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Tor is free software for enabling anonymous communication. The name is an acronym derived from the original software project name ''The Onion Router''.〔 Tor directs Internet traffic through a free, worldwide, volunteer network consisting of more than six thousand relays〔 to conceal a user's location and usage from anyone conducting network surveillance or traffic analysis. Using Tor makes it more difficult for Internet activity to be traced back to the user: this includes "visits to Web sites, online posts, instant messages, and other communication forms".〔 Tor's use is intended to protect the personal privacy of users, as well as their freedom and ability to conduct confidential communication by keeping their Internet activities from being monitored. An extract of a Top Secret appraisal by the National Security Agency (NSA) characterized Tor as "the King of high-secure, low-latency Internet anonymity" with "no contenders for the throne in waiting",〔 and the Parliamentary Office of Science and Technology deemed it, with approximately 2.5 million users daily "by far the most popular anonymous internet communication system." 〔(【引用サイトリンク】title=U.K. Parliament says banning Tor is unacceptable and impossible )〕 Furthermore, a July 2015 NATO analysis opines that "the use of anonymisation technologies such as Tor will continue to thrive. Despite the attention that Tor has received worldwide, the technical and legal questions surrounding it remain relatively unexplored." 〔https://ccdcoe.org/sites/default/files/multimedia/pdf/TOR_Anonymity_Network.pdf〕 Onion routing is implemented by encryption in the application layer of a communication protocol stack, nested like the layers of an onion. Tor encrypts the data, including the destination IP address, multiple times and sends it through a virtual circuit comprising successive, randomly selected Tor relays. Each relay decrypts a layer of encryption to reveal only the next relay in the circuit in order to pass the remaining encrypted data on to it. The final relay decrypts the innermost layer of encryption and sends the original data to its destination without revealing, or even knowing, the source IP address. Because the routing of the communication is partly concealed at every hop in the Tor circuit, this method eliminates any single point at which the communicating peers can be determined through network surveillance that relies upon knowing its source and destination. An adversary unable to defeat the strong anonymity that Tor provides may try to de-anonymize the communication by other means. One way this may be achieved is by exploiting vulnerable software on the user's computer.〔 The NSA has a technique that targets outdated Firefox browsers codenamed EgotisticalGiraffe,〔 and targets Tor users in general for close monitoring under its XKeyscore program.〔http://daserste.ndr.de/panorama/xkeyscorerules100.txt〕 Attacks against Tor are an active area of academic research,〔(【引用サイトリンク】title=Tor developers vow to fix bug that can uncloak users )〕〔(【引用サイトリンク】title=Free Haven's Selected Papers in Anonymity )〕 which is welcomed by the Tor Project itself.〔(【引用サイトリンク】title=Tor Research Home )〕 ==History== The core principle of Tor, "onion routing", was developed in the mid-1990s by United States Naval Research Laboratory employees, mathematician Paul Syverson and computer scientists Michael G. Reed and David Goldschlag, with the purpose of protecting U.S. intelligence communications online. Onion routing was further developed by DARPA in 1997. The alpha version of Tor, developed by Syverson and computer scientists Roger Dingledine and Nick Mathewson and then called The Onion Routing project, or TOR project, launched on 20 September 2002.〔〔 On 13 August 2004, Syverson, Dingledine and Mathewson presented "Tor: The Second-Generation Onion Router" at the 13th USENIX Security Symposium.〔 In 2004, the Naval Research Laboratory released the code for Tor under a free licence, and the Electronic Frontier Foundation (EFF) began funding Dingledine and Mathewson to continue its development.〔 In December 2006, Dingledine, Mathewson and five others founded The Tor Project, a Massachusetts-based 501(c)(3) research-education nonprofit organization responsible for maintaining Tor.〔 The EFF acted as The Tor Project's fiscal sponsor in its early years, and early financial supporters of The Tor Project included the U.S. International Broadcasting Bureau, Internews, Human Rights Watch, the University of Cambridge, Google, and Netherlands-based Stichting NLnet.〔〔 From this period onwards, the majority of funding sources came from the US government.〔 In November 2014 there was speculation in the aftermath of Operation Onymous that a Tor weakness has been exploited. A representative of Europol was secretive about the method used, saying: "''This is something we want to keep for ourselves. The way we do this, we can’t share with the whole world, because we want to do it again and again and again''" A BBC source cited a 'technical breakthrough' that allowed the tracking of the physical location of servers, and the number of sites that police initially claimed to have infiltrated led to speculation that a weakness in the Tor network had been exploited. This possibility was downplayed by Andrew Lewman, a representative of the not-for-profit Tor project, suggesting that execution of more traditional police work was more likely. However, in November 2015 court documents on the matter〔(【引用サイトリンク】title=Court Docs Show a University Helped FBI Bust Silk Road 2, Child Porn Suspects )〕 generated serious ethical security research〔(【引用サイトリンク】title=Did the FBI Pay a University to Attack Tor Users? )〕 as well as Fourth Amendment concerns.〔(【引用サイトリンク】title=Tor Project claims FBI paid university researchers $1m to unmask Tor users )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tor」の詳細全文を読む スポンサード リンク
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