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- #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);
- 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;
- }
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