Re: [PracticalSecurity] Anonymity - great technology but hardly used
On Wed, 26 Oct 2005, JЖrn Schmidt wrote: --- Travis H. [EMAIL PROTECTED] wrote: [snip] Another issue involves the ease of use when switching between a [slower] anonymous service and a fast non-anonymous service. I have a tool called metaprox on my website (see URL in sig) that allows you to choose what proxies you use on a domain-by-domain basis. Something like this is essential if you want to be consistent about accessing certain sites only through an anonymous proxy. Short of that, perhaps a Firefox plug-in that allows you to select proxies with a single click would be useful. You can already do the latter with SwitchProxy (http://www.roundtwo.com/product/switchproxy). Basically, it's a Firefox extension that saves you the trouble of going into the 'preferences' dialogue everytime you want to switch from one proxy to another (or go from using a proxy to not using one, that is). In fact, it is possible to setup it all thru privoxy alone: # 5. FORWARDING # = # # This feature allows routing of HTTP requests through a chain # of multiple proxies. It can be used to better protect privacy # and confidentiality when accessing specific domains by routing # requests to those domains through an anonymous public proxy (see # e.g. http://www.multiproxy.org/anon_list.htm) Or to use a caching # proxy to speed up browsing. Or chaining to a parent proxy may be # necessary because the machine that Privoxy runs on has no direct # Internet access. # # Also specified here are SOCKS proxies. Privoxy supports the SOCKS # 4 and SOCKS 4A protocols. [...] # 5.1. forward # # # Specifies: # # To which parent HTTP proxy specific requests should be routed. # # Type of value: # # target_pattern http_parent[:port] # # where target_pattern is a URL pattern that specifies to which # requests (i.e. URLs) this forward rule shall apply. Use / # to denote all URLs. http_parent[:port] is the DNS name or # IP address of the parent HTTP proxy through which the requests # should be forwarded, optionally followed by its listening port # (default: 8080). Use a single dot (.) to denote no forwarding. Btw, I guess everybody who installs tor with privoxy has to know about this since he has to change this section. The problem is that it is not clear how to protect against `malicious' sites: if you separate fast and tor-enabled sites by the site's name, e.g., tor for search.yahoo.com, and no proxy for everything else, yahoo can trace you thru images served from .yimg.com; OTOH if you change proxy `with one click' first of all you can easily forget to do it, but also a site can create a time-bomb -- a javascript (or just http/html refresh) which waits some time in background (presumably, until you switch tor off) and makes another request which allows to find out your real ip. -- Regards, ASK - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
Re: [PracticalSecurity] Anonymity - great technology but hardly used
Travis H. wrote: Part of the problem is using a packet-switched network; if we had circuit-based, then thwarting traffic analysis is easy; you just fill the link with random garbage when not transmitting packets. I considered doing this with SLIP back before broadband (back when my friend was my ISP). There are two problems with this; one, getting enough random data, and two, distinguishing the padding from the real data in a computationally efficient manner on the remote side without giving away anything to someone analyzing your traffic. I guess both problems could be solved by using synchronized PRNGs on both ends to generate the chaff. The two sides getting desynchronzied would be problematic. Please CC me with any ideas you might have on doing something like this, perhaps it will become useful again one day. But this is trivial. Since the traffic is encrypted, you just have a bit that says this is garbage or this is traffic. OTOH, this can leave you open to traffic marking attacks. George Danezis and I wrote a paper on a protocol (Minx) designed to avoid marking attacks by making all packets meaningful. You can find it here: http://www.cl.cam.ac.uk/users/gd216/minx.pdf. Cheers, Ben. -- http://www.apache-ssl.org/ben.html http://www.thebunker.net/ There is no limit to what a man can do or how far he can go if he doesn't mind who gets the credit. - Robert Woodruff - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
Re: [PracticalSecurity] Anonymity - great technology but hardly used
--- Travis H. [EMAIL PROTECTED] wrote: [snip] Another issue involves the ease of use when switching between a [slower] anonymous service and a fast non-anonymous service. I have a tool called metaprox on my website (see URL in sig) that allows you to choose what proxies you use on a domain-by-domain basis. Something like this is essential if you want to be consistent about accessing certain sites only through an anonymous proxy. Short of that, perhaps a Firefox plug-in that allows you to select proxies with a single click would be useful. You can already do the latter with SwitchProxy (http://www.roundtwo.com/product/switchproxy). Basically, it's a Firefox extension that saves you the trouble of going into the 'preferences' dialogue everytime you want to switch from one proxy to another (or go from using a proxy to not using one, that is). It works like a charm with tor and a local proxy. It also has a Anonymizer mode, which cycles through a list of proxies in an attempt to give you some kind of pseudo-anonymity (which I guess is good enough for many people). Jörn __ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
[PracticalSecurity] Anonymity - great technology but hardly used
--- begin forwarded text Date: Mon, 24 Oct 2005 23:31:34 +0200 To: [EMAIL PROTECTED] From: Hagai Bar-El [EMAIL PROTECTED] Subject: [PracticalSecurity] Anonymity - great technology but hardly used Sender: [EMAIL PROTECTED] Hello, I wrote a short essay about anonymity and pseudonymity being technologies that are well advanced but seldom used. Following are excerpts from the essay that can be found at: http://www.hbarel.com/Blog/entry0006.html In spite of our having the ability to establish anonymous surfing, have untraceable digital cash tokens, and carry out anonymous payments, we don't really use these abilities, at large. If you are not in the security business you are not even likely to be aware of these technical abilities. If I may take a shot at guessing the reason for the gap between what we know how to do and what we do, I would say it's due to the overall lack of interest of the stakeholders. Fact probably is, most people don't care that much about anonymity, and most of the ones who do, are not security geeks who appreciate the technology and thus trust it. So, we use what does not require mass adoption and do not use what does. Anonymous browsing is easy, because it does not need an expensive infrastructure that requires a viable business model behind it; fortunately. A few anonymity supporters run TOR servers on their already-existent machines, anonymity-aware users run TOR clients and proxy their browsers through them, and the anonymity need is met. The onion routing technology that TOR is based on is used; not too often, but is used. The problem starts with systems that require a complex infrastructure to run, such as anonymous payment systems. As much as some of us don't like to admit it, most consumers do not care about the credit card company compiling a profile of their money spending habits. Furthermore, of the ones who do, most are not security engineers and thus have no reason to trust anonymity schemes they don't see or feel intuitively (as one feels when paying with cash). The anonymous payment systems are left to be used primarily by the security-savvy guys who care; they do not form a mass market. I believe that for anonymity and pseudonymity technologies to survive they have to be applied to applications that require them by design, rather than to mass-market applications that can also do (cheaper) without. If anonymity mechanisms are deployed just to fulfill the wish of particular users then it may fail, because most users don't have that wish strong enough to pay for fulfilling it. An example for such an application (that requires anonymity by design) could be E-Voting, which, unfortunately, suffers from other difficulties. I am sure there are others, though. Regards, Hagai. ___ PracticalSecurity mailing list [EMAIL PROTECTED] http://hbarel.com/mailman/listinfo/practicalsecurity_hbarel.com --- end forwarded text -- - R. A. Hettinga mailto: [EMAIL PROTECTED] The Internet Bearer Underwriting Corporation http://www.ibuc.com/ 44 Farquhar Street, Boston, MA 02131 USA ... however it may deserve respect for its usefulness and antiquity, [predicting the end of the world] has not been found agreeable to experience. -- Edward Gibbon, 'Decline and Fall of the Roman Empire' - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
