src/mpin192.c.in [82:208]:
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
        HASH512_hash(&sha512,h);
        break;
    }

    OCT_jbytes(w,h,AESKEY_ZZZ);
    for (i=0; i<hlen; i++) h[i]=0;
}

/* these next two functions help to implement elligator squared - http://eprint.iacr.org/2014/043 */
/* maps a random u to a point on the curve */
static void map(ECP_ZZZ *P,BIG_XXX u,int cb)
{
    BIG_XXX x,q;

    BIG_XXX_rcopy(q,Modulus_YYY);
    BIG_XXX_copy(x,u);
    BIG_XXX_mod(x,q);

    while (!ECP_ZZZ_setx(P,x,cb))
    {
        BIG_XXX_inc(x,1);
        BIG_XXX_norm(x);
    }
}

/* returns u derived from P. Random value in range 1 to return value should then be added to u */
static int unmap(BIG_XXX u,int *cb,ECP_ZZZ *P)
{
    int s,r=0;
    BIG_XXX x;

    s=ECP_ZZZ_get(x,x,P);
    BIG_XXX_copy(u,x);
    do
    {
        BIG_XXX_dec(u,1);
        BIG_XXX_norm(u);
        r++;
    }
    while (!ECP_ZZZ_setx(P,u,s));
    ECP_ZZZ_setx(P,x,s);

    *cb=s;

    return r;
}

/* these next two functions implement elligator squared - http://eprint.iacr.org/2014/043 */
/* Elliptic curve point E in format (0x04,x,y} is converted to form {0x0-,u,v} */
/* Note that u and v are indistinguisible from random strings */
int MPIN_ZZZ_ENCODING(csprng *RNG,octet *E)
{
    int rn,m,su,sv,res=0;

    BIG_XXX q,u,v;
    ECP_ZZZ P,W;

    if (!ECP_ZZZ_fromOctet(&P,E)) res=MPIN_INVALID_POINT;
    if (res==0)
    {
        BIG_XXX_rcopy(q,Modulus_YYY);

        BIG_XXX_randomnum(u,q,RNG);

        su=RAND_byte(RNG);
        if (su<0) su=-su;
        su%=2;
        map(&W,u,su);
        ECP_ZZZ_sub(&P,&W);

        rn=unmap(v,&sv,&P);
        m=RAND_byte(RNG);
        if (m<0) m=-m;
        m%=rn;
        BIG_XXX_inc(v,m+1);
        E->val[0]=su+2*sv;
        BIG_XXX_toBytes(&(E->val[1]),u);
        BIG_XXX_toBytes(&(E->val[PFS_ZZZ+1]),v);
    }
    return res;
}

int MPIN_ZZZ_DECODING(octet *D)
{
    int su,sv;
    BIG_XXX u,v;
    ECP_ZZZ P,W;
    int res=0;

    if ((D->val[0]&0x04)!=0) res=MPIN_INVALID_POINT;
    if (res==0)
    {

        BIG_XXX_fromBytes(u,&(D->val[1]));
        BIG_XXX_fromBytes(v,&(D->val[PFS_ZZZ+1]));

        su=D->val[0]&1;
        sv=(D->val[0]>>1)&1;
        map(&W,u,su);
        map(&P,v,sv);
        ECP_ZZZ_add(&P,&W);
        ECP_ZZZ_toOctet(D,&P,false);
    }

    return res;
}

/* R=R1+R2 in group G1 */
int MPIN_ZZZ_RECOMBINE_G1(octet *R1,octet *R2,octet *R)
{
    ECP_ZZZ P,T;
    int res=0;
    if (res==0)
    {
        if (!ECP_ZZZ_fromOctet(&P,R1)) res=MPIN_INVALID_POINT;
        if (!ECP_ZZZ_fromOctet(&T,R2)) res=MPIN_INVALID_POINT;
    }
    if (res==0)
    {
        ECP_ZZZ_add(&P,&T);
        ECP_ZZZ_toOctet(R,&P,false);
    }
    return res;
}

/* W=W1+W2 in group G2 */
int MPIN_ZZZ_RECOMBINE_G2(octet *W1,octet *W2,octet *W)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -



src/mpin256.c.in [105:231]:
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
        HASH512_hash(&sha512,h);
        break;
    }

    OCT_jbytes(w,h,AESKEY_ZZZ);
    for (i=0; i<hlen; i++) h[i]=0;
}

/* these next two functions help to implement elligator squared - http://eprint.iacr.org/2014/043 */
/* maps a random u to a point on the curve */
static void map(ECP_ZZZ *P,BIG_XXX u,int cb)
{
    BIG_XXX x,q;

    BIG_XXX_rcopy(q,Modulus_YYY);
    BIG_XXX_copy(x,u);
    BIG_XXX_mod(x,q);

    while (!ECP_ZZZ_setx(P,x,cb))
    {
        BIG_XXX_inc(x,1);
        BIG_XXX_norm(x);
    }
}

/* returns u derived from P. Random value in range 1 to return value should then be added to u */
static int unmap(BIG_XXX u,int *cb,ECP_ZZZ *P)
{
    int s,r=0;
    BIG_XXX x;

    s=ECP_ZZZ_get(x,x,P);
    BIG_XXX_copy(u,x);
    do
    {
        BIG_XXX_dec(u,1);
        BIG_XXX_norm(u);
        r++;
    }
    while (!ECP_ZZZ_setx(P,u,s));
    ECP_ZZZ_setx(P,x,s);

    *cb=s;

    return r;
}

/* these next two functions implement elligator squared - http://eprint.iacr.org/2014/043 */
/* Elliptic curve point E in format (0x04,x,y} is converted to form {0x0-,u,v} */
/* Note that u and v are indistinguisible from random strings */
int MPIN_ZZZ_ENCODING(csprng *RNG,octet *E)
{
    int rn,m,su,sv,res=0;

    BIG_XXX q,u,v;
    ECP_ZZZ P,W;

    if (!ECP_ZZZ_fromOctet(&P,E)) res=MPIN_INVALID_POINT;
    if (res==0)
    {
        BIG_XXX_rcopy(q,Modulus_YYY);

        BIG_XXX_randomnum(u,q,RNG);

        su=RAND_byte(RNG);
        if (su<0) su=-su;
        su%=2;
        map(&W,u,su);
        ECP_ZZZ_sub(&P,&W);

        rn=unmap(v,&sv,&P);
        m=RAND_byte(RNG);
        if (m<0) m=-m;
        m%=rn;
        BIG_XXX_inc(v,m+1);
        E->val[0]=su+2*sv;
        BIG_XXX_toBytes(&(E->val[1]),u);
        BIG_XXX_toBytes(&(E->val[PFS_ZZZ+1]),v);
    }
    return res;
}

int MPIN_ZZZ_DECODING(octet *D)
{
    int su,sv;
    BIG_XXX u,v;
    ECP_ZZZ P,W;
    int res=0;

    if ((D->val[0]&0x04)!=0) res=MPIN_INVALID_POINT;
    if (res==0)
    {

        BIG_XXX_fromBytes(u,&(D->val[1]));
        BIG_XXX_fromBytes(v,&(D->val[PFS_ZZZ+1]));

        su=D->val[0]&1;
        sv=(D->val[0]>>1)&1;
        map(&W,u,su);
        map(&P,v,sv);
        ECP_ZZZ_add(&P,&W);
        ECP_ZZZ_toOctet(D,&P,false);
    }

    return res;
}

/* R=R1+R2 in group G1 */
int MPIN_ZZZ_RECOMBINE_G1(octet *R1,octet *R2,octet *R)
{
    ECP_ZZZ P,T;
    int res=0;
    if (res==0)
    {
        if (!ECP_ZZZ_fromOctet(&P,R1)) res=MPIN_INVALID_POINT;
        if (!ECP_ZZZ_fromOctet(&T,R2)) res=MPIN_INVALID_POINT;
    }
    if (res==0)
    {
        ECP_ZZZ_add(&P,&T);
        ECP_ZZZ_toOctet(R,&P,false);
    }
    return res;
}

/* W=W1+W2 in group G2 */
int MPIN_ZZZ_RECOMBINE_G2(octet *W1,octet *W2,octet *W)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -