curve_generic.go raw

   1  package x448
   2  
   3  import (
   4  	"encoding/binary"
   5  	"math/bits"
   6  
   7  	"github.com/cloudflare/circl/math/fp448"
   8  )
   9  
  10  func doubleGeneric(x, z *fp448.Elt) {
  11  	t0, t1 := &fp448.Elt{}, &fp448.Elt{}
  12  	fp448.AddSub(x, z)
  13  	fp448.Sqr(x, x)
  14  	fp448.Sqr(z, z)
  15  	fp448.Sub(t0, x, z)
  16  	mulA24Generic(t1, t0)
  17  	fp448.Add(t1, t1, z)
  18  	fp448.Mul(x, x, z)
  19  	fp448.Mul(z, t0, t1)
  20  }
  21  
  22  func diffAddGeneric(w *[5]fp448.Elt, b uint) {
  23  	mu, x1, z1, x2, z2 := &w[0], &w[1], &w[2], &w[3], &w[4]
  24  	fp448.Cswap(x1, x2, b)
  25  	fp448.Cswap(z1, z2, b)
  26  	fp448.AddSub(x1, z1)
  27  	fp448.Mul(z1, z1, mu)
  28  	fp448.AddSub(x1, z1)
  29  	fp448.Sqr(x1, x1)
  30  	fp448.Sqr(z1, z1)
  31  	fp448.Mul(x1, x1, z2)
  32  	fp448.Mul(z1, z1, x2)
  33  }
  34  
  35  func ladderStepGeneric(w *[5]fp448.Elt, b uint) {
  36  	x1, x2, z2, x3, z3 := &w[0], &w[1], &w[2], &w[3], &w[4]
  37  	t0 := &fp448.Elt{}
  38  	t1 := &fp448.Elt{}
  39  	fp448.AddSub(x2, z2)
  40  	fp448.AddSub(x3, z3)
  41  	fp448.Mul(t0, x2, z3)
  42  	fp448.Mul(t1, x3, z2)
  43  	fp448.AddSub(t0, t1)
  44  	fp448.Cmov(x2, x3, b)
  45  	fp448.Cmov(z2, z3, b)
  46  	fp448.Sqr(x3, t0)
  47  	fp448.Sqr(z3, t1)
  48  	fp448.Mul(z3, x1, z3)
  49  	fp448.Sqr(x2, x2)
  50  	fp448.Sqr(z2, z2)
  51  	fp448.Sub(t0, x2, z2)
  52  	mulA24Generic(t1, t0)
  53  	fp448.Add(t1, t1, z2)
  54  	fp448.Mul(x2, x2, z2)
  55  	fp448.Mul(z2, t0, t1)
  56  }
  57  
  58  func mulA24Generic(z, x *fp448.Elt) {
  59  	const A24 = 39082
  60  	const n = 8
  61  	var xx [7]uint64
  62  	for i := range xx {
  63  		xx[i] = binary.LittleEndian.Uint64(x[i*n : (i+1)*n])
  64  	}
  65  	h0, l0 := bits.Mul64(xx[0], A24)
  66  	h1, l1 := bits.Mul64(xx[1], A24)
  67  	h2, l2 := bits.Mul64(xx[2], A24)
  68  	h3, l3 := bits.Mul64(xx[3], A24)
  69  	h4, l4 := bits.Mul64(xx[4], A24)
  70  	h5, l5 := bits.Mul64(xx[5], A24)
  71  	h6, l6 := bits.Mul64(xx[6], A24)
  72  
  73  	l1, c0 := bits.Add64(h0, l1, 0)
  74  	l2, c1 := bits.Add64(h1, l2, c0)
  75  	l3, c2 := bits.Add64(h2, l3, c1)
  76  	l4, c3 := bits.Add64(h3, l4, c2)
  77  	l5, c4 := bits.Add64(h4, l5, c3)
  78  	l6, c5 := bits.Add64(h5, l6, c4)
  79  	l7, _ := bits.Add64(h6, 0, c5)
  80  
  81  	l0, c0 = bits.Add64(l0, l7, 0)
  82  	l1, c1 = bits.Add64(l1, 0, c0)
  83  	l2, c2 = bits.Add64(l2, 0, c1)
  84  	l3, c3 = bits.Add64(l3, l7<<32, c2)
  85  	l4, c4 = bits.Add64(l4, 0, c3)
  86  	l5, c5 = bits.Add64(l5, 0, c4)
  87  	l6, l7 = bits.Add64(l6, 0, c5)
  88  
  89  	xx[0], c0 = bits.Add64(l0, l7, 0)
  90  	xx[1], c1 = bits.Add64(l1, 0, c0)
  91  	xx[2], c2 = bits.Add64(l2, 0, c1)
  92  	xx[3], c3 = bits.Add64(l3, l7<<32, c2)
  93  	xx[4], c4 = bits.Add64(l4, 0, c3)
  94  	xx[5], c5 = bits.Add64(l5, 0, c4)
  95  	xx[6], _ = bits.Add64(l6, 0, c5)
  96  
  97  	for i := range xx {
  98  		binary.LittleEndian.PutUint64(z[i*n:(i+1)*n], xx[i])
  99  	}
 100  }
 101