1=pod 2 3=head1 NAME 4 5BN_rand, BN_priv_rand, BN_pseudo_rand, 6BN_rand_range, BN_priv_rand_range, BN_pseudo_rand_range 7- generate pseudo-random number 8 9=head1 SYNOPSIS 10 11 #include <openssl/bn.h> 12 13 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom); 14 15 int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom); 16 17 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom); 18 19 int BN_rand_range(BIGNUM *rnd, BIGNUM *range); 20 21 int BN_priv_rand_range(BIGNUM *rnd, BIGNUM *range); 22 23 int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range); 24 25=head1 DESCRIPTION 26 27BN_rand() generates a cryptographically strong pseudo-random number of 28B<bits> in length and stores it in B<rnd>. 29If B<bits> is less than zero, or too small to 30accommodate the requirements specified by the B<top> and B<bottom> 31parameters, an error is returned. 32The B<top> parameters specifies 33requirements on the most significant bit of the generated number. 34If it is B<BN_RAND_TOP_ANY>, there is no constraint. 35If it is B<BN_RAND_TOP_ONE>, the top bit must be one. 36If it is B<BN_RAND_TOP_TWO>, the two most significant bits of 37the number will be set to 1, so that the product of two such random 38numbers will always have 2*B<bits> length. 39If B<bottom> is B<BN_RAND_BOTTOM_ODD>, the number will be odd; if it 40is B<BN_RAND_BOTTOM_ANY> it can be odd or even. 41If B<bits> is 1 then B<top> cannot also be B<BN_RAND_TOP_TWO>. 42 43BN_rand_range() generates a cryptographically strong pseudo-random 44number B<rnd> in the range 0 E<lt>= B<rnd> E<lt> B<range>. 45 46BN_priv_rand() and BN_priv_rand_range() have the same semantics as 47BN_rand() and BN_rand_range() respectively. They are intended to be 48used for generating values that should remain private, and mirror the 49same difference between L<RAND_bytes(3)> and L<RAND_priv_bytes(3)>. 50 51=head1 NOTES 52 53Always check the error return value of these functions and do not take 54randomness for granted: an error occurs if the CSPRNG has not been 55seeded with enough randomness to ensure an unpredictable byte sequence. 56 57=head1 RETURN VALUES 58 59The functions return 1 on success, 0 on error. 60The error codes can be obtained by L<ERR_get_error(3)>. 61 62=head1 SEE ALSO 63 64L<ERR_get_error(3)>, 65L<RAND_add(3)>, 66L<RAND_bytes(3)>, 67L<RAND_priv_bytes(3)>, 68L<RAND(7)>, 69L<RAND_DRBG(7)> 70 71=head1 HISTORY 72 73=over 2 74 75=item * 76 77Starting with OpenSSL release 1.1.0, BN_pseudo_rand() has been identical 78to BN_rand() and BN_pseudo_rand_range() has been identical to 79BN_rand_range(). 80The "pseudo" functions should not be used and may be deprecated in 81a future release. 82 83=item * 84 85The 86BN_priv_rand() and BN_priv_rand_range() functions were added in OpenSSL 1.1.1. 87 88=back 89 90=head1 COPYRIGHT 91 92Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. 93 94Licensed under the OpenSSL license (the "License"). You may not use 95this file except in compliance with the License. You can obtain a copy 96in the file LICENSE in the source distribution or at 97L<https://www.openssl.org/source/license.html>. 98 99=cut 100