=head1 RETURN VALUES
-EVP_BytesToKey() returns the size of the derived key in bytes, or 0 on error.
+If B<data> is NULL, then EVP_BytesToKey() returns the number of bytes
+needed to store the derived key.
+Otherwise, EVP_BytesToKey() returns the size of the derived key in bytes,
+or 0 on error.
=head1 SEE ALSO
L<evp(3)|evp(3)>, L<rand(3)|rand(3)>,
+L<PKCS5_PBKDF2_HMAC(3)|PKCS5_PBKDF2_HMAC(3)>,
L<EVP_EncryptInit(3)|EVP_EncryptInit(3)>
=head1 HISTORY