匿名通信システムTorにおけるウルフウェブサイトの提案
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(2) Vol.2015-CSEC-70 No.19 Vol.2015-SPT-14 No.19 2015/7/2. ใॲཧֶձڀݚใࠂ IPSJ SIG Technical Report. SSL ௨৴ʹද͞ΕΔ҉߸Խ௨৴ɼ௨৴ͷ༰Λୈࡾऀ. ࢤ͕ఏ͢ڙΔ 6,500[2] ͷϊʔυͱͦΕΒͷใΛཧ͢. ʹରͯ͠Ӆณ͠ɼҰఆͷϓϥΠόγΛ֬อ͢Δɽ͔͠͠ͳ. ΔσΟϨΫτϦαʔόʹΑͬͯΦʔόʔϨΠωοτϫʔΫ. ͕Β͕ࣗ௨৴Λͨ͠ͱ͍͏ࣄ࣮ͦͷͷΛӅณ͍ͨ͠. Λߏங͢ΔɼϨΠςϯγͷ௨৴γεςϜͰ͋ΔɽTor . ߹ଘࡏ͠ɼ͜ͷΑ͏ͳ࣌ʹಗ໊௨৴γεςϜ͕ඞཁͱ. ҰͨΓ 2,000,000 ͷϢʔβʹ༻͍ΒΕ͓ͯΓɼຖඵ. ͳΔɽ ࣾձతʹσϦέʔτͳΛѻ͏ͱ͖ɼಗ໊௨৴γε ςϜ༗༻Ͱ͋Δ [5]ɽྫ͑ɼWikiLeaks ͷ෦ࠂൃ. 6,000MB ͷσʔλ௨৴Λߦ͍ͬͯΔɽຊઅͰɼࢦ ߈ܸʹؔ࿈͢Δ෦Λத৺ʹ Tor Λհ͢Δɽ. 2.2.1 ΦχΦϯϧʔςΟϯά. αʔϏεͰɼϢʔβ͕ࣗࠂൃͨ͠ͱ͍͏ࣄ࣮ΛӅณ. ΦχΦϯϧʔςΟϯάͱɼΠϯλʔωοτ্Ͱಗ໊. ͨ͠··ࠂൃΛߦ͍͍ͨͣͰ͋Δɽ·ͨɼࠃऀه͖ͳڥ. ௨৴Λ࣮ͤ͞ݱΔͨΊͷٕज़Ͱ͋Δɽ͜ΕɼMichael G.. ஂͳͲɼࠂൃΠϯλʔωοτ্Ͱͷใௐࠪʹಗ໊௨. ReedɼPaul F. SyversonɼDavid M. Goldschlag ΒʹΑͬ. ৴γεςϜΛ༻͍Δ͜ͱʹΑΓใఏऀڙͷϓϥΠόγͱ. ͯൃ໌͞ΕɼΞϝϦΧւʹ܉Αͬͯถࠃಛ ڐNo.6266704. ҆શΛक͍ͬͯΔɽ͜ͷ༷ͳࠂൃऀͷಗ໊ੑΛ֬อ͢Δ͜. ͕औಘ͞Ε͍ͯΔ [17]ɽTor ΦχΦϯϧʔςΟϯάΛ࠾. ͱɼಗ໊௨৴γεςϜͷ༗ྗͳ༻్Ͱ͋Δɽ·ͨɼΠϯ. ༻͍ͯ͠Δ࠷ී͋Ͱ࣮ͨ͠ٴΓɼ͜͜Ͱ Tor ͕ΦχΦ. λʔωοτݕӾ͕͍͠ݫҰ෦ҬͰɼΠϯλʔωοτΛ. ϯϧʔςΟϯάΛͲͷΑ͏ʹ࣮͍ͯ͠Δ͔ͷུ֓Λઆ໌. ௨ͨ͡ݴͷࣗ༝͕ಘΒΕͳ͍ɽྫ͑தࠃͰۚ६ͱݺ. ͢Δɽ. ΕΔωοτݕӾγεςϜΛಋೖ͓ͯ͠ΓɼΠϯλʔωο. Tor Ͱɼࡾͭͷ Tor ϊʔυ (OR1,OR2,OR3 ͱ͢Δ) Λ. τϢʔβ͕ʹର͠ෆརͳใΛൃ৴͢Δͱɼۚ६ʹ. ༻͍ͯΦχΦϯϧʔςΟϯάΛ࣮ߦ͢Δɽ࠷ॳʹɼΫϥ. Αͬͯใఏऀڙͷಛఆ͕ͳ͞ΕΔɽ͔͠͠ɼ͜ͷΑ͏ͳ. ΠΞϯτ Diffie-Hellman ަݤΛ༻͍ͯɼOR1ɼOR2ɼ. ݕӾ͕ߦΘΕ͍ͯΔΠϯλʔωοτ্Ͱಗ໊௨৴γες. OR3 ͦΕͧΕͱηογϣϯݤΛڞ༗͢Δɽ࣍ʹɼΫϥΠΞ. ϜΛಋೖ͢Δ͜ͱʹΑΓɼࣗ༝ͳ͕ٞߦ͑ΔΑ͏ʹͳΔɽ. ϯτͦͷࡾͭͷݤΛ༻͍ͯɼਤ 1 ͷ༷ʹϝοηʔδΛଟ. ͜ͷΑ͏ͳ༻్͕ߟ͑ΒΕΔಗ໊௨৴γεςϜͰ͋Δ͕ɼ. ॏʹ҉߸Խ͠ɼࡾͭͷϊʔυΛதͯ͠ܧϝοηʔδΛૹ৴. ͦͷجຊ֓೦ 1986 ʹ Pfitzmann ͱ Waidner ʹΑͬͯ. ͢Δɽ͜ͷͱ͖ɼϝοηʔδ͕֤ϊʔυΛ௨ͬͯஈ֊తʹ. ఏএ͞Εͨ [15]ɽͦͷதͰɼ൴Βಗ໊௨৴ʹ͓͍ͯ࠷. ෮߸͞Ε͍༷͕ͯ͘ɼۄͶ͗ͷൽΛΉ͍͍༷ͯ͘ࢠʹͳͧ. ॏཁͳཁૉҎԼͷࡾͭͰ͋Δ͜ͱΛࣔͨ͠ɽ. Β͑ΒΕͯΦχΦϯϧʔςΟϯάͱݺΕ͍ͯΔɽ. • ड৴ऀಗ໊ੑ recipient anonymity. ΦχΦϯϧʔςΟϯάΛߦ͏ͱɼதࢀʹܧՃ֤ͨ͠ϊʔ. ϝοηʔδ M ͕ड৴ऀΛ࣋ͨͳ͍ͱ͖ɼड৴ऀಗ໊. υࣗͷલؔ͢ʹޙΔͭͳ͕Γ͔͠Δ͜ͱͰ͖. ੑΛߟ͑Δඞཁͳ͍ɽҰํͰɼಛఆͷड৴ऀ R ͷΈ. ͳ͍ɽैͬͯɼ֤ϊʔυ్தͷ௨৴Λ౪ௌͨ͠ୈࡾऀ͕. ʹ M ΛૹΔͱ͖ɼʮM ͷड৴ऀ͕ R Ͱ͋Δ͜ͱʯΛ. ૹ৴ऀͱड৴ऀͷਅͷͭͳ͕ΓΛΔ͜ͱͰ͖ͳ͍ɽΦ. ୈࡾऀʹରͯ͠ൿಗͰ͖Δ͔Ͳ͏͔ɼΛड৴ऀಗ໊ੑ. χΦϯϧʔςΟϯάͷརʹɼͯ͢ͷϊʔυΛ৴པ͢Δ. ͱͿݺɽ. ඞཁ͕ͳ͍ͱ͍͏͜ͱ͕͛ڍΒΕΔɽԾʹ͋ΔҰͭͷϊʔ. • ૹ৴ऀಗ໊ੑ sender anonymity. υ͕ѱҙͷ͋Δୈࡾऀʹ͞ڌΕͨ߹Ͱ͋ͬͯɼ্ه. ϝοηʔδ M ͷૹ৴ऀ S ͕ɼ ʮM ͷૹ৴ऀ͕ S Ͱ͋. ͷཧ༝ʹΑΓಗ໊௨৴ͷಗ໊ੑഁΒΕͳ͍ɽ. Δ͜ͱʯΛୈࡾऀʹରͯ͠ൿಗͰ͖Δ͔Ͳ͏͔ɼΛૹ. 2.2.2 Tor ͷσβΠϯ. ৴ऀಗ໊ੑͱͿݺɽ. • ૹ৴ऀͱड৴ऀͷͭͳ͕Γͷಗ໊ੑ unlinkability of. Tor ɼΫϥΠΞϯτ͕ͦͷ௨৴ઌͱ݁ͼ͚ΒΕΔͷ Λࢭ͢Δ͜ͱΛతͱ͍ͯ͠Δɽ͢ͳΘͪɼΫϥΠΞϯ. sender and recipient. τΛ͢ࢹΔୈࡾऀ͕ɼΫϥΠΞϯτ͕ͲͷαʔόʹΞΫ. ૹ৴ऀ S ͕ड৴ऀ R ʹϝοηʔδ M ΛૹΔͱ͖ɼM. ηε͍ͯ͠Δ͔Λಛఆ͢Δ͜ͱ͕Ͱ͖ͳ͍Α͏ʹ͠ɼ·ͨ. ʹ͍ͭͯʮS ͕ R ʹૹ৴ͨ͠ϝοηʔδͰ͋Δ͜ͱʯ. αʔόଆ͔ΒɼTor Λ༻͍ͯ͠ΔΫϥΠΞϯτΛҰҙ. Λୈࡾऀʹରͯ͠ൿಗͰ͖Δ͔Ͳ͏͔ɼΛૹ৴ऀͱड. ʹಛఆ͢Δ͜ͱ͕Ͱ͖ͳ͍Α͏ʹ͢Δɽ. ৴ऀͷͭͳ͕Γͷಗ໊ੑͱͿݺɽ. ΫϥΠΞϯτϑϦʔιϑτΣΞΛμϯϩʔυɼΠ. ಗ໊௨৴ɼ࣮༻্ͷͰ؍ૹ৴ऀͱड৴ऀͷͭͳ͕. ϯετʔϧ͢Δ͜ͱʹΑͬͯ Tor Λར༻͢Δ͜ͱ͕Ͱ͖. Γͷಗ໊ੑ͕ຬͨ͞ΕΕेͰ͋Δ͜ͱ͕ଟ͘ɼैͬͯ. Δɽ؆୯ʹ Tor ϒϥβΛհͯ͠ΠϯλʔωοτʹΞΫ. ΄ͱΜͲͷಗ໊௨৴γεςϜ͜ͷಗ໊ੑͷΈΛอূͯ͠. ηε͢ΕΑ͘ɼ͜Ε Tor ͷརศੑΛߴΊ͍ͯΔɽ. ͍Δɽ. σΟϨΫτϦαʔό֤ Tor ϊʔυͷՄ༻ੑଳҬ෯ͳ ͲΛ؍ଌ͓ͯ͠Γɼఆظతʹطͷ Tor ϊʔυͷঢ়ଶϦε. 2.2 Tor. τΛ࡞͍ͯ͠ΔɽΫϥΠΞϯτ͕ Tor Λར༻͢Δࡍʹɼ. ࠷ࡏݱී͍ͯ͠ٴΔಗ໊௨৴γεςϜɼୈೋੈͷ. ·ͣσΟϨΫτϦαʔόʹଓ͜͠ͷϦετ (consensus. ΦχΦϯϧʔςΟϯάʹ͋ͨΔ Tor[6] Ͱ͋ΔɽTor ɼ༗. file ͱݺΕΔ) Λμϯϩʔυ͢ΔɽͦͷޙΫϥΠΞϯ. c 2015 Information Processing Society of Japan . 2.
(3) Vol.2015-CSEC-70 No.19 Vol.2015-SPT-14 No.19 2015/7/2. ใॲཧֶձڀݚใࠂ IPSJ SIG Technical Report. ਤ 1. ΦχΦϯϧʔςΟϯά. τϦετதͷϊʔυ͔Βࡾͭͷϊʔυ (OR1,OR2,OR3) Λબ͠ɼ࠷ॳͷதܧϊʔυ OR1 ͱͷ҉߸Խ௨৴࿏Λܗ ͢Δɽ͜ͷ௨৴࿏ Diffie-Hellman ަݤΛ༻͍ͨηο γϣϯݤͷڞ༗ʹΑͬͯ҉߸Խ͞ΕΔɽͦͯ͠ɼ͜ͷ҉߸ Խ௨৴࿏Λ༻͍ͯ OR1 ͱ OR2 ͷؒʹؔͯ͠ಉ༷ͷ҉߸ Խ௨৴࿏Λܗ͠ɼ·ͨ OR2 ͱ OR3 ʹ͍ͭͯಉ༷ͷૢ ࡞Λߦ͏ɽ֤҉߸Խ௨৴࿏Ͱ TLS ௨৴͕ߦΘΕΔɽ͜ ͷΑ͏ʹͯ͠ɼΫϥΠΞϯτࡾ൪ͷϊʔυ OR3 ͱͷ ଓΛอ͍࣋ͯ͠Δ͕ɼOR3 OR1 ΫϥΠΞϯτʹͭ ͍ͯͷใΛΔ͜ͱͳ͍ɽಉ༷ʹɼOR1 ΫϥΠΞϯ τ͕ OR3 ʹͲͷϊʔυΛબ͔ͨ͠ΛΔ͜ͱͳ͍ɽ ΫϥΠΞϯτͷ IP ΞυϨεΛΔ OR1 ʹΑͬͯಗ໊ੑ ͕ഁΒΕΔ֬Λ͘͢ΔͨΊʹɼEntry guard ͱݺΕ ΔΈ͕࠾༻͞Ε͍ͯΔɽ·ͣɼTor ϊʔυͷ͏ͪे ͳଳҬ෯Λ࣋ͬͨϊʔυͷΈ͕ Guard ϑϥάΛಘΔɽΫ ϥΠΞϯτϑϥάΛ࣋ͬͨϊʔυͷத͔Β͍͔ͭ͘ (σ ϑΥϧτͰࡾͭ) ϥϯμϜʹબ͠ɼͦΕΒΛ Guard Ϧε τͱͯ͠อ࣋͢Δɽ͜ͷϦετΛ࡞͢ΔࡍɼͦΕͧΕͷ. guard ʹ͍ͭͯຬྃ࣌ؒΛ 30 ͔Β 60 ͷؒͰϥϯμϜ ʹઃఆ͢Δɽ͜ͷຬ͕ྃ࣌ؒա͗Δͱɼͦͷ guard Ϧε τ͔Β֎ΕɼϑϥάΛ࣋ͬͨผͷϊʔυ͕ϦετʹΈ ࠐ·ΕΔɼͱ͍ͬͨΑ͏ʹϩʔςʔγϣϯ͍ͤͯ͞Δɽ࣮ ࡍʹΘΕΔ OR1 ɼTor ͷύε͕৽͘͠࡞ΒΕΔ͝ͱ ʹϦετͷத͔ΒϥϯμϜʹબΕΔɽ͜ͷΑ͏ʹ Entry. ਤ 2. ࢦ߈ܸ. guard ͱ࣮ͯ͠ࡍʹΘΕΔϊʔυΛݶఆ͢Δ͜ͱͰɼTor Ͱ߈ܸऀͷڌɼࢹରͱͳΔ֬ΛԼ͍͛ͯΔɽ. Tor ͷ௨৴ɼ512bytes ݻఆαΠζͷɼϔομͱϖΠϩʔ υ͔Βߏ͞ΕΔηϧʹΑΓߦΘΕΔɽϔομʹαʔ Ωοτ ID(circID) ͱίϚϯυ (CMD) ͕·ؚΕΔɽίϚϯ υʹΑΓηϧ੍ޚηϧ͔ϦϨʔηϧʹ͚ΒΕɼϦϨʔ ηϧʹϖΠϩʔυͷલʹՃతͳϔομ͕·ؚΕΔɽ. 2.3 ࢦ߈ܸ ಗ໊௨৴γεςϜʹର͢Δ߈ܸख๏ͷதͰ༗ޮͳख๏. c 2015 Information Processing Society of Japan . 3.
(4) Vol.2015-CSEC-70 No.19 Vol.2015-SPT-14 No.19 2015/7/2. ใॲཧֶձڀݚใࠂ IPSJ SIG Technical Report. ʹɼࢦ߈ܸ͕͋Δ [18]ɽTor ʹର͢Δࢦ߈ܸͷ֓؍Λ. ηϧΛ༻͍ͯݻఆͷσʔλ୯ҐͰ௨৴Λߦ͍ͬͯΔͨΊ. ਤ 2 ʹࣔ͢ɽTor ͷࢦ߈ܸͰɼ͋ΔΠϯλʔωοτ. Ͱ͋Δɽ͜ΕʹՃ͑ɼTor Ͱճઢߏஙʹ༻͍ΒΕΔ੍ޚ. Ϣʔβ͕ಗ໊௨৴γεςϜ Tor Λ༻͍ͯ͋ΔΣϒαΠτ. ηϧͳͲ͕ύέοτͱͯ͠ྲྀΕ͓ͯΓɼࢦ߈ܸΛߦ͏ࡍ. ʹΞΫηε͓ͯ͠ΓɼͦͷϢʔβ͕ར༻͢Δ Entry guard. ʹϊΠζͱͳΓ߈ܸͷੑೳΛԼͤ͞Δɽ. Λ߈ܸऀ͕͍ͯ͠؍Δঢ়ଶΛఆ͢Δɽ ҰൠతͳΣϒϖʔδɼը૾ϑΝΠϧ javascript ͷ ιʔεϑΝΠϧͳͲɼଟ͘ͷؔ࿈ϑΝΠϧΛಡΈࠐΜͩ͏. 3. ؔ࿈ڀݚ ຊষͰɼࢦ߈ܸʹؔ͢Δ͍͔ͭ͘ͷख๏ʹ͍ͭͯɼ. ͑Ͱදࣔ͞ΕΔɽ͢ͳΘͪɼΣϒαΠτʹΞΫηε͢Δ. ޚख๏ͱ߈ܸख๏ʹ͚ͯهड़͢Δɽͳ͓ɼ͜͜Ͱհ. ࡍɼΣϒϖʔδϑΝΠϧ͚ͩͰͳͦ͘ΕΒͷϑΝΠϧ. ͢Δޚख๏ඞͣ͠ Tor ͷͨΊʹߟҊ͞ΕͨͷͰ. ʹରͯ͠ϦΫΤετΛߦ͏ɽΣϒϖʔδϑΝΠϧࣗମ. ͳ͍ɽ. ͷαΠζؔ࿈ϑΝΠϧͷ૯ɼݸͼٴʑͷαΠζΣ ϒαΠτຖʹҟͳΔͨΊɼΣϒαΠτʹΞΫηεͨ͠ࡍ. 3.1 ޚ. ʹੜ͡Δ௨৴ͷྲྀΕΣϒαΠτຖʹҟͳͬͨͷͱͳ. ͢Ͱʹ Tor Ͱ࣮͞Ε͍ͯΔޚख๏ʹɼpipeline ran-. Δɽ͜ͷ௨৴ͷྲྀΕ (ΣϒτϥϑΟοΫͱ )Ϳݺͷதʹੜ. domization ͕͋Δ [14]ɽ͜Ε Tor ͷ։ൃऀͨͪʹΑΓఏ. ͡ΔΣϒαΠτಠࣗͷಛ (͜ΕΛࢦͱ )ͿݺΛͱΒ. এ͞ΕͨͷͰɼHTTP ύΠϓϥΠϯΛ༻Մೳʹ͠ɼύ. ͑ɼϢʔβ͕ͲͷΣϒαΠτʹΞΫηε͍ͯ͠Δ͔Λಛ. ΠϓϥΠϯαΠζͼٴϦΫΤετͷॱ൪ΛϥϯμϜʹఆ. ఆ͢Δɼͱ͍͏͜ͱ͕ࢦ߈ܸͷجຊతͳํͰ͋Δɽ. ΊΔɽ࣮ίετ͕খ͘͞ɼΦʔόʔϔου͕ൃੜ͠ͳ͍. ࢦ߈ܸ͕ଞͷ߈ܸͱେ͖͘ҟͳΔͷɼ͖͢؍. ͨΊͰࡏݱ༻͍ΒΕ͍ͯΔɽ͔͠͠ͳ͕Βɼ͜ͷख๏ʹ. ϊʔυ͕Ұ͔ॴͰΑ͍ͱ͍͏Ͱ͋ΔɽTor ʹ͓͍ͯɼ. Αͬͯࢦ߈ܸͷޭΛେ͖͘Լ͛ͨͱ͍͏ใࠂͳ͍ɽ. OR1 ͘͠ΫϥΠΞϯτ͔Β OR1 ʹࢸΔܦ࿏্Ͱύ. ଞͷϥϯμϜੑΛ͍༻ʹޚΔख๏ʹɼtraffic morph-. έοτΛ౪ΈݟΔ͜ͱ͕Ͱ͖ΕΑ͍ɽಗ໊௨৴γεςϜ. ing[21] Panchenko Βͷ background noise[13] ͕͋Δɽ. ʹର͢Δ߈ܸख๏ʹɼ݁ୗ߈ܸ (sybil attack)[7] ઌߦ. traffic morphing Ͱɼ͋ΔΣϒαΠτʹΞΫηεͨ͠. ߈ܸ (predecessor attack)[22]ɼλΠϛϯά߈ܸ (timing. ࡍʹੜͨ͡τϥϑΟοΫ (ҎԼΠϯελϯεͱ )Ϳݺͷύ. attack)[10], [11] ࣹ߈ܸ (replay attack)[16] ͱ͍ͬͨख. έοταΠζΛɼผͷΠϯελϯεͷύέοταΠζ. ๏͕ߟҊ͞Ε͍ͯΔ͕ɼ͍ͣΕͷख๏ೋͭҎ্ͷϊʔυ. ʹ֬తʹ͚ۙͮΔɽ͔͠͠খ͘͞ͳ͍Φʔόʔϔο. ͷ͕؍ඞཁͰ͋Γɼ࣮ݱՄೳੑ͕͍ɽ͜Εʹର͠ɼࢦ. υ͕ੜ͡Δ͜ͱɼ੩తʹద༻͞ΕΔ͜ͱɼTor ্Ͱద༻͠. ߈ܸඞཁͳԾఆ͕ଞͷख๏ͱൺͯඇৗʹऑ͘ɼ߈ܸ. ͨͱ͖ʹ͋·ΓޮՌ͕ݟΒΕͳ͔ͬͨͱ͍͏ใࠂ͕͋Δ͜. ͷ࣮ݱੑ͕ߴ͍ͨΊ࣮ݱతͳڴҖͱͳΓ͏Δɽ. ͱ͔Β [3]ɼղܾ๏ͱͳΓʹ͍͘ɽBackground noise Ͱ. Ұൠతͳࢦ߈ܸͷखॱҎԼͰ͋Δɽ·ͣɼ߈ܸऀ. ɼΫϥΠΞϯτ͕ΣϒϖʔδʹΞΫηε͢Δͷͱಉ࣌. ͍ͨ͠ࢹΣϒϖʔδʹ܈ΞΫηε͠ɼੜ͡Δύέοτ. ʹɼϥϯμϜʹબΕͨผͷϖʔδʹΞΫηε͢Δɽ͜. ྻΛऩू͢Δɽ࣍ʹ߈ܸऀɼඃ߈ܸऀ͕Σϒϖʔδʹ. ΕʹΑΓ߈ܸޭେ͖͘ݮগ͢Δ͕ɼେ͖ͳΦʔόʔ. ΞΫηε͢Δ͜ͱͰੜ͡ΔύέοτྻΛ͢؍Δɽͦͯ͠. ϔουΛඞཁͱ͢Δɽ. ࢣڭ༗ֶश͞ΕͨྨͰثඃ߈ܸऀ͕ͲͷΣϒϖʔδʹ ΞΫηε͔ͨ͠Λಛఆ͢Δɽ ࢦ߈ܸΛߦ͏߈ܸऀجຊతʹҎԼࡾͭͷԾఆΛஔ͘. ( 1 ) ߈ܸऀ؍ଌ͢Δύέοτʹ͍ͭͯ͋ΔҰͭͷϖʔδ ϩʔυͷ࢝ͱऴΛΔɽ. ܾఆతͳޚख๏ʹ HTTPOS[12] BuFLO[8] ͕͋ ΔɽTor ͕ݻఆηϧΛ༻͍ͯ௨৴Λߦ͍ͬͯΔͷܾఆ తख๏ʹ͋ͨΔɽHTTPOS ΫϥΠΞϯτͷϒϥβ ্Ͱಈ࡞͠ɼMSS ΟϯυαΠζͷύϥϝʔλΛௐ અ͢Δ͜ͱͰύέοτͷେ͖͞Λෆ໌ྎʹ͢ΔɽΦʔόʔ. ( 2 ) ඃ߈ܸऀҰʹҰͭͷϖʔδΛϩʔυ͠ɼϖʔδ. ϔουখ͍͕͞ɼ͜ͷޚख๏ޮՌ͕খ͍͞ͱ͍͏ओ. ϩʔσΟϯάͱϑΝΠϧμϯϩʔυΛಉ࣌ʹߦ͏ͱ. ு͕͋Δ [3]ɽBuFLO Ͱɼૹड৴྆ํʹɼ௨৴͕ऴΘ. ͍ͬͨߦҝߦΘͳ͍ɽ. Δ·ͰɼҰఆִؒͰσʔλΛૹΓଓ͚Δɽ߈ܸޭΛେ. ( 3 ) ߈ܸऀඃ߈ܸऀͱಉ݅͡ͰྨثΛֶशͤ͞Δ. ͖͘Լ͛Δ͕ɼΦʔόʔϔου͕ඇৗʹେ͖͍ɽ. ͜ͱ͕Ͱ͖Δɽͭ·ΓɼΫϥΠΞϯτͷ OS ωοτ ϫʔΫଓɼTor ϒϥβͷόʔδϣϯͳͲΛಉ༷ʹ ͨ͠͏͑Ͱ߈ܸΛߦ͏͜ͱ͕Ͱ͖Δɽ ͜ΕΒͷԾఆΛ؆୯ʹ͢ΔͨΊʹஔ͔Ε͓ͯΓɼ ߈ܸऀ༏ҐͳԾఆͰ͋Δɽ. 3.2 ߈ܸ Tor ʹର͢Δࢦ߈ܸͷॳظͷ͍͓ͯʹڀݚͬͱΑ ͘ΒΕ͍ͯΔͷɼ2009 ͷ Herrmann Βͷ͋Ͱڀݚ Δ [9]ɽ൴Β༷ʑͳϓϥΠόγอٕޢज़ʹର͠୯७ϕΠ. ࢦ߈ܸΛ Tor Ͱޭͤ͞ΔͷɼSSH VPN tunnel-. ζྨثΛ༻͍ͨࢦ߈ܸΛߦ͕ͬͨɼTor ʹର͢Δ߈ܸ. ing ্Ͱޭͤ͞Δ͜ͱΑΓ͍͠ [9]ɽ͜ΕɼTor . ޭඇৗʹখ͔ͬͨ͞ɽ2011 ɼPanchenko Β Tor. c 2015 Information Processing Society of Japan . 4.
(5) Vol.2015-CSEC-70 No.19 Vol.2015-SPT-14 No.19 2015/7/2. ใॲཧֶձڀݚใࠂ IPSJ SIG Technical Report. ΣϒαΠτͷൃِͼٴݟͷڀݚΛਐΊΔ͜ͱʹΑΓɼ ௨৴ྔͷΦʔόʔϔουΛ࠷খʹݶ͑ͨ··ࢦ߈ܸͷ ޭΛେ͖͘Լͤ͞Δ͜ͱ͕Ͱ͖Δͱߟ͑Δɽ. 5. ݧ࣮ૅج ຊষͰɼϧϑΣϒαΠτͷఏҊʹ͚ͯߦͬͨج ૅ࣮ه͍ͯͭʹݧड़͢Δɽओʹड़Δͷ੩తͳ࣮͋Ͱݧ Δɽͭ·Γɼ௨৴ͷ్தͰϊΠζΛՃ͑ΔͳͲ͢ΔͷͰ ͳ͘ɼ͋Β͔͡Ίऩूͨ͠ύέοτྻʹର͠ϊΠζΛՃ͑ ධՁΛߦ͏ɽͨͩ͠ɼ͜ͷγφϦΦ Tor ʹద༻͢Δʹ ਤ 3. ϧϑΣϒαΠτͷΠϝʔδ. ෆదͰ͋ΔɽTor ϨΠςϯγΛಛͱ͢Δ࣮ڥγ εςϜͰ͋ΓɼԆͷݪҼͱͳΔΑ͏ͳύέοτόοϑΝ. ্ͰΣϒαΠτʹΞΫηε͢ΔΫϥΠΞϯτʹର͠߈ܸ. ϦϯάߦΘͳ͍ɽ͕ͨͬͯ͠ Tor ্Ͱಇ͘ޚख๏Λߟ. Λޭͤͨ͞ [13]ɽ൴Βྨ ʹثSVM Λ༻͍ɼHTTP. ͑Δࡍʹɼͦͷख๏ಈతʹಈ࡞ͤ͞Δඞཁ͕͋Δɽ͠. υΩϡϝϯτͷେ͖͞ૹड৴ύέοτͷׂ߹ͳͲΛಛ. ͔͠ͳ͕Βɼ࣮ݧͷॳظஈ֊ͱͯ͠ɼຊߘͰಈతͳख๏. ྔͱͯ͠༻͍ͨɽ2012 ɼCai Β Tor ʹ͓͚Δࢦ߈ܸ. ΛఏҊ͢Δֻ͔Γͱͯ͠੩తͳख๏Λߟ͑Δɽ. ޭΛେ্͖ͤͨ͘͞ [3]ɽͦ͜ͰɼύέοτྻΛൺ. ຊ࣮ݧγεςϜͷ֓؍Λਤ 4 ʹࣔ͢ɽ࣮Ͱݧ·͢Σ. ֱ͢ΔͨΊʹฤू͍༻͕ڑΒΕͨɽ2013 ɼWang ͼٴ. ϒτϥϑΟοΫΛऩू͠ɼՃΛՃ͑Δɽͦͷ֤ޙύέο. Goldberg ฤूڑΛ͢ࢉܭΔΞϧΰϦζϜΛมߋ͢Δ. τྻʹ͍ͭͯޚΛࢪͨ͠ύέοτྻΛ༻ҙ͢Δɽͦͯ͠. ͜ͱͰ߈ܸਫ਼Λ͞Βʹ্ͤͨ͞ [20]ɽ2014 ɼWang. ಛྔΛநग़͠ɼͦΕΛଟΫϥεྨ͚͔ʹثΔ͜ͱͰɼ. Βߴ࠷ࡏݱͷ߈ܸޭΛͭख๏ΛఏҊͨ͠ [19]ɽઌ. ߈ܸޭΛग़͢ɽ͜͜Ͱɼ߈ܸޭ (Accuracy) Ҏ. ߦ͍༻ͰڀݚΒΕͨಛྔΛ΄ͱΜͲͯ͢நग़͠ɼͦΕ. ԼͷࣜͰ͋ΒΘ͞ΕΔɽ. ΒʹࣗಈతʹॏΈ͚ͮΛߦ͏͜ͱͰ࠷దͳΫϥεྨΛ ࢦͨ͠ɽྨʹ k ۙ๏Λ༻͍͍ͯΔɽଟ͘ͷಛྔΛ ༻͍ࣗಈతʹॏΈ͚ͮΛߦ͏͜ͱͰɼ֤ޚख๏͕कΔ͜. Accuracy = Success/All. (1). ͜͜Ͱ All ɼ߈ܸऀ͕ࢦ߈ܸΛߦͬͨ૯Ͱ͋ΔɽҰ. ͱ͕Ͱ͖ͳ͍෦Λྨʹ͏͜ͱ͕Ͱ͖Δͱ͠ɼ͜ͷख. ͷࢦ߈ܸͰɼ߈ܸऀ 1 ͭͷΣϒτϥϑΟοΫʹ. ๏ͷ݈ؤੑΛओு͍ͯ͠Δɽ. ରͯ͠ 1 ͭͷ URL Λਪఆ͢Δɽ͜ͷਪఆ݁Ռ͕ਖ਼͔ͬ͠. 4. ϧϑΣϒαΠτ ຊͰڀݚɼࢦ߈ܸͷޮՌతͳޚͷࢳͯ͠ͱޱɼ. ͨࢦ߈ܸͷ૯͕ Success Ͱ͋Δɽ. 5.1 ධՁʹ༻͍Δࢦ߈ܸ. ϧϑΣϒαΠτΛఏҊ͢Δɽϧϑͱɼଟ͘ͷొ. ఏҊ͢Δޚख๏ΛධՁ͢ΔͨΊͷࢦ߈ܸͱͯ͠༻͍. ςϯϓϨʔτʹରͯͬ͠ޡड͚ೖΕΒΕΔೖྗใͷ͜ͱ. Δͷɼ2014 ͷ Wang Βͷࢦ߈ܸͰ͋Δ [19]ɽTor ʹ. Ͱ͋ΔɻզʑɼϧϑΣϒαΠτΛʮࢦ߈ܸͷ͛. ର͢Δࢦ߈ܸͷதͰߴ࠷ࡏݱͷ߈ܸޭΛތΔ͜ͷ߈. ͱͳΔ΄Ͳɺଟ͘ͷΣϒαΠτͱࣅͨࢦʹͳΔΣϒ. ܸɼաڈͷࢦ߈ܸ͍༻ͰڀݚΒΕͨಛྔΛඇৗʹଟ. αΠτʯͱఆٛ͢Δɽ. ͘࠾༻͍ͯ͠Δɽख๏Ͱɼ֤τϥϑΟοΫ͔Β 3736. ͜ͷΠϝʔδΛਤ 3 ʹࣔ͢ɽొใʹෳͷΣϒα. ݸͷಛྔΛநग़͠ɼͦΕΒʹࣗಈతʹॏΈ͚ͮΛ͢Δ͜. Πτ A,B,C, ... ͕ଘࡏͨ͠ͱ͠ɼ͜ͷ͏ͪΣϒαΠτ C. ͱͰ࠷దͳΫϥεྨΛߦ͏ɽ֤ޚख๏ʹର͠कΒΕͯ. ͕ϧϑΣϒαΠτͰ͋ͬͨͱԾఆ͢Δɽ͜ͷͱ͖ɼτ. ͍ͳ͍෦ʹࣗಈతʹूத͢ΔͨΊɼΒΕ͍ͯΔͯ͢. ϥϑΟοΫΛऀܸ߈ͨ͠؍ɼΣϒαΠτ A ͷτϥ. ͷޚख๏ʹ༗ޮͰ͋Δͱͯ͠ख๏ͷ݈ؤੑΛචऀΒओ. ϑΟοΫʹ͍ͭͯߴ֬ͰͦͷτϥϑΟοΫ͕ A ͷ. ு͍ͯ͠Δɽ. ͷͰ͋Δͱผ͢Δ͜ͱ͕Ͱ͖Δ͕ɼΣϒαΠτ C ͱ ͍͏ϧϑΣϒαΠτͷτϥϑΟοΫʹ͍ͭͯͦͷτ. ຊͰڀݚɼ߈ܸͷ݈ؤੑʹ͠ɼ͜ͷࢦ߈ܸʹ Αͬͯޚख๏ͷධՁΛߦ͏ɽ. ϥϑΟοΫ͕ͲͷαΠτͷͷͰ͋Δ͔ผ͢Δͷ͕͠ ͍ɼͱ͍͏͜ͱʹͳΔɽ. 5.2 σʔληοτ. ࣮ੈքʹϧϑΣϒαΠτଘࡏ͢Δͷ͔ɼϧϑ. ࣮͍༻ʹݧΔσʔληοτɼWang Β͕ࢦ߈ܸΛධ. ΣϒαΠτ͕͖ͱ͔ͨͬͭݟɼ͋ΔΣϒαΠτΛϧ. Ձ͢Δࡍʹ༻͍ΒΕͨσʔληοτͰ͋Δ [19]ɽ͜ͷσʔ. ϑΣϒαΠτʹِͤ͞Δํ๏ʹͲͷΑ͏ͳํ๏͕͋. ληοτ࣮ݧͷ࠶ݱੑͷͨΊʹࢦ߈ܸͷίʔυͱͱ. Δ͔ɼͱ͍ͬͨ͜ͱΛ୳Δͷ͕ڀݚͷతͰ͋Δɽϧϑ. ʹஶऀΒʹΑͬͯެ։͞Ε͓ͯΓɼ100 ͷΣϒαΠτ. c 2015 Information Processing Society of Japan . 5.
(6) Vol.2015-CSEC-70 No.19 Vol.2015-SPT-14 No.19 2015/7/2. ใॲཧֶձڀݚใࠂ IPSJ SIG Technical Report. ਤ 4 ද 1. ࣮ݧͷ֓؍. ࣮ ݧ1 ͷ݁Ռ. ૹ৴ηϧૠೖ. ड৴ηϧૠೖ. Φʔόʔϔου. ૠೖͳ͠. 0.9053. 0.9053. 0. 5 ηϧຖʹૠೖ. 0.9003. 0.9033. 20%. 3 ηϧຖʹૠೖ. 0.8937. 0.9041. 33%. 1 ηϧຖʹૠೖ. 0.8708. 0.9047. 100%. ͷෳճΞΫηεΛΩϟϓνϟ͠ɼՃͨ͠ͷͰ͋Δɽ. 100 ͷΣϒαΠτͱͯ͠બΕͨͷதࠃӳࠃɼα δΞϥϏΞͰϒϩοΫ͞Ε͍ͯΔαΠτͰ܈ɼ͜͜ͰΞ μϧτίϯςϯπτϨϯτɼफڭతɼ࣏తͱ͍ͬ ͨͷ͕औΓѻΘΕ͍ͯΔɽͦΕͧΕͷαΠτʹ͍ͭͯ. 90 ճͷΞΫηεΛΩϟϓνϟ͠ɼηϧΛऔΓग़͢ՃΛߦ ͍σʔληοτͱ͢ΔɽՃͷํ๏ҎԼͰ͋Δɽ·֤ͣ. TCP/IP ύέοτʹ͍ͭͯૹ৴ύέοτΛ 1ɼड৴ύέο ද 2. τΛ-1 ͱఆΊΔɽͦͯ͠ϖΠϩʔυͷ͞Λ 512 ͰׂΓɼ. ࣮ ݧ2 ͷ݁Ռ. ͦͷΛηϧͷͱͯ͠ 1 ͘͠-1 ͱՃ͢Δɽ֤αΠ. ૠೖͳ͠. 0.9053. τͷ 90 ͷΠϯελϯε 60 ͕ݸk ۙ๏ͷֶशʹ༻͍Β. ͖ٯʹޙηϧૠೖ. 0.6301. ΕɼΓ 30 ͕ݸAccuracy ͷ͍༻ʹࢉܭΒΕΔɽ. લʹ͖ٯηϧૠೖ. 0.6301. ૹ৴ͱड৴͕ަͳʹޓΔΑ͏ૠೖ. 0.3630. 5.3 ࣮ํݧ๏ ϧϑΣϒαΠτൃج͚ͯʹݟຊతͳ࣮ݧΛओʹ 2 ͭߦͬͨɽ͜͜Ͱɼ߈ܸऀޚख๏Λ͍ͬͯΔͱԾ ఆ͢Δɼͭ·Γ߈ܸऀηϧ͕ૠೖ͞ΕͨޙͷσʔλΛֶ शσʔλͱͯ͠༻͍Δɽ࣮݁ݧՌͱͯࣔͯ͢͢͠. Accuracy Ͱ͋Δɽ ࣮ ݧ1 ɼఆظతͳηϧͷૠೖͰ͋ΔɽΩϟϓνϟ͠ ͨૹ৴ɼड৴ηϧΛ͠߹Θ͕ͤͨ 5ɼ3ɼ1 ͷഒɼͱ ͳͬͨͱ͖ʹૹ৴ηϧΛૠೖͨ͠ɽड৴ηϧͷૠೖಉ༷ ʹߦͬͨɽ ࣮ ݧ2 ɼૹड৴ηϧͷฒͼසΛফ͢ૠೖͰ͋Δɽ ड৴ηϧͷૹʹޙ৴ηϧΛૠೖ͠ɼૹ৴ηϧͷʹޙड ৴ηϧΛૠೖ͢Δͱ͍͏ૢ࡞ɼड৴ηϧͷલʹૹ৴η ϧΛૠೖ͠ɼૹ৴ηϧͷʹޙड৴ηϧΛૠೖ͢Δͱ͍͏ ૢ࡞Λߦͬͨɽ·ͨɼηϧͷॱংΛશʹফͨ͢Ίɼड৴ ηϧͷલʹૹ৴ηϧΛૠೖ͠ɼૹ৴ηϧͷʹޙड৴η ϧΛૠೖ͢Δͱ͍͏ૢ࡞ߦͬͨɽ. c 2015 Information Processing Society of Japan . 6.
(7) Vol.2015-CSEC-70 No.19 Vol.2015-SPT-14 No.19 2015/7/2. ใॲཧֶձڀݚใࠂ IPSJ SIG Technical Report. 5.4 ࣮݁ݧՌ. σʔλͰಉ͡ Tor αʔΩοτ͕༻͍ΒΕͳ͍Α͏͢Δɽ. ࣮ ݧ1ɼ࣮ ݧ2 ͷ݁ՌΛͦΕͧΕද 1ɼ2 ʹࣔ͢ɽ͜ͷ ɼ֤߹ຖʹ 5 ճࢦ߈ܸΛߦ͍ɼͦͷ Accuracy ͷฏ ۉΛͱͬͨͷͰ͋Δɽ. 6.2 ಛྔͷ ϧϑొςϯϓϨʔτͷಛྔ͕ภΔ͜ͱʹ. ࣮ ݧ1 ͰఆظతͳηϧͷૠೖΛߦͬͨɽड৴ηϧΛૠ. Αͬͯੜ͡ΔɽͦͷͨΊࠓޙಛྔͷΛௐΔ͜ͱʹ. ೖͨ͠߹ɼૠೖ͠ͳ͔ͬͨ߹ͱൺࢦ߈ܸʹର͠΄. ͳΔ͕ɼ5 ষͷ࣮͔ݧΒΘ͔ΔΑ͏ʹɼ͋Δఔࣅͨ૯௨. ͱΜͲޮՌΛൃ͕ͱ͍͜ͳ͍ͯ͠شΘ͔Δɽૹ৴ηϧΛૠ. ৴ྔΛͭσʔλؒͰΛूΊΔඞཁ͕͋Δɽ૯௨৴ྔ. ೖͨ͠߹ɼड৴ηϧૠೖʹൺࢦ߈ܸʹର͠ޮՌΛൃ. ͱ͍͏ಛΛࣅͤΑ͏ͱ͢Δͱɼେ͖ͳΦʔόʔϔου͕. ͍ͯ͠شΔɽ͔͠͠ૠೖʹΑͬͯ௨৴ྔΛೋഒʹͨ͠ͱ͖. ඞཁͱͳΓڀݚͷత͔Β֎ΕΔͨΊͰ͋Δɽ͜͜Ͱɼಛ. Ͱ 87%ͷ߈ܸޭͱͳ͓ͬͯΓɼఆظతͳηϧૠೖ. ྔͱͯ͠ͷ૯௨৴ྔΛͲ͏͚۠Δ͔ͱ͍͏ͷେ͖ͳ. ͷޮՌͷ͕͞ݱΕ͍ͯΔɽ͜Εɼࢦ߈ܸͰ༻͍Δد. ՝ͩͱߟ͑Δɽ. ༩ͷେ͖͍ಛྔͷ͏ͪɼ௨৴ྔηϧͷॱংͱ͍ͬͨಛ ͕͋·ΓมԽ͍ͯ͠ͳ͍͜ͱʹґΔͱߟ͑ΒΕΔɽ ࣮ ݧ2 Ͱɼ࣮ ݧ1 ͷ݁ՌΛ౿·͑ɼηϧͷॱংΛେ͖. 6.3 ϧϑΣϒαΠτͷධՁํ๏ߟҊ ຊߘͰɼݧ࣮ૅجͷ݁ՌΛදͨ͢Ίʹ Accuracy Λ༻. ͘ཚ͢Α͏ʹૠೖΛՃ͑ͨɽ͜ͷͱ͖࣮ݧͷͲͷ߹Ͱɼ. ͍͕ͨɼ͜ΕΛϧϑΣϒαΠτͷධՁʹ༻͍Δ. 1 ͭͷηϧʹର͠ 1 ͭͷηϧΛૠೖ͍ͯ͠ΔͷͰɼ௨৴ྔ. ͜ͱͰ͖ͳ͍ɽ·ͨɼੜମೝূͷʹ͓͍ͯϧϑ. ͷΦʔόʔϔου 100%Ͱ͋ΔɽΩϟϓνϟͨ͠શͯͷ. ͷධՁʹྑ͘༻͍ΒΕ͍ͯΔࢦඪʹ WAP (Wolf Attack. ηϧʹର͠ɼͦΕͧΕͷલ·ͨʹޙɼํ͕ͳͱٯ. Probability) ͕͋Δ͕ɼ͜ΕϧϑΣϒαΠτͷධՁ. ΔηϧΛૠೖͨ͠ɽಛʹɼ3 ͭΊͷ߹Ͱɼड৴ηϧͷ. ʹ༻͍Δ͜ͱͰ͖ͳ͍ɽͱ͍͏ͷɼੜମೝূʹ͓͍ͯ. ૹʹޙ৴ηϧΛɼૹ৴ηϧͷલʹड৴ηϧΛૠೖ͢Δ. ϧϑͷධՁΛ͢ΔࡍͦͷೝূҰରҰೝূͰ͋Δͷʹର. ͜ͱʹΑΓɼૹ৴ηϧͱड৴ηϧ͕શʹަʹޓฒͿΑ͏. ͠ɼϧϑΣϒαΠτͷධՁΛ͢ΔࡍͦͷೝূҰରଟ. ʹͨ͠ɽ࣮ ݧ1 ͷ݁ՌͱൺΔ͜ͱͰɼಉ͡Φʔόʔϔο. ೝূͰ͋ΓҟͳΔೝূ͕͞Ε͍ͯΔͨΊͰ͋Δɽैͬͯ. υ͕ 100%ͱͳΔૠೖͰɼ࣮ ݧ2 Ͱߦͬͨૠೖͷ΄͏͕. ϧϑΣϒαΠτͷධՁʹ͚ͯ৽ͨͳධՁج४ΛߟҊ͢. ޮՌతͰ͋Δ͜ͱ͕Θ͔Δɽ·ͨɼ࣮ ݧ1 ͷ݁Ռɼ1 ͭ. Δඞཁ͕͋Γɼ͜Εࠓޙͷ՝Ͱ͋Δɽ. ɼ2 ͭͷ߹ͷ݁ՌɼશʹηϧͷॱংใΛফͨ͠. 3 ͭͷ߹ͷ݁ՌΛൺΔͱɼηϧͷॱং͕ඇৗʹେ͖. ࢀߟจݙ. ͳಛͱͳ͍ͬͯΔ͜ͱ͕Θ͔Δɽ͞Βʹ 3 ͭͷ݁Ռ͔. [1] [2] [3]. Βɼ૯௨৴ྔͱ࣌ؒใͷΈ͔Βɼ 36%ͷਫ਼Ͱ߈ܸ͕ ޭ͢Δ͜ͱ͕Θ͔Δɽ. 6. ࠓޙͷ՝ ୈ 5 ষͰड़ͨݧ࣮ૅجΛ౿·͑ɼϧϑΣϒαΠτ. [4]. ͷੑ࣭Λ୳ΔͨΊࠓޙҎԼͷ͕՝ͱͯ͛͠ڍΒΕΔɽ. 6.1 σʔλऩू. [5]. ຊߘͰ༻͍ͨσʔληοτ Wang Β͕աʹڈऩू͠Ճ ΛߦͬͨͷͰ͋ΔɽࠓޙϧϑͷڀݚΛਐΊΔʹ͋ͨ. [6]. ΓɼಛͷภΓΛൃ͢ݟΔͨΊʹΑΓଟ͘ͷΣϒαΠτ Λରͱ͢Δඞཁੑ͕ߟ͑ΒΕΔɽ͔͠͠ Tor ͷόʔδϣ ϯωοτϫʔΫڥͷҧ͍͔Βɼެ։͞Ε͍ͯΔσʔλ. [7]. ʹ৽ͨͳτϥϑΟοΫΛ૿͢͜ͱ͍͠ɽͦ͜Ͱ ಠࣗʹσʔληοτΛऔΔඞཁ͕͋Δͱߟ͑Δɽ͜ͷͱ͖. [8]. σʔληοτҎԼͷΑ͏ʹ࡞͢Δɽରͱ͢ΔαΠτ ܈ɼAlexa Top sites[1] ͱ͢Δɽ͜Εʹઌߦ͠Ͱڀݚ ͠༻͍ΒΕ͓ͯΓɼൺֱݕ౼͕͍͢͠ͱ͍͏ར͕ ͋Δɽ·ͨɼαΠτ༰ͷେ͖ͳมԽΛ͙ͨΊɼͦΕͧ ΕͷαΠτͷτϥϑΟοΫऩू 12 ࣌ؒҎ্͚͓͋ͯ͜ ͳ͏͜ͱ͕ͳ͍Α͏ʹ͢Δɽ͞Βʹɼֶशσʔλͱςετ. c 2015 Information Processing Society of Japan . [9]. Alexa. http://www.alexa.com/. Tor metrics. https://metrics.torproject.org/. Xiang Cai, Xin Cheng Zhang, Brijesh Joshi, and Rob Johnson. Touching from a distance: Website fingerprinting attacks and defenses. In Proceedings of the 2012 ACM conference on Computer and communications security, pages 605–616. ACM, 2012. David L Chaum. Untraceable electronic mail, return addresses, and digital pseudonyms. Communications of the ACM, 24(2):84–90, 1981. Roger Dingledine. Tor and circumvention: Lessons learned. In Advances in Cryptology–CRYPTO 2011, pages 485–486. Springer, 2011. Roger Dingledine, Nick Mathewson, and Paul Syverson. Tor: The second-generation onion router. In In Proceedings of the 13th USENIX Security Symposium, pages 303–320. USENIX Association, Aug. 2004. John R Douceur. The sybil attack. In Peer-to-peer Systems, pages 251–260. Springer, 2002. Kevin P Dyer, Scott E Coull, Thomas Ristenpart, and Thomas Shrimpton. Peek-a-boo, i still see you: Why efficient traffic analysis countermeasures fail. In Security and Privacy (SP), 2012 IEEE Symposium on, pages 332–346. IEEE, 2012. Dominik Herrmann, Rolf Wendolsky, and Hannes Federrath. Website fingerprinting: attacking popular privacy enhancing technologies with the multinomial na¨ıve-bayes classifier. In Proceedings of the 2009. 7.
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