BN_div_word(3) arithmetic

Other Alias

BN_add_word, BN_sub_word, BN_mul_word, BN_mod_word


#include <openssl/bn.h>
int BN_add_word(BIGNUM *a, BN_ULONG w);
int BN_sub_word(BIGNUM *a, BN_ULONG w);
int BN_mul_word(BIGNUM *a, BN_ULONG w);
BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w);
BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w);


These functions perform arithmetic operations on BIGNUMs with unsigned integers. They are much more efficient than the normal BIGNUM arithmetic operations.

BN_add_word() adds w to a ("a+=w").

BN_sub_word() subtracts w from a ("a-=w").

BN_mul_word() multiplies a and w ("a*=w").

BN_div_word() divides a by w ("a/=w") and returns the remainder.

BN_mod_word() returns the remainder of a divided by w ("a%w").

For BN_div_word() and BN_mod_word(), w must not be 0.


BN_add_word(), BN_sub_word() and BN_mul_word() return 1 for success, 0 on error. The error codes can be obtained by ERR_get_error(3).

BN_mod_word() and BN_div_word() return a%w on success and (BN_ULONG)-1 if an error occurred.


BN_add_word() and BN_mod_word() are available in all versions of SSLeay and OpenSSL. BN_div_word() was added in SSLeay 0.8, and BN_sub_word() and BN_mul_word() in SSLeay 0.9.0.

Before 0.9.8a the return value for BN_div_word() and BN_mod_word() in case of an error was 0.