Subversion Repositories planix.SVN

#include "os.h"
#include <mp.h>
#include <libsec.h>

mpint*
dh_new(DHstate *dh, mpint *p, mpint *q, mpint *g)
{
        mpint *pm1;
        int n;

        memset(dh, 0, sizeof(*dh));
        if(mpcmp(g, mpone) <= 0)
                return nil;

        n = mpsignif(p);
        pm1 = mpnew(n);
        mpsub(p, mpone, pm1);
        dh->p = mpcopy(p);
        dh->g = mpcopy(g);
        dh->q = mpcopy(q != nil ? q : pm1);
        dh->x = mpnew(mpsignif(dh->q));
        dh->y = mpnew(n);
        for(;;){
                mpnrand(dh->q, genrandom, dh->x);
                mpexp(dh->g, dh->x, dh->p, dh->y);
                if(mpcmp(dh->y, mpone) > 0 && mpcmp(dh->y, pm1) < 0)
                        break;
        }
        mpfree(pm1);

        return dh->y;
}

mpint*
dh_finish(DHstate *dh, mpint *y)
{
        mpint *k = nil;

        if(y == nil || dh->x == nil || dh->p == nil || dh->q == nil)
                goto Out;

        /* y > 1 */
        if(mpcmp(y, mpone) <= 0)
                goto Out;

        k = mpnew(mpsignif(dh->p));

        /* y < p-1 */
        mpsub(dh->p, mpone, k);
        if(mpcmp(y, k) >= 0){
Bad:
                mpfree(k);
                k = nil;
                goto Out;
        }

        /* y**q % p == 1 if q < p-1 */
        if(mpcmp(dh->q, k) < 0){
                mpexp(y, dh->q, dh->p, k);
                if(mpcmp(k, mpone) != 0)
                        goto Bad;
        }

        mpexp(y, dh->x, dh->p, k);

Out:
        mpfree(dh->p);
        mpfree(dh->q);
        mpfree(dh->g);
        mpfree(dh->x);
        mpfree(dh->y);
        memset(dh, 0, sizeof(*dh));
        return k;
}