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 #include "os.h" #include #include 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); 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); } 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; }