| 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_rand, BN_priv_rand, BN_pseudo_rand,
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| 6 | BN_rand_range, BN_priv_rand_range, BN_pseudo_rand_range
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| 7 | - generate pseudo-random number
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| 8 |
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| 9 | =head1 SYNOPSIS
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| 10 |
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| 11 | #include <openssl/bn.h>
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| 12 |
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| 13 | int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
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| 14 |
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| 15 | int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom);
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| 16 |
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| 17 | int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
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| 18 |
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| 19 | int BN_rand_range(BIGNUM *rnd, BIGNUM *range);
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| 20 |
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| 21 | int BN_priv_rand_range(BIGNUM *rnd, BIGNUM *range);
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| 22 |
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| 23 | int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range);
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| 24 |
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| 25 | =head1 DESCRIPTION
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| 26 |
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| 27 | BN_rand() generates a cryptographically strong pseudo-random number of
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| 28 | B<bits> in length and stores it in B<rnd>.
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| 29 | If B<bits> is less than zero, or too small to
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| 30 | accommodate the requirements specified by the B<top> and B<bottom>
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| 31 | parameters, an error is returned.
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| 32 | The B<top> parameters specifies
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| 33 | requirements on the most significant bit of the generated number.
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| 34 | If it is B<BN_RAND_TOP_ANY>, there is no constraint.
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| 35 | If it is B<BN_RAND_TOP_ONE>, the top bit must be one.
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| 36 | If it is B<BN_RAND_TOP_TWO>, the two most significant bits of
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| 37 | the number will be set to 1, so that the product of two such random
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| 38 | numbers will always have 2*B<bits> length.
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| 39 | If B<bottom> is B<BN_RAND_BOTTOM_ODD>, the number will be odd; if it
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| 40 | is B<BN_RAND_BOTTOM_ANY> it can be odd or even.
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| 41 | If B<bits> is 1 then B<top> cannot also be B<BN_RAND_FLG_TOPTWO>.
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| 42 |
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| 43 | BN_rand_range() generates a cryptographically strong pseudo-random
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| 44 | number B<rnd> in the range 0 E<lt>= B<rnd> E<lt> B<range>.
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| 45 |
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| 46 | BN_priv_rand() and BN_priv_rand_range() have the same semantics as
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| 47 | BN_rand() and BN_rand_range() respectively. They are intended to be
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| 48 | used for generating values that should remain private, and mirror the
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| 49 | same difference between L<RAND_bytes(3)> and L<RAND_priv_bytes(3)>.
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| 50 |
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| 51 | =head1 NOTES
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| 52 |
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| 53 | Always check the error return value of these functions and do not take
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| 54 | randomness for granted: an error occurs if the CSPRNG has not been
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| 55 | seeded with enough randomness to ensure an unpredictable byte sequence.
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| 56 |
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| 57 | =head1 RETURN VALUES
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| 58 |
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| 59 | The functions return 1 on success, 0 on error.
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| 60 | The error codes can be obtained by L<ERR_get_error(3)>.
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| 61 |
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| 62 | =head1 SEE ALSO
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| 63 |
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| 64 | L<ERR_get_error(3)>,
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| 65 | L<RAND_add(3)>,
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| 66 | L<RAND_bytes(3)>,
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| 67 | L<RAND_priv_bytes(3)>,
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| 68 | L<RAND(7)>,
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| 69 | L<RAND_DRBG(7)>
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| 70 |
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| 71 | =head1 HISTORY
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| 72 |
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| 73 | =over 2
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| 74 |
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| 75 | =item *
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| 76 |
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| 77 | Starting with OpenSSL release 1.1.0, BN_pseudo_rand() has been identical
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| 78 | to BN_rand() and BN_pseudo_rand_range() has been identical to
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| 79 | BN_rand_range().
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| 80 | The "pseudo" functions should not be used and may be deprecated in
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| 81 | a future release.
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| 82 |
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| 83 | =item *
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| 84 |
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| 85 | The
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| 86 | BN_priv_rand() and BN_priv_rand_range() functions were added in OpenSSL 1.1.1.
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| 87 |
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| 88 | =back
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| 89 |
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| 90 | =head1 COPYRIGHT
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| 91 |
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| 92 | Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
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| 93 |
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| 94 | Licensed under the OpenSSL license (the "License"). You may not use
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| 95 | this file except in compliance with the License. You can obtain a copy
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| 96 | in the file LICENSE in the source distribution or at
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| 97 | L<https://www.openssl.org/source/license.html>.
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| 98 |
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| 99 | =cut
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