The paper itself was posted a few days ago.
Sounds neat, but i wonder why they didnt add it to tor, and reuse the tor infrastructure, rather than spin off a new network.
“There’s no downloadable version of Riffle right now — Kwon said he’d like to clean up the code a bit first, since it’s really just a prototype at present. There’s no plan to commercialize it, either, nor will it be a replacement for Tor, even though it does some things vastly better.”
I get the impression that it’s intended as a proof-of-concept, not as something they plan to actually run. It does make sense to start over to illustrate a small idea in isolation.