Boneh Franklin IBC using the PBC library

/***
    Boneh & Franklin encryption scheme as presented in the article "Id-based encryption from the Weil pairing"
***/

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<assert.h>
#include<fcntl.h>
#include<math.h>
#include<string.h>
#include<openssl/sha.h>
#include<openssl/err.h>
#include<openssl/ssl.h>
#include<pbc/pbc.h>
#include<pbc/pbc_test.h>


int main(int argc, char **argv)
{
  pairing_t pairing;
  element_t P, Ppub, Did, Qid, U, s, r, xt, gid;
  int fd=0,i=0;
  char m[80]={0}, mv[80]={0}, c[80]={0}, id[20]="157.157.157.157", hash[20]={0}, err[80]={0}, *gs=NULL;


  /***
      errors strings initialization for SHA1 & clock initialization for times computation
  ***/
  ERR_load_crypto_strings();
  SSL_load_error_strings();

  /***initialize the message which is going to be signed***/
  fd = open("/dev/urandom",O_RDONLY);
  read(fd, m, 80);
  close(fd);

  /***
      pairing function initalization from the input file which contains the pairing parameters
  ***/
  pbc_demo_pairing_init(pairing, argc, argv);
  if (!pairing_is_symmetric(pairing)) pbc_die("pairing must be symmetric");

  /***
      initialization of G1 elements
  ***/
  element_init_G1(P, pairing);
  element_init_G1(Ppub, pairing);
  element_init_G1(Qid, pairing);
  element_init_G1(Did, pairing);
  element_init_G1(U, pairing);

  /***
      initialization of Zr elements
  ***/
  element_init_Zr(s, pairing);
  element_init_Zr(r, pairing);

  /***
      initialization of GT elements
  ***/
  element_init_GT(gid, pairing);
  element_init_GT(xt, pairing);
  /***
      PKG generation of P, s and Ppub
  ***/
  element_random(P);
  element_random(s);
  element_mul_zn(Ppub, P, s);
  element_printf("++s: %B\n",s);
  element_printf("++P:  %B\n", P);
  element_printf("++Ppub: %B\n", Ppub);


  /***
      key generation
  ***/
  if(SHA1(id, 20, (unsigned char *)hash)==NULL)
    {
      ERR_error_string(ERR_get_error(),err);
      printf("%s\n",err);
    }
  element_from_hash(Qid, hash, strlen(hash));
  element_mul_zn(Did, Qid, s);
  element_printf("++Qid: %B\n", Qid);
  element_printf("++Did: %B\n", Did);

  /***
      encryption
  ***/
  element_random(r);
  element_mul_zn(U, P, r);
  element_pairing(gid, Qid, Ppub);
  element_pow_zn(gid, gid, r);
  gs=malloc(element_length_in_bytes(gid));
  element_to_bytes(gs,gid);
  if(SHA1(gs , 20, (unsigned char *)hash)==NULL)
    {
      ERR_error_string(ERR_get_error(),err);
      printf("%s\n",err);
    }
  for(i=0;i<20;i++)
    {
      c[i]=m[i]^hash[i];
      c[i+20]=m[i+20]^hash[i];
      c[i+40]=m[i+40]^hash[i];
      c[i+60]=m[i+60]^hash[i];
    }
  free(gs);

  element_printf("++r: %B\n",r);
  element_printf("++U: %B\n",U);
  element_printf("++gid: %B\n",gid);

  /***
      decryption
  ***/
  element_pairing(xt, Did, U);
  gs=malloc(element_length_in_bytes(xt));
  element_to_bytes(gs,xt);
  if(SHA1(gs , 20, (unsigned char *)hash)==NULL)
    {
      ERR_error_string(ERR_get_error(),err);
      printf("%s\n",err);
    }
  for(i=0;i<20;i++)
    {
      mv[i]=c[i]^hash[i];
      mv[i+20]=c[i+20]^hash[i];
      mv[i+40]=c[i+40]^hash[i];
      mv[i+60]=c[i+60]^hash[i];
    }

  element_printf("e(Did,U):%B\n",xt);
  for(i=0;i<80;i++)
    {
      printf(":%d %d %d\n",i,m[i],mv[i]);
    }

  printf("\n%d\n",strncmp(m,mv,80));

  /***free mem***/
  element_clear(P);
  element_clear(Ppub);
  element_clear(Qid);
  element_clear(Did);
  element_clear(U);
  element_clear(gid);
  element_clear(r);
  element_clear(xt);
  element_clear(s);
  pairing_clear(pairing);
  free(gs);
  ERR_free_strings();

  return 0;
}