I hate to say this, but ECB is actually the right way to go here. There's no way to send information to the headset, so CBC with a rolling IV wouldn't work wel

I hate to say this, but ECB is actually the right way to go here. There's no way to send information to the headset, so CBC with a rolling IV wouldn't work well -- if one HID report dropped, you'd have no way of regaining the stream again. Of course, they could've XORed the second half of the output report with the first (CBC across the output report itself), but that really gets you nothing. This is, amazingly, one of the few places where ECB actually makes sense. That said, when will people learn to encrypt/pack/invert/anything their S-boxes? Edit: Scratch what I said defending ECB mode. I totally forgot about CTR mode until a friend just mentioned it. Would've been the perfect solution here.