.\" $OpenBSD: BN_new.3,v 1.14 2018/04/29 15:58:21 schwarze Exp $ .\" full merge up to: OpenSSL man3/BN_new 2457c19d Mar 6 08:43:36 2004 +0000 .\" selective merge up to: man3/BN_new 681acb31 Sep 29 13:10:34 2017 +0200 .\" full merge up to: OpenSSL man7/bn 05ea606a May 20 20:52:46 2016 -0400 .\" .\" This file was written by Ulf Moeller . .\" Copyright (c) 2000, 2004 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: April 29 2018 $ .Dt BN_NEW 3 .Os .Sh NAME .Nm BN_new , .Nm BN_init , .Nm BN_clear , .Nm BN_free , .Nm BN_clear_free .Nd allocate and free BIGNUMs .Sh SYNOPSIS .In openssl/bn.h .Ft BIGNUM * .Fo BN_new .Fa void .Fc .Ft void .Fo BN_init .Fa "BIGNUM *" .Fc .Ft void .Fo BN_clear .Fa "BIGNUM *a" .Fc .Ft void .Fo BN_free .Fa "BIGNUM *a" .Fc .Ft void .Fo BN_clear_free .Fa "BIGNUM *a" .Fc .Sh DESCRIPTION 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. .Pp 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. .Pp The basic object in this library is a .Vt 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. .Pp .Fn BN_new allocates and initializes a .Vt BIGNUM structure, in particular setting the value to zero and the flags to .Dv BN_FLG_MALLOCED . The security-relevant flag .Dv BN_FLG_CONSTTIME is not set by default. .Pp .Fn BN_init initializes an existing uninitialized .Vt BIGNUM . It is deprecated and dangerous: see .Sx CAVEATS . .Pp .Fn BN_clear is used to destroy sensitive data such as keys when they are no longer needed. It erases the memory used by .Fa a and sets it to the value 0. .Pp .Fn BN_free frees the components of the .Vt BIGNUM and, if it was created by .Fn BN_new , also the structure itself. .Fn BN_clear_free additionally overwrites the data before the memory is returned to the system. If .Fa a is a .Dv NULL pointer, no action occurs. .Sh RETURN VALUES .Fn BN_new returns a pointer to the .Vt BIGNUM . If the allocation fails, it returns .Dv NULL and sets an error code that can be obtained by .Xr ERR_get_error 3 . .Sh SEE ALSO .Xr BN_add 3 , .Xr BN_add_word 3 , .Xr BN_BLINDING_new 3 , .Xr BN_bn2bin 3 , .Xr BN_cmp 3 , .Xr BN_copy 3 , .Xr BN_CTX_new 3 , .Xr BN_CTX_start 3 , .Xr BN_generate_prime 3 , .Xr BN_get0_nist_prime_521 3 , .Xr BN_mod_inverse 3 , .Xr BN_mod_mul_montgomery 3 , .Xr BN_mod_mul_reciprocal 3 , .Xr BN_num_bytes 3 , .Xr BN_rand 3 , .Xr BN_set_bit 3 , .Xr BN_set_flags 3 , .Xr BN_set_negative 3 , .Xr BN_swap 3 , .Xr BN_zero 3 .Sh HISTORY .Fn BN_new , .Fn BN_clear , .Fn BN_free , and .Fn BN_clear_free first appeared in SSLeay 0.5.1 and have been available since .Ox 2.4 . .Pp .Fn BN_init first appeared in SSLeay 0.9.1 and has been available since .Ox 2.6 . .Sh CAVEATS .Fn BN_init must not be called on a .Vt 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 .Fn BN_new , or the .Vt BIGNUM structure itself will likely be leaked later on. It can only be used on static .Vt BIGNUM structures, on .Vt BIGNUM structures on the stack, or on .Vt BIGNUM structures .Xr malloc 3 Ap ed manually, but all of these options are discouraged because they will no longer work once the .Vt BIGNUM data type is made opaque.