public static void SetAllGroupElementJacobianVariable(Span <GE> r, ReadOnlySpan <GEJ> a, int len)
{
FE u;
int i;
int last_i = SIZE_MAX;
for (i = 0; i < len; i++)
{
if (!a[i].infinity)
{
/* Use destination's x coordinates as scratch space */
if (last_i == SIZE_MAX)
{
r[i] = new GE(a[i].z, r[i].y, r[i].infinity);
}
else
{
FE rx = r[last_i].x * a[i].z;
r[i] = new GE(rx, r[i].y, r[i].infinity);
}
last_i = i;
}
}
if (last_i == SIZE_MAX)
{
return;
}
u = r[last_i].x.InverseVariable();
i = last_i;
while (i > 0)
{
i--;
if (!a[i].infinity)
{
FE rx = r[i].x * u;
r[last_i] = new GE(rx, r[last_i].y, r[last_i].infinity);
u = u * a[last_i].z;
last_i = i;
}
}
VERIFY_CHECK(!a[last_i].infinity);
r[last_i] = new GE(u, r[last_i].y, r[last_i].infinity);
for (i = 0; i < len; i++)
{
r[i] = new GE(r[i].x, r[i].y, a[i].infinity);
if (!a[i].infinity)
{
r[i] = a[i].ToGroupElementZInv(r[i].x);
}
}
}
public static bool TryCreateXOVariable(FE x, bool odd, out GE result)
{
if (!TryCreateXQuad(x, out result))
{
return(false);
}
var ry = result.y.NormalizeVariable();
if (ry.IsOdd != odd)
{
ry = ry.Negate(1);
}
result = new GE(result.x, ry, result.infinity);
return(true);
}
public static bool TryCreateXQuad(FE x, out GE result)
{
result = GE.Zero;
FE rx, ry;
bool rinfinity;
FE x2, x3, c;
rx = x;
x2 = x.Sqr();
x3 = x * x2;
rinfinity = false;
c = new FE(EC.CURVE_B);
c += x3;
if (!c.Sqrt(out ry))
{
return(false);
}
result = new GE(rx, ry, rinfinity);
return(true);
}
public ECMultGenContext()
{
Span <GE> prec = stackalloc GE[1024];
GEJ gj;
GEJ nums_gej;
int i, j;
this.prec = new GEStorage[64, 16];
gj = EC.G.ToGroupElementJacobian();
/* Construct a group element with no known corresponding scalar (nothing up my sleeve). */
{
var nums_b32 = "The scalar for this x is unknown".ToCharArray().Select(b => (byte)b).ToArray();
FE nums_x;
GE nums_ge;
var r = FE.TryCreate(nums_b32, out nums_x);
VERIFY_CHECK(r);
r = GE.TryCreateXOVariable(nums_x, false, out nums_ge);
VERIFY_CHECK(r);
nums_gej = nums_ge.ToGroupElementJacobian();
/* Add G to make the bits in x uniformly distributed. */
nums_gej = nums_gej.AddVariable(EC.G, out _);
}
/* compute prec. */
{
Span <GEJ> precj = stackalloc GEJ[1024]; /* Jacobian versions of prec. */
GEJ gbase;
GEJ numsbase;
gbase = gj; /* 16^j * G */
numsbase = nums_gej; /* 2^j * nums. */
for (j = 0; j < 64; j++)
{
/* Set precj[j*16 .. j*16+15] to (numsbase, numsbase + gbase, ..., numsbase + 15*gbase). */
precj[j * 16] = numsbase;
for (i = 1; i < 16; i++)
{
precj[j * 16 + i] = precj[j * 16 + i - 1].AddVariable(gbase, out _);
}
/* Multiply gbase by 16. */
for (i = 0; i < 4; i++)
{
gbase = gbase.DoubleVariable();
}
/* Multiply numbase by 2. */
numsbase = numsbase.DoubleVariable();
if (j == 62)
{
/* In the last iteration, numsbase is (1 - 2^j) * nums instead. */
numsbase = numsbase.Negate();
numsbase = numsbase.AddVariable(nums_gej, out _);
}
}
GE.SetAllGroupElementJacobianVariable(prec, precj, 1024);
}
for (j = 0; j < 64; j++)
{
for (i = 0; i < 16; i++)
{
this.prec[j, i] = prec[j * 16 + i].ToStorage();
}
}
Blind();
}
