- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- SEE ALSO
- HISTORY

# NAME

BN_mod_inverse - compute inverse modulo n

# SYNOPSIS

     #include <openssl/bn.h>

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

# DESCRIPTION

`BN_mod_inverse()` computes the inverse of a modulo n places the result in r (`(a*r)%n==1`). If r is NULL, a new BIGNUM is created.

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

# RETURN VALUES

`BN_mod_inverse()` returns the BIGNUM containing the inverse, and NULL on error. The error codes can be obtained by ERR_get_error.

# SEE ALSO

bn, ERR_get_error, BN_add

# HISTORY

`BN_mod_inverse()` is available in all versions of SSLeay and OpenSSL.