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BN_CTX_start(3)                     OpenSSL                    BN_CTX_start(3)

       BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables

       libcrypto, -lcrypto

        #include <openssl/bn.h>

        void BN_CTX_start(BN_CTX *ctx);

        BIGNUM *BN_CTX_get(BN_CTX *ctx);

        void BN_CTX_end(BN_CTX *ctx);

       These functions are used to obtain temporary BIGNUM variables from a
       BN_CTX (which can been created by using BN_CTX_new(3)) in order to save
       the overhead of repeatedly creating and freeing BIGNUMs in functions
       that are called from inside a loop.

       A function must call BN_CTX_start() first. Then, BN_CTX_get() may be
       called repeatedly to obtain temporary BIGNUMs. All BN_CTX_get() calls
       must be made before calling any other functions that use the ctx as an

       Finally, BN_CTX_end() must be called before returning from the
       function.  If ctx is NULL, nothing is done.  When BN_CTX_end() is
       called, the BIGNUM pointers obtained from BN_CTX_get() become invalid.

       BN_CTX_start() and BN_CTX_end() return no values.

       BN_CTX_get() returns a pointer to the BIGNUM, or NULL on error.  Once
       BN_CTX_get() has failed, the subsequent calls will return NULL as well,
       so it is sufficient to check the return value of the last BN_CTX_get()
       call. In case of an error, an error code is set, which can be obtained
       by ERR_get_error(3).


       Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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

1.1.1i                            2019-06-09                   BN_CTX_start(3)