Editing Onion routing (section)

== Weaknesses ==
{{see also|Tor (network)#Weaknesses}}

=== Timing analysis ===
{{see also|Traffic analysis}}
One of the reasons why the typical Internet connections are not considered anonymous is the ability of [[Internet service provider]]s to trace and log connections between computers. For example, when a person accesses a particular website, the data itself may be secured through a connection like [[HTTPS]] such that the user's password, emails, or other content is not visible to an outside party, but there is a record of the connection itself, what time it occurred, and the amount of data transferred. Onion routing creates and obscures a path between two computers such that there is no discernible connection directly from a person to a website, but there still exist records of connections between computers. Traffic analysis searches those records of connections made by a potential originator and tries to match the timing and data transfers to connections made to a potential recipient. If an attacker has compromised both ends of a route, a sender may be seen to have transferred an amount of data to an unknown computer a specified amount of seconds before a different unknown computer transferred data of the same exact size to a particular destination.<ref>{{Cite book |last=Shmatikov |first=Wang |author2=Ming-Hsiu Vitaly |title=Computer Security – ESORICS 2006 |chapter=Timing Analysis in Low-Latency Mix Networks: Attacks and Defenses |journal=Proceedings of the 11th European Conference on Research in Computer Security |volume=4189 |year=2006 |series=ESORICS'06 |pages=18–33 |doi=10.1007/11863908_2 |isbn=978-3-540-44601-9 |citeseerx=10.1.1.64.8818 }}</ref><ref name="Dingledine">{{cite web|url=https://svn.torproject.org/svn/projects/design-paper/tor-design.html|title=Tor: The Second-Generation Onion Router|last1=Dingledine|first1=Roger|last2=Mathewson|first2=Nick|publisher=USENIX Association|language=en-US|location=San Diego, CA|date=August 2004|access-date=24 October 2012|last3=Syverson|first3=Paul}}</ref> Factors that may facilitate traffic analysis include nodes failing or leaving the network<ref name="Dingledine"/> and a compromised node keeping track of a session as it occurs when chains are periodically rebuilt.<ref>{{Cite journal | last1 = Wright | first1 = Matthew. K. | last2 = Adler | first2 = Micah | last3 = Levine | first3 = Brian Neil | last4 = Shields | first4 = Clay | title = The Predecessor Attack: An Analysis of a Threat to Anonymous Communications Systems | doi = 10.1145/1042031.1042032 | journal = ACM Transactions on Information and System Security | volume = 7 | issue = 4 | pages = 489–522 | date = November 2004 | s2cid = 7711031 | url = https://gnunet.org/sites/default/files/Wright-2004.pdf | access-date = 2012-07-04 | archive-url = https://web.archive.org/web/20160304185948/https://gnunet.org/sites/default/files/Wright-2004.pdf | archive-date = 2016-03-04 | url-status = dead }}</ref>

[[Garlic routing]] is a variant of onion routing associated with the [[I2P]] network that encrypts multiple messages together, which both increases the speed of data transfer and makes it more difficult<ref>{{Cite web|url=http://privacy-pc.com/articles/common-darknet-weaknesses-2-tor-and-i2p.html|title=Common Darknet Weaknesses: An Overview of Attack Strategies|date=27 January 2014}}</ref> for attackers to perform traffic analysis.<ref>{{cite journal|last1=Zantour|first1=Bassam|last2=Haraty|first2=Ramzi A.|title=I2P Data Communication System|journal=Proceedings of ICN 2011: The Tenth International Conference on Networks|date=2011|pages=401–409}}</ref>

===Exit node vulnerability===
Although the message being sent is transmitted inside several layers of encryption, the job of the exit node, as the final node in the chain, is to decrypt the final layer and deliver the message to the recipient. A compromised exit node is thus able to acquire the raw data being transmitted, potentially including passwords, private messages, bank account numbers, and other forms of personal information. Dan Egerstad, a Swedish researcher, used such an attack to collect the passwords of over 100 email accounts related to foreign embassies.<ref>{{cite web |last=Bangeman |first=Eric |url=https://arstechnica.com/news.ars/post/20070830-security-researcher-stumbles-across-embassy-e-mail-log-ins.html |title=Security researcher stumbles across embassy e-mail log-ins |publisher=[[Ars Technica]] |date=2007-08-30 |access-date=2010-03-17}}</ref>

Exit node vulnerabilities are similar to those on unsecured wireless networks, where the data being transmitted by a user on the network may be intercepted by another user or by the router operator. Both issues are solved by using a secure end-to-end connection like [[Transport Layer Security|SSL/TLS]] or [[secure HTTP]] (S-HTTP). If there is [[end-to-end encryption]] between the sender and the recipient, and the sender isn't lured into trusting a false SSL certificate offered by the exit node, then not even the last intermediary can view the original message.