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Manual Reference Pages  - RAND_bytes (3)

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RAND_bytes, RAND_pseudo_bytes - generate random data

CONTENTS

 #include <openssl/rand.h>

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

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

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.

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.

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

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.

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