Improve/fix using IPCL installation

[skmono]

Some issues have been found when trying to compile with the Intel Paillier Cryptosystem Library, after installing it in /usr/local.

test code

#include <climits>
#include <iostream>
#include <vector>
#include <random>

#include "ipcl/ciphertext.hpp"
#include "ipcl/keygen.hpp"
#include "ipcl/plaintext.hpp"

int main(){
  const uint32_t num_values = 9;

  ipcl::keyPair key = ipcl::generateKeypair(2048, true);

  std::vector<uint32_t> exp_value(num_values);
  ipcl::PlainText pt;
  ipcl::CipherText ct;
  ipcl::PlainText dt;

  std::random_device dev;
  std::mt19937 rng(dev());
  std::uniform_int_distribution<std::mt19937::result_type> dist(0, UINT_MAX);

  for (int i = 0; i < num_values; i++) {
    exp_value[i] = dist(rng);
  }

  pt = ipcl::PlainText(exp_value);
  ct = key.pub_key->encrypt(pt);
  dt = key.priv_key->decrypt(ct);

  for (int i = 0; i < num_values; i++) {
    std::vector<uint32_t> v = dt.getElementVec(i);
    bool chk = v[0]==exp_value[i];
    std::cout<<(chk?"pass":"fail")<<std::endl;
  }

  delete key.pub_key;
  delete key.priv_key;
}

Trying to compile the code fails as follows:

$ g++ test.cpp -o test -lipcl -fopenmp -lnuma
/usr/bin/ld: /usr/local/lib/libipcl.a(ifma_cvt52.c.o): in function `ifma_BN_to_mb8':
ifma_cvt52.c:(.text+0x71): undefined reference to `BN_num_bits'
/usr/bin/ld: ifma_cvt52.c:(.text+0xa0): undefined reference to `BN_bn2lebinpad'
/usr/bin/ld: /usr/local/lib/libipcl.a(ifma_cvt52.c.o): in function `ifma_BN_transpose_copy':
ifma_cvt52.c:(.text+0x229c): undefined reference to `BN_bn2lebinpad'
collect2: error: ld returned 1 exit status

ifma_BN_to_mb8 is a function found in libcrypto_mb and it is correctly included in the static library libipcl.a, but somehow compiler still complains that it is not linked.

As an additional note, we can also improve including the library. Currently more than 1 headers need to be included, as seen in the source code above. We could use a single public header, such as ipcl/ipcl.h which contains all the necessary information.

After taking care of these issues, we also need to add documentation of how to use the library after installation for both cases (using direct linkage and using CMake).
(Related to #13)

[skmono]

@justalittlenoob, The fixes are to be included in v1.1.5

[justalittlenoob]

Hi @skmono
I really appreciate your advice. I'll take care of it.

Adding -lcrypto in the end of the compile command could solve the undefined reference issue.
(i.e. g++ test.cpp -o test -lipcl -fopenmp -lnuma -lcrypto).

[skmono]

@justalittlenoob I verified it working with the addition of the -lcrypto flag.