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.
If your threat model includes the attacker looking at clear traffic on both sides, you have lost anyway, because the attacker can already read the transactions senders send and know who the senders are. Otherwise, the attacker cannot tell the way the packet looked when the sender sent it, because from the side of the sender the attacker only sees say 100 packets per second of constant size sent to 16 different nodes each, which also behave this way.
Please understand that this proposal is intended to counteract opaque timing attacks only, not sybil attacks.
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).
I entreat you to stop mentioning Tor. It is a different system than I2P, which is being implemented.
It is still a haystack, just of different size. It is still better than nothing at all. A hypothetical attacker with infinite budget cannot be defeated. We can model an attacker with specific capabilities and attempt to design system which defeats the attacker with a given probability. We do not actually disagree on this?