.\"	$OpenBSD: BN_rand.3,v 1.14 2018/12/24 10:07:22 schwarze Exp $
.\" full merge up to: OpenSSL 05ea606a May 20 20:52:46 2016 -0400
.\" selective merge up to: OpenSSL df75c2bf Dec 9 01:02:36 2018 +0100
.\"
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.Dd $Mdocdate: December 24 2018 $
.Dt BN_RAND 3
.Os
.Sh NAME
.Nm BN_rand ,
.Nm BN_rand_range ,
.Nm BN_pseudo_rand ,
.Nm BN_pseudo_rand_range
.Nd generate pseudo-random number
.Sh SYNOPSIS
.In openssl/bn.h
.Ft int
.Fo BN_rand
.Fa "BIGNUM *rnd"
.Fa "int bits"
.Fa "int top"
.Fa "int bottom"
.Fc
.Ft int
.Fo BN_rand_range
.Fa "BIGNUM *rnd"
.Fa "BIGNUM *range"
.Fc
.Sh DESCRIPTION
.Fn BN_rand
generates a cryptographically strong pseudo-random number of
.Fa bits
in length and stores it in
.Fa rnd .
If
.Fa top
is -1, the most significant bit of the random number can be zero.
If
.Fa top
is 0, it is set to 1, and if
.Fa top
is 1, the two most significant bits of the number will be set to 1, so
that the product of two such random numbers will always have
.Pf 2* Fa bits
length.
If
.Fa bottom
is true, the number will be odd.
The value of
.Fa bits
must be zero or greater.
If
.Fa bits
is +1 then
.Fa top
cannot also be 1.
.Pp
.Fn BN_rand_range
generates a cryptographically strong pseudo-random number
.Fa rnd
in the range 0 <=
.Fa rnd No < Fa range .
.Pp
.Fn BN_pseudo_rand
is a deprecated alias for
.Fn BN_rand ,
and
.Fn BN_pseudo_rand_range
for
.Fn BN_rand_range .
.Sh RETURN VALUES
The functions return 1 on success, 0 on error.
The error codes can be obtained by
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr BN_new 3 ,
.Xr ERR_get_error 3 ,
.Xr RAND_add 3 ,
.Xr RAND_bytes 3
.Sh HISTORY
.Fn BN_rand
first appeared in SSLeay 0.5.1 and has been available since
.Ox 2.4 .
.Pp
The
.Fa top
== -1 case and the function
.Fn BN_rand_range
first appeared in OpenSSL 0.9.6a and have been available since
.Ox 3.0 .