I realize that this is an old post, but I am still using CS6 to produce ePubs with embedded fonts. I’m posting so that someone Googling for the probe can see how I solved it.

Earlier, Gabriel had said: “Unfortunatley, this leaves out the iBooks app for Apple devices and all Kindle devices because they don’t support the encryption method used.”

After spending quite a bit of time, I finally figured out why an ePub generated by CS6 produced font files that would not be decoded by iBooks. (For Kindle, as Gabriel mentioned, you can substitute the unencrypted fonts). The problem lies in the fact that CS6 is not following the IDPF spec they claim they did (and which CC does follow). The problem is that before they obfuscate the font per the spec, they first compress it. Hence, iBooks (and others) that follow the spec, attempt to un-obfuscate the font, but they are left with a compressed font file that they don’t recognize.

The trick then is to take the CS6 ePub file’s fonts, un-obfuscate them, uncompress them, and then obfuscate them again. You then replace those font files. For Kindle, you can use the un-obfuscated, un-compressed font files. These will also be truncated files, meaning that they only include the glyphs that are used in the ePub.

I have added the above to my post processing scripts and it works marvelously. (Before I was using CC Trial to produce the font files, but it was a pain when to keep doing that when I used a new glyph in InDesign). In fact, with this new process I realized that I did not have the “+” in my embedded font, so it was displaying with the default font of the e-reader.