BN_new, BN_init, BN_clear, BN_free, BN_clear_free — allocate and free BIGNUMs
void BN_init(BIGNUM *);
void BN_clear(BIGNUM *a);
void BN_free(BIGNUM *a);
void BN_clear_free(BIGNUM *a);
BN_new() allocates and initializes a BIGNUM structure. BN_init() initializes an existing uninitialized BIGNUM.
BN_clear() is used to destroy sensitive data such as keys when they are no longer needed. It erases the memory used by a and sets it to the value 0.
BN_free() frees the components of the BIGNUM, and if it was created by BN_new(), also the structure itself. BN_clear_free() additionally overwrites the data before the memory is returned to the system.
BN_new() returns a pointer to the BIGNUM. If the allocation fails, it returns NULL and sets an error code that can be obtained by ERR_get_error(3).
BN_init(), BN_clear(), BN_free() and BN_clear_free() have no return values.
BN_new(), BN_clear(), BN_free() and BN_clear_free() are available in all versions on SSLeay and OpenSSL. BN_init() was added in SSLeay 0.9.1b.