-RAND_bytes() puts B<num> random bytes into B<buf>. An error occurs if
-the PRNG has not been seeded with enough randomness.
+RAND_bytes() puts B<num> cryptographically strong pseudo-random bytes
+into B<buf>. An error occurs if the PRNG has not been seeded with
+enough randomness to ensure an unpredictable byte sequence.
+
+RAND_pseudo_bytes() has been deprecated. Users should use RAND_bytes() instead.
+RAND_pseudo_bytes() puts B<num> pseudo-random bytes into B<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.