First, using SecureURLParams you will not see an authentication challenge in any encoder, it will just fail if the querystring is not correct.
With doPublish set, the encoder can connect but it should not be able to publish. With RTMP live encoders connecting and publishing are distinct. Try this instead:
<Property>
<Name>secureurlparams.connect</Name>
<Value>12345.doConnect</Value>
</Property>
If publishing with ffpmeg
rtmp://localhost/live?doConnect=12345/myStream
In FMLE add the querystring to the FMS URL: rtmp://[wowza-address]:1935/live?doConnect=12345
Richard