I am getting segmentation fault in the program below. I have initialised all the GMP variables properly... But still i am getting segmentation fault at mpz_powm( ); The loop runs only once and second time it gives segmentation fault at mpz_powm... The code is as follows: mpz_t bigbody,encbody,decbody,n,d,e; mpz_init(bigbody); mpz_init(decbody); while(i<noOfBlocks) { strncpy(substring, data_buffer + lower, upper); *(substring+308)='\0'; lower=upper; upper=upper+308; i++; mpz_set_str(bigbody,substring,10); //size=len; mpz_powm (decbody, bigbody, d, n); } The again i tried to use arrays but this time the loop runs for 2 times and then gives segmentation fault... The code is as follows.. mpz_t array[10]; //mpz_array_init (array, 10, 308); mpz_t array1[10]; //mpz_array_init (array1, 10, 308); while(i<noOfBlocks) { strncpy(substring, data_buffer + lower, upper); lower=upper; upper=upper+308; mpz_init_set_str(array[i],substring,10); mpz_get_str (STR, 10, array[i]); strcat(STR,"\0"); syslog( LOG_INFO, "conn# %d - Encrypted-Biginteger = %s", cd->connection_num, STR ); mpz_init(array1[i]); mpz_powm (array1[i], array[i], d, n); }