; i < 50; i++ {
FeSquare(&t1, &t1)
}
FeMul(&t1, &t1, &t0)
FeSquare(&t2, &t1)
for i = 1; i < 100; i++ {
FeSquare(&t2, &t2)
}
FeMul(&t1, &t2, &t1)
FeSquare(&t1, &t1)
for i = 1; i < 50; i++ {
FeSquare(&t1, &t1)
}
FeMul(&t0, &t1, &t0)
FeSquare(&t0, &t0)
for i = 1; i < 2; i++ {
FeSquare(&t0, &t0)
}
FeMul(out, &t0, z)
}
// Group elements are members of the elliptic curve -x^2 + y^2 = 1 + d * x^2 *
// y^2 where d = -121665/121666.
//
// Several representations are used:
// ProjectiveGroupElement: (X:Y:Z) satisfying x=X/Z, y=Y/Z
// ExtendedGroupElement: (X:Y:Z:T) satisfying x=X/Z, y=Y/Z, XY=ZT
// CompletedGroupElement: ((X:Z),(Y:T)) satisfying x=X/Z, y=Y/T
// PreComputedGroupElement: (y+x,y-x,2dxy)
type ProjectiveGroupElement struct {
X, Y, Z FieldElement
}
type ExtendedGroupElement struct {
X, Y, Z, T FieldElement
}
type CompletedGroupElement struct {
X, Y, Z, T FieldElement
}
type PreComputedGroupElement struct {
yPlusX, yMinusX, xy2d FieldElement
}
type CachedGroupElement struct {
yPlusX, yMinusX, Z, T2d FieldElement
}
func (p *ProjectiveGroupElement) Zero() {
FeZero(&p.X)
FeOne(&p.Y)
FeOne(&p.Z)
}
func (p *ProjectiveGroupElement) Double(r *CompletedGroupElement) {
var t0 FieldElement
FeSquare(&r.X, &p.X)
FeSquare(&r.Z, &p.Y)
FeSquare2(&r.T, &p.Z)
FeAdd(&r.Y, &p.X, &p.Y)
FeSquare(&t0, &r.Y)
FeAdd(&r.Y, &r.Z, &r.X)
FeSub(&r.Z, &r.Z, &r.X)
FeSub(&r.X, &t0, &r.Y)
FeSub(&r.T, &r.T, &r.Z)
}
func (p *ProjectiveGroupElement) ToBytes(s *[32]byte) {
var recip, x, y FieldElement
FeInvert(&recip, &p.Z)
FeMul(&x, &p.X, &recip)
FeMul(&y, &p.Y, &recip)
FeToBytes(s, &y)
s[31] ^= FeIsNegative(&x) << 7
}
func (p *ExtendedGroupElement) Zero() {
FeZero(&p.X)
FeOne(&p.Y)
FeOne(&p.Z)
FeZero(&p.T)
}
func (p *ExtendedGroupElement) Double(r *CompletedGroupElement) {
var q ProjectiveGroupElement
p.ToProjective(&q)
q.Double(r)
}
func (p *ExtendedGroupElement) ToCached(r *CachedGroupElement) {
FeAdd(&r.yPlusX, &p.Y, &p.X)
FeSub(&r.yMinusX, &p.Y, &p.X)
FeCopy(&r.Z, &p.Z)
FeMul(&r.T2d, &p.T, &d2)
}
func (p *ExtendedGroupElement) ToProjective(r *ProjectiveGroupElement) {
FeCopy(&r.X, &p.X)
FeCopy(&r.Y, &p.Y)
FeCopy(&r.Z, &p.Z)
}
func (p *ExtendedGroupElement) ToBytes(s *[32]byte) {
var recip, x, y FieldElement
FeInvert(&recip, &p.Z)
FeMul(&x, &p.X, &recip)
FeMul(&y, &p.Y, &recip)
FeToBytes(s, &y)
s[31] ^= FeIsNegative(&x) << 7
}
func (p *ExtendedGroupElement) FromBytes(s *[32]byte) bool {
var u, v, v3, vxx, check FieldElement
FeFromBytes(&p.Y, s)
FeOne(&p.Z)
FeSquare(&u, &p.Y)
FeMul(&v, &u, &d)
FeSub(&u, &u, &p.Z) // y = y^2-1
FeAdd(&v, &v, &p.Z) // v = dy^2+1
FeSquare(&v3, &v)
FeMul(&v3, &v3, &v) // v3 = v^3
FeSquare(&p.X, &v3)
FeMul(&p.X, &p.X, &v)
FeMul(&p.X, &p.X, &u) // x = uv^7
fePow22523(&p.X, &p.X) // x = (uv^7)^((q-5)/8)
FeMul(&p.X, &p.X, &v3)
FeMul(&p.X, &p.X, &u) // x = uv^3(uv^7)^((q-5)/8)
var tmpX, tmp2 [32]byte
FeSquare(&vxx, &p.X)
FeMul(&vxx, &vxx, &v)
FeSub(&check, &vxx, &u) // vx^2-u
if FeIsNonZero(&check) == 1 {
FeAdd(&check, &vxx, &u) // vx^2+u
if FeIsNonZero(&check) == 1 {
return false
}
FeMul(&p.X, &p.X, &SqrtM1)
FeToBytes(&tmpX, &p.X)
for i, v := range tmpX {
tmp2[31-i] = v
}
}
if FeIsNegative(&p.X) != (s[31] >> 7) {
FeNeg(&p.X, &p.X)
}
FeMul(&p.T, &p.X, &p.Y)
return true
}
func (p *CompletedGroupElement) ToProjective(r *ProjectiveGroupElement) {
FeMul(&r.X, &p.X, &p.T)
FeMul(&r.Y, &p.Y, &p.Z)
FeMul(&r.Z, &p.Z, &p.T)
}
func (p *CompletedGroupElement) ToExtended(r *ExtendedGroupElement) {
FeMul(&r.X, &p.X, &p.T)
FeMul(&r.Y, &p.Y, &p.Z)
FeMul(&r.Z, &p.Z, &p.T)
FeMul(&r.T, &p.X, &p.Y)
}
func (p *PreComputedGroupElement) Zero() {
FeOne(&p.yPlusX)
FeOne(&p.yMinusX)
FeZero(&p.xy2d)
}
func geAdd(r *CompletedGroupElement, p *ExtendedGroupElement, q *CachedGroupElement) {
var t0 FieldElement
FeAdd(&r.X, &p.Y, &p.X)
FeSub(&r.Y, &p.Y, &p.X)
FeMul(&r.Z, &r.X, &q.yPlusX)
FeMul(&r.Y, &r.Y, &q.yMinusX)
FeMul(&r.T, &q.T2d, &p.T)
FeMul(&r.X, &p.Z, &q.Z)
FeAdd(&t0, &r.X, &r.X)
FeSub(&r.X, &r.Z, &r.Y)
FeAdd(&r.Y, &r.Z, &r.Y)
FeAdd(&r.Z, &t0, &r.T)
FeSub(&r.T, &t0, &r.T)
}
func geSub(r *CompletedGroupElement, p *ExtendedGroupElement, q *CachedGroupElement) {
var t0 FieldElement
FeAdd(&r.X, &p.Y, &p.X)
FeSub(&r.Y, &p.Y, &p.X)
FeMul(&r.Z, &r.X, &q.yMinusX)
FeMul(&r.Y, &r.Y, &q.yPlusX)
FeMul(&r.T, &q.T2d, &p.T)
FeMul(&r.X, &p.Z, &q.Z)
FeAdd(&t0, &r.X, &r.X)
FeSub(&r.X, &r.Z, &r.Y)
FeAdd(&r.Y, &r.Z, &r.Y)
FeSub(&r.Z, &t0, &r.T)
FeAdd(&r.T, &t0, &r.T)
}
func geMixedAdd(r *CompletedGroupElement, p *ExtendedGroupElement, q *PreComputedGroupElement) {
var t0 FieldElement
FeAdd(&r.X, &p.Y, &p.X)
FeSub(&r.Y, &p.Y, &p.X)
FeMul(&r.Z, &r.X, &q.yPlusX)
FeMul(&r.Y, &r.Y, &q.yMinusX)
FeMul(&r.T, &q.xy2d, &p.T)
FeAdd(&t0, &p.Z, &p.Z)
FeSub(&r.X, &r.Z, &r.Y)
FeAdd(&r.Y, &r.Z, &r.Y)
FeAdd(&r.Z, &t0, &r.T)
FeSub(&r.T, &t0, &r.T)
}
func geMixedSub(r *CompletedGroupElement, p *ExtendedGroupElement, q *PreComputedGroupElement) {
var t0 FieldElement
FeAdd(&r.X, &p.Y, &p.X)
FeSub(&r.Y, &p.Y, &p.X)
FeMul(&r.Z, &r.X, &q.yMinusX)
FeMul(&r.Y, &r.Y, &q.yPlusX)
FeMul(&r.T, &q.xy2d, &p.T)
FeAdd(&t0, &p.Z, &p.Z)
FeSub(&r.X, &r.Z, &r.Y)
FeAdd(&r.Y, &r.Z, &r.Y)
FeSub(&r.Z, &t0, &r.T)
FeAdd(&r.T, &t0, &r.T)
}
func slide(r *[256]int8, a *[32]byte) {
for i := range r {
r[i] = int8(1 & (a[i>>3] >> uint(i&7)))
}
for i := range r {
if r[i] != 0 {
for b := 1; b <= 6 && i+b < 256; b++ {
if r[i+b] != 0 {
if r[i]+(r[i+b]<<uint(b)) <= 15 {
r[i] += r[i+b] << uint(b)
r[i+b] = 0
} else if r[i]-(r[i+b]<<uint(b)) >= -15 {
r[i] -= r[i+b] << uint(b)
for k := i + b; k < 256; k++ {
if r[k] == 0 {
r[k] = 1
break
}
r[k] = 0
}
} else {
break
}
}
}
}
}
}
// GeDoubleScalarMultVartime sets 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.
func GeDoubleScalarMultVartime(r *ProjectiveGroupElement, a *[32]byte, A *ExtendedGroupElement, b *[32]byte) {
var aSlide, bSlide [256]int8
var Ai [8]CachedGroupElement // A,3A,5A,7A,9A,11A,13A,15A
var t CompletedGroupElement
var u, A2 ExtendedGroupElement
var i int
slide(&aSlide, a)
slide(&bSlide, b)
A.ToCached(&Ai[0])
A.Double(&t)
t.ToExtended(&A2)
for i := 0; i < 7; i++ {
geAdd(&t, &A2, &Ai[i])
t.ToExtended(&u)
u.ToCached(&Ai[i+1])
}
r.Zero()
for i = 255; i >= 0; i-- {
if aSlide[i] != 0 || bSlide[i] != 0 {
break
}
}
for ; i >= 0; i-- {
r.Double(&t)
if aSlide[i] > 0 {
t.ToExtended(&u)
geAdd(&t, &u, &Ai[aSlide[i]/2])
} else if aSlide[i] < 0 {
t.ToExtended(&u)
geSub(&t, &u, &Ai[(-aSlide[i])/2])
}
if bSlide[i] > 0 {
t.ToExtended(&u)
geMixedAdd(&t, &u, &bi[bSlide[i]/2])
} else if bSlide[i] < 0 {
t.ToExtended(&u)
geMixedSub(&t, &u, &bi[(-bSlide[i])/2])
}
t.ToProjective(r)
}
}
// equal returns 1 if b == c and 0 otherwise, assuming that b and c are
// non-negative.
func equal(b, c int32) int32 {
x := uint32(b ^ c)
x--
return int32(x >> 31)
}
// negative returns 1 if b < 0 and 0 otherwise.
func negative(b int32) int32 {
return (b >> 31) & 1
}
func PreComputedGroupElementCMove(t, u *PreComputedGroupElement, b int32) {
FeCMove(&t.yPlusX, &u.yPlusX, b)
FeCMove(&t.yMinusX, &u.yMinusX, b)
FeCMove(&t.xy2d, &u.xy2d, b)
}
func selectPoint(t *PreComputedGroupElement, pos int32, b int32) {
var minusT PreComputedGroupElement
bNegative := negative(b)
bAbs := b - (((-bNegative) & b) << 1)
t.Zero()
for i := int32(0); i < 8; i++ {
PreComputedGroupElementCMove(t, &base[pos][i], equal(bAbs, i+1))
}
FeCopy(&minusT.yPlusX, &t.yMinusX)
FeCopy(&minusT.yMinusX, &t.yPlusX)
FeNeg(&minusT.xy2d, &t.xy2d)
PreComputedGroupElementCMove(t, &minusT, bNegative)
}
// GeScalarMultBase computes h = a*B, where
// a = a[0]+256*a[1]+...+256^31 a[31]
// B is the Ed25519 base point (x,4/5) with x positive.
//
// Preconditions:
// a[31] <= 127
func GeScalarMultBase(h *ExtendedGroupElement, a *[32]byte) {
var e [64]int8
for i, v := range a {
e[2*i] = int8(v & 15)
e[2*i+1] = int8((v >> 4) & 15)
}
// each e[i] is between 0 and 15 and e[63] is between 0 and 7.
carry := int8(0)
for i := 0; i < 63; i++ {
e[i] += carry
carry = (e[i] + 8) >> 4
e[i] -= carry << 4
}
e[63] += carry
// each e[i] is between -8 and 8.
h.Zero()
var t PreComputedGroupElement
var r CompletedGroupElement
for i := int32(1); i < 64; i += 2 {
selectPoint(&t, i/2, int32(e[i]))
geMixedAdd(&r, h, &t)
r.ToExtended(h)
}
var s ProjectiveGroupElement
h.Double(&r)
r.ToProjective(&s)
s.Double(&r)
r.ToProjective(&s)
s.Double(&r)
r.ToProjective(&s)
s.Double(&r)
r.ToExtended(h)
for i := int32(0); i < 64; i += 2 {
selectPoint(&t, i/2, int32(e[i]))
geMixedAdd(&r, h, &t)
r.ToExtended(h)
}
}
// The scalars are GF(2^252 + 27742317777372353535851937790883648493).
// Input:
// a[0]+256*a[1]+...+256^31*a[31] = a
// b[0]+256*b[1]+...+256^31*b[31] = b
// c[0]+256*c[1]+...+256^31*c[31] = c
//
// Output:
// s[0]+256*s[1]+...+256^31*s[31] = (ab+c) mod l
// where l = 2^252 + 27742317777372353535851937790883648493.
func ScMulAdd(s, a, b, c *[32]byte) {
a0 := 2097151 & load3(a[:])
a1 := 2097151 & (load4(a[2:]) >> 5)
a2 := 2097151 & (load3(a[5:]) >> 2)
a3 := 2097151 & (load4(a[7:]) >> 7)
a4 := 2097151 & (load4(a[10:]) >> 4)
a5 := 2097151 & (load3(a[13:]) >> 1)
a6 := 2097151 & (load4(a[15:]) >> 6)
a7 := 2097151 & (load3(a[18:]) >> 3)
a8 := 2097151 & load3(a[21:])
a9 := 2097151 & (load4(a[23:]) >> 5)
a10 := 2097151 & (load3(a[26:]) >> 2)
a11 := (load4(a[28:]) >> 7)
b0 := 2097151 & load3(b[:])
b1 := 2097151 & (load4(b[2:]) >> 5)
b2 := 2097151 & (load3(b[5:]) >> 2)
b3 := 2097151 & (load4(b[7:]) >> 7)
b4 := 2097151 & (load4(b[10:]) >> 4)
b5 := 2097151 & (load3(b[13:]) >> 1)
b6 := 2097151 & (load4(b[15:]) >> 6)
b7 := 2097151 & (load3(b[18:]) >> 3)
b8 := 2097151 & load3(b[21:])
b9 := 2097151 & (load4(b[23:]) >> 5)
b10 := 2097151 & (load3(b[26:]) >> 2)
b11 := (load4(b[28:]) >> 7)
c0 := 2097151 & load3(c[:])
c1 := 2097151 & (load4(c[2:]) >> 5)
c2 := 2097151 & (load3(c[5:]) >> 2)
c3 := 2097151 & (load4(c[7:]) >> 7)
c4 := 2097151 & (load4(c[10:]) >> 4)
c5 := 2097151 & (load3(c[13:]) >> 1)
c6 := 2097151 & (load4(c[15:]) >> 6)
c7 := 2097151 & (load3(c[18:]) >> 3)
c8 := 2097151 & load3(c[21:])
c9 := 2097151 & (load4(c[23:]) >> 5)
c10 := 2097151 & (load3(c[26:]) >> 2)
c11 := (load4(c[28:]) >> 7)
var carry [23]int64
s0 := c0 + a0*b0
s1 := c1 + a0*b1 + a1*b0
s2 := c2 + a0*b2 + a1*b1 + a2*b0
s3 := c3 + a0*b3 + a1*b2 + a2*b1 + a3*b0
s4 := c4 + a0*b4 + a1*b3 + a2*b2 + a3*b1 + a4*b0
s5 := c5 + a0*b5 + a1*b4 + a2*b3 + a3*b2 + a4*b1 + a5*b0
s6 := c6 + a0*b6 + a1*b5 + a2*b4 + a3*b3 + a4*b2 + a5*b1 + a6*b0
s7 := c7 + a0*b7 + a1*b6 + a2*b5 + a3*b4 + a4*b3 + a5*b2 + a6*b1 + a7*b0
s8 := c8 + a0*b8 + a1*b7 + a2*b6 + a3*b5 + a4*b4 + a5*b3 + a6*b2 + a7*b1 + a8*b0
s9 := c9 + a0*b9 + a1*b8 + a2*b7 + a3*b6 + a4*b5 + a5*b4 + a6*b3 + a7*b2 + a8*b1 + a9*b0
s10 := c10 + a0*b10 + a1*b9 + a2*b8 + a3*b7 + a4*b6 + a5*b5 + a6*b4 + a7*b3 + a8*b2 + a9*b1 + a10*b0
s11 := c11 + a0*b11 + a1*b10 + a2*b9 + a3*b8 + a4*b7 + a5*b6 + a6*b5 + a7*b4 + a8*b3 + a9*b2 + a10*b1 + a11*b0
s12 := a1*b11 + a2*b10 + a3*b9 + a4*b8 + a5*b7 + a6*b6 + a7*b5 + a8*b4 + a9*b3 + a10*b2 + a11*b1
s13 := a2*b11 + a3*b10 + a4*b9 + a5*b8 + a6*b7 + a7*b6 + a8*b5 + a9*b4 + a10*b3 + a11*b2
s14 := a3*b11 + a4*b10 + a5*b9 + a6*b8 + a7*b7 + a8*b6 + a9*b5 + a10*b4 + a11*b3
s15 := a4*b11 + a5*b10 + a6*b9 + a7*b8 + a8*b7 + a9*b6 + a10*b5 + a11*b4
s16 := a5*b11 + a6*b10 + a7*b9 + a8*b8 + a9*b7 + a10*b6 + a11*b5
s17 := a6*b11 + a7*b10 + a8*b9 + a9*b8 + a10*b7 + a11*b6
s18 := a7*b11 + a8*b10 + a9*b9 + a10*b8 + a11*b7
s19 := a8*b11 + a9*b10 + a10*b9 + a11*b8
s20 := a9*b11 + a10*b10 + a11*b9
s21 := a10*b11 + a11*b10
s22 := a11 * b11
s23 := int64(0)
carry[0] = (s0 + (1 << 20)) >> 21
s1 += carry[0]
s0 -= carry[0] << 21
carry[2] = (s2 + (1 << 20)) >> 21
s3 += carry[2]
s2 -= carry[2] << 21
carry[4] = (s4 + (1 << 20)) >> 21
s5 += carry[4]
s4 -= carry[4] << 21
carry[6] = (s6 + (1 << 20)) >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[8] = (s8 + (1 << 20)) >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[10] = (s10 + (1 << 20)) >> 21
s11 += carry[10]
s10 -= carry[10] << 21
carry[12] = (s12 + (1 << 20)) >> 21
s13 += carry[12]
s12 -= carry[12] << 21
carry[14] = (s14 + (1 << 20)) >> 21
s15 += carry[14]
s14 -= carry[14] << 21
carry[16] = (s16 + (1 << 20)) >> 21
s17 += carry[16]
s16 -= carry[16] << 21
carry[18] = (s18 + (1 << 20)) >> 21
s19 += carry[18]
s18 -= carry[18] << 21
carry[20] = (s20 + (1 << 20)) >> 21
s21 += carry[20]
s20 -= carry[20] << 21
carry[22] = (s22 + (1 << 20)) >> 21
s23 += carry[22]
s22 -= carry[22] << 21
carry[1] = (s1 + (1 << 20)) >> 21
s2 += carry[1]
s1 -= carry[1] << 21
carry[3] = (s3 + (1 << 20)) >> 21
s4 += carry[3]
s3 -= carry[3] << 21
carry[5] = (s5 + (1 << 20)) >> 21
s6 += carry[5]
s5 -= carry[5] << 21
carry[7] = (s7 + (1 << 20)) >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[9] = (s9 + (1 << 20)) >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[11] = (s11 + (1 << 20)) >> 21
s12 += carry[11]
s11 -= carry[11] << 21
carry[13] = (s13 + (1 << 20)) >> 21
s14 += carry[13]
s13 -= carry[13] << 21
carry[15] = (s15 + (1 << 20)) >> 21
s16 += carry[15]
s15 -= carry[15] << 21
carry[17] = (s17 + (1 << 20)) >> 21
s18 += carry[17]
s17 -= carry[17] << 21
carry[19] = (s19 + (1 << 20)) >> 21
s20 += carry[19]
s19 -= carry[19] << 21
carry[21] = (s21 + (1 << 20)) >> 21
s22 += carry[21]
s21 -= carry[21] << 21
s11 += s23 * 666643
s12 += s23 * 470296
s13 += s23 * 654183
s14 -= s23 * 997805
s15 += s23 * 136657
s16 -= s23 * 683901
s23 = 0
s10 += s22 * 666643
s11 += s22 * 470296
s12 += s22 * 654183
s13 -= s22 * 997805
s14 += s22 * 136657
s15 -= s22 * 683901
s22 = 0
s9 += s21 * 666643
s10 += s21 * 470296
s11 += s21 * 654183
s12 -= s21 * 997805
s13 += s21 * 136657
s14 -= s21 * 683901
s21 = 0
s8 += s20 * 666643
s9 += s20 * 470296
s10 += s20 * 654183
s11 -= s20 * 997805
s12 += s20 * 136657
s13 -= s20 * 683901
s20 = 0
s7 += s19 * 666643
s8 += s19 * 470296
s9 += s19 * 654183
s10 -= s19 * 997805
s11 += s19 * 136657
s12 -= s19 * 683901
s19 = 0
s6 += s18 * 666643
s7 += s18 * 470296
s8 += s18 * 654183
s9 -= s18 * 997805
s10 += s18 * 136657
s11 -= s18 * 683901
s18 = 0
carry[6] = (s6 + (1 << 20)) >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[8] = (s8 + (1 << 20)) >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[10] = (s10 + (1 << 20)) >> 21
s11 += carry[10]
s10 -= carry[10] << 21
carry[12] = (s12 + (1 << 20)) >> 21
s13 += carry[12]
s12 -= carry[12] << 21
carry[14] = (s14 + (1 << 20)) >> 21
s15 += carry[14]
s14 -= carry[14] << 21
carry[16] = (s16 + (1 << 20)) >> 21
s17 += carry[16]
s16 -= carry[16] << 21
carry[7] = (s7 + (1 << 20)) >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[9] = (s9 + (1 << 20)) >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[11] = (s11 + (1 << 20)) >> 21
s12 += carry[11]
s11 -= carry[11] << 21
carry[13] = (s13 + (1 << 20)) >> 21
s14 += carry[13]
s13 -= carry[13] << 21
carry[15] = (s15 + (1 << 20)) >> 21
s16 += carry[15]
s15 -= carry[15] << 21
s5 += s17 * 666643
s6 += s17 * 470296
s7 += s17 * 654183
s8 -= s17 * 997805
s9 += s17 * 136657
s10 -= s17 * 683901
s17 = 0
s4 += s16 * 666643
s5 += s16 * 470296
s6 += s16 * 654183
s7 -= s16 * 997805
s8 += s16 * 136657
s9 -= s16 * 683901
s16 = 0
s3 += s15 * 666643
s4 += s15 * 470296
s5 += s15 * 654183
s6 -= s15 * 997805
s7 += s15 * 136657
s8 -= s15 * 683901
s15 = 0
s2 += s14 * 666643
s3 += s14 * 470296
s4 += s14 * 654183
s5 -= s14 * 997805
s6 += s14 * 136657
s7 -= s14 * 683901
s14 = 0
s1 += s13 * 666643
s2 += s13 * 470296
s3 += s13 * 654183
s4 -= s13 * 997805
s5 += s13 * 136657
s6 -= s13 * 683901
s13 = 0
s0 += s12 * 666643
s1 += s12 * 470296
s2 += s12 * 654183
s3 -= s12 * 997805
s4 += s12 * 136657
s5 -= s12 * 683901
s12 = 0
carry[0] = (s0 + (1 << 20)) >> 21
s1 += carry[0]
s0 -= carry[0] << 21
carry[2] = (s2 + (1 << 20)) >> 21
s3 += carry[2]
s2 -= carry[2] << 21
carry[4] = (s4 + (1 << 20)) >> 21
s5 += carry[4]
s4 -= carry[4] << 21
carry[6] = (s6 + (1 << 20)) >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[8] = (s8 + (1 << 20)) >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[10] = (s10 + (1 << 20)) >> 21
s11 += carry[10]
s10 -= carry[10] << 21
carry[1] = (s1 + (1 << 20)) >> 21
s2 += carry[1]
s1 -= carry[1] << 21
carry[3] = (s3 + (1 << 20)) >> 21
s4 += carry[3]
s3 -= carry[3] << 21
carry[5] = (s5 + (1 << 20)) >> 21
s6 += carry[5]
s5 -= carry[5] << 21
carry[7] = (s7 + (1 << 20)) >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[9] = (s9 + (1 << 20)) >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[11] = (s11 + (1 << 20)) >> 21
s12 += carry[11]
s11 -= carry[11] << 21
s0 += s12 * 666643
s1 += s12 * 470296
s2 += s12 * 654183
s3 -= s12 * 997805
s4 += s12 * 136657
s5 -= s12 * 683901
s12 = 0
carry[0] = s0 >> 21
s1 += carry[0]
s0 -= carry[0] << 21
carry[1] = s1 >> 21
s2 += carry[1]
s1 -= carry[1] << 21
carry[2] = s2 >> 21
s3 += carry[2]
s2 -= carry[2] << 21
carry[3] = s3 >> 21
s4 += carry[3]
s3 -= carry[3] << 21
carry[4] = s4 >> 21
s5 += carry[4]
s4 -= carry[4] << 21
carry[5] = s5 >> 21
s6 += carry[5]
s5 -= carry[5] << 21
carry[6] = s6 >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[7] = s7 >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[8] = s8 >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[9] = s9 >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[10] = s10 >> 21
s11 += carry[10]
s10 -= carry[10] << 21
carry[11] = s11 >> 21
s12 += carry[11]
s11 -= carry[11] << 21
s0 += s12 * 666643
s1 += s12 * 470296
s2 += s12 * 654183
s3 -= s12 * 997805
s4 += s12 * 136657
s5 -= s12 * 683901
s12 = 0
carry[0] = s0 >> 21
s1 += carry[0]
s0 -= carry[0] << 21
carry[1] = s1 >> 21
s2 += carry[1]
s1 -= carry[1] << 21
carry[2] = s2 >> 21
s3 += carry[2]
s2 -= carry[2] << 21
carry[3] = s3 >> 21
s4 += carry[3]
s3 -= carry[3] << 21
carry[4] = s4 >> 21
s5 += carry[4]
s4 -= carry[4] << 21
carry[5] = s5 >> 21
s6 += carry[5]
s5 -= carry[5] << 21
carry[6] = s6 >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[7] = s7 >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[8] = s8 >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[9] = s9 >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[10] = s10 >> 21
s11 += carry[10]
s10 -= carry[10] << 21
s[0] = byte(s0 >> 0)
s[1] = byte(s0 >> 8)
s[2] = byte((s0 >> 16) | (s1 << 5))
s[3] = byte(s1 >> 3)
s[4] = byte(s1 >> 11)
s[5] = byte((s1 >> 19) | (s2 << 2))
s[6] = byte(s2 >> 6)
s[7] = byte((s2 >> 14) | (s3 << 7))
s[8] = byte(s3 >> 1)
s[9] = byte(s3 >> 9)
s[10] = byte((s3 >> 17) | (s4 << 4))
s[11] = byte(s4 >> 4)
s[12] = byte(s4 >> 12)
s[13] = byte((s4 >> 20) | (s5 << 1))
s[14] = byte(s5 >> 7)
s[15] = byte((s5 >> 15) | (s6 << 6))
s[16] = byte(s6 >> 2)
s[17] = byte(s6 >> 10)
s[18] = byte((s6 >> 18) | (s7 << 3))
s[19] = byte(s7 >> 5)
s[20] = byte(s7 >> 13)
s[21] = byte(s8 >> 0)
s[22] = byte(s8 >> 8)
s[23] = byte((s8 >> 16) | (s9 << 5))
s[24] = byte(s9 >> 3)
s[25] = byte(s9 >> 11)
s[26] = byte((s9 >> 19) | (s10 << 2))
s[27] = byte(s10 >> 6)
s[28] = byte((s10 >> 14) | (s11 << 7))
s[29] = byte(s11 >> 1)
s[30] = byte(s11 >> 9)
s[31] = byte(s11 >> 17)
}
// Input:
// s[0]+256*s[1]+...+256^63*s[63] = s
//
// Output:
// s[0]+256*s[1]+...+256^31*s[31] = s mod l
// where l = 2^252 + 27742317777372353535851937790883648493.
func ScReduce(out *[32]byte, s *[64]byte) {
s0 := 2097151 & load3(s[:])
s1 := 2097151 & (load4(s[2:]) >> 5)
s2 := 2097151 & (load3(s[5:]) >> 2)
s3 := 2097151 & (load4(s[7:]) >> 7)
s4 := 2097151 & (load4(s[10:]) >> 4)
s5 := 2097151 & (load3(s[13:]) >> 1)
s6 := 2097151 & (load4(s[15:]) >> 6)
s7 := 2097151 & (load3(s[18:]) >> 3)
s8 := 2097151 & load3(s[21:])
s9 := 2097151 & (load4(s[23:]) >> 5)
s10 := 2097151 & (load3(s[26:]) >> 2)
s11 := 2097151 & (load4(s[28:]) >> 7)
s12 := 2097151 & (load4(s[31:]) >> 4)
s13 := 2097151 & (load3(s[34:]) >> 1)
s14 := 2097151 & (load4(s[36:]) >> 6)
s15 := 2097151 & (load3(s[39:]) >> 3)
s16 := 2097151 & load3(s[42:])
s17 := 2097151 & (load4(s[44:]) >> 5)
s18 := 2097151 & (load3(s[47:]) >> 2)
s19 := 2097151 & (load4(s[49:]) >> 7)
s20 := 2097151 & (load4(s[52:]) >> 4)
s21 := 2097151 & (load3(s[55:]) >> 1)
s22 := 2097151 & (load4(s[57:]) >> 6)
s23 := (load4(s[60:]) >> 3)
s11 += s23 * 666643
s12 += s23 * 470296
s13 += s23 * 654183
s14 -= s23 * 997805
s15 += s23 * 136657
s16 -= s23 * 683901
s23 = 0
s10 += s22 * 666643
s11 += s22 * 470296
s12 += s22 * 654183
s13 -= s22 * 997805
s14 += s22 * 136657
s15 -= s22 * 683901
s22 = 0
s9 += s21 * 666643
s10 += s21 * 470296
s11 += s21 * 654183
s12 -= s21 * 997805
s13 += s21 * 136657
s14 -= s21 * 683901
s21 = 0
s8 += s20 * 666643
s9 += s20 * 470296
s10 += s20 * 654183
s11 -= s20 * 997805
s12 += s20 * 136657
s13 -= s20 * 683901
s20 = 0
s7 += s19 * 666643
s8 += s19 * 470296
s9 += s19 * 654183
s10 -= s19 * 997805
s11 += s19 * 136657
s12 -= s19 * 683901
s19 = 0
s6 += s18 * 666643
s7 += s18 * 470296
s8 += s18 * 654183
s9 -= s18 * 997805
s10 += s18 * 136657
s11 -= s18 * 683901
s18 = 0
var carry [17]int64
carry[6] = (s6 + (1 << 20)) >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[8] = (s8 + (1 << 20)) >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[10] = (s10 + (1 << 20)) >> 21
s11 += carry[10]
s10 -= carry[10] << 21
carry[12] = (s12 + (1 << 20)) >> 21
s13 += carry[12]
s12 -= carry[12] << 21
carry[14] = (s14 + (1 << 20)) >> 21
s15 += carry[14]
s14 -= carry[14] << 21
carry[16] = (s16 + (1 << 20)) >> 21
s17 += carry[16]
s16 -= carry[16] << 21
carry[7] = (s7 + (1 << 20)) >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[9] = (s9 + (1 << 20)) >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[11] = (s11 + (1 << 20)) >> 21
s12 += carry[11]
s11 -= carry[11] << 21
carry[13] = (s13 + (1 << 20)) >> 21
s14 += carry[13]
s13 -= carry[13] << 21
carry[15] = (s15 + (1 << 20)) >> 21
s16 += carry[15]
s15 -= carry[15] << 21
s5 += s17 * 666643
s6 += s17 * 470296
s7 += s17 * 654183
s8 -= s17 * 997805
s9 += s17 * 136657
s10 -= s17 * 683901
s17 = 0
s4 += s16 * 666643
s5 += s16 * 470296
s6 += s16 * 654183
s7 -= s16 * 997805
s8 += s16 * 136657
s9 -= s16 * 683901
s16 = 0
s3 += s15 * 666643
s4 += s15 * 470296
s5 += s15 * 654183
s6 -= s15 * 997805
s7 += s15 * 136657
s8 -= s15 * 683901
s15 = 0
s2 += s14 * 666643
s3 += s14 * 470296
s4 += s14 * 654183
s5 -= s14 * 997805
s6 += s14 * 136657
s7 -= s14 * 683901
s14 = 0
s1 += s13 * 666643
s2 += s13 * 470296
s3 += s13 * 654183
s4 -= s13 * 997805
s5 += s13 * 136657
s6 -= s13 * 683901
s13 = 0
s0 += s12 * 666643
s1 += s12 * 470296
s2 += s12 * 654183
s3 -= s12 * 997805
s4 += s12 * 136657
s5 -= s12 * 683901
s12 = 0
carry[0] = (s0 + (1 << 20)) >> 21
s1 += carry[0]
s0 -= carry[0] << 21
carry[2] = (s2 + (1 << 20)) >> 21
s3 += carry[2]
s2 -= carry[2] << 21
carry[4] = (s4 + (1 << 20)) >> 21
s5 += carry[4]
s4 -= carry[4] << 21
carry[6] = (s6 + (1 << 20)) >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[8] = (s8 + (1 << 20)) >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[10] = (s10 + (1 << 20)) >> 21
s11 += carry[10]
s10 -= carry[10] << 21
carry[1] = (s1 + (1 << 20)) >> 21
s2 += carry[1]
s1 -= carry[1] << 21
carry[3] = (s3 + (1 << 20)) >> 21
s4 += carry[3]
s3 -= carry[3] << 21
carry[5] = (s5 + (1 << 20)) >> 21
s6 += carry[5]
s5 -= carry[5] << 21
carry[7] = (s7 + (1 << 20)) >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[9] = (s9 + (1 << 20)) >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[11] = (s11 + (1 << 20)) >> 21
s12 += carry[11]
s11 -= carry[11] << 21
s0 += s12 * 666643
s1 += s12 * 470296
s2 += s12 * 654183
s3 -= s12 * 997805
s4 += s12 * 136657
s5 -= s12 * 683901
s12 = 0
carry[0] = s0 >> 21
s1 += carry[0]
s0 -= carry[0] << 21
carry[1] = s1 >> 21
s2 += carry[1]
s1 -= carry[1] << 21
carry[2] = s2 >> 21
s3 += carry[2]
s2 -= carry[2] << 21
carry[3] = s3 >> 21
s4 += carry[3]
s3 -= carry[3] << 21
carry[4] = s4 >> 21
s5 += carry[4]
s4 -= carry[4] << 21
carry[5] = s5 >> 21
s6 += carry[5]
s5 -= carry[5] << 21
carry[6] = s6 >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[7] = s7 >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[8] = s8 >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[9] = s9 >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[10] = s10 >> 21
s11 += carry[10]
s10 -= carry[10] << 21
carry[11] = s11 >> 21
s12 += carry[11]
s11 -= carry[11] << 21
s0 += s12 * 666643
s1 += s12 * 470296
s2 += s12 * 654183
s3 -= s12 * 997805
s4 += s12 * 136657
s5 -= s12 * 683901
s12 = 0
carry[0] = s0 >> 21
s1 += carry[0]
s0 -= carry[0] << 21
carry[1] = s1 >> 21
s2 += carry[1]
s1 -= carry[1] << 21
carry[2] = s2 >> 21
s3 += carry[2]
s2 -= carry[2] << 21
carry[3] = s3 >> 21
s4 += carry[3]
s3 -= carry[3] << 21
carry[4] = s4 >> 21
s5 += carry[4]
s4 -= carry[4] << 21
carry[5] = s5 >> 21
s6 += carry[5]
s5 -= carry[5] << 21
carry[6] = s6 >> 21
s7 += carry[6]
s6 -= carry[6] << 21
carry[7] = s7 >> 21
s8 += carry[7]
s7 -= carry[7] << 21
carry[8] = s8 >> 21
s9 += carry[8]
s8 -= carry[8] << 21
carry[9] = s9 >> 21
s10 += carry[9]
s9 -= carry[9] << 21
carry[10] = s10 >> 21
s11 += carry[10]
s10 -= carry[10] << 21
out[0] = byte(s0 >> 0)
out[1] = byte(s0 >> 8)
out[2] = byte((s0 >> 16) | (s1 << 5))
out[3] = byte(s1 >> 3)
out[4] = byte(s1 >> 11)
out[5] = byte((s1 >> 19) | (s2 << 2))
out[6] = byte(s2 >> 6)
out[7] = byte((s2 >> 14) | (s3 << 7))
out[8] = byte(s3 >> 1)
out[9] = byte(s3 >> 9)
out[10] = byte((s3 >> 17) | (s4 << 4))
out[11] = byte(s4 >> 4)
out[12] = byte(s4 >> 12)
out[13] = byte((s4 >> 20) | (s5 << 1))
out[14] = byte(s5 >> 7)
out[15] = byte((s5 >> 15) | (s6 << 6))
out[16] = byte(s6 >> 2)
out[17] = byte(s6 >> 10)
out[18] = byte((s6 >> 18) | (s7 << 3))
out[19] = byte(s7 >> 5)
out[20] = byte(s7 >> 13)
out[21] = byte(s8 >> 0)
out[22] = byte(s8 >> 8)
out[23] = byte((s8 >> 16) | (s9 << 5))
out[24] = byte(s9 >> 3)
out[25] = byte(s9 >> 11)
out[26] = byte((s9 >> 19) | (s10 << 2))
out[27] = byte(s10 >> 6)
out[28] = byte((s10 >> 14) | (s11 << 7))
out[29] = byte(s11 >> 1)
out[30] = byte(s11 >> 9)
out[31] = byte(s11 >> 17)
}
// order is the order of Curve25519 in little-endian form.
var order = [4]uint64{0x5812631a5cf5d3ed, 0x14def9dea2f79cd6, 0, 0x1000000000000000}
// ScMinimal returns true if the given scalar is less than the order of the
// curve.
func ScMinimal(scalar *[32]byte) bool {
for i := 3; ; i-- {
v := binary.LittleEndian.Uint64(scalar[i*8:])
if v > order[i] {
return false
} else if v < order[i] {
break
} else if i == 0 {
return false
}
}
return true
}
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