Automatically generated by Pod::Man 4.14 (Pod::Simple 3.42)

Standard preamble:
========================================================================
..

..

.. Set up some character translations and predefined strings. \*(-- will
give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
double quote, and \*(R" will give a right double quote. \*(C+ will
give a nicer C++. Capital omega is used to do unbreakable dashes and
therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
nothing in troff, for use with C<>.
.tr \(*W- . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\}
Escape single quotes in literal strings from groff's Unicode transform.

If the F register is >0, we'll generate index entries on stderr for
titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
entries marked with X<> in POD. Of course, you'll have to process the
output yourself in some meaningful fashion.

Avoid warning from groff about undefined register 'F'.
.. .nr rF 0 . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF Fear. Run. Save yourself. No user-serviceable parts.
. \" fudge factors for nroff and troff . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] .\} . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents . \" corrections for vroff . \" for low resolution devices (crt and lpr) \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} ========================================================================

Title "RAND_BYTES 3ossl" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
RAND_bytes, RAND_priv_bytes, RAND_bytes_ex, RAND_priv_bytes_ex, RAND_pseudo_bytes - generate random data Header "SYNOPSIS" .Vb 1 #include <openssl/rand.h> \& int RAND_bytes(unsigned char *buf, int num); int RAND_priv_bytes(unsigned char *buf, int num); \& int RAND_bytes_ex(OSSL_LIB_CTX *ctx, unsigned char *buf, size_t num, unsigned int strength); int RAND_priv_bytes_ex(OSSL_LIB_CTX *ctx, unsigned char *buf, size_t num, unsigned int strength); .Ve

The following function has been deprecated since OpenSSL 1.1.0, and can be hidden entirely by defining \s-1OPENSSL_API_COMPAT\s0 with a suitable version value, see openssl_user_macros\|(7):

.Vb 1 int RAND_pseudo_bytes(unsigned char *buf, int num); .Ve

Header "DESCRIPTION" \fBRAND_bytes() generates num random bytes using a cryptographically secure pseudo random generator (\s-1CSPRNG\s0) and stores them in buf.

\fBRAND_priv_bytes() has the same semantics as RAND_bytes(). It is intended to be used for generating values that should remain private. If using the default \s-1RAND_METHOD,\s0 this function uses a separate \*(L"private\*(R" \s-1PRNG\s0 instance so that a compromise of the \*(L"public\*(R" \s-1PRNG\s0 instance will not affect the secrecy of these private values, as described in \s-1RAND\s0\|(7) and \s-1EVP_RAND\s0\|(7).

\fBRAND_bytes_ex() and RAND_priv_bytes_ex() are the same as RAND_bytes() and \fBRAND_priv_bytes() except that they both take additional strength and \fIctx parameters. The bytes generated will have a security strength of at least strength bits. The \s-1DRBG\s0 used for the operation is the public or private \s-1DRBG\s0 associated with the specified ctx. The parameter can be \s-1NULL,\s0 in which case the default library context is used (see \s-1OSSL_LIB_CTX\s0\|(3). If the default \s-1RAND_METHOD\s0 has been changed then for compatibility reasons the \s-1RAND_METHOD\s0 will be used in preference and the \s-1DRBG\s0 of the library context ignored.

Header "NOTES" By default, the OpenSSL \s-1CSPRNG\s0 supports a security level of 256 bits, provided it was able to seed itself from a trusted entropy source. On all major platforms supported by OpenSSL (including the Unix-like platforms and Windows), OpenSSL is configured to automatically seed the \s-1CSPRNG\s0 on first use using the operating systems's random generator.

If the entropy source fails or is not available, the \s-1CSPRNG\s0 will enter an error state and refuse to generate random bytes. For that reason, it is important to always check the error return value of RAND_bytes() and RAND_priv_bytes() and not take randomness for granted.

On other platforms, there might not be a trusted entropy source available or OpenSSL might have been explicitly configured to use different entropy sources. If you are in doubt about the quality of the entropy source, don't hesitate to ask your operating system vendor or post a question on GitHub or the openssl-users mailing list.

Header "RETURN VALUES" \fBRAND_bytes() and RAND_priv_bytes() return 1 on success, -1 if not supported by the current \s-1RAND\s0 method, or 0 on other failure. The error code can be obtained by ERR_get_error\|(3). Header "SEE ALSO" \fBRAND_add\|(3), \fBRAND_bytes\|(3), \fBRAND_priv_bytes\|(3), \fBERR_get_error\|(3), \s-1RAND\s0\|(7), \s-1EVP_RAND\s0\|(7) Header "HISTORY" \fBRAND_pseudo_bytes() was deprecated in OpenSSL 1.1.0; use RAND_bytes() instead. The RAND_priv_bytes() function was added in OpenSSL 1.1.1. The RAND_bytes_ex() and RAND_priv_bytes_ex() functions were added in OpenSSL 3.0 Header "COPYRIGHT" Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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>.