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RAND(3) 			   LibreSSL			       RAND(3)

NAME

RAND - pseudo-random number generator

SYNOPSIS

#include <openssl/rand.h> int RAND_bytes(unsigned char *buf, int num); int RAND_pseudo_bytes(unsigned char *buf, int num);

DESCRIPTION

These functions give access to the systems cryptographically secure pseudo-random number generator (PRNG). It is used by other library functions for example to generate random keys, and applications can use it when they need randomness. RAND_bytes(3) describes how to obtain random data from the PRNG.

INTERNALS

The RAND_SSLeay() method implements a PRNG based on the systems' arc4random_buf(3) random number generator.

SEE ALSO

BN_rand(3), RAND_bytes(3) LibreSSL 2017-01-09 RAND(3) RAND_bytes(3) OpenSSL RAND_bytes(3)

NAME

RAND_bytes, RAND_pseudo_bytes - generate random data

SYNOPSIS

#include <openssl/rand.h> int RAND_bytes(unsigned char *buf, int num); int RAND_pseudo_bytes(unsigned char *buf, int num);

DESCRIPTION

RAND_bytes() puts num cryptographically strong pseudo-random bytes into buf. An error occurs if the PRNG has not been seeded with enough randomness to ensure an unpredictable byte sequence. RAND_pseudo_bytes() puts num pseudo-random bytes into buf. Pseudo- random byte sequences generated by RAND_pseudo_bytes() will be unique if they are of sufficient length, but are not necessarily unpredictable. They can be used for non-cryptographic purposes and for certain purposes in cryptographic protocols, but usually not for key generation etc. The contents of buf is mixed into the entropy pool before retrieving the new pseudo-random bytes unless disabled at compile time (see FAQ).

RETURN VALUES

RAND_bytes() returns 1 on success, 0 otherwise. The error code can be obtained by ERR_get_error(3). RAND_pseudo_bytes() returns 1 if the bytes generated are cryptographically strong, 0 otherwise. Both functions return -1 if they are not supported by the current RAND method.

SEE ALSO

rand(3), ERR_get_error(3), RAND_add(3)

HISTORY

RAND_bytes() is available in all versions of SSLeay and OpenSSL. It has a return value since OpenSSL 0.9.5. RAND_pseudo_bytes() was added in OpenSSL 0.9.5. 1.0.2h 2016-05-03 RAND_bytes(3)

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