BN_add(3)BN_add(3)NAME
BN_add, BN_sub, BN_mul, BN_div, BN_sqr, BN_mod, BN_mod_mul, BN_exp,
BN_mod_exp, BN_gcd - Arithmetic operations on BIGNUMs
SYNOPSIS
#include <openssl/bn.h>
int BN_add(
BIGNUM *r, const BIGNUM *a, const BIGNUM *b ); int BN_sub(
BIGNUM *r, const BIGNUM *a, const BIGNUM *b ); int BN_mul(
BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_CTX *ctx ); int BN_div(
BIGNUM *dv, BIGNUM *rem, const BIGNUM *a, const BIGNUM *d,
BN_CTX *ctx ); int BN_sqr(
BIGNUM *r, BIGNUM *a, BN_CTX *ctx ); int BN_mod(
BIGNUM *rem, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx );
int BN_mod_mul(
BIGNUM *ret, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx
); int BN_exp(
BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx ); int BN_mod_exp(
BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m, BN_CTX
*ctx ); int BN_gcd(
BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_CTX *ctx );
DESCRIPTION
The BN_add() function adds a and b and places the result in r (r=a+b).
The r value can be the same BIGNUM as a or b.
The BN_sub() function subtracts b from a and places the result in r
(r=a-b).
The BN_mul() function multiplies a and b and places the result in r
(r=a*b). The r value may be the same BIGNUM as a or b. For multiplica‐
tion by powers of 2, use the BN_lshift() function.
The BN_div() function divides a by d and places the result in dv and
the remainder in rem (dv=a/d, rem=a%d). Either of dv and rem may be
NULL, in which case the respective value is not returned. For division
by powers of 2, use the BN_rshift() function.
The BN_sqr() function takes the square of a and places the result in r
(r=a^2). The r and a values may be the same BIGNUM. This function is
faster than BN_mul(r,a,a).
The BN_mod() function finds the remainder of a divided by m and places
it in rem (rem=a%m).
The BN_mod_mul() function multiplies a by b and finds the remainder
when divided by m (r=(a*b)%m). The r value may be the same BIGNUM as a
or b. For a more efficient algorithm, see BN_mod_mul_montgomery(3); for
repeated computations using the same modulus, see BN_mod_mul_recipro‐
cal(3).
The BN_exp() function raises a to the p power and places the result in
r (r=a^p). This function is faster than repeated applications of
BN_mul().
BN_mod_exp() computes a to the p power modulo m (r=a^p % m). This
function uses less time and space than BN_exp().
BN_gcd() computes the greatest common divisor of a and b and places the
result in r. The r value may be the same BIGNUM as a or b.
For all functions, ctx is a previously allocated BN_CTX used for tempo‐
rary variables. See BN_CTX_new(3).
Unless noted otherwise, the result BIGNUM must be different from the
arguments.
RETURN VALUES
For all functions, 1 is returned for success, 0 on error. The return
value should always be checked (e.g., if (!BN_add(r,a,b)) goto err;).
The error codes can be obtained by using the ERR_get_error() function.
HISTORY
The BN_add(), BN_sub(), BN_div(), BN_sqr(), BN_mod(), BN_mod_mul(),
BN_mod_exp(), and BN_gcd() are available in all versions of SSLeay and
OpenSSL. The ctx argument to BN_mul() was added in SSLeay 0.9.1b. The
BN_exp() function appeared in SSLeay 0.9.0.
SEE ALSO
Functions: bn(3), err(3), BN_CTX_new(3), BN_add_word(3), BN_set_bit(3)BN_add(3)