BN_MOD_INVERSE(3)          Library Functions Manual          BN_MOD_INVERSE(3)

NAME
     BN_mod_inverse - compute inverse modulo m

SYNOPSIS
     #include <openssl/bn.h>

     BIGNUM *
     BN_mod_inverse(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);

DESCRIPTION
     BN_mod_inverse() computes the inverse of a modulo m and places the result
     in r, so that r satisfies a * r == 1 (mod m).  If r is NULL, a new BIGNUM
     is allocated.

     If the flag BN_FLG_CONSTTIME is set on a or m, it operates in constant
     time.

     ctx is a previously allocated BN_CTX used for temporary variables.  r may
     be the same BIGNUM as a or m.

RETURN VALUES
     BN_mod_inverse() returns the BIGNUM containing the inverse, or NULL on
     error.  The error codes can be obtained by ERR_get_error(3).

SEE ALSO
     BN_add(3), BN_new(3), BN_set_flags(3)

HISTORY
     BN_mod_inverse() first appeared in SSLeay 0.5.1 and has been available
     since OpenBSD 2.4.

     The r argument was added in SSLeay 0.9.1 and OpenBSD 2.6.

Linux 6.8.2-arch2-1            October 21, 2023            Linux 6.8.2-arch2-1