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author | Nick Mathewson <nickm@torproject.org> | 2003-11-05 01:58:07 +0000 |
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committer | Nick Mathewson <nickm@torproject.org> | 2003-11-05 01:58:07 +0000 |
commit | b6f88fc066b8529ee7a1977280d8e40a5868d646 (patch) | |
tree | 458ed8aacc563ad2a781239f52c3cf39bdced986 /doc | |
parent | 6c68317577eec83a8fed9a0abf4e15a7399585f7 (diff) | |
download | tor-b6f88fc066b8529ee7a1977280d8e40a5868d646.tar tor-b6f88fc066b8529ee7a1977280d8e40a5868d646.tar.gz |
Edits to edits. Revert change to central gutter width; cut back down to under 15 pages.
svn:r766
Diffstat (limited to 'doc')
-rw-r--r-- | doc/latex8.sty | 4 | ||||
-rw-r--r-- | doc/tor-design.tex | 46 |
2 files changed, 23 insertions, 27 deletions
diff --git a/doc/latex8.sty b/doc/latex8.sty index be2e75a59..2028cee9c 100644 --- a/doc/latex8.sty +++ b/doc/latex8.sty @@ -59,8 +59,8 @@ % set dimensions of columns, gap between columns, and paragraph indent \setlength{\textheight}{8.875in} \setlength{\textwidth}{6.875in} -%\setlength{\columnsep}{0.3125in} -\setlength{\columnsep}{0.26in} +\setlength{\columnsep}{0.3125in} +%\setlength{\columnsep}{0.26in} \setlength{\topmargin}{0in} \setlength{\headheight}{0in} \setlength{\headsep}{.5in} diff --git a/doc/tor-design.tex b/doc/tor-design.tex index 34fc9fea4..f7a8bcbd8 100644 --- a/doc/tor-design.tex +++ b/doc/tor-design.tex @@ -124,7 +124,7 @@ assumed padding between ORs, and in later designs added padding between onion proxies (users) and ORs \cite{or-ih96,or-jsac98}. Tradeoffs between padding protection and cost were discussed, and \emph{traffic shaping} algorithms were -theorized \cite{or-pet00} that provide good security without expensive +theorized \cite{or-pet00} to provide good security without expensive padding, but no concrete padding scheme was suggested. Recent research \cite{econymics} and deployment experience \cite{freedom21-security} suggest that this @@ -1242,8 +1242,7 @@ points, informs him of her rendezvous point, and then waits for him to connect to the rendezvous point. This extra level of indirection helps Bob's introduction points avoid problems associated with serving unpopular files directly (for example, if Bob serves -material that the introduction point's neighbors find objectionable, -%XXX neighbors is a technical term +material that the introduction point's community finds objectionable, or if Bob's service tends to get attacked by network vandals). The extra level of indirection also allows Bob to respond to some requests and ignore others. @@ -1256,9 +1255,7 @@ application integration is described more fully below. \item Bob chooses some introduction points, and advertises them on the DHT. He can add more later. \item Bob builds a circuit to each of his introduction points, - and waits. No data is yet transmitted. -% XXX what do we mean No data? Bob obviously tells the IP about -% his hash-of-public key, auth scheme, etc + and waits. No more data is transmitted before the first request. \item Alice learns about Bob's service out of band (perhaps Bob told her, or she found it on a website). She retrieves the details of Bob's service from the DHT. @@ -1272,7 +1269,7 @@ application integration is described more fully below. first half of a DH handshake. The introduction point sends the message to Bob. \item If Bob wants to talk to Alice, he builds a circuit to Alice's - RP and provides the rendezvous cookie, the second half of the DH + RP and sends the rendezvous cookie, the second half of the DH handshake, and a hash of the session key they now share. By the same argument as in Section~\ref{subsubsec:constructing-a-circuit}, Alice knows she @@ -1342,13 +1339,13 @@ those users can switch to accessing Bob's service via the Tor rendezvous system. Since Bob's introduction points might themselves be subject to DoS he -could be faced with a choice between keeping many +could have to choose between keeping many introduction connections open or risking such an attack. In this case, -similar to the authentication tokens, he can provide selected users +he can provide selected users with a current list and/or future schedule of introduction points that are not advertised in the DHT\@. This is most likely to be practical if there is a relatively stable and large group of introduction points -generally available. Alternatively, Bob could give secret public keys +available. Alternatively, Bob could give secret public keys to selected users for consulting the DHT\@. All of these approaches have the advantage of limiting exposure even when some of the selected high-priority users collude in the DoS\@. @@ -1460,11 +1457,11 @@ been shown to be effective against SafeWeb \cite{hintz-pet02}. %possibility that multiple streams are exiting the circuit at %different places concurrently. % XXX How does that help? Roger and I don't know. -NM -It may slightly less effective against Tor, since +It may be less effective against Tor, since fingerprinting will be limited to the granularity of cells, currently 256 bytes. Further potential defenses include -larger cell sizes and/or minimal padding schemes to group websites +larger cell sizes and/or padding schemes to group websites into large sets. But this remains an open problem. Link padding or long-range dummies may also make fingerprints harder to detect.\footnote{Note that @@ -1681,10 +1678,10 @@ blocking of valid requests, however, he should periodically test the introduction point by sending it introduction requests, and making sure he receives them. -\emph{Compromise a rendezvous point.} Controlling a rendezvous -point gains an attacker no more than controlling any other OR along -a circuit, since all data passing through the rendezvous is protected -by the session key shared by the client and server. +\emph{Compromise a rendezvous point.} A rendezvous +point is no more sensitive than any other OR on +a circuit, since all data passing through the rendezvous is encrypted +with a session key shared by Alice and Bob. \Section{Open Questions in Low-latency Anonymity} \label{sec:maintaining-anonymity} @@ -1747,8 +1744,8 @@ by batching and re-ordering packets, but it is unclear whether this could improve anonymity without introducing so much latency as to render the network unusable. -A cascade topology may better defend against traffic confirmation by a -large adversary through aggregating users, and making padding and +A cascade topology may better defend against traffic confirmation by +aggregating users, and making padding and mixing more affordable. Does the hydra topology (many input nodes, few output nodes) work better against some adversaries? Are we going to get a hydra anyway because most nodes will be middleman nodes? @@ -1819,11 +1816,11 @@ and possibly better anonymity \cite{econymics}. More nodes means increased scalability, and more users can mean more anonymity. We need to continue examining the incentive structures for participating in Tor. -\emph{Cover traffic:} Currently Tor avoids cover traffic because its costs +\emph{Cover traffic:} Currently Tor omits cover traffic because its costs in performance and bandwidth are clear, whereas its security benefits are -not well understood. We must pursue more research on both link-level cover -traffic and long-range cover traffic to determine some simple padding -schemes that offer provable protection against our chosen adversary. +not well understood. We must pursue more research on link-level cover +traffic and long-range cover traffic to determine whether some simple padding +method offers provable protection against our chosen adversary. %%\emph{Offer two relay cell sizes:} Traffic on the Internet tends to be %%large for bulk transfers and small for interactive traffic. One cell @@ -1837,10 +1834,9 @@ On the other hand, forward security is weakened because caches constitute a record of retrieved files. We must find the right balance between usability and security. -\emph{Better directory distribution:} %Directory retrieval presents -%a scaling problem, since +\emph{Better directory distribution:} Clients currently download a description of -the entire network state every 15 minutes. As the state grows larger +the entire network every 15 minutes. As the state grows larger and clients more numerous, we may need a solution in which clients receive incremental updates to directory state. More generally, we must find more |