+If the PKCS#12 structure does not have a password, then you must use the empty
+string "" for B<oldpass>. Using NULL for B<oldpass> will result in a
+PKCS12_newpass() failure.
+
+If the wrong password is used for B<oldpass> then the function will fail,
+with a MAC verification error. In rare cases the PKCS12 structure does not
+contain a MAC: in this case it will usually fail with a decryption padding
+error.
+