Here's a quick dump of what I can remember about the protection:
- Sega's patents and the operation of the check strongly suggest that the ring is a physically standard pit/land pattern. The patent doesn't cover the particular bit allocation, but it does strongly suggest that the Sega logo embodies the signature itself. Note that this does not imply that the pattern is simply an optical image; the patents specifically mention avoiding optical recognition for cost and reliability reasons.
- CD-ROM drives with stock firmware can't read past the end of a CD's TOC, so the ring hasn't been analyzed or ripped.
- Saturn discs seem to be padded from the end of the TOC to the ring area, most likely with Mode 0 sectors (although there's no data on this, it would be the logical choice, and Sega has shown a strong willingness to stick to industry standards when it comes to disc formats).
- We can't know whether or not a burner can burn the ring signature without reading it. It really just depends on whether or not the "pixels" are encoded into a standard sector layout (there's reason to believe that they are, but no proof, and even if the layout is standard there may be something else preventing a normal burn). Hacked firmware would probably be necessary to investigate further.
As an aside, the information on PSX I referred to earlier in this thread is completely wrong. Sony was in fact devilishly clever in coming up with their protection scheme: it uses the same encoding and area as the ATIP information (i.e. the stuff that the burner reads to find out how long the recordable area is, which write strategy to use, manufacturer of the media, and so on) on CD-R/RW discs. In other words, even if you got some shady outfit willing to produce "PSX CD-Rs" with the signature pre-written, your CD burner wouldn't know what to do with them - you'd need specially-manufactured CD-Rs and hacked burner firmware to make bootable PSX copies...
I don;t know... anyone knows how the protection actually works?
