BN_rand.pod revision 76866 
1=pod
2
3=head1 NAME
4
5BN_rand, BN_pseudo_rand - generate pseudo-random number
6
7=head1 SYNOPSIS
8
9 #include <openssl/bn.h>
10
11 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
12
13 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
14
15 int BN_rand_range(BIGNUM *rnd, BIGNUM *range);
16
17=head1 DESCRIPTION
18
19BN_rand() generates a cryptographically strong pseudo-random number of
20B<bits> bits in length and stores it in B<rnd>. If B<top> is -1, the
21most significant bit of the random number can be zero. If B<top> is 0,
22it is set to 1, and if B<top> is 1, the two most significant bits of
23the number will be set to 1, so that the product of two such random
24numbers will always have 2*B<bits> length.  If B<bottom> is true, the
25number will be odd.
26
27BN_pseudo_rand() does the same, but pseudo-random numbers generated by
28this function are not necessarily unpredictable. They can be used for
29non-cryptographic purposes and for certain purposes in cryptographic
30protocols, but usually not for key generation etc.
31
32BN_rand_range() generates a cryptographically strong pseudo-random
33number B<rnd> in the range 0 <lt>= B<rnd> E<lt> B<range>.
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35The PRNG must be seeded prior to calling BN_rand() or BN_rand_range().
36
37=head1 RETURN VALUES
38
39The functions return 1 on success, 0 on error.
40The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
41
42=head1 SEE ALSO
43
44L<bn(3)|bn(3)>, L<err(3)|err(3)>, L<rand(3)|rand(3)>,
45L<RAND_add(3)|RAND_add(3)>, L<RAND_bytes(3)|RAND_bytes(3)>
46
47=head1 HISTORY
48
49BN_rand() is available in all versions of SSLeay and OpenSSL.
50BN_pseudo_rand() was added in OpenSSL 0.9.5. The B<top> == -1 case
51and the function BN_rand_range() were added in OpenSSL 0.9.6a.
52
53=cut
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