OpenSSL

Cryptography and SSL/TLS Toolkit

RAND_bytes

NAME

RAND_bytes, RAND_priv_bytes, RAND_pseudo_bytes - generate random data

SYNOPSIS

 #include <openssl/rand.h>

 int RAND_bytes(unsigned char *buf, int num);
 int RAND_priv_bytes(unsigned char *buf, int num);

Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

 int RAND_pseudo_bytes(unsigned char *buf, int num);

DESCRIPTION

RAND_bytes() puts num cryptographically strong pseudo-random bytes into buf.

RAND_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 RAND_METHOD, this function uses a separate "private" PRNG instance so that a compromise of the "public" PRNG instance will not affect the secrecy of these private values, as described in RAND(7) and RAND_DRBG(7).

NOTES

Always check the error return value of RAND_bytes() and RAND_priv_bytes() and do not take randomness for granted: an error occurs if the CSPRNG has not been seeded with enough randomness to ensure an unpredictable byte sequence.

RETURN VALUES

RAND_bytes() and RAND_priv_bytes() return 1 on success, -1 if not supported by the current RAND method, or 0 on other failure. The error code can be obtained by ERR_get_error(3).

HISTORY

  • RAND_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.

SEE ALSO

RAND_add(3), RAND_bytes(3), RAND_priv_bytes(3), ERR_get_error(3), RAND(7), RAND_DRBG(7)

Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.