src/RsaCrt.cpp

   1 #include "RsaCrt.h"
   2
   3 using namespace std;
   4
   5 #include "Rand.h"
   6 #include "Utils.h"
   7
   8 pair<Rsa::KeyPub, RsaCrt::KeyPriv> RsaCrt::generateRSAKeys(uint exponent, uint keySizeBits)
   9 {
  10    mpz_class phi, d;
  11    Rsa::KeyPub kPub;
  12    KeyPriv kPriv;
  13
  14    do
  15    {
  16       kPub.e = exponent;
  17       kPriv.p = Rand::randPrime(keySizeBits / 2);
  18       kPriv.q = Rand::randPrime(keySizeBits / 2);
  19
  20       kPub.n = kPriv.p * kPriv.q;
  21       phi = (kPriv.p - 1) * (kPriv.q - 1);
  22
  23    // d = e^-1 (mode phi).
  24    } while (mpz_invert(d.get_mpz_t(), kPub.e.get_mpz_t(), phi.get_mpz_t()) == 0);
  25
  26    kPriv.dp = d % (kPriv.p - 1);
  27    kPriv.dq = d % (kPriv.q - 1);
  28
  29    // qInv = q^-1 (mod p)
  30    mpz_invert(kPriv.qInv.get_mpz_t(), kPriv.q.get_mpz_t(), kPriv.p.get_mpz_t());
  31
  32    return make_pair(kPub, kPriv);
  33 }
  34
  35 mpz_class RsaCrt::sign(const mpz_class& m, const KeyPriv& kPriv)
  36 {
  37    return sign(m, kPriv, false);
  38 }
  39
  40 mpz_class RsaCrt::signWithFaultySp(const mpz_class& m, const KeyPriv& kPriv)
  41 {
  42    return sign(m, kPriv, true);
  43 }
  44
  45 mpz_class RsaCrt::sign(const mpz_class& m, const KeyPriv& kPriv, bool withError)
  46 {
  47    mpz_class sp, sq;
  48
  49    mpz_powm_sec(sp.get_mpz_t(), m.get_mpz_t(), kPriv.dp.get_mpz_t(), kPriv.p.get_mpz_t());
  50    mpz_powm_sec(sq.get_mpz_t(), m.get_mpz_t(), kPriv.dq.get_mpz_t(), kPriv.q.get_mpz_t());
  51
  52    if (withError)
  53       mpz_combit(sp.get_mpz_t(), 42); // Flip the fourty second bit.
  54
  55    return sq + ((kPriv.qInv * (sp - sq)) % kPriv.p) * kPriv.q;
  56 }