Ring sigs are only one part of the Shadow system. They serve as an added layer of obfuscation and are just one piece of the puzzle. The other pieces of the puzzle are dual-key stealth addresses, and non-interactive zero knowledge proofs. If you don't know what those are you should look into them, its cutting edge tech. Its a unique system, and its better than cryptonote imho.
Then you are quite confused because cryptonote includes (cryptonote paper sections):
a) ring sigs (4.4)
b) dual-key stealth addresses (4.3)
c) nizkp (4.4, under 2nd heading "SIG")
Shadow's implementation is a warmed-over reimplementation using different elliptic curve paramters. That's analogous to (and about as substantive as) using hexadecimal instead of octal for arithmetic.
I don't know about this Zeuner guy. He might be an expert, but I've seen no evidence of it.
Thanks smooth, I didn't realize that. You seem to be right from what I saw in the cryptonote whitepaper:
So does Monero also use these dual-key stealth addresses? Also is Monero completely a trustless setup?