fp4.c

/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/

/* AMCL Fp^4 functions */
/* SU=m, m is Stack Usage (no lazy )*/

/* FP4 elements are of the form a+ib, where i is sqrt(-1+sqrt(-1)) */

#include "amcl.h"

/* test x==0 ? */
/* SU= 8 */
int FP4_iszilch(FP4 *x)
{
    if (FP2_iszilch(&(x->a)) && FP2_iszilch(&(x->b))) return 1;
    return 0;
}

/* test x==1 ? */
/* SU= 8 */
int FP4_isunity(FP4 *x)
{
    if (FP2_isunity(&(x->a)) && FP2_iszilch(&(x->b))) return 1;
    return 0;
}

/* test is w real? That is in a+ib test b is zero */
int FP4_isreal(FP4 *w)
{
    return FP2_iszilch(&(w->b));
}

/* return 1 if x==y, else 0 */
/* SU= 16 */
int FP4_equals(FP4 *x,FP4 *y)
{
    if (FP2_equals(&(x->a),&(y->a)) && FP2_equals(&(x->b),&(y->b)))
        return 1;
    return 0;
}

/* set FP4 from two FP2s */
/* SU= 16 */
void FP4_from_FP2s(FP4 *w,FP2 * x,FP2* y)
{
    FP2_copy(&(w->a), x);
    FP2_copy(&(w->b), y);
}

/* set FP4 from FP2 */
/* SU= 8 */
void FP4_from_FP2(FP4 *w,FP2 *x)
{
    FP2_copy(&(w->a), x);
    FP2_zero(&(w->b));
}

/* FP4 copy w=x */
/* SU= 16 */
void FP4_copy(FP4 *w,FP4 *x)
{
    if (w==x) return;
    FP2_copy(&(w->a), &(x->a));
    FP2_copy(&(w->b), &(x->b));
}

/* FP4 w=0 */
/* SU= 8 */
void FP4_zero(FP4 *w)
{
    FP2_zero(&(w->a));
    FP2_zero(&(w->b));
}

/* FP4 w=1 */
/* SU= 8 */
void FP4_one(FP4 *w)
{
    FP2_one(&(w->a));
    FP2_zero(&(w->b));
}

/* Set w=-x */
/* SU= 160 */
void FP4_neg(FP4 *w,FP4 *x)
{
    /* Just one field neg */
    FP2 m,t;
    FP2_add(&m,&(x->a),&(x->b));
    FP2_neg(&m,&m);
    FP2_norm(&m);
    FP2_add(&t,&m,&(x->b));
    FP2_add(&(w->b),&m,&(x->a));
    FP2_copy(&(w->a),&t);
}

/* Set w=conj(x) */
/* SU= 16 */
void FP4_conj(FP4 *w,FP4 *x)
{
    FP2_copy(&(w->a), &(x->a));
    FP2_neg(&(w->b), &(x->b));
    FP2_norm(&(w->b));
}

/* Set w=-conj(x) */
/* SU= 16 */
void FP4_nconj(FP4 *w,FP4 *x)
{
    FP2_copy(&(w->b),&(x->b));
    FP2_neg(&(w->a), &(x->a));
    FP2_norm(&(w->a));
}

/* Set w=x+y */
/* SU= 16 */
void FP4_add(FP4 *w,FP4 *x,FP4 *y)
{
    FP2_add(&(w->a), &(x->a), &(y->a));
    FP2_add(&(w->b), &(x->b), &(y->b));
}

/* Set w=x-y */
/* SU= 160 */
void FP4_sub(FP4 *w,FP4 *x,FP4 *y)
{
    FP4 my;
    FP4_neg(&my, y);
    FP4_add(w, x, &my);

}
/* SU= 8 */
/* reduce all components of w mod Modulus */
void FP4_reduce(FP4 *w)
{
    FP2_reduce(&(w->a));
    FP2_reduce(&(w->b));
}

/* SU= 8 */
/* normalise all elements of w */
void FP4_norm(FP4 *w)
{
    FP2_norm(&(w->a));
    FP2_norm(&(w->b));
}

/* Set w=s*x, where s is FP2 */
/* SU= 16 */
void FP4_pmul(FP4 *w,FP4 *x,FP2 *s)
{
    FP2_mul(&(w->a),&(x->a),s);
    FP2_mul(&(w->b),&(x->b),s);
}

/* SU= 16 */
/* Set w=s*x, where s is int */
void FP4_imul(FP4 *w,FP4 *x,int s)
{
    FP2_imul(&(w->a),&(x->a),s);
    FP2_imul(&(w->b),&(x->b),s);
}

/* Set w=x^2 */
/* SU= 232 */
void FP4_sqr(FP4 *w,FP4 *x)
{
    FP2 t1,t2,t3;

    FP2_mul(&t3,&(x->a),&(x->b)); /* norms x */
    FP2_copy(&t2,&(x->b));
    FP2_add(&t1,&(x->a),&(x->b));
    FP2_mul_ip(&t2);

    FP2_add(&t2,&(x->a),&t2);

    FP2_mul(&(w->a),&t1,&t2);

    FP2_copy(&t2,&t3);
    FP2_mul_ip(&t2);

    FP2_add(&t2,&t2,&t3);

    FP2_neg(&t2,&t2);
    FP2_add(&(w->a),&(w->a),&t2);  /* a=(a+b)(a+i^2.b)-i^2.ab-ab = a*a+ib*ib */
    FP2_add(&(w->b),&t3,&t3);  /* b=2ab */

    FP4_norm(w);
}

/* Set w=x*y */
/* SU= 312 */
void FP4_mul(FP4 *w,FP4 *x,FP4 *y)
{

    FP2 t1,t2,t3,t4;
    FP2_mul(&t1,&(x->a),&(y->a)); /* norms x */
    FP2_mul(&t2,&(x->b),&(y->b)); /* and y */
    FP2_add(&t3,&(y->b),&(y->a));
    FP2_add(&t4,&(x->b),&(x->a));


    FP2_mul(&t4,&t4,&t3); /* (xa+xb)(ya+yb) */
    FP2_sub(&t4,&t4,&t1);
#if CHUNK<64
    FP2_norm(&t4);
#endif
    FP2_sub(&(w->b),&t4,&t2);
    FP2_mul_ip(&t2);
    FP2_add(&(w->a),&t2,&t1);

    FP4_norm(w);
}

/* output FP4 in format [a,b] */
/* SU= 8 */
void FP4_output(FP4 *w)
{
    printf("[");
    FP2_output(&(w->a));
    printf(",");
    FP2_output(&(w->b));
    printf("]");
}

/* SU= 8 */
void FP4_rawoutput(FP4 *w)
{
    printf("[");
    FP2_rawoutput(&(w->a));
    printf(",");
    FP2_rawoutput(&(w->b));
    printf("]");
}

/* Set w=1/x */
/* SU= 160 */
void FP4_inv(FP4 *w,FP4 *x)
{
    FP2 t1,t2;
    FP2_sqr(&t1,&(x->a));
    FP2_sqr(&t2,&(x->b));
    FP2_mul_ip(&t2);
    FP2_sub(&t1,&t1,&t2);
    FP2_inv(&t1,&t1);
    FP2_mul(&(w->a),&t1,&(x->a));
    FP2_neg(&t1,&t1);
    FP2_mul(&(w->b),&t1,&(x->b));
}

/* w*=i where i = sqrt(-1+sqrt(-1)) */
/* SU= 200 */
void FP4_times_i(FP4 *w)
{
    BIG z;
    FP2 s,t;
#if CHUNK<64
    FP4_norm(w);
#endif
    FP2_copy(&t,&(w->b));

    FP2_copy(&s,&t);

    BIG_copy(z,s.a);
    FP_neg(s.a,s.b);
    BIG_copy(s.b,z);

    FP2_add(&t,&t,&s);
#if CHUNK<64
    FP2_norm(&t);
#endif
    FP2_copy(&(w->b),&(w->a));
    FP2_copy(&(w->a),&t);
}

/* Set w=w^p using Frobenius */
/* SU= 16 */
void FP4_frob(FP4 *w,FP2 *f)
{
    FP2_conj(&(w->a),&(w->a));
    FP2_conj(&(w->b),&(w->b));
    FP2_mul( &(w->b),f,&(w->b));
}

/* Set r=a^b mod m */
/* SU= 240 */
void FP4_pow(FP4 *r,FP4* a,BIG b)
{
    FP4 w;
    BIG z,zilch;
    int bt;

    BIG_zero(zilch);
    BIG_norm(b);
    BIG_copy(z,b);
    FP4_copy(&w,a);
    FP4_one(r);

    while(1)
    {
        bt=BIG_parity(z);
        BIG_shr(z,1);
        if (bt) FP4_mul(r,r,&w);
        if (BIG_comp(z,zilch)==0) break;
        FP4_sqr(&w,&w);
    }
    FP4_reduce(r);
}

/* SU= 304 */
/* XTR xtr_a function */
void FP4_xtr_A(FP4 *r,FP4 *w,FP4 *x,FP4 *y,FP4 *z)
{
    FP4 t1,t2;

    FP4_copy(r,x);

    FP4_sub(&t1,w,y);

    FP4_pmul(&t1,&t1,&(r->a));
    FP4_add(&t2,w,y);
    FP4_pmul(&t2,&t2,&(r->b));
    FP4_times_i(&t2);

    FP4_add(r,&t1,&t2);
    FP4_add(r,r,z);

    FP4_norm(r);
}

/* SU= 152 */
/* XTR xtr_d function */
void FP4_xtr_D(FP4 *r,FP4 *x)
{
    FP4 w;
    FP4_copy(r,x);
    FP4_conj(&w,r);
    FP4_add(&w,&w,&w);
    FP4_sqr(r,r);
    FP4_sub(r,r,&w);
    FP4_reduce(r);    /* reduce here as multiple calls trigger automatic reductions */
}

/* SU= 728 */
/* r=x^n using XTR method on traces of FP12s */
void FP4_xtr_pow(FP4 *r,FP4 *x,BIG n)
{
    int i,par,nb;
    BIG v;
    FP2 w;
    FP4 t,a,b,c;

    BIG_zero(v);
    BIG_inc(v,3);
    FP2_from_BIG(&w,v);
    FP4_from_FP2(&a,&w);
    FP4_copy(&b,x);
    FP4_xtr_D(&c,x);

    BIG_norm(n);
    par=BIG_parity(n);
    BIG_copy(v,n);
    BIG_shr(v,1);
    if (par==0)
    {
        BIG_dec(v,1);
        BIG_norm(v);
    }

    nb=BIG_nbits(v);

    for (i=nb-1; i>=0; i--)
    {
        if (!BIG_bit(v,i))
        {
            FP4_copy(&t,&b);
            FP4_conj(x,x);
            FP4_conj(&c,&c);
            FP4_xtr_A(&b,&a,&b,x,&c);
            FP4_conj(x,x);
            FP4_xtr_D(&c,&t);
            FP4_xtr_D(&a,&a);
        }
        else
        {
            FP4_conj(&t,&a);
            FP4_xtr_D(&a,&b);
            FP4_xtr_A(&b,&c,&b,x,&t);
            FP4_xtr_D(&c,&c);
        }
    }
    if (par==0) FP4_copy(r,&c);
    else FP4_copy(r,&b);
    FP4_reduce(r);
}

/* SU= 872 */
/* r=ck^a.cl^n using XTR double exponentiation method on traces of FP12s. See Stam thesis. */
void FP4_xtr_pow2(FP4 *r,FP4 *ck,FP4 *cl,FP4 *ckml,FP4 *ckm2l,BIG a,BIG b)
{
    int i,f2;
    BIG d,e,w;
    FP4 t,cu,cv,cumv,cum2v;

    BIG_norm(a);
    BIG_norm(b);
    BIG_copy(e,a);
    BIG_copy(d,b);
    FP4_copy(&cu,ck);
    FP4_copy(&cv,cl);
    FP4_copy(&cumv,ckml);
    FP4_copy(&cum2v,ckm2l);

    f2=0;
    while (BIG_parity(d)==0 && BIG_parity(e)==0)
    {
        BIG_shr(d,1);
        BIG_shr(e,1);
        f2++;
    }
    while (BIG_comp(d,e)!=0)
    {
        if (BIG_comp(d,e)>0)
        {
            BIG_imul(w,e,4);
            BIG_norm(w);
            if (BIG_comp(d,w)<=0)
            {
                BIG_copy(w,d);
                BIG_copy(d,e);
                BIG_sub(e,w,e);
                BIG_norm(e);
                FP4_xtr_A(&t,&cu,&cv,&cumv,&cum2v);
                FP4_conj(&cum2v,&cumv);
                FP4_copy(&cumv,&cv);
                FP4_copy(&cv,&cu);
                FP4_copy(&cu,&t);
            }
            else if (BIG_parity(d)==0)
            {
                BIG_shr(d,1);
                FP4_conj(r,&cum2v);
                FP4_xtr_A(&t,&cu,&cumv,&cv,r);
                FP4_xtr_D(&cum2v,&cumv);
                FP4_copy(&cumv,&t);
                FP4_xtr_D(&cu,&cu);
            }
            else if (BIG_parity(e)==1)
            {
                BIG_sub(d,d,e);
                BIG_norm(d);
                BIG_shr(d,1);
                FP4_xtr_A(&t,&cu,&cv,&cumv,&cum2v);
                FP4_xtr_D(&cu,&cu);
                FP4_xtr_D(&cum2v,&cv);
                FP4_conj(&cum2v,&cum2v);
                FP4_copy(&cv,&t);
            }
            else
            {
                BIG_copy(w,d);
                BIG_copy(d,e);
                BIG_shr(d,1);
                BIG_copy(e,w);
                FP4_xtr_D(&t,&cumv);
                FP4_conj(&cumv,&cum2v);
                FP4_conj(&cum2v,&t);
                FP4_xtr_D(&t,&cv);
                FP4_copy(&cv,&cu);
                FP4_copy(&cu,&t);
            }
        }
        if (BIG_comp(d,e)<0)
        {
            BIG_imul(w,d,4);
            BIG_norm(w);
            if (BIG_comp(e,w)<=0)
            {
                BIG_sub(e,e,d);
                BIG_norm(e);
                FP4_xtr_A(&t,&cu,&cv,&cumv,&cum2v);
                FP4_copy(&cum2v,&cumv);
                FP4_copy(&cumv,&cu);
                FP4_copy(&cu,&t);
            }
            else if (BIG_parity(e)==0)
            {
                BIG_copy(w,d);
                BIG_copy(d,e);
                BIG_shr(d,1);
                BIG_copy(e,w);
                FP4_xtr_D(&t,&cumv);
                FP4_conj(&cumv,&cum2v);
                FP4_conj(&cum2v,&t);
                FP4_xtr_D(&t,&cv);
                FP4_copy(&cv,&cu);
                FP4_copy(&cu,&t);
            }
            else if (BIG_parity(d)==1)
            {
                BIG_copy(w,e);
                BIG_copy(e,d);
                BIG_sub(w,w,d);
                BIG_norm(w);
                BIG_copy(d,w);
                BIG_shr(d,1);
                FP4_xtr_A(&t,&cu,&cv,&cumv,&cum2v);
                FP4_conj(&cumv,&cumv);
                FP4_xtr_D(&cum2v,&cu);
                FP4_conj(&cum2v,&cum2v);
                FP4_xtr_D(&cu,&cv);
                FP4_copy(&cv,&t);
            }
            else
            {
                BIG_shr(d,1);
                FP4_conj(r,&cum2v);
                FP4_xtr_A(&t,&cu,&cumv,&cv,r);
                FP4_xtr_D(&cum2v,&cumv);
                FP4_copy(&cumv,&t);
                FP4_xtr_D(&cu,&cu);
            }
        }
    }
    FP4_xtr_A(r,&cu,&cv,&cumv,&cum2v);
    for (i=0; i<f2; i++)	FP4_xtr_D(r,r);
    FP4_xtr_pow(r,r,d);
}
/*
int main(){
		FP2 w0,w1,f;
		FP4 w,t;
		FP4 c1,c2,c3,c4,cr;
		BIG a,b;
		BIG e,e1,e2;
		BIG p,md;


		BIG_rcopy(md,Modulus);
		//Test w^(P^4) = w mod p^2
		BIG_zero(a); BIG_inc(a,27);
		BIG_zero(b); BIG_inc(b,45);
		FP2_from_BIGs(&w0,a,b);

		BIG_zero(a); BIG_inc(a,33);
		BIG_zero(b); BIG_inc(b,54);
		FP2_from_BIGs(&w1,a,b);

		FP4_from_FP2s(&w,&w0,&w1);
		FP4_reduce(&w);

		printf("w= ");
		FP4_output(&w);
		printf("\n");


		FP4_copy(&t,&w);


		BIG_copy(p,md);
		FP4_pow(&w,&w,p);

		printf("w^p= ");
		FP4_output(&w);
		printf("\n");
//exit(0);

		BIG_rcopy(a,CURVE_Fra);
		BIG_rcopy(b,CURVE_Frb);
		FP2_from_BIGs(&f,a,b);

		FP4_frob(&t,&f);
		printf("w^p= ");
		FP4_output(&t);
		printf("\n");

		FP4_pow(&w,&w,p);
		FP4_pow(&w,&w,p);
		FP4_pow(&w,&w,p);
		printf("w^p4= ");
		FP4_output(&w);
		printf("\n");

// Test 1/(1/x) = x mod p^4
		FP4_from_FP2s(&w,&w0,&w1);
		printf("Test Inversion \nw= ");
		FP4_output(&w);
		printf("\n");

		FP4_inv(&w,&w);
		printf("1/w mod p^4 = ");
		FP4_output(&w);
		printf("\n");

		FP4_inv(&w,&w);
		printf("1/(1/w) mod p^4 = ");
		FP4_output(&w);
		printf("\n");

		BIG_zero(e); BIG_inc(e,12);



	//	FP4_xtr_A(&w,&t,&w,&t,&t);
		FP4_xtr_pow(&w,&w,e);

		printf("w^e= ");
		FP4_output(&w);
		printf("\n");


		BIG_zero(a); BIG_inc(a,37);
		BIG_zero(b); BIG_inc(b,17);
		FP2_from_BIGs(&w0,a,b);

		BIG_zero(a); BIG_inc(a,49);
		BIG_zero(b); BIG_inc(b,31);
		FP2_from_BIGs(&w1,a,b);

		FP4_from_FP2s(&c1,&w0,&w1);
		FP4_from_FP2s(&c2,&w0,&w1);
		FP4_from_FP2s(&c3,&w0,&w1);
		FP4_from_FP2s(&c4,&w0,&w1);

		BIG_zero(e1); BIG_inc(e1,3331);
		BIG_zero(e2); BIG_inc(e2,3372);

		FP4_xtr_pow2(&w,&c1,&w,&c2,&c3,e1,e2);

		printf("c^e= ");
		FP4_output(&w);
		printf("\n");


		return 0;
}
*/