I don't know how to convert the encrypted version to plain-text. Chas supplied the plain-text version (which is from the 6.9 version of Loquendo TTS engine). Loquendo will work with encrypted or plain-text version, so you do not need to convert it back to encrypted (don't know how to do that either). Would love to know to to un-encrypt the files though!
Supposedly, there is an Android app that can do the un-encryption, but I've not been able to find it (read that somewhere)...