BN_new,
BN_init,
BN_clear,
BN_free,
BN_clear_free —
allocate and free BIGNUMs
#include
<openssl/bn.h>
BIGNUM *
BN_new(
void);
void
BN_init(
BIGNUM
*);
void
BN_clear(
BIGNUM
*a);
void
BN_free(
BIGNUM
*a);
void
BN_clear_free(
BIGNUM
*a);
The BN library performs arithmetic operations on integers of arbitrary size. It
was written for use in public key cryptography, such as RSA and
Diffie-Hellman.
It uses dynamic memory allocation for storing its data structures. That means
that there is no limit on the size of the numbers manipulated by these
functions, but return values must always be checked in case a memory
allocation error has occurred.
The basic object in this library is a
BIGNUM.
It is used to hold a single large integer. This type should be considered
opaque and fields should not be modified or accessed directly.
BN_new() allocates and initializes a
BIGNUM structure, in particular setting the
value to zero and the flags to
BN_FLG_MALLOCED. The security-relevant flag
BN_FLG_CONSTTIME is not set by default.
BN_init() initializes an existing
uninitialized
BIGNUM. It is deprecated and
dangerous: see
CAVEATS.
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. If
a is a
NULL pointer, no action occurs.
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_add(3),
BN_add_word(3),
BN_BLINDING_new(3),
BN_bn2bin(3),
BN_cmp(3),
BN_copy(3),
BN_CTX_new(3),
BN_CTX_start(3),
BN_generate_prime(3),
BN_get0_nist_prime_521(3),
BN_mod_inverse(3),
BN_mod_mul_montgomery(3),
BN_mod_mul_reciprocal(3),
BN_num_bytes(3),
BN_rand(3),
BN_set_bit(3),
BN_set_flags(3),
BN_set_negative(3),
BN_swap(3),
BN_zero(3)
BN_new(),
BN_clear(),
BN_free(), and
BN_clear_free() first appeared in SSLeay
0.5.1 and have been available since
OpenBSD 2.4.
BN_init() first appeared in SSLeay 0.9.1 and
has been available since
OpenBSD 2.6.
BN_init() must not be called on a
BIGNUM that was used and contains an actual
number, or the memory used for storing the number is leaked immediately.
Besides, it must not be called on a number allocated with
BN_new(), or the
BIGNUM structure itself will likely be leaked
later on. It can only be used on static
BIGNUM structures, on
BIGNUM structures on the stack, or on
BIGNUM structures
malloc(3)'ed manually, but all
of these options are discouraged because they will no longer work once the
BIGNUM data type is made opaque.
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