c - elliptic curve discrete logarithm -

i trying solve elliptic curve discrete logarithm using pollard rho (find k g=kp), searched implementation in c , found 1 after adding problem specific data in main function got segmentation fault (core dumped)

#include <stdlib.h> #include <stdio.h> #include <string.h> #include <gmp.h> #include <limits.h> #include <sys/time.h>  #include <openssl/ec.h> #include <openssl/bn.h> #include <openssl/obj_mac.h> // nid_secp256k1  #define pollard_set_count 16  #if defined(win32) || defined(_win32) #define export __declspec(dllexport) #else #define export #endif  #define max_restart 100  int ec_point_partition(const ec_group *ecgrp, const ec_point *x) {        size_t len = ec_point_point2oct( ecgrp, x, point_conversion_uncompressed, null, 0, null );     unsigned char ret[len];      ec_point_point2oct( ecgrp, x, point_conversion_uncompressed, ret, len, null );      int id = ( ret[len - 1] & 0xff ) % pollard_set_count;      return id; }  // p generator  // q result*p // order of curve // result //reference: j. sattler , c. p. schnorr, "generating random walks in groups"  int elliptic_pollard_rho_dlog(const ec_group *group, const ec_point *p, const ec_point *q, const bignum *order, bignum *res) {      printf("pollard rho discrete log algorithm... \n");      bn_ctx* ctx;     ctx = bn_ctx_new();      int i, j;     int iterations = 0;      if ( !ec_point_is_on_curve(group, p, ctx ) || !ec_point_is_on_curve(group, q, ctx ) ) return 1;      ec_point *x1 = ec_point_new(group);     ec_point *x2 = ec_point_new(group);      bignum *c1 = bn_new();     bignum *d1 = bn_new();     bignum *c2 = bn_new();     bignum *d2 = bn_new();      bignum* a[pollard_set_count];     bignum* b[pollard_set_count];     ec_point* r[pollard_set_count];      bn_zero(c1); bn_zero(d1);     bn_zero(c2); bn_zero(d2);       (i = 0; < pollard_set_count; i++) {             a[i] = bn_new();         b[i] = bn_new();         r[i] = ec_point_new(group);          bn_rand_range(a[i], order);              bn_rand_range(b[i], order);          // r = ap + bq          ec_point_mul(group, r[i], a[i], q, b[i], ctx);         //ep_norm(r[i], r[i]);     }      bn_rand_range(c1, order);            bn_rand_range(d1, order);              // x1 = c1*p + d1*q     ec_point_mul(group, x1, c1, q, d1,  ctx);       //ep_norm(x1, x1);      bn_copy(c2, c1);     bn_copy(d2, d1);     ec_point_copy(x2, x1);       double work_time = (double) clock();     {         j = ec_point_partition(group, x1);         ec_point_add(group, x1, x1, r[j], ctx);          bn_mod_add(c1, c1, a[j], order, ctx);           bn_mod_add(d1, d1, b[j], order, ctx);           (i = 0; < 2; i++) {             j = ec_point_partition(group, x2);              ec_point_add(group, x2, x2, r[j], ctx);              bn_mod_add(c2, c2, a[j], order, ctx);               bn_mod_add(d2, d2, b[j], order, ctx);         }          iterations++;         printf("iteration %d \r",iterations );     } while ( ec_point_cmp(group, x1, x2, ctx) != 0 ) ;       printf("\n ");      work_time = ( (double) clock() - work_time ) / (double)clocks_per_sec;      printf("number of iterations %d %f\n",iterations, work_time );      bn_mod_sub(c1, c1, c2, order, ctx);     bn_mod_sub(d2, d2, d1, order, ctx);      if (bn_is_zero(d2) == 1) return 1;       //d1 = d2^-1 mod order       bn_mod_inverse(d1, d2, order, ctx);      bn_mod_mul(res, c1, d1, order, ctx);      (int k = 0; k < pollard_set_count; ++k) {         bn_free(a[k]);          bn_free(b[k]);         ec_point_free(r[k]);     }     bn_free(c1); bn_free(d1);     bn_free(c2); bn_free(d2);     ec_point_free(x1); ec_point_free(x2);      bn_ctx_free(ctx);     return 0; }   int main(int argc, char *argv[]) {     unsigned char *p_str="134747661567386867366256408824228742802669457";     unsigned char *a_str="-1";     unsigned char *b_str="0";     bignum *p = bn_bin2bn(p_str, sizeof(p_str), null);     bignum *a = bn_bin2bn(a_str, sizeof(a_str), null);     bignum *b = bn_bin2bn(b_str, sizeof(b_str), null);     bn_ctx* ctx;     ctx = bn_ctx_new();     ec_group* g = ec_group_new(ec_gfp_simple_method());     ec_group_set_curve_gfp(g,p,a,b,ctx);         unsigned char *xp_str="18185174461194872234733581786593019886770620";     unsigned char *yp_str="74952280828346465277451545812645059041440154";      bn_ctx* ctx1;     ctx1 = bn_ctx_new();     bignum *xp = bn_bin2bn(xp_str, sizeof(xp_str), null);     bignum *yp = bn_bin2bn(yp_str, sizeof(yp_str), null);     ec_point* p = ec_point_new(g);     ec_point_set_affine_coordinates_gfp(g,p,xp,yp,ctx1);      unsigned char *xq_str="76468233972358960368422190121977870066985660";     unsigned char *yq_str="33884872380845276447083435959215308764231090";     bignum* xq = bn_bin2bn(xq_str, sizeof(xq_str), null);     bignum* yq = bn_bin2bn(yq_str, sizeof(yq_str), null);     ec_point *q = ec_point_new(g);     bn_ctx* ctx2;     ctx2 = bn_ctx_new();     ec_point_set_affine_coordinates_gfp(g,q,xq,yq,ctx2);     char * str;       unsigned char *n_str="2902021510595963727029";     bignum *n = bn_bin2bn(n_str, sizeof(n_str), null);     bignum *res;     elliptic_pollard_rho_dlog (g,p,q,n,res);     bn_bn2mpi(res,str);      printf("%s\n", str);     return 0; } 

this statement cause segmentation fault

    bn_bn2mpi(res,str);