| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/bn.h>
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| 10 |
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| 11 | void BN_CTX_start(BN_CTX *ctx);
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| 12 |
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| 13 | BIGNUM *BN_CTX_get(BN_CTX *ctx);
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| 14 |
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| 15 | void BN_CTX_end(BN_CTX *ctx);
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| 16 |
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| 17 | =head1 DESCRIPTION
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| 18 |
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| 19 | These functions are used to obtain temporary B<BIGNUM> variables from
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| 20 | a B<BN_CTX> (which can been created by using L<BN_CTX_new(3)>)
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| 21 | in order to save the overhead of repeatedly creating and
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| 22 | freeing B<BIGNUM>s in functions that are called from inside a loop.
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| 23 |
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| 24 | A function must call BN_CTX_start() first. Then, BN_CTX_get() may be
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| 25 | called repeatedly to obtain temporary B<BIGNUM>s. All BN_CTX_get()
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| 26 | calls must be made before calling any other functions that use the
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| 27 | B<ctx> as an argument.
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| 28 |
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| 29 | Finally, BN_CTX_end() must be called before returning from the function.
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| 30 | If B<ctx> is NULL, nothing is done.
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| 31 | When BN_CTX_end() is called, the B<BIGNUM> pointers obtained from
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| 32 | BN_CTX_get() become invalid.
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| 33 |
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| 34 | =head1 RETURN VALUES
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| 35 |
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| 36 | BN_CTX_start() and BN_CTX_end() return no values.
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| 37 |
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| 38 | BN_CTX_get() returns a pointer to the B<BIGNUM>, or B<NULL> on error.
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| 39 | Once BN_CTX_get() has failed, the subsequent calls will return B<NULL>
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| 40 | as well, so it is sufficient to check the return value of the last
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| 41 | BN_CTX_get() call. In case of an error, an error code is set, which
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| 42 | can be obtained by L<ERR_get_error(3)>.
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| 43 |
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| 44 |
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| 45 | =head1 SEE ALSO
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| 46 |
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| 47 | L<BN_CTX_new(3)>
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| 48 |
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| 49 | =head1 COPYRIGHT
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| 50 |
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| 51 | Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 52 |
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| 53 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 54 | this file except in compliance with the License. You can obtain a copy
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| 55 | in the file LICENSE in the source distribution or at
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| 56 | L<https://www.openssl.org/source/license.html>.
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| 57 |
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| 58 | =cut
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