Subversion Repositories planix.SVN

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

static void
genrand(mpint *p, int n)
{
        mpdigit x;

        // generate n random bits with high set
        mpbits(p, n);
        genrandom((uchar*)p->p, (n+7)/8);
        p->top = (n+Dbits-1)/Dbits;
        x = 1;
        x <<= ((n-1)%Dbits);
        p->p[p->top-1] &= (x-1);
        p->p[p->top-1] |= x;
}

RSApriv*
rsagen(int nlen, int elen, int rounds)
{
        mpint *p, *q, *e, *d, *phi, *n, *t1, *t2, *kp, *kq, *c2;
        RSApriv *rsa;

        p = mpnew(nlen/2);
        q = mpnew(nlen/2);
        n = mpnew(nlen);
        e = mpnew(elen);
        d = mpnew(0);
        phi = mpnew(nlen);

        // create the prime factors and euclid's function
        genstrongprime(p, nlen/2, rounds);
        genstrongprime(q, nlen - mpsignif(p) + 1, rounds);
        mpmul(p, q, n);
        mpsub(p, mpone, e);
        mpsub(q, mpone, d);
        mpmul(e, d, phi);

        // find an e relatively prime to phi
        t1 = mpnew(0);
        t2 = mpnew(0);
        genrand(e, elen);
        for(;;){
                mpextendedgcd(e, phi, d, t1, t2);
                if(mpcmp(d, mpone) == 0)
                        break;
                mpadd(mpone, e, e);
        }
        mpfree(t1);
        mpfree(t2);

        // d = e**-1 mod phi
        mpinvert(e, phi, d);

        // compute chinese remainder coefficient
        c2 = mpnew(0);
        mpinvert(p, q, c2);

        // for crt a**k mod p == (a**(k mod p-1)) mod p
        kq = mpnew(0);
        kp = mpnew(0);
        mpsub(p, mpone, phi);
        mpmod(d, phi, kp);
        mpsub(q, mpone, phi);
        mpmod(d, phi, kq);

        rsa = rsaprivalloc();
        rsa->pub.ek = e;
        rsa->pub.n = n;
        rsa->dk = d;
        rsa->kp = kp;
        rsa->kq = kq;
        rsa->p = p;
        rsa->q = q;
        rsa->c2 = c2;

        mpfree(phi);

        return rsa;
}