NAME    [Toc]    [Back]

       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    [Toc]    [Back]

       #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    [Toc]    [Back]

       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  multiplication  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_reciprocal(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 temporary variables. See BN_CTX_new(3).

       Unless noted otherwise, the result BIGNUM must be  different
 from the arguments.

RETURN VALUES    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       Functions: bn(3), err(3),  BN_CTX_new(3),  BN_add_word(3),
       BN_set_bit(3)



                                                        BN_add(3)