I've seen the .ODTTF files in .XPS files and want to know why not simply store the fonts without obfuscation?
(Consider the de-obfuscation answer of this question)
Because XPS uses the ZIP archive format, it would be straightforward to open an XPS file as a ZIP archive, retrieve embedded fonts, and install them on the system.
Because of this, the font foundries asked for this obfuscation facility to make it more difficult for everyday users to install fonts embedded in XPS documents. According to XPS conformance rules, XPS producers must obfuscate fonts that have Editable or Print & Preview licensing.