100 lines
2.9 KiB
Plaintext
100 lines
2.9 KiB
Plaintext
=pod
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=head1 NAME
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BN_rand, BN_priv_rand, BN_pseudo_rand,
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BN_rand_range, BN_priv_rand_range, BN_pseudo_rand_range
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- generate pseudo-random number
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=head1 SYNOPSIS
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#include <openssl/bn.h>
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int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
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int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom);
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int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
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int BN_rand_range(BIGNUM *rnd, BIGNUM *range);
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int BN_priv_rand_range(BIGNUM *rnd, BIGNUM *range);
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int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range);
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=head1 DESCRIPTION
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BN_rand() generates a cryptographically strong pseudo-random number of
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B<bits> in length and stores it in B<rnd>.
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If B<bits> is less than zero, or too small to
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accommodate the requirements specified by the B<top> and B<bottom>
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parameters, an error is returned.
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The B<top> parameters specifies
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requirements on the most significant bit of the generated number.
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If it is B<BN_RAND_TOP_ANY>, there is no constraint.
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If it is B<BN_RAND_TOP_ONE>, the top bit must be one.
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If it is B<BN_RAND_TOP_TWO>, the two most significant bits of
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the number will be set to 1, so that the product of two such random
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numbers will always have 2*B<bits> length.
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If B<bottom> is B<BN_RAND_BOTTOM_ODD>, the number will be odd; if it
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is B<BN_RAND_BOTTOM_ANY> it can be odd or even.
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If B<bits> is 1 then B<top> cannot also be B<BN_RAND_TOP_TWO>.
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BN_rand_range() generates a cryptographically strong pseudo-random
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number B<rnd> in the range 0 E<lt>= B<rnd> E<lt> B<range>.
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BN_priv_rand() and BN_priv_rand_range() have the same semantics as
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BN_rand() and BN_rand_range() respectively. They are intended to be
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used for generating values that should remain private, and mirror the
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same difference between L<RAND_bytes(3)> and L<RAND_priv_bytes(3)>.
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=head1 NOTES
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Always check the error return value of these functions and do not take
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randomness for granted: an error occurs if the CSPRNG has not been
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seeded with enough randomness to ensure an unpredictable byte sequence.
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=head1 RETURN VALUES
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The functions return 1 on success, 0 on error.
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The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 SEE ALSO
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L<ERR_get_error(3)>,
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L<RAND_add(3)>,
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L<RAND_bytes(3)>,
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L<RAND_priv_bytes(3)>,
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L<RAND(7)>,
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L<RAND_DRBG(7)>
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=head1 HISTORY
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=over 2
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=item *
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Starting with OpenSSL release 1.1.0, BN_pseudo_rand() has been identical
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to BN_rand() and BN_pseudo_rand_range() has been identical to
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BN_rand_range().
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The "pseudo" functions should not be used and may be deprecated in
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a future release.
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=item *
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The
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BN_priv_rand() and BN_priv_rand_range() functions were added in OpenSSL 1.1.1.
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=back
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=head1 COPYRIGHT
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Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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