Isn't the masternode scheme a more decentralized approach than ring signatures? My point being: If someone finds a way or backdoor to 'break' the ring signatures, pretty much all transactions becomes unlocked(thus centralized to the concept). While in the case of masternodes, you'd have to gain control over the entire network?
Am I completely out in the blue?
Ring signatures in Monero rely on the security properties of Curve25519. The signature algorithm uses a specific EdDSA implementation, that is based on the Twisted Edwards ed25519 curve. The long and the short of this is that there are no known or theorised or suggested ed25519 attacks that is any better than just brute-forcing a 128-bit cipher. There's an excellent Microsoft Research publication that backs this up:
http://research.microsoft.com/apps/pubs/default.aspx?id=209303It's also worth noting that Curve25519's security properties are well known and well used. If you can crack Monero's ring signatures you can also crack the entire Tor network, crack SSH access to servers, crack all i2p routing, crack TextSecure messages, crack Cryptocat messages, and crack
every iCloud Backup key, HomeKit, and AirPlay connections.
Even if that did happen and overnight Tor, i2p, SSH, and Apple were all broken, all you would be able to do is determine which ring signature is the real one. You still wouldn't be able to know where the outputs of a transaction were going, because that is computed using a dual-key stealth address (simplified: padded with random data and then hashed).