RAND_bytes.3 revision 180208
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Title "RAND_bytes 3"
RAND_bytes 3 "2007-03-15" "0.9.8e" "OpenSSL"
"NAME"
RAND_bytes, RAND_pseudo_bytes - generate random data
"SYNOPSIS"
Header "SYNOPSIS" .Vb 1 #include <openssl/rand.h> .Ve

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

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

"DESCRIPTION"
Header "DESCRIPTION" \fIRAND_bytes() puts num cryptographically strong pseudo-random bytes into buf. An error occurs if the \s-1PRNG\s0 has not been seeded with enough randomness to ensure an unpredictable byte sequence.

\fIRAND_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.

"RETURN VALUES"
Header "RETURN VALUES" \fIRAND_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 \s-1RAND\s0 method.
"SEE ALSO"
Header "SEE ALSO" \fIrand\|(3), ERR_get_error\|(3), \fIRAND_add\|(3)
"HISTORY"
Header "HISTORY" \fIRAND_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.