NAME

       BN_CTX_new_ex, BN_CTX_new, BN_CTX_secure_new_ex, BN_CTX_secure_new, BN_CTX_free - allocate
       and free BN_CTX structures

SYNOPSIS

        #include <openssl/bn.h>

        BN_CTX *BN_CTX_new_ex(OSSL_LIB_CTX *ctx);
        BN_CTX *BN_CTX_new(void);

        BN_CTX *BN_CTX_secure_new_ex(OSSL_LIB_CTX *ctx);
        BN_CTX *BN_CTX_secure_new(void);

        void BN_CTX_free(BN_CTX *c);

DESCRIPTION

       A BN_CTX is a structure that holds BIGNUM temporary variables used by library functions.
       Since dynamic memory allocation to create BIGNUMs is rather expensive when used in
       conjunction with repeated subroutine calls, the BN_CTX structure is used.

       BN_CTX_new_ex() allocates and initializes a BN_CTX structure for the given library context
       ctx. The <ctx> value may be NULL in which case the default library context will be used.
       BN_CTX_new() is the same as BN_CTX_new_ex() except that the default library context is
       always used.

       BN_CTX_secure_new_ex() allocates and initializes a BN_CTX structure but uses the secure
       heap (see CRYPTO_secure_malloc(3)) to hold the BIGNUMs for the given library context ctx.
       The <ctx> value may be NULL in which case the default library context will be used.
       BN_CTX_secure_new() is the same as BN_CTX_secure_new_ex() except that the default library
       context is always used.

       BN_CTX_free() frees the components of the BN_CTX and the structure itself.  Since
       BN_CTX_start() is required in order to obtain BIGNUMs from the BN_CTX, in most cases
       BN_CTX_end() must be called before the BN_CTX may be freed by BN_CTX_free().  If c is
       NULL, nothing is done.

       A given BN_CTX must only be used by a single thread of execution.  No locking is
       performed, and the internal pool allocator will not properly handle multiple threads of
       execution.

RETURN VALUES

       BN_CTX_new() and BN_CTX_secure_new() return a pointer to the BN_CTX.  If the allocation
       fails, they return NULL and sets an error code that can be obtained by ERR_get_error(3).

       BN_CTX_free() has no return values.

REMOVED FUNCTIONALITY

        void BN_CTX_init(BN_CTX *c);

       BN_CTX_init() is no longer available as of OpenSSL 1.1.0. Applications should replace use
       of BN_CTX_init with BN_CTX_new instead:

        BN_CTX *ctx;
        ctx = BN_CTX_new();
        if (!ctx)
            /* error */
        ...
        BN_CTX_free(ctx);

SEE ALSO

       ERR_get_error(3), BN_add(3), BN_CTX_start(3)

HISTORY

       BN_CTX_init() was removed in OpenSSL 1.1.0.

COPYRIGHT

       Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except
       in compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.