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.\" ========================================================================
.\"
.IX Title "RAND_DRBG_NEW 3"
.TH RAND_DRBG_NEW 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
RAND_DRBG_new, RAND_DRBG_secure_new, RAND_DRBG_set, RAND_DRBG_set_defaults, RAND_DRBG_instantiate, RAND_DRBG_uninstantiate, RAND_DRBG_free \&\- initialize and cleanup a RAND_DRBG instance
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/rand_drbg.h>
\&
\&
\& RAND_DRBG *RAND_DRBG_new(int type,
\&                          unsigned int flags,
\&                          RAND_DRBG *parent);
\&
\& RAND_DRBG *RAND_DRBG_secure_new(int type,
\&                                 unsigned int flags,
\&                                 RAND_DRBG *parent);
\&
\& int RAND_DRBG_set(RAND_DRBG *drbg,
\&                   int type, unsigned int flags);
\&
\& int RAND_DRBG_set_defaults(int type, unsigned int flags);
\&
\& int RAND_DRBG_instantiate(RAND_DRBG *drbg,
\&                           const unsigned char *pers, size_t perslen);
\&
\& int RAND_DRBG_uninstantiate(RAND_DRBG *drbg);
\&
\& void RAND_DRBG_free(RAND_DRBG *drbg);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBRAND_DRBG_new()\fR and \fBRAND_DRBG_secure_new()\fR
create a new \s-1DRBG\s0 instance of the given \fBtype\fR, allocated from the heap resp.
the secure heap
(using \fBOPENSSL_zalloc()\fR resp. \fBOPENSSL_secure_zalloc()\fR).
.PP
\&\fBRAND_DRBG_set()\fR initializes the \fBdrbg\fR with the given \fBtype\fR and \fBflags\fR.
.PP
\&\fBRAND_DRBG_set_defaults()\fR sets the default \fBtype\fR and \fBflags\fR for new \s-1DRBG\s0
instances.
.PP
Currently, all \s-1DRBG\s0 types are based on AES-CTR, so \fBtype\fR can be one of the
following values: NID_aes_128_ctr, NID_aes_192_ctr, NID_aes_256_ctr.
Before the \s-1DRBG\s0 can be used to generate random bits, it is necessary to set
its type and to instantiate it.
.PP
The optional \fBflags\fR argument specifies a set of bit flags which can be
joined using the | operator. Currently, the only flag is
\&\s-1RAND_DRBG_FLAG_CTR_NO_DF,\s0 which disables the use of the derivation function
ctr_df. For an explanation, see [\s-1NIST SP 800\-90A\s0 Rev. 1].
.PP
If a \fBparent\fR instance is specified then this will be used instead of
the default entropy source for reseeding the \fBdrbg\fR. It is said that the
\&\fBdrbg\fR is \fIchained\fR to its \fBparent\fR.
For more information, see the \s-1NOTES\s0 section.
.PP
\&\fBRAND_DRBG_instantiate()\fR
seeds the \fBdrbg\fR instance using random input from trusted entropy sources.
Optionally, a personalization string \fBpers\fR of length \fBperslen\fR can be
specified.
To omit the personalization string, set \fBpers\fR=NULL and \fBperslen\fR=0;
.PP
\&\fBRAND_DRBG_uninstantiate()\fR
clears the internal state of the \fBdrbg\fR and puts it back in the
uninstantiated state.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBRAND_DRBG_new()\fR and \fBRAND_DRBG_secure_new()\fR return a pointer to a \s-1DRBG\s0
instance allocated on the heap, resp. secure heap.
.PP
\&\fBRAND_DRBG_set()\fR,
\&\fBRAND_DRBG_instantiate()\fR, and
\&\fBRAND_DRBG_uninstantiate()\fR
return 1 on success, and 0 on failure.
.PP
\&\fBRAND_DRBG_free()\fR does not return a value.
.SH "NOTES"
.IX Header "NOTES"
The \s-1DRBG\s0 design supports \fIchaining\fR, which means that a \s-1DRBG\s0 instance can
use another \fBparent\fR \s-1DRBG\s0 instance instead of the default entropy source
to obtain fresh random input for reseeding, provided that \fBparent\fR \s-1DRBG\s0
instance was properly instantiated, either from a trusted entropy source,
or from yet another parent \s-1DRBG\s0 instance.
For a detailed description of the reseeding process, see \s-1\fBRAND_DRBG\s0\fR\|(7).
.PP
The default \s-1DRBG\s0 type and flags are applied only during creation of a \s-1DRBG\s0
instance.
To ensure that they are applied to the global and thread-local \s-1DRBG\s0 instances
(<master>, resp. <public> and <private>), it is necessary to call
\&\fBRAND_DRBG_set_defaults()\fR before creating any thread and before calling any
cryptographic routines that obtain random data directly or indirectly.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBOPENSSL_zalloc\fR\|(3),
\&\fBOPENSSL_secure_zalloc\fR\|(3),
\&\fBRAND_DRBG_generate\fR\|(3),
\&\s-1\fBRAND_DRBG\s0\fR\|(7)
.SH "HISTORY"
.IX Header "HISTORY"
The \s-1RAND_DRBG\s0 functions were added in OpenSSL 1.1.1.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2017\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.