If mining is centralized then the exit points are probably easy to find.
Neither are there exit nodes, nor are transactions sent directly to miners. Transactions are broadcast through the whole network. How do known miners make it easier to perform traffic analysis in a cover traffic scenario?
The adversary could hijack the upstream router/ISP of the miner and peer at all traffic incoming to the miner.
I assume you mean relay nodes sending out dummy packets at random intervals, so latency doesn't increase for legitimate traffic (as long as relay nodes can handle the additional bandwidth).
I have been thinking about establishing fixed capacity channels between sets of nodes instead. The negotiated capacity is filled completely at all times, either with padding or real data. Because channels are encrypted, an attacker cannot differentiate between them.
The user's packet has to be in the same form as it entered the network when it leaves the network going the miner. Afaics, your proposed cover channels accomplish exactly nothing.
Sybil attacks are very hard to defend against...Despite all, in 2012 the NSA was still obstructed in some degree by even Tor use. The least we can do is make it a bit harder for them.
A Sybil attack doesn't mean you succeed 100% of the time, as you don't have 100% of the relay nodes.
I want anonymity by needle-in-haystack, not anonymity by pair of dice.
Apparently nobody knows what percentage level of relay nodes the NSA controls on Tor (or I2P).