On Wed, Oct 08, 2003 at 08:18:12PM +0200, Michal Zalewski composed: > > The higher level juggling is still pointless. Lets assume I still have > > the 1 Gb link to the outside world, and the data round trip latency is a > > minute (the amount of time data can be stored externally before it comes > > back to me). Thats still just 60 Gb of data, or 7.5 GB. And I'm having > > to burn a 1 Gb link to do it! > > Should you actually read the paper, it would be easier to comprehend the > idea. The paper proposes several approaches that do not require you to > send the data back and forth all the time; in some cases, you can achieve > near-infinite latency with a very low "sustaining traffic" necessary to > prevent the data from being discarded. Besides, the storage size is not > the main point, the entire approach is much more interesting from the > limited deniability high-privacy storage point of view.
You have some refresh time required, just like DRAM or any other lossy/decaying medium. Without the refresh, you will have uncorrectible data decay. Its simply the refresh bandwidth and refresh rate. So lets assume a 1 DAY refresh time, and a 1 Gb refresh bandwidth. That's still a maximum of ~10 TB of storage (3600 * 24 / 8), and you are going to have to be saturating the link to maintain it. With a 100 Mb refresh bandwidth, thats 1 TB. I can go out and buy a box which holds nearly 1 TB for <$2000. Heck, I can buy a >2 TB RAID array, FROM APPLE (hardly a low price vendor) for $11k! In terms of serving data, CDN's reportedly charge around $20/GB served or so, or you can always construct a BitTorrent-like network to use the edge-hosts, which is what Valve wants to do for selling/patching HalfLife. Even given a low/moderate-user (~100 user) network, the data cost is going to be pretty extreem to maintain refresh, and as a result, rather/very unstealthy. Lets assume 1 TB shared between 1k users, and a 1 hour refresh time (probably still way high). Thats still 200 Kb/s/user continuous bandwidth. I don't know about you, but I can't get that reliably on my cable modem upload, and if I DID use that much bandwidth, ALL THE TIME, the cable company would probably come knocking. Why not just build a distributed filesystem for those 1K users? The only real advantage is a monocrum of stealth, but it isn't really stealthy if you are storing a non-trivial amount of data: the network traffic is "Storage volume / refresh time", and the refresh time is going to have to be fairly short to have a monocrum of reliability. Burning even just 10Kb/s/user isn't going to be "stealthy" in practice, due to the continual load. For storing a small quantity of data (eg, ~1-2 GB or less), there are much better covert repositories one could consider. > The second observation is that not all the data has to be send back and > forth all the time. Interesting. The refresh rate is required for parasitic storages, to prevent data decay and to recompute checksums etc to handle data loss. Even given a 1 WEEK refresh cycle, a 100 Mb continual refresh bandwidth only gets you 7 TB of storage, 1 Gb aggregate bandwidth gets 70 TB. -- Nicholas C. Weaver [EMAIL PROTECTED] _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
