/* reduces this DBIG mod a BIG, and returns the BIG */ public virtual BIG Mod(BIG c) { int k = 0; Norm(); DBIG m = new DBIG(c); DBIG r = new DBIG(0); if (Comp(this, m) < 0) { return(new BIG(this)); } do { m.Shl(1); k++; } while (Comp(this, m) >= 0); while (k > 0) { m.Shr(1); r.Copy(this); r.Sub(m); r.Norm(); CMove(r, (int)(1 - ((r.w[BIG.DNLEN - 1] >> (BIG.CHUNK - 1)) & 1))); k--; } return(new BIG(this)); }
/* this*=y */ /* Now uses Lazy reduction */ public void Mul(FP2 y) { if ((long)(a.XES + b.XES) * (y.a.XES + y.b.XES) > (long)FP.FEXCESS) { if (a.XES > 1) { a.Reduce(); } if (b.XES > 1) { b.Reduce(); } } DBIG pR = new DBIG(0); BIG C = new BIG(a.x); BIG D = new BIG(y.a.x); pR.UCopy(new BIG(ROM.Modulus)); DBIG A = BIG.Mul(a.x, y.a.x); DBIG B = BIG.Mul(b.x, y.b.x); C.Add(b.x); C.Norm(); D.Add(y.b.x); D.Norm(); DBIG E = BIG.Mul(C, D); DBIG F = new DBIG(A); F.Add(B); B.RSub(pR); A.Add(B); A.Norm(); E.Sub(F); E.Norm(); a.x.Copy(FP.Mod(A)); a.XES = 3; b.x.Copy(FP.Mod(E)); b.XES = 2; }
/* return this/c */ public virtual BIG Div(BIG c) { int d, k = 0; DBIG m = new DBIG(c); DBIG dr = new DBIG(0); BIG r = new BIG(0); BIG a = new BIG(0); BIG e = new BIG(1); Norm(); while (Comp(this, m) >= 0) { e.FShl(1); m.Shl(1); k++; } while (k > 0) { m.Shr(1); e.Shr(1); dr.Copy(this); dr.Sub(m); dr.Norm(); d = (int)(1 - ((dr.w[BIG.DNLEN - 1] >> (BIG.CHUNK - 1)) & 1)); CMove(dr, d); r.Copy(a); r.Add(e); r.Norm(); a.CMove(r, d); k--; } return(a); }