/* P=u0.Q0+u1*Q1+u2*Q2+u3*Q3 */
/*
* public static ECP2 mul4(ECP2[] Q,BIG[] u)
* {
* int i,j,nb;
* int[] a=new int[4];
* ECP2 T=new ECP2();
* ECP2 C=new ECP2();
* ECP2 P=new ECP2();
* ECP2[] W=new ECP2[8];
*
* BIG mt=new BIG();
* BIG[] t=new BIG[4];
*
* byte[] w=new byte[BIG.NLEN*BIG.BASEBITS+1];
*
* for (i=0;i<4;i++)
* {
* t[i]=new BIG(u[i]);
* Q[i].affine();
* }
*
* // precompute table
*
* W[0]=new ECP2(); W[0].copy(Q[0]); W[0].sub(Q[1]);
*
* W[1]=new ECP2(); W[1].copy(W[0]);
* W[2]=new ECP2(); W[2].copy(W[0]);
* W[3]=new ECP2(); W[3].copy(W[0]);
* W[4]=new ECP2(); W[4].copy(Q[0]); W[4].add(Q[1]);
* W[5]=new ECP2(); W[5].copy(W[4]);
* W[6]=new ECP2(); W[6].copy(W[4]);
* W[7]=new ECP2(); W[7].copy(W[4]);
* T.copy(Q[2]); T.sub(Q[3]);
* W[1].sub(T);
* W[2].add(T);
* W[5].sub(T);
* W[6].add(T);
* T.copy(Q[2]); T.add(Q[3]);
* W[0].sub(T);
* W[3].add(T);
* W[4].sub(T);
* W[7].add(T);
*
* // if multiplier is even add 1 to multiplier, and add P to correction
* mt.zero(); C.inf();
* for (i=0;i<4;i++)
* {
* if (t[i].parity()==0)
* {
* t[i].inc(1); t[i].norm();
* C.add(Q[i]);
* }
* mt.add(t[i]); mt.norm();
* }
*
* nb=1+mt.nbits();
*
* // convert exponent to signed 1-bit window
* for (j=0;j<nb;j++)
* {
* for (i=0;i<4;i++)
* {
* a[i]=(byte)(t[i].lastbits(2)-2);
* t[i].dec(a[i]); t[i].norm();
* t[i].fshr(1);
* }
* w[j]=(byte)(8*a[0]+4*a[1]+2*a[2]+a[3]);
* }
* w[nb]=(byte)(8*t[0].lastbits(2)+4*t[1].lastbits(2)+2*t[2].lastbits(2)+t[3].lastbits(2));
*
* P.copy(W[(w[nb]-1)/2]);
* for (i=nb-1;i>=0;i--)
* {
* T.select(W,w[i]);
* P.dbl();
* P.add(T);
* }
* P.sub(C); // apply correction
*
* P.affine();
* return P;
* }
*/
/* needed for SOK */
public static ECP2 MapIt(sbyte[] h)
{
BIG q = new BIG(ROM.Modulus);
BIG x = BIG.FromBytes(h);
BIG one = new BIG(1);
FP2 X;
ECP2 Q;
x.Mod(q);
while (true)
{
X = new FP2(one, x);
Q = new ECP2(X);
if (!Q.IsInfinity())
{
break;
}
x.Inc(1);
x.Norm();
}
BIG Fra = new BIG(ROM.Fra);
BIG Frb = new BIG(ROM.Frb);
X = new FP2(Fra, Frb);
if (ECP.SEXTIC_TWIST == ECP.M_TYPE)
{
X.Inverse();
X.Norm();
}
x = new BIG(ROM.CURVE_Bnx);
/* Fast Hashing to G2 - Fuentes-Castaneda, Knapp and Rodriguez-Henriquez */
if (ECP.CURVE_PAIRING_TYPE == ECP.BN)
{
ECP2 T, K;
T = new ECP2();
T.Copy(Q);
T = T.Mul(x);
if (ECP.SIGN_OF_X == ECP.NEGATIVEX)
{
T.Neg();
}
K = new ECP2();
K.Copy(T);
K.Dbl();
K.Add(T); //K.affine();
K.Frob(X);
Q.Frob(X);
Q.Frob(X);
Q.Frob(X);
Q.Add(T);
Q.Add(K);
T.Frob(X);
T.Frob(X);
Q.Add(T);
}
/* Efficient hash maps to G2 on BLS curves - Budroni, Pintore */
/* Q -> x2Q -xQ -Q +F(xQ -Q) +F(F(2Q)) */
if (ECP.CURVE_PAIRING_TYPE == ECP.BLS)
{
// ECP2 xQ,x2Q;
// xQ=new ECP2();
// x2Q=new ECP2();
ECP2 xQ = Q.Mul(x);
ECP2 x2Q = xQ.Mul(x);
if (ECP.SIGN_OF_X == ECP.NEGATIVEX)
{
xQ.Neg();
}
x2Q.Sub(xQ);
x2Q.Sub(Q);
xQ.Sub(Q);
xQ.Frob(X);
Q.Dbl();
Q.Frob(X);
Q.Frob(X);
Q.Add(x2Q);
Q.Add(xQ);
}
Q.Affine();
return(Q);
}
