public static int ge_frombytes(out GroupElementP3 h, byte[] data, int offset)
{
FieldElement u;
FieldElement v;
FieldElement v3;
FieldElement vxx;
FieldElement check;
FieldOperations.fe_frombytes(out h.Y, data, offset);
FieldOperations.fe_1(out h.Z);
FieldOperations.fe_sq(out u, ref h.Y);
FieldOperations.fe_mul(out v, ref u, ref LookupTables.d);
FieldOperations.fe_sub(out u, ref u, ref h.Z); /* u = y^2-1 */
FieldOperations.fe_add(out v, ref v, ref h.Z); /* v = dy^2+1 */
FieldOperations.fe_sq(out v3, ref v);
FieldOperations.fe_mul(out v3, ref v3, ref v); /* v3 = v^3 */
FieldOperations.fe_sq(out h.X, ref v3);
FieldOperations.fe_mul(out h.X, ref h.X, ref v);
FieldOperations.fe_mul(out h.X, ref h.X, ref u); /* x = uv^7 */
FieldOperations.fe_pow22523(out h.X, ref h.X); /* x = (uv^7)^((q-5)/8) */
FieldOperations.fe_mul(out h.X, ref h.X, ref v3);
FieldOperations.fe_mul(out h.X, ref h.X, ref u); /* x = uv^3(uv^7)^((q-5)/8) */
FieldOperations.fe_sq(out vxx, ref h.X);
FieldOperations.fe_mul(out vxx, ref vxx, ref v);
FieldOperations.fe_sub(out check, ref vxx, ref u); /* vx^2-u */
if (FieldOperations.fe_isnonzero(ref check) != 0)
{
FieldOperations.fe_add(out check, ref vxx, ref u); /* vx^2+u */
if (FieldOperations.fe_isnonzero(ref check) != 0)
{
h = default(GroupElementP3);
return(-1);
}
FieldOperations.fe_mul(out h.X, ref h.X, ref LookupTables.sqrtm1);
FieldOperations.fe_reduce(out h.X, ref h.X);
}
if (FieldOperations.fe_isnegative(ref h.X) != (data[offset + 31] >> 7))
{
FieldOperations.fe_neg(out h.X, ref h.X);
}
FieldOperations.fe_mul(out h.T, ref h.X, ref h.Y);
return(0);
}
public static void ge_fromfe_frombytes_vartime(out GroupElementP2 r, byte[] s, int offset)
{
FieldElement u, v, w, x, y, z;
byte sign;
FieldOperations.fe_frombytes(out u, s, offset);
FieldOperations.fe_sq2(out v, ref u); /* 2 * u^2 */
FieldOperations.fe_1(out w);
FieldOperations.fe_add(out w, ref v, ref w); /* w = 2 * u^2 + 1 */
FieldOperations.fe_sq(out x, ref w); /* w^2 */
FieldOperations.fe_mul(out y, ref FieldOperations.fe_ma2, ref v); /* -2 * A^2 * u^2 */
FieldOperations.fe_add(out x, ref x, ref y); /* x = w^2 - 2 * A^2 * u^2 */
FieldOperations.fe_divpowm1(out r.X, ref w, ref x); /* (w / x)^(m + 1) */
FieldOperations.fe_sq(out y, ref r.X);
FieldOperations.fe_mul(out x, ref y, ref x);
FieldOperations.fe_sub(out y, ref w, ref x);
FieldOperations.fe_copy(out z, ref FieldOperations.fe_ma);
if (FieldOperations.fe_isnonzero(ref y) != 0)
{
FieldOperations.fe_add(out y, ref w, ref x);
if (FieldOperations.fe_isnonzero(ref y) != 0)
{
goto negative;
}
else
{
FieldOperations.fe_mul(out r.X, ref r.X, ref FieldOperations.fe_fffb1);
}
}
else
{
FieldOperations.fe_mul(out r.X, ref r.X, ref FieldOperations.fe_fffb2);
}
FieldOperations.fe_mul(out r.X, ref r.X, ref u); /* u * sqrt(2 * A * (A + 2) * w / x) */
FieldOperations.fe_mul(out z, ref z, ref v); /* -2 * A * u^2 */
sign = 0;
goto setsign;
negative:
FieldOperations.fe_mul(out x, ref x, ref FieldOperations.fe_sqrtm1);
FieldOperations.fe_sub(out y, ref w, ref x);
if (FieldOperations.fe_isnonzero(ref y) != 0)
{
//assert((fe_add(y, w, x), !fe_isnonzero(y)));
FieldOperations.fe_mul(out r.X, ref r.X, ref FieldOperations.fe_fffb3);
}
else
{
FieldOperations.fe_mul(out r.X, ref r.X, ref FieldOperations.fe_fffb4);
}
/* r->X = sqrt(A * (A + 2) * w / x) */
/* z = -A */
sign = 1;
setsign:
if (FieldOperations.fe_isnegative(ref r.X) != sign)
{
//assert(fe_isnonzero(r->X));
FieldOperations.fe_neg(out r.X, ref r.X);
}
FieldOperations.fe_add(out r.Z, ref z, ref w);
FieldOperations.fe_sub(out r.Y, ref z, ref w);
FieldOperations.fe_mul(out r.X, ref r.X, ref r.Z);
}