/usr/man/cat.3/BN_sub.3(/usr/man/cat.3/BN_sub.3)
BN_add(3) OpenSSL BN_add(3)
NAME
BN_add, BN_sub, BN_mul, BN_sqr, BN_div, BN_mod, BN_nnmod,
BN_mod_add, BN_mod_sub, BN_mod_mul, BN_mod_sqr, 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_sqr(BIGNUM *r, BIGNUM *a, BN_CTX *ctx);
int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *a, const BIGNUM *d,
BN_CTX *ctx);
int BN_mod(BIGNUM *rem, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);
int BN_nnmod(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);
int BN_mod_add(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
BN_CTX *ctx);
int BN_mod_sub(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
BN_CTX *ctx);
int BN_mod_mul(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
BN_CTX *ctx);
int BN_mod_sqr(BIGNUM *r, BIGNUM *a, 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
BN_add() adds a and b and places the result in r ("r=a+b").
r may be the same BIGNUM as a or b.
BN_sub() subtracts b from a and places the result in r
("r=a-b").
BN_mul() multiplies a and b and places the result in r
("r=a*b"). r may be the same BIGNUM as a or b. For
multiplication by powers of 2, use BN_lshift(3).
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BN_add(3) OpenSSL BN_add(3)
BN_sqr() takes the square of a and places the result in r
("r=a^2"). r and a may be the same BIGNUM. This function is
faster than BN_mul(r,a,a).
BN_div() 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. The result is rounded towards zero; thus if a is
negative, the remainder will be zero or negative. For
division by powers of 2, use BN_rshift(3).
BN_mod() corresponds to BN_div() with dv set to NULL.
BN_nnmod() reduces a modulo m and places the non-negative
remainder in r.
BN_mod_add() adds a to b modulo m and places the non-
negative result in r.
BN_mod_sub() subtracts b from a modulo m and places the
non-negative result in r.
BN_mod_mul() multiplies a by b and finds the non-negative
remainder respective to modulus m ("r=(a*b) mod m"). r may
be the same BIGNUM as a or b. For more efficient algorithms
for repeated computations using the same modulus, see
BN_mod_mul_montgomery(3) and BN_mod_mul_reciprocal(3).
BN_mod_sqr() takes the square of a modulo m and places the
result in r.
BN_exp() raises a to the p-th 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-th power modulo m ("r=a^p %
m"). This function uses less time and space than BN_exp().
Do not call this function when m is even and any of the
parameters have the BN_FLG_CONSTTIME flag set.
BN_gcd() computes the greatest common divisor of a and b and
places the result in r. r may be the same BIGNUM as a or b.
For all functions, ctx is a previously allocated BN_CTX used
for temporary 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
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BN_add(3) OpenSSL BN_add(3)
(!BN_add(r,a,b)) goto err;"). The error codes can be
obtained by ERR_get_error(3).
SEE ALSO
bn(3), ERR_get_error(3), BN_CTX_new(3), BN_add_word(3),
BN_set_bit(3)
HISTORY
BN_add(), BN_sub(), BN_sqr(), BN_div(), 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. BN_exp() appeared in SSLeay
0.9.0. BN_nnmod(), BN_mod_add(), BN_mod_sub(), and
BN_mod_sqr() were added in OpenSSL 0.9.7.
1.0.2t Last change: 2019-09-10 3
See also BN_add(3)
See also BN_div(3)
See also BN_exp(3)
See also BN_gcd(3)
See also BN_mod(3)
See also BN_mod_add(3)
See also BN_mod_exp(3)
See also BN_mod_mul(3)
See also BN_mod_sqr(3)
See also BN_mod_sub(3)
See also BN_mul(3)
See also BN_nnmod(3)
See also BN_sqr(3)
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