问题
I am trying to convert a string p_str
representing a big integer to a BIGNUM
p
using the OpenSSL library.
#include <stdio.h>
#include <openssl/bn.h>
int main ()
{
/* I shortened the integer */
unsigned char *p_str = "82019154470699086128524248488673846867876336512717";
BIGNUM *p = BN_bin2bn(p_str, sizeof(p_str), NULL);
BN_print_fp(stdout, p);
puts("");
BN_free(p);
return 0;
}
Compiled it with:
gcc -Wall -Wextra -g -o convert convert.c -lcrypto
But, when I execute it, I get the following result:
3832303139313534
回答1:
unsigned char *p_str = "82019154470699086128524248488673846867876336512717"; BIGNUM *p = BN_bin2bn(p_str, sizeof(p_str), NULL);
Use int BN_dec2bn(BIGNUM **a, const char *str)
instead.
You would use BN_bin2bn
when you have an array of bytes
(and not a NULL terminated ASCII string).
The man pages are located at BN_bin2bn(3).
The correct code would look like this:
#include <stdio.h>
#include <openssl/bn.h>
int main ()
{
static const
char p_str[] = "82019154470699086128524248488673846867876336512717";
BIGNUM *p = BN_new();
BN_dec2bn(&p, p_str);
char * number_str = BN_bn2hex(p);
printf("%s\n", number_str);
OPENSSL_free(number_str);
BN_free(p);
return 0;
}
来源:https://stackoverflow.com/questions/30077562/convert-a-big-number-given-as-a-string-to-an-openssl-bignum