KGC_TEST/miracl/source/curve/pairing/cp_pair.cpp

1074 lines
18 KiB
C++

/*
*
* cp_pair.cpp
*
* Cocks-Pinch curve, Tate pairing embedding degree 2, ideal for security level AES-80
*
* Provides high level interface to pairing functions
*
* GT=pairing(G2,G1)
*
* This is calculated on a Pairing Friendly Curve (PFC), which must first be defined.
*
* G1 is a point over the base field, G2 is a point on the quadratic twist
* GT is a finite field point over the 2nd extension, where 2 is the embedding degree.
*
*/
#define MR_PAIRING_CP
#include "pairing_3.h"
// Cocks-Pinch curve parameters, A,B and n, where p=3 mod 4
// AES_SECURITY=80 bit curve
// Curve E:y^2=x^3-3x+B, #E=COF*order, modulus p
static char MODtext[]="8D5006492B424C09D2FEBE717EE382A57EBE3A352FC383E1AC79F21DDB43706CFB192333A7E9CF644636332E83D90A1E56EFBAE8715AA07883483F8267E80ED3";
static char Btext[]="609993837367998001C95B87A6BA872135E26906DB4C192D6E038486177A3EDF6C50B9BB20DF881F2BD05842F598F3E037B362DBF89F0A62E5871D41D951BF8E";
static char COFtext[]="11AA00C9256849813A5FD7CE2FDC7054AFD7809E7F7FD948C4B9C1C1E76FFEFF4ECAB83C950112DECB41D6EDA";
void read_only_error(void)
{
cout << "Attempt to write to read-only object" << endl;
exit(0);
}
// Using SHA256 as basic hash algorithm
//
// Hash function
//
#define HASH_LEN 32
Big H1(char *string)
{ // Hash a zero-terminated string to a number < modulus
Big h,p;
char s[HASH_LEN];
int i,j;
sha256 sh;
shs256_init(&sh);
for (i=0;;i++)
{
if (string[i]==0) break;
shs256_process(&sh,string[i]);
}
shs256_hash(&sh,s);
p=get_modulus();
h=1; j=0; i=1;
forever
{
h*=256;
if (j==HASH_LEN) {h+=i++; j=0;}
else h+=s[j++];
if (h>=p) break;
}
h%=p;
return h;
}
void PFC::start_hash(void)
{
shs256_init(&SH);
}
Big PFC::finish_hash_to_group(void)
{
Big hash;
char s[HASH_LEN];
shs256_hash(&SH,s);
hash=from_binary(HASH_LEN,s);
return hash%(*ord);
}
void PFC::add_to_hash(const GT& x)
{ // compress it and add
ZZn2 u=x.g;
Big a;
int m;
u.get(a);
while (a>0)
{
m=a%256;
shs256_process(&SH,m);
a/=256;
}
}
void PFC::add_to_hash(const G1& x)
{
Big a,X,Y;
int i,m;
x.g.get(X,Y);
a=X;
while (a>0)
{
m=a%256;
shs256_process(&SH,m);
a/=256;
}
a=Y;
while (a>0)
{
m=a%256;
shs256_process(&SH,m);
a/=256;
}
}
void PFC::add_to_hash(const G2& x)
{
Big a,X,Y;
int i,m;
x.g.get(X,Y);
a=X;
while (a>0)
{
m=a%256;
shs256_process(&SH,m);
a/=256;
}
a=Y;
while (a>0)
{
m=a%256;
shs256_process(&SH,m);
a/=256;
}
}
void PFC::add_to_hash(const Big& x)
{
int m;
Big a=x;
while (a>0)
{
m=a%256;
shs256_process(&SH,m);
a/=256;
}
}
void PFC::add_to_hash(char *x)
{
int i=0;
while (x[i]!=0)
{
shs256_process(&SH,x[i]);
i++;
}
}
Big H2(ZZn2 y)
{ // Hash and compress an Fp2 to a big number
sha256 sh;
Big a,h;
char s[HASH_LEN];
int m;
shs256_init(&sh);
y.get(a);
while (a>0)
{
m=a%256;
shs256_process(&sh,m);
a/=256;
}
shs256_hash(&sh,s);
h=from_binary(HASH_LEN,s);
return h;
}
#ifndef MR_AFFINE_ONLY
void force(ZZn& x,ZZn& y,ZZn& z,ECn& A)
{ // A=(x,y,z)
copy(getbig(x),A.get_point()->X);
copy(getbig(y),A.get_point()->Y);
copy(getbig(z),A.get_point()->Z);
A.get_point()->marker=MR_EPOINT_GENERAL;
}
void extract(ECn &A, ZZn& x,ZZn& y,ZZn& z)
{ // (x,y,z) <- A
big t;
x=(A.get_point())->X;
y=(A.get_point())->Y;
t=(A.get_point())->Z;
if (A.get_status()!=MR_EPOINT_GENERAL) z=1;
else z=t;
}
#endif
void force(ZZn& x,ZZn& y,ECn& A)
{ // A=(x,y)
copy(getbig(x),A.get_point()->X);
copy(getbig(y),A.get_point()->Y);
A.get_point()->marker=MR_EPOINT_NORMALIZED;
}
void extract(ECn& A,ZZn& x,ZZn& y)
{ // (x,y) <- A
x=(A.get_point())->X;
y=(A.get_point())->Y;
}
void extractZ(ECn& A,ZZn& z)
{
big t;
t=(A.get_point())->Z;
if (A.get_status()!=MR_EPOINT_GENERAL) z=1;
else z=t;
}
//
// Line from A to destination C. Let A=(x,y)
// Line Y-slope.X-c=0, through A, so intercept c=y-slope.x
// Line Y-slope.X-y+slope.x = (Y-y)-slope.(X-x) = 0
// Now evaluate at Q -> return (Qy-y)-slope.(Qx-x)
//
ZZn2 line(ECn& A,ECn& C,ECn& B,int type,ZZn& slope,ZZn& ex1,ZZn& ex2,ZZn& Px,ZZn& Py)
{
ZZn2 w;
ZZn x,y,z3;
extractZ(C,z3);
if (type==MR_ADD)
{
extract(B,x,y);
w.set(slope*(x+Px)-z3*y,z3*Py);
}
if (type==MR_DOUBLE)
{
extract(A,x,y);
w.set(-(slope*ex2)*Px-slope*x+ex1,-(z3*ex2)*Py);
}
/*
extract(A,x,y,z);
x*=z; t=z; z*=z; z*=t; // 9 ZZn muls
n*=z; n+=x; n*=slope;
d*=z; w.set(-y,d);
extractZ(C,z3);
w*=z3; w+=n;
*/
// w.set(Px*z*z*z*slope+slope*x*z-y*z3,Py*z*z*z*z3);
return w;
}
//
// Add A=A+B (or A=A+A)
// Return line function value
//
ZZn2 g(ECn& A,ECn& B,ZZn& Px,ZZn& Py)
{
int type;
ZZn lam,extra1,extra2;
ZZn2 u;
ECn P=A;
big ptr,ex1,ex2;
type=A.add(B,&ptr,&ex1,&ex2);
if (!type) return (ZZn2)1;
lam=ptr;
extra1=ex1;
extra2=ex2;
return line(P,A,B,type,lam,extra1,extra2,Px,Py);
}
// if multiples of G2 can be precalculated, its a lot faster!
ZZn2 gp(ZZn* ptable,int &j,ZZn& Px,ZZn& Py)
{
ZZn2 w;
w.set(ptable[j]*Px+ptable[j+1],Py);
j+=2;
return w;
}
//
// Spill precomputation on pairing to byte array
//
int PFC::spill(G2& w,char *& bytes)
{
int i,j,n=2*(bits(*ord-1)-2+ham(*ord));
int bytes_per_big=(MIRACL/8)*(get_mip()->nib-1);
int len=n*bytes_per_big;
Big x;
if (w.ptable==NULL) return 0;
bytes=new char[len];
for (i=j=0;i<n;i++)
{
x=w.ptable[i];
to_binary(x,bytes_per_big,&bytes[j],TRUE);
j+=bytes_per_big;
}
delete [] w.ptable;
w.ptable=NULL;
return len;
}
//
// Restore precomputation on pairing to byte array
//
void PFC::restore(char * bytes,G2& w)
{
int i,j,n=2*(bits(*ord-1)-2+ham(*ord));
int bytes_per_big=(MIRACL/8)*(get_mip()->nib-1);
int len=n*bytes_per_big;
Big x;
if (w.ptable!=NULL) return;
w.ptable=new ZZn[n];
for (i=j=0;i<n;i++)
{
x=from_binary(bytes_per_big,&bytes[j]);
w.ptable[i]=x;
j+=bytes_per_big;
}
for (i=0;i<len;i++) bytes[i]=0;
delete [] bytes;
}
// precompute G2 table for pairing
int PFC::precomp_for_pairing(G2& w)
{
int i,j,nb,len;
ECn A,Q,B;
ZZn lam,x,y;
big ptr;
Big iters=*ord-1;
A=w.g;
normalise(A);
B=A;
nb=bits(iters);
j=0;
len=2*(nb-2+ham(*ord));
w.ptable=new ZZn[len];
get_mip()->coord=MR_AFFINE;
for (i=nb-2;i>=0;i--)
{
Q=A;
// Evaluate line from A to A+B
A.add(A,&ptr);
lam=ptr;
extract(Q,x,y);
w.ptable[j++]=lam; w.ptable[j++]=lam*x-y;
if (bit(iters,i)==1)
{
Q=A;
A.add(B,&ptr);
lam=ptr;
extract(Q,x,y);
w.ptable[j++]=lam; w.ptable[j++]=lam*x-y;
}
}
get_mip()->coord=MR_PROJECTIVE;
return len;
}
GT PFC::multi_miller(int n,G2** QQ,G1** PP)
{
GT z;
ZZn *Px,*Py;
int i,j,*k,nb;
ECn *Q,*A;
ECn P;
ZZn2 res;
Big iters=*ord-1;
Px=new ZZn[n];
Py=new ZZn[n];
Q=new ECn[n];
A=new ECn[n];
k=new int[n];
nb=bits(iters);
res=1;
for (j=0;j<n;j++)
{
k[j]=0;
P=PP[j]->g; normalise(P); Q[j]=QQ[j]->g; normalise(Q[j]);
extract(P,Px[j],Py[j]);
}
for (j=0;j<n;j++) A[j]=Q[j];
for (i=nb-2;i>=0;i--)
{
res*=res;
for (j=0;j<n;j++)
{
if (QQ[j]->ptable==NULL)
res*=g(A[j],A[j],Px[j],Py[j]);
else
res*=gp(QQ[j]->ptable,k[j],Px[j],Py[j]);
}
if (bit(iters,i)==1)
for (j=0;j<n;j++)
{
if (QQ[j]->ptable==NULL)
res*=g(A[j],Q[j],Px[j],Py[j]);
else
res*=gp(QQ[j]->ptable,k[j],Px[j],Py[j]);
}
if (res.iszero()) return 0;
}
delete [] k;
delete [] A;
delete [] Q;
delete [] Py;
delete [] Px;
z.g=res;
return z;
}
//
// Tate Pairing G1 x G1 -> GT
//
// P and Q are points of order q in G1.
//
GT PFC::miller_loop(const G2& QQ,const G1& PP)
{
GT z;
int i,j,n,nb,nbw,nzs;
ECn A,Q;
ECn P;
ZZn Px,Py;
BOOL precomp;
ZZn2 res;
Big iters=*ord-1; // can omit last addition
P=PP.g; Q=QQ.g;
precomp=FALSE;
if (QQ.ptable!=NULL) precomp=TRUE;
normalise(P);
normalise(Q);
extract(P,Px,Py);
//Px=-Px;
res=1;
A=Q; // reset A
nb=bits(iters);
j=0;
for (i=nb-2;i>=0;i--)
{
res*=res;
if (precomp) res*=gp(QQ.ptable,j,Px,Py);
else res*=g(A,A,Px,Py);
if (bit(iters,i)==1)
{
if (precomp) res*=gp(QQ.ptable,j,Px,Py);
else res*=g(A,Q,Px,Py);
}
}
z.g=res;
return z;
}
GT PFC::final_exp(const GT& z)
{
GT y;
ZZn2 res;
res=z.g;
res=conj(res)/res;
res=pow(res,(*mod+1)/(*ord)); // raise to power of (p^2-1)/q
y.g=res;
return y;
}
PFC::PFC(int s, csprng *rng)
{
int mod_bits,words;
if (s!=80)
{
cout << "No suitable curve available" << endl;
exit(0);
}
mod_bits=512;
if (mod_bits%MIRACL==0)
words=(mod_bits/MIRACL);
else
words=(mod_bits/MIRACL)+1;
#ifdef MR_SIMPLE_BASE
miracl *mip=mirsys((MIRACL/4)*words,16);
#else
miracl *mip=mirsys(words,0);
mip->IOBASE=16;
#endif
B=new Big;
mod=new Big;
ord=new Big;
cof=new Big;
npoints=new Big;
trace=new Big;
*B=Btext;
*cof=COFtext;
*ord=pow((Big)2,159)+pow((Big)2,17)+1;
*npoints=*cof*(*ord);
S=s;
*mod=MODtext;
*trace=*mod+1-*npoints;
ecurve(-3,*B,*mod,MR_PROJECTIVE);
RNG=rng;
}
PFC::~PFC()
{
delete B;
delete mod;
delete ord;
delete cof;
delete npoints;
delete trace;
mirexit();
}
G1 PFC::mult(const G1& w,const Big& k)
{
G1 z;
if (w.mtable!=NULL)
{ // we have precomputed values
Big e=k;
if (k<0) e=-e;
int i,j,t=w.mtbits; // MR_ROUNDUP(2*S,WINDOW_SIZE);
j=recode(e,t,WINDOW_SIZE,t-1);
z.g=w.mtable[j];
for (i=t-2;i>=0;i--)
{
j=recode(e,t,WINDOW_SIZE,i);
z.g+=z.g;
if (j>0) z.g+=w.mtable[j];
}
if (k<0) z.g=-z.g;
}
else
{
z.g=w.g;
z.g*=k;
}
return z;
}
G2 PFC::mult(const G2& w,const Big& k)
{
G2 z;
if (w.mtable!=NULL)
{ // we have precomputed values
Big e=k;
if (k<0) e=-e;
int i,j,t=w.mtbits; // MR_ROUNDUP(2*S,WINDOW_SIZE);
j=recode(e,t,WINDOW_SIZE,t-1);
z.g=w.mtable[j];
for (i=t-2;i>=0;i--)
{
j=recode(e,t,WINDOW_SIZE,i);
z.g+=z.g;
if (j>0) z.g+=w.mtable[j];
}
if (k<0) z.g=-z.g;
}
else
{
z.g=w.g;
z.g*=k;
}
return z;
}
GT PFC::power(const GT& w,const Big& k)
{
GT z;
Big e=k;
if (k<0) e=-e;
if (w.etable!=NULL)
{ // precomputation is available
int i,j,t=w.etbits; //MR_ROUNDUP(2*S,WINDOW_SIZE);
j=recode(e,t,WINDOW_SIZE,t-1);
z.g=w.etable[j];
for (i=t-2;i>=0;i--)
{
j=recode(e,t,WINDOW_SIZE,i);
z.g*=z.g;
if (j>0) z.g*=w.etable[j];
}
}
else
{
z.g=powu(w.g,e);
}
if (k<0) z.g=conj(z.g);
return z;
}
// random group member
void PFC::random(Big& w)
{
if (RNG==NULL) w=rand(*ord);
else w=strong_rand(RNG,*ord);
}
// random AES key
void PFC::rankey(Big& k)
{
if (RNG==NULL) k=rand(S,2);
else k=strong_rand(RNG,S,2);
}
// Can be done deterministicly
void PFC::hash_and_map(G1& w,char *ID)
{
Big x0=H1(ID);
while (!w.g.set(x0,x0)) x0+=1;
w.g*=*cof;
}
void PFC::hash_and_map(G2& w,char *ID)
{
Big x0=H1(ID);
*B=-(*B);
ecurve((Big)-3,*B,*mod,MR_PROJECTIVE); // move to twist
while (!w.g.set(x0,x0)) x0+=1;
w.g*=(*mod+1+*trace)/(*ord);
*B=-(*B);
ecurve((Big)-3,*B,*mod,MR_PROJECTIVE); // move back
}
void PFC::random(G1& w)
{
Big x0;
if (RNG==NULL) x0=rand(*mod);
else x0=strong_rand(RNG,*mod);
while (!w.g.set(x0,x0)) x0+=1;
w.g*=*cof;
}
void PFC::random(G2& w)
{
Big x0;
if (RNG==NULL) x0=rand(*mod);
else x0=strong_rand(RNG,*mod);
*B=-(*B);
ecurve((Big)-3,*B,*mod,MR_PROJECTIVE); // move to twist
while (!w.g.set(x0,x0)) x0+=1;
w.g*=(*mod+1+*trace)/(*ord);
*B=-(*B);
ecurve((Big)-3,*B,*mod,MR_PROJECTIVE); // move back
}
Big PFC::hash_to_aes_key(const GT& w)
{
Big m=pow((Big)2,S);
return H2(w.g)%m;
}
Big PFC::hash_to_group(char *ID)
{
Big m=H1(ID);
return m%(*ord);
}
GT operator*(const GT& x,const GT& y)
{
GT z=x;
z.g*=y.g;
return z;
}
GT operator/(const GT& x,const GT& y)
{
GT z=x;
z.g*=conj(y.g); // elements in GT are unitary
return z;
}
//
// spill precomputation on GT to byte array
//
int GT::spill(char *& bytes)
{
int i,j,n=(1<<WINDOW_SIZE);
int bytes_per_big=(MIRACL/8)*(get_mip()->nib-1);
int len=n*2*bytes_per_big+1;
Big x,y;
if (etable==NULL) return 0;
bytes=new char[len];
for (i=j=0;i<n;i++)
{
etable[i].get(x,y);
to_binary(x,bytes_per_big,&bytes[j],TRUE);
j+=bytes_per_big;
to_binary(y,bytes_per_big,&bytes[j],TRUE);
j+=bytes_per_big;
}
bytes[j]=etbits;
delete [] etable;
etable=NULL;
return len;
}
//
// restore precomputation for GT from byte array
//
void GT::restore(char *bytes)
{
int i,j,n=(1<<WINDOW_SIZE);
int bytes_per_big=(MIRACL/8)*(get_mip()->nib-1);
// int len=n*2*bytes_per_big;
Big x,y;
if (etable!=NULL) return;
etable=new ZZn2[1<<WINDOW_SIZE];
for (i=j=0;i<n;i++)
{
x=from_binary(bytes_per_big,&bytes[j]);
j+=bytes_per_big;
y=from_binary(bytes_per_big,&bytes[j]);
j+=bytes_per_big;
etable[i].set(x,y);
}
etbits=bytes[j];
delete [] bytes;
}
G1 operator+(const G1& x,const G1& y)
{
G1 z=x;
z.g+=y.g;
return z;
}
G1 operator-(const G1& x)
{
G1 z=x;
z.g=-z.g;
return z;
}
//
// spill precomputation on G1 to byte array
//
int G1::spill(char *& bytes)
{
int i,j,n=(1<<WINDOW_SIZE);
int bytes_per_big=(MIRACL/8)*(get_mip()->nib-1);
int len=n*2*bytes_per_big+1;
Big x,y;
if (mtable==NULL) return 0;
bytes=new char[len];
for (i=j=0;i<n;i++)
{
mtable[i].get(x,y);
to_binary(x,bytes_per_big,&bytes[j],TRUE);
j+=bytes_per_big;
to_binary(y,bytes_per_big,&bytes[j],TRUE);
j+=bytes_per_big;
}
bytes[j]=mtbits;
delete [] mtable;
mtable=NULL;
return len;
}
//
// restore precomputation for G1 from byte array
//
void G1::restore(char *bytes)
{
int i,j,n=(1<<WINDOW_SIZE);
int bytes_per_big=(MIRACL/8)*(get_mip()->nib-1);
// int len=n*2*bytes_per_big;
Big x,y;
if (mtable!=NULL) return;
mtable=new ECn[1<<WINDOW_SIZE];
for (i=j=0;i<n;i++)
{
x=from_binary(bytes_per_big,&bytes[j]);
j+=bytes_per_big;
y=from_binary(bytes_per_big,&bytes[j]);
j+=bytes_per_big;
mtable[i].set(x,y);
}
mtbits=bytes[j];
delete [] bytes;
}
G2 operator+(const G2& x,const G2& y)
{
G2 z=x;
z.g+=y.g;
return z;
}
G2 operator-(const G2& x)
{
G2 z=x;
z.g=-z.g;
return z;
}
//
// spill precomputation on G2 to byte array
//
int G2::spill(char *& bytes)
{
int i,j,n=(1<<WINDOW_SIZE);
int bytes_per_big=(MIRACL/8)*(get_mip()->nib-1);
int len=n*2*bytes_per_big+1;
Big x,y;
if (mtable==NULL) return 0;
bytes=new char[len];
for (i=j=0;i<n;i++)
{
mtable[i].get(x,y);
to_binary(x,bytes_per_big,&bytes[j],TRUE);
x=from_binary(bytes_per_big,&bytes[j]);
j+=bytes_per_big;
to_binary(y,bytes_per_big,&bytes[j],TRUE);
j+=bytes_per_big;
}
bytes[j]=mtbits;
delete [] mtable;
mtable=NULL;
return len;
}
//
// restore precomputation for G2 from byte array
//
void G2::restore(char *bytes)
{
int i,j,n=(1<<WINDOW_SIZE);
int bytes_per_big=(MIRACL/8)*(get_mip()->nib-1);
// int len=n*2*bytes_per_big;
Big x,y,B;
if (mtable!=NULL) return;
mtable=new ECn[1<<WINDOW_SIZE];
B=getB();
B=-B;
ecurve((Big)-3,B,get_modulus(),MR_PROJECTIVE); // move to twist
for (i=j=0;i<n;i++)
{
x=from_binary(bytes_per_big,&bytes[j]);
j+=bytes_per_big;
y=from_binary(bytes_per_big,&bytes[j]);
j+=bytes_per_big;
mtable[i].set(x,y);
}
mtbits=bytes[j];
B=-B;
ecurve((Big)-3,B,get_modulus(),MR_PROJECTIVE); // move back
delete [] bytes;
}
BOOL PFC::member(const GT& z)
{
ZZn2 r=z.g;
if (pow(r,*ord)!=(ZZn2)1) return FALSE;
return TRUE;
}
GT PFC::pairing(const G2& x,const G1& y)
{
GT z;
z=miller_loop(x,y);
z=final_exp(z);
return z;
}
GT PFC::multi_pairing(int n,G2 **y,G1 **x)
{
GT z;
z=multi_miller(n,y,x);
z=final_exp(z);
return z;
}
int PFC::precomp_for_mult(G1& w,BOOL small)
{
ECn v=w.g;
int i,j,k,bp,is,t;
if (small) t=MR_ROUNDUP(2*S,WINDOW_SIZE);
else t=MR_ROUNDUP(bits(*ord),WINDOW_SIZE);
w.mtable=new ECn[1<<WINDOW_SIZE];
w.mtable[1]=v;
w.mtbits=t;
for (j=0;j<t;j++)
v+=v;
k=1;
for (i=2;i<(1<<WINDOW_SIZE);i++)
{
if (i==(1<<k))
{
k++;
normalise(v);
w.mtable[i]=v;
for (j=0;j<t;j++)
v+=v;
continue;
}
bp=1;
for (j=0;j<k;j++)
{
if (i&bp)
{
is=1<<j;
w.mtable[i]+=w.mtable[is];
}
bp<<=1;
}
normalise(w.mtable[i]);
}
return (1<<WINDOW_SIZE);
}
int PFC::precomp_for_mult(G2& w,BOOL small)
{
ECn v;
int i,j,k,bp,is,t;
if (small) t=MR_ROUNDUP(2*S,WINDOW_SIZE);
else t=MR_ROUNDUP(bits(*ord),WINDOW_SIZE);
normalise(w.g);
v=w.g;
w.mtable=new ECn[1<<WINDOW_SIZE];
w.mtable[1]=v;
w.mtbits=t;
for (j=0;j<t;j++)
v+=v;
k=1;
for (i=2;i<(1<<WINDOW_SIZE);i++)
{
if (i==(1<<k))
{
k++;
normalise(v);
w.mtable[i]=v;
for (j=0;j<t;j++)
v+=v;
continue;
}
bp=1;
for (j=0;j<k;j++)
{
if (i&bp)
{
is=1<<j;
w.mtable[i]+=w.mtable[is];
}
bp<<=1;
}
normalise(w.mtable[i]);
}
return (1<<WINDOW_SIZE);
}
int PFC::precomp_for_power(GT& w,BOOL small)
{
ZZn2 v=w.g;
int i,j,k,bp,is,t;
if (small) t=MR_ROUNDUP(2*S,WINDOW_SIZE);
else t=MR_ROUNDUP(bits(*ord),WINDOW_SIZE);
w.etable=new ZZn2[1<<WINDOW_SIZE];
w.etable[0]=1;
w.etable[1]=v;
w.etbits=t;
for (j=0;j<t;j++)
v*=v;
k=1;
for (i=2;i<(1<<WINDOW_SIZE);i++)
{
if (i==(1<<k))
{
k++;
w.etable[i]=v;
for (j=0;j<t;j++)
v*=v;
continue;
}
bp=1;
w.etable[i]=1;
for (j=0;j<k;j++)
{
if (i&bp)
{
is=1<<j;
w.etable[i]*=w.etable[is];
}
bp<<=1;
}
}
return (1<<WINDOW_SIZE);
}