Subversion Repositories planix.SVN

#include "os.h"

#include <mp.h>

#include <libsec.h>

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

	genprime(p, nlen/2, rounds);

	genprime(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);

	if(elen == 0)

		itomp(65537, e);

	else {

		mprand(elen, genrandom, e);

		if(mpcmp(e,mptwo) <= 0)

			itomp(3, e);

	}

	// See Menezes et al. p.291 "8.8 Note (selecting primes)" for discussion

	// of the merits of various choices of primes and exponents.  e=3 is a

	// common and recommended exponent, but doesn't necessarily work here

	// because we chose strong rather than safe primes.

	for(;;){

		mpextendedgcd(e, phi, t1, d, t2);

		if(mpcmp(t1, mpone) == 0)

			break;

		mpadd(mpone, e, e);

	}

	if(d->sign < 0)

		mpadd(phi, d, d);

	mpfree(t1);

	mpfree(t2);

	// 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;

}