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Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Thaum koj hnov ​​lo lus "cryptography," qee tus neeg nco ntsoov lawv tus password WiFi, lub xauv ntsuab ntawm ib sab ntawm qhov chaw nyob ntawm lawv lub vev xaib nyiam, thiab nws nyuaj npaum li cas kom nkag mus rau lwm tus email. Lwm tus neeg nco qab txog cov teeb meem tsis zoo nyob rau xyoo tas los no nrog kev qhia luv luv (DROWN, FREAK, POODLE ...), cov cim zoo nkauj thiab ceeb toom kom hloov kho koj tus browser sai.

Cryptography npog nws tag nrho, tab sis qhov tseem ceeb hauv lwm qhov. Lub ntsiab lus yog muaj ib txoj kab zoo ntawm qhov yooj yim thiab complex. Qee yam yooj yim ua, tab sis nyuaj rau muab rov qab ua ke, zoo li tawg qe. Lwm yam ua tau yooj yim tab sis nyuaj kom rov qab tau thaum qhov me me, qhov tseem ceeb, qhov tseem ceeb ploj lawm: piv txwv li, qhib lub qhov rooj xauv thaum "qhov tseem ceeb" yog qhov tseem ceeb. Cryptography kawm txog cov xwm txheej no thiab seb lawv tuaj yeem siv tau li cas hauv kev xyaum.

Nyob rau hauv xyoo tas los no, kev sau ntawm cryptographic tawm tsam tau hloov mus rau hauv lub vaj tsiaj ntawm flashy logos, muaj cov qauv los ntawm cov ntaub ntawv tshawb fawb, thiab ua rau muaj kev ntxhov siab dav dav tias txhua yam tawg. Tab sis qhov tseeb, ntau qhov kev tawm tsam yog ua raws li ob peb lub hauv paus ntsiab lus, thiab cov nplooj ntawv tsis kawg ntawm cov qauv feem ntau yog boiled rau cov tswv yim yooj yim to taub.

Hauv cov kab lus no, peb yuav saib ntau hom kev tawm tsam cryptographic, nrog rau cov ntsiab lus tseem ceeb. Hauv cov ntsiab lus dav dav thiab tsis yog raws nraim hauv qhov kev txiav txim no, tab sis peb yuav npog cov hauv qab no:

  • Cov tswv yim yooj yim: brute force, zaus tsom xam, interpolation, downgrading thiab cross-protocols.
  • Branded vulnerabilities: FREAK, CRIME, POODLE, DROWN, Logjam.
  • Advanced Strategies: oracle tawm tsam (Vodenet nres, Kelsey nres); Txoj kev sib ntsib-hauv-tus-nrab nruab nrab, hnub yug tua, statistical bias (differential cryptanalysis, integral cryptanalysis, thiab lwm yam).
  • Sab channel tawm tsam thiab lawv cov txheeb ze ze, kev ua tsis tiav kev tsom xam.
  • Kev tawm tsam ntawm pej xeem tus yuam sij cryptography: lub voos xwmfab hauv paus, tshaj tawm, xov xwm ntsig txog, Coppersmith nres, Pohlig-Hellman algorithm, tus lej sieve, Wiener nres, Bleichenbacher nres.

Cov kab lus tshwj xeeb no npog cov ntaub ntawv saum toj no mus txog Kelsey qhov kev tawm tsam.

Cov tswv yim yooj yim

Cov kev tawm tsam hauv qab no yog qhov yooj yim hauv kev nkag siab tias lawv tuaj yeem piav qhia yuav luag tag yam tsis muaj kev nthuav dav ntau. Cia peb piav qhia txhua hom kev tawm tsam hauv cov ntsiab lus yooj yim tshaj plaws, tsis tas yuav mus rau hauv cov piv txwv nyuaj lossis kev siv siab heev.

Qee qhov kev tawm tsam no tau dhau los ua qhov qub thiab tsis tau siv ntau xyoo. Lwm tus yog cov laus-timers uas tseem niaj hnub ua rau tsis txaus ntseeg cryptosystem developers nyob rau hauv lub xyoo pua 21st. Lub sijhawm ntawm niaj hnub cryptography tuaj yeem suav hais tias tau pib nrog qhov tshwm sim ntawm IBM DES, thawj tus lej uas tiv thaiv txhua qhov kev tawm tsam ntawm daim ntawv teev npe no.

Yooj yim brute quab yuam

Cryptographic attacks: piav qhia rau lub siab tsis meej pemCov txheej txheem encryption muaj ob ntu: 1) encryption muaj nuj nqi, uas siv cov lus (plaintext) ua ke nrog tus yuam sij, thiab tom qab ntawd tsim cov lus encrypted - ciphertext; 2) ib qho kev decryption muaj nuj nqi uas siv cov ntawv ciphertext thiab tus yuam sij thiab tsim cov ntawv dawb. Ob leeg encryption thiab decryption yuav tsum yooj yim xam nrog tus yuam sij - thiab nyuaj rau xam yam tsis muaj nws.

Cia peb xav tias peb pom cov ntawv ciphertext thiab sim decrypt nws yam tsis muaj cov ntaub ntawv ntxiv (qhov no hu ua ciphertext-tsuas yog nres). Yog tias peb pom qhov yuam kev tiag tiag, peb tuaj yeem tshawb xyuas tau yooj yim tias nws yog qhov tseeb yog tias qhov tshwm sim yog cov lus tsim nyog.

Nco ntsoov tias muaj ob qhov kev xav tsis tseeb ntawm no. Ua ntej, peb paub yuav ua li cas decryption, uas yog, yuav ua li cas lub cryptosystem ua haujlwm. Qhov no yog tus qauv kev xav thaum tham txog cryptography. Nkaum cov ntsiab lus ntawm kev siv lub cipher los ntawm cov neeg tawm tsam yuav zoo li kev ntsuas kev nyab xeeb ntxiv, tab sis thaum tus neeg tawm tsam pom cov ntsiab lus no, qhov kev ruaj ntseg ntxiv no nyob ntsiag to thiab ploj mus tsis tau. Yog li ntawd Kerchhoffs txoj cai: Lub kaw lus poob rau hauv cov yeeb ncuab txhais tes yuav tsum tsis txhob ua rau tsis xis nyob.

Qhov thib ob, peb xav tias tus yuam sij raug yog tus yuam sij nkaus xwb uas yuav ua rau kev txiav txim siab tsim nyog. Qhov no kuj yog ib qho kev xav uas tsim nyog; nws txaus siab yog tias cov ntawv ciphertext ntev dua li tus yuam sij thiab nyeem tau. Qhov no feem ntau tshwm sim hauv lub ntiaj teb tiag tiag, tshwj tsis yog cov yuam sij loj heev los yog lwm cov shenanigans uas zoo tshaj plaws sab laug (yog tias koj tsis nyiam qhov peb tau hla qhov kev piav qhia, thov saib Theorem 3.8 no).

Muab cov saum toj no, ib lub tswv yim tshwm sim: xyuas txhua tus yuam sij ua tau. Qhov no yog hu ua brute quab yuam, thiab qhov kev tawm tsam no tau lees tias ua haujlwm tawm tsam txhua qhov kev siv dag zog - thaum kawg. Piv txwv li, brute quab yuam yog txaus rau hack Caesar cipher, ib qho kev cipher thaum ub qhov twg tus yuam sij yog ib tsab ntawv ntawm cov tsiaj ntawv, implying tshaj 20 tus yuam sij tau.

Hmoov tsis zoo rau cryptanalysts, nce qhov loj me yog qhov kev tiv thaiv zoo tiv thaiv brute quab yuam. Raws li tus yuam sij loj nce, tus naj npawb ntawm cov yuam sij tau nce exponentially. Nrog rau qhov tseem ceeb niaj hnub no, qhov yooj yim brute quab yuam yog kiag li impractical. Txhawm rau kom nkag siab qhov peb txhais tau li cas, cia peb siv lub khoos phis tawj paub ceev tshaj plaws thaum nruab nrab xyoo 2019: qhov ua siab tshaj los ntawm IBM, nrog rau qhov ua tau zoo tshaj plaws ntawm 1017 kev ua haujlwm ib ob. Niaj hnub no, qhov ntev ntawm qhov tseem ceeb yog 128 khoom, uas txhais tau hais tias 2128 kev sib txuas ua ke. Txhawm rau tshawb xyuas txhua tus yuam sij, Summit supercomputer yuav xav tau lub sijhawm uas kwv yees li 7800 npaug ntawm lub hnub nyoog ntawm Lub Ntiaj Teb.

Yuav tsum brute quab yuam suav hais tias yog keeb kwm xav paub? Tsis yog tag nrho: nws yog ib qho tsim nyog muaj nyob rau hauv phau ntawv cryptanalysis. Tsis tshua muaj cov ciphers tsis muaj zog uas lawv tsuas tuaj yeem tawg los ntawm kev tawm tsam ntse, tsis muaj kev siv dag zog rau ib qib lossis lwm qhov. Ntau qhov kev vam meej hacks siv txoj kev algorithmic kom tsis muaj zog rau lub hom phiaj cipher ua ntej, thiab tom qab ntawd ua qhov kev tawm tsam brute force.

Kev soj ntsuam zaus

Cryptographic attacks: piav qhia rau lub siab tsis meej pemFeem ntau cov ntawv tsis yog gibberish. Piv txwv li, hauv cov ntawv Askiv muaj ntau cov ntawv 'e' thiab cov ntawv 'the'; Hauv cov ntaub ntawv binary, muaj ntau yam xoom bytes ua padding ntawm cov ntaub ntawv. Kev tshuaj xyuas zaus yog ib qho kev tawm tsam uas siv qhov zoo ntawm qhov tseeb.

Cov piv txwv canonical ntawm lub cipher yooj yim rau qhov kev tawm tsam no yog qhov yooj yim hloov pauv cipher. Hauv qhov cipher no, tus yuam sij yog lub rooj nrog tag nrho cov ntawv hloov. Piv txwv li, 'g' yog hloov los ntawm 'h', 'o' los ntawm j, yog li lo lus 'go' dhau los ua 'hj'. Qhov cipher no nyuaj rau brute quab yuam vim tias muaj ntau lub rooj nrhiav tau. Yog tias koj txaus siab rau kev ua lej, qhov ntev ntawm qhov tseem ceeb yog hais txog 88 khoom: qhov ntawd yog
Cryptographic attacks: piav qhia rau lub siab tsis meej pem. Tab sis kev txheeb xyuas zaus feem ntau tau ua tiav sai.

Xav txog cov ntawv ciphertext hauv qab no ua tiav nrog ib qho yooj yim hloov cipher:

XDYLY ALY UGLY XDWNKE WN DYAJYN ANF YALXD DGLAXWG XDAN ALY FLYAUX GR WN OGQL ZDWBGEGZDO

Txij thaum lub Y tshwm sim ntau zaus, suav nrog qhov kawg ntawm ntau lo lus, peb tuaj yeem ua siab ntev xav tias qhov no yog tsab ntawv e:

XDeLe Ale UGLe XDWNKE WN DeAJeN ANF eALXD DGLAXWG XDAN Ale FleAUX GR WN OGQL ZDWBGEGZDO

Ob peb XD rov hais dua thaum pib ntawm ob peb lo lus. Tshwj xeeb, kev sib xyaw XDeLe qhia meej cov lus these los yog there, yog li cia peb mus ntxiv:

KUV XAV PAUB TIAS KUV PAUB TIAS KUV PAUB TIAS KUV PAUB TIAS KUV PAUB TIAS KUV PAUB TIAS KUV HLUB KUV

Cia peb xav ntxiv tias L соответствует r, A - a thiab lwm yam. Tej zaum nws yuav siv sij hawm ob peb zaug, tab sis piv rau tag nrho brute quab yuam tawm tsam, qhov kev tawm tsam no rov ua dua cov ntawv qub tsis muaj sijhawm:

muaj ntau yam nyob saum ntuj ceeb tsheej thiab lub ntiaj teb horatio tshaj li npau suav ntawm koj lub tswv yim

Rau qee tus, kev daws qhov "cryptograms" yog qhov kev nyiam ua haujlwm zoo.

Lub tswv yim ntawm kev tsom xam zaus yog qhov tseem ceeb tshaj qhov nws zoo li thaum xub thawj siab ib muag. Thiab nws siv rau ntau ntau cov ciphers complex. Thoob plaws hauv keeb kwm, ntau yam cipher tsim tau sim tawm tsam xws li kev tawm tsam siv "polyalphabetic hloov pauv". Ntawm no, thaum lub sij hawm encryption txheej txheem, tsab ntawv hloov lub rooj yog hloov nyob rau hauv complex tab sis kwv yees txoj kev uas nyob ntawm tus yuam sij. Tag nrho cov ciphers no tau pom tias nyuaj rau kev tawg ntawm ib zaug; thiab tseem tsis tshua muaj zaus tsom xam thaum kawg kov yeej lawv tag nrho.

Lub siab tshaj plaws polyalphabetic cipher hauv keeb kwm, thiab tej zaum lub npe nrov tshaj plaws, yog Enigma cipher ntawm Ntiaj Teb Tsov Rog II. Nws yog qhov nyuaj heev piv rau nws cov neeg ua ntej, tab sis tom qab ua haujlwm hnyav heev, British cryptanalysts tawg nws siv zaus tsom xam. Tau kawg, lawv tsis tuaj yeem tsim qhov kev tawm tsam zoo nkauj zoo li qhov qhia saum toj no; lawv yuav tsum tau sib piv cov ntaub ntawv paub tseeb thiab ciphertext (lub npe hu ua "plaintext nres"), txawm tias ua rau cov neeg siv Enigma los encrypt qee cov lus thiab txheeb xyuas qhov tshwm sim (qhov "xaiv plaintext nres"). Tab sis qhov no tsis ua rau txoj hmoo ntawm cov yeeb ncuab swb rog thiab poob submarines yooj yim dua.

Tom qab qhov kev vam meej no, kev soj ntsuam zaus ploj ntawm keeb kwm ntawm cryptanalysis. Ciphers hauv lub hnub nyoog digital niaj hnub no yog tsim los ua haujlwm nrog cov khoom, tsis yog ntawv. Qhov tseem ceeb tshaj, cov ciphers no tau tsim los nrog kev nkag siab qhov tsaus ntuj ntawm dab tsi tom qab los ua lub npe hu ua Schneier txoj cai: Txhua tus tuaj yeem tsim qhov encryption algorithm uas lawv tus kheej tsis tuaj yeem tawg. Nws tsis txaus rau lub kaw lus encryption zoo li nyuaj: txhawm rau ua pov thawj nws tsim nyog, nws yuav tsum tau ua raws li kev saib xyuas kev nyab xeeb tsis muaj kev cia siab los ntawm ntau tus kws tshawb fawb cryptanalyst uas yuav ua lawv qhov zoo tshaj plaws kom tawg lub cipher.

Kev suav ua ntej

Cryptographic attacks: piav qhia rau lub siab tsis meej pemCoj lub nroog hypothetical ntawm Precom Heights, cov pejxeem 200. Txhua lub tsev nyob hauv lub nroog muaj qhov nruab nrab ntawm $ 000 tus nqi ntawm cov khoom muaj nqis, tab sis tsis pub ntau tshaj $ 30. Kev lag luam kev ruaj ntseg hauv Precom yog monopolized los ntawm ACME Industries, uas tsim cov lus dab neeg Coyote ™ chav tsev kaw qhov rooj. Raws li cov kws tshaj lij kev soj ntsuam, Coyote-chav kawm xauv tsuas tuaj yeem tawg los ntawm lub tshuab kev xav tsis zoo, kev tsim uas yuav tsum muaj txog tsib xyoos thiab $ 000 hauv peev. Lub nroog puas nyab xeeb?

Feem ntau yuav tsis muaj. Thaum kawg, ib qho kev ua txhaum cai ncaj ncees yuav tshwm sim. Nws yuav xav li no: “Yog lawm, kuv yuav raug nqi ntau dua. Tsib xyoos ntawm tus neeg mob tos, thiab $ 50. Tab sis thaum kuv ua tiav, kuv yuav nkag mus rau tag nrho cov nplua nuj ntawm lub nroog no. Yog tias kuv ua si kuv daim npav raug cai, qhov kev nqis peev no yuav them rau nws tus kheej ntau zaus. "

Ib yam yog muaj tseeb hauv cryptoography. Kev tawm tsam tawm tsam ib qho kev cipher tshwj xeeb yog raug rau kev txheeb xyuas qhov txiaj ntsig tsis zoo. Yog tias qhov piv tau zoo, qhov kev tawm tsam yuav tsis tshwm sim. Tab sis kev tawm tsam uas ua haujlwm tawm tsam ntau tus neeg raug tsim txom ib zaug yuav luag ib txwm them nyiaj, nyob rau hauv qhov xwm txheej zoo tshaj plaws tsim qauv yog xav tias lawv pib txij hnub ib. Peb muaj qhov tseem ceeb ntawm cov ntawv pov thawj ntawm Murphy Txoj Cai Lij Choj: "Txhua yam uas tuaj yeem ua txhaum lub kaw lus yuav ua rau lub kaw lus."

Qhov piv txwv yooj yim tshaj plaws ntawm lub cryptosystem uas muaj kev cuam tshuam rau qhov kev tawm tsam ua ntej yog qhov tsis tas li-keyless cipher. Qhov no yog qhov teeb meem nrog Caesar lub cipher, uas yooj yim hloov txhua tsab ntawv ntawm cov tsiaj ntawv peb tsab ntawv rau pem hauv ntej (lub rooj yog looped, yog li tsab ntawv kawg hauv cov tsiaj ntawv yog encrypted thib peb). Ntawm no dua Kerchhoffs txoj cai los rau hauv kev ua si: ib zaug ib lub kaw lus raug hacked, nws yog hacked mus ib txhis.

Lub tswvyim yog yooj yim. Txawm tias tus tsim tawm cryptosystem novice yuav paub txog qhov kev hem thawj thiab npaj kom haum. Saib ntawm evolution ntawm cryptography, xws li kev tawm tsam tsis tsim nyog rau feem ntau cov ntawv ciphers, los ntawm thawj qhov kev txhim kho ntawm Caesar cipher mus txog rau qhov poob ntawm polyalphabetic ciphers. Xws li kev tawm tsam tsuas yog rov qab los nrog qhov tshwm sim ntawm lub sijhawm niaj hnub ntawm cryptography.

Qhov kev rov qab los no yog vim ob yam. Ua ntej, txaus txaus cryptosystems thaum kawg tshwm sim, qhov twg muaj peev xwm ntawm kev siv tom qab nyiag khoom tsis pom tseeb. Qhov thib ob, crypto txiaj tau dhau los ua qhov dav heev uas ntau lab tus tib neeg tau txiav txim siab txhua hnub txog qhov twg thiab qhov twg ntawm cryptography rov qab siv dua. Nws siv qee lub sijhawm ua ntej cov kws tshaj lij paub txog qhov txaus ntshai thiab tsa lub tswb.

Nco ntsoov qhov kev tawm tsam ua ntej: thaum kawg ntawm tsab xov xwm peb yuav saib ob qho piv txwv ntawm lub neej tiag tiag uas nws tau ua lub luag haujlwm tseem ceeb.

Interpolation

Ntawm no yog tus naas ej detective Sherlock Holmes, ua ib tug interpolation nres ntawm lub hapless Dr. Watson:

Kuv tam sim ntawd kwv yees tias koj tuaj ntawm Afghanistan ... Kuv lub tsheb ciav hlau xav tau raws li hauv qab no: "Tus txiv neej no yog kws kho mob, tab sis nws muaj tub rog. Yog li, tus kws kho mob tub rog. Nws nyuam qhuav tuaj txog ntawm lub tropics - nws lub ntsej muag yog tsaus, tab sis qhov no tsis yog lub ntuj ntxoov ntxoo ntawm nws daim tawv nqaij, vim hais tias nws lub dab teg yog ntau whiter. Lub ntsej muag haggard - pom tseeb, nws tau raug kev txom nyem ntau heev thiab raug mob los ntawm kev mob. Nws raug mob ntawm nws sab laug tes - nws tuav nws motionless thiab me ntsis unnaturally. Qhov twg nyob rau hauv lub tropics yuav ib tug kws kho mob tub rog Askiv tiv kev txom nyem thiab raug mob? Tau kawg, hauv Afghanistan. " Tag nrho lub tsheb ciav hlau ntawm kev xav tsis tau siv txawm tias ib pliag. Thiab yog li kuv hais tias koj tuaj ntawm Afghanistan, thiab koj xav tsis thoob.

Holmes tuaj yeem rho tawm cov ntaub ntawv me me los ntawm txhua daim ntawv pov thawj ntawm tus kheej. Nws tsuas tuaj yeem ncav cuag nws qhov xaus los ntawm kev txiav txim siab lawv txhua tus ua ke. Ib qho kev cuam tshuam cuam tshuam ua haujlwm zoo ib yam los ntawm kev tshuaj xyuas cov ntaub ntawv paub tseeb thiab cov ntawv ciphertext ua los ntawm tib tus yuam sij. Los ntawm txhua tus khub, cov kev soj ntsuam ntawm tus kheej raug muab rho tawm uas tso cai rau kev txiav txim siab dav dav txog tus yuam sij kom kos. Tag nrho cov lus xaus no tsis meej thiab zoo li tsis muaj txiaj ntsig kom txog thaum lawv maj mam ncav cuag qhov tseem ceeb thiab ua rau tib qho kev txiav txim siab: txawm tias nws zoo kawg li cas, nws yuav tsum muaj tseeb. Tom qab ntawd, tus yuam sij raug nthuav tawm, lossis cov txheej txheem decryption ua kom zoo kom nws tuaj yeem rov ua dua.

Cia peb piav qhia nrog ib qho piv txwv yooj yim li cas interpolation ua haujlwm. Cia peb hais tias peb xav nyeem phau ntawv teev npe ntawm peb tus yeeb ncuab, Bob. Nws encrypts txhua tus lej hauv nws phau ntawv journal siv ib qho yooj yim cryptosystem nws kawm txog los ntawm kev tshaj tawm hauv phau ntawv xov xwm "Ib tug Mock of Cryptography." Lub kaw lus ua haujlwm zoo li no: Bob xaiv ob tus lej uas nws nyiam: Cryptographic attacks: piav qhia rau lub siab tsis meej pem и Cryptographic attacks: piav qhia rau lub siab tsis meej pem. Txij no mus, kom encrypt tej tus lej Cryptographic attacks: piav qhia rau lub siab tsis meej pem, nws xam Cryptographic attacks: piav qhia rau lub siab tsis meej pem. Piv txwv li, yog tias Bob xaiv Cryptographic attacks: piav qhia rau lub siab tsis meej pem и Cryptographic attacks: piav qhia rau lub siab tsis meej pem, ces tus lej Cryptographic attacks: piav qhia rau lub siab tsis meej pem yuav encrypted li Cryptographic attacks: piav qhia rau lub siab tsis meej pem.

Cia peb hais tias thaum Lub Kaum Ob Hlis 28th peb pom tias Bob tau khawb ib yam dab tsi hauv nws qhov chaw teev cia. Thaum nws tiav lawm, peb yuav ntsiag to khaws nws thiab saib qhov kev nkag zaum kawg:

Hnub tim: 235/520

Nyob zoo Diary,

Hnub no yog ib hnub zoo. Los ntawm 64 hnub no kuv muaj ib hnub nrog Alisa, uas nyob hauv ib chav tsev 843. Kuv yeej xav tias nws yuav yog 26!

Txij li thaum peb mob siab rau ua raws li Bob ntawm nws hnub (peb ob leeg 15 nyob rau hauv qhov xwm txheej no), nws yog ib qho tseem ceeb kom paub hnub thiab Alice qhov chaw nyob. Hmoov zoo, peb pom tias Bob's cryptosystem yog qhov yooj yim rau kev cuam tshuam kev cuam tshuam. Tej zaum peb tsis paub Cryptographic attacks: piav qhia rau lub siab tsis meej pem и Cryptographic attacks: piav qhia rau lub siab tsis meej pem, tab sis peb paub hnub no, yog li peb muaj ob lub ntsiab lus-ciphertext khub. Namely, peb paub qhov ntawd Cryptographic attacks: piav qhia rau lub siab tsis meej pem encrypted hauv Cryptographic attacks: piav qhia rau lub siab tsis meej pemthiab Cryptographic attacks: piav qhia rau lub siab tsis meej pem - ntawm Cryptographic attacks: piav qhia rau lub siab tsis meej pem. Nov yog qhov peb yuav sau tseg:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Txij li thaum peb muaj 15 xyoo, peb twb paub txog ib qho kev sib npaug ntawm ob qhov sib npaug nrog ob qhov tsis paub, uas nyob rau hauv qhov xwm txheej no txaus los nrhiav. Cryptographic attacks: piav qhia rau lub siab tsis meej pem и Cryptographic attacks: piav qhia rau lub siab tsis meej pem tsis muaj teeb meem. Txhua tus khub plaintext-ciphertext muab qhov txwv ntawm Bob tus yuam sij, thiab ob qho kev txwv ua ke txaus los ua kom rov qab tus yuam sij. Hauv peb qhov piv txwv cov lus teb yog Cryptographic attacks: piav qhia rau lub siab tsis meej pem и Cryptographic attacks: piav qhia rau lub siab tsis meej pem (ntawm Cryptographic attacks: piav qhia rau lub siab tsis meej pem Cryptographic attacks: piav qhia rau lub siab tsis meej pem, yog li 26 nyob rau hauv lub chaw muag mis nyuj sib raug rau lo lus 'ib tug', uas yog, "ib yam" - approx. txoj kab).

Interpolation tawm tsam yog, ntawm chav kawm, tsis txwv rau cov piv txwv yooj yim. Txhua lub cryptosystem uas txo qis rau cov khoom siv lej nkag siab zoo thiab cov npe ntawm cov tsis muaj kev pheej hmoo ntawm kev cuam tshuam kev cuam tshuam - qhov nkag siab ntau dua cov khoom, qhov kev pheej hmoo siab dua.

Cov neeg tuaj tshiab feem ntau yws yws tias cryptography yog "kev kos duab ntawm kev tsim cov khoom phem li ua tau." Interpolation tawm tsam tej zaum yuav raug liam ntau. Bob tuaj yeem siv tus qauv lej zoo nkauj lossis khaws nws hnub nrog Alice ntiag tug - tab sis alas, koj feem ntau tsis tuaj yeem muaj ob txoj hauv kev. Qhov no yuav dhau los ua kom meej meej thaum peb kawg tau mus rau lub ntsiab lus ntawm pej xeem tus yuam sij crypto txiaj.

Hla raws tu qauv / downgrade

Cryptographic attacks: piav qhia rau lub siab tsis meej pemNyob rau tam sim no Koj Pom Kuv (2013), ib pab pawg neeg illusionists sim swindle corrupt insurance magnate Arthur Tressler tawm ntawm nws tag nrho cov hmoov zoo. Txhawm rau nkag mus rau Arthur lub txhab nyiaj hauv txhab nyiaj, cov neeg tsis pom kev yuav tsum muab nws tus username thiab password lossis yuam kom nws tshwm sim hauv tus neeg hauv lub txhab nyiaj thiab koom nrog cov tswv yim.

Ob qho kev xaiv nyuaj heev; Cov txiv neej tau siv los ua yeeb yam ntawm theem, thiab tsis koom nrog kev ua haujlwm txawj ntse. Yog li lawv xaiv qhov kev xaiv thib peb: lawv cov neeg koom nrog hu rau lub txhab nyiaj thiab ua txuj ua Arthur. Lub txhab nyiaj nug ob peb lo lus nug los txheeb xyuas tus kheej, xws li tus txiv ntxawm lub npe thiab lub npe ntawm thawj tus tsiaj; peb cov phab ej ua ntej lawv yooj yim rho tawm cov ntaub ntawv no los ntawm Arthur siv ntse social engineering. Txij ntawm no mus, kev ruaj ntseg password zoo heev tsis muaj teeb meem ntxiv lawm.

(Raws li cov lus dab neeg hauv nroog uas peb tau txheeb xyuas thiab txheeb xyuas tus kheej, tus kws sau nyiaj txiag Eli Beaham ib zaug ntsib tus kws qhia nyiaj hauv tuam txhab uas tau hais kom teeb tsa cov lus nug txog kev nyab xeeb. Thaum tus kws qhia nug txog lub npe ntawm nws niam pog, Beaham pib hais: "Capital X, me y, peb ... ").

Nws zoo ib yam nyob rau hauv cryptography, yog hais tias ob lub cryptographic raws tu qauv siv nyob rau hauv parallel los tiv thaiv tib lub cuab tam, thiab ib tug yog npaum li cas zog dua lwm yam. Cov txheej txheem ua tau dhau los ua qhov tsis zoo rau kev tawm tsam ntawm tus ntoo khaub lig-txoj cai, qhov twg cov txheej txheem tsis muaj zog raug tawm tsam kom tau txais txiaj ntsig yam tsis tau kov lub zog.

Hauv qee qhov xwm txheej nyuaj, nws tsis txaus los tsuas yog hu rau tus neeg rau zaub mov uas siv cov txheej txheem tsis muaj zog, tab sis yuav tsum muaj kev koom tes ntawm tus neeg siv khoom raug cai. Qhov no tuaj yeem raug teeb tsa siv qhov hu ua downgrade nres. Yuav kom nkag siab txog qhov kev tawm tsam no, cia peb xav tias peb cov illusionists muaj txoj haujlwm nyuaj dua li hauv zaj duab xis. Cia peb xav tias tus neeg ua haujlwm hauv tuam txhab nyiaj (cashier) thiab Arthur ntsib qee qhov xwm txheej tsis tau pom dua, ua rau muaj kev sib tham hauv qab no:

Tub sab: Nyob zoo? Qhov no yog Arthur Tressler. Kuv xav rov pib dua kuv tus password.

Tus neeg txais nyiaj: Zoo heev. Thov saib koj tus kheej cov ntaub ntawv zais cia, nplooj 28, lo lus 3. Txhua cov lus hauv qab no yuav raug encrypted siv lo lus tshwj xeeb no ua tus yuam sij. PQJGH. LOTJNAM PGGY MXVRL ZZLQ SRIU HHNMLPPPV…

Tub sab: Hav, nyob, tos, tos. Qhov no puas tsim nyog? Peb tsis tuaj yeem hais lus zoo li cov neeg ib txwm muaj?

Tus neeg txais nyiaj: Kuv tsis pom zoo ua qhov no.

Tub sab: Kuv tsuas yog ... saib, Kuv muaj ib hnub phem, tsis ua li cas? Kuv yog tus neeg siv VIP thiab kuv tsis nyob hauv lub siab mus khawb los ntawm cov ntawv ruam ruam no.

Tus neeg txais nyiaj: Zoo. Yog koj hais, Mr. Tressler. Koj xav li cas?

Tub sab: Thov, kuv xav pub nyiaj pub dawb rau Arthur Tressler National Victims Fund.

(Pause).

Tus neeg txais nyiaj: Puas yog tam sim no. Thov muab koj tus PIN rau kev lag luam loj.

Tub sab: Kuv yog dab tsi?

Tus neeg txais nyiaj: Ntawm koj tus kheej thov, kev lag luam ntawm qhov loj me no xav tau tus PIN rau kev lag luam loj. Cov lej no tau muab rau koj thaum koj qhib koj tus account.

Tub sab:... Kuv poob nws. Qhov no puas tsim nyog? Koj tsis tuaj yeem pom zoo rau qhov deal?

Tus neeg txais nyiaj: Tsis muaj. Kuv thov txim, Mr. Tressler. Ntxiv dua thiab, qhov no yog qhov ntsuas kev nyab xeeb uas koj tau thov. Yog tias koj xav tau, peb tuaj yeem xa tus lej PIN tshiab rau koj lub thawv ntawv.

Peb tus phab ej ncua sijhawm ua haujlwm. Lawv eavesdrop ntawm ob peb ntawm Tressler cov kev lag luam loj, vam tias yuav hnov ​​​​tus PIN; tab sis txhua zaus kev sib tham hloov mus rau hauv coded gibberish ua ntej muaj dab tsi nthuav yog hais. Thaum kawg, ib hnub zoo, txoj kev npaj tau muab tso rau hauv kev nqis tes ua. Lawv ua siab ntev tos lub sijhawm thaum Tressler yuav tsum ua lag luam loj hauv xov tooj, nws tau txais ntawm kab, thiab tom qab ntawd ...

Tressler: Nyob zoo. Kuv xav ua kom tiav qhov kev hloov pauv nyob deb, thov.

Tus neeg txais nyiaj: Zoo heev. Thov mus saib koj tus kheej phau ntawv zais cia, nplooj ...

(Tus tub sab nias lub khawm; tus neeg tuav nyiaj lub suab hloov mus rau hauv lub suab tsis paub meej).

Tus neeg txais nyiaj: - #@$#@$#*@$$@#* yuav tau encrypted nrog lo lus no ua tus yuam sij. UA TSAUG NTAU NTAU OS...

Tressler: Thov txim, kuv tsis nkag siab. Ib zaug ntxiv? Nyob rau nplooj ntawv twg? Lo lus twg?

Tus neeg txais nyiaj: Nov yog nplooj ntawv @#$@#*$)#*#@()#@$(#@*$(#@*.

Tressler: Dab tsi?

Tus neeg txais nyiaj: Lo lus thib nees nkaum @$#@$#%#$.

Tressler: Tiag tiag! txaus lawm! Koj thiab koj qhov kev ruaj ntseg raws tu qauv yog qee yam ntawm circus. Kuv paub tias koj tuaj yeem tham nrog kuv ib txwm.

Tus neeg txais nyiaj: Kuv tsis pom zoo…

Tressler: Thiab kuv tsis qhia koj kom nkim kuv lub sijhawm. Kuv tsis xav hnov ​​ntxiv txog qhov no kom txog thaum koj kho koj cov teeb meem hauv xov tooj. Peb puas tuaj yeem ua tiav qhov kev cog lus no lossis tsis tau?

Tus neeg txais nyiaj:… Yog. Zoo. Koj xav li cas?

Tressler: Kuv xav hloov $20 rau Tswv Lag Luam Lag Luam, tus lej account ...

Tus neeg txais nyiaj: Ib feeb, thov. Nws yog ib qho loj. Thov muab koj tus PIN rau kev lag luam loj.

Tressler: Dab tsi? Auj, raws nraim. 1234 ib.

Ntawm no yog downward nres. Cov txheej txheem tsis muaj zog "tsuas yog hais ncaj qha" tau pom zoo li kev xaiv thaum muaj xwm ceev. Thiab tseem nyob ntawm no peb nyob.

Tej zaum koj yuav xav tsis thoob tias leej twg hauv lawv lub siab zoo yuav tsim qhov "kev nyab xeeb tiag tiag kom txog thaum nug lwm yam" zoo li qhov tau piav qhia saum toj no. Tab sis ib yam li lub txhab nyiaj tsis tseeb yuav muaj kev pheej hmoo los khaws cov neeg siv khoom uas tsis nyiam cryptography, cov tshuab feem ntau ua rau muaj kev xav tsis thoob lossis txawm tias muaj kev kub ntxhov rau kev nyab xeeb.

Qhov no yog qhov tshwm sim nrog SSLv2 raws tu qauv hauv xyoo 1995. Tsoom Fwv Teb Chaws Asmeskas tau pib ntev los saib cryptography ua riam phom uas zoo tshaj plaws kom deb ntawm cov yeeb ncuab txawv teb chaws thiab hauv tsev. Cov kab lus ntawm tus kheej tau pom zoo rau kev xa tawm los ntawm Tebchaws Meskas, feem ntau nrog cov xwm txheej uas cov txheej txheem tau txhob txwm tsis muaj zog. Netscape, tus tsim tawm ntawm qhov browser nrov tshaj plaws, Netscape Navigator, tau txais kev tso cai rau SSLv2 nkaus xwb nrog rau qhov tseem ceeb ntawm 512-ntsis RSA yuam sij (thiab 40-ntsis rau RC4).

Thaum kawg ntawm lub xyoo txhiab, cov kev cai tau so thiab nkag mus rau niaj hnub encryption tau dav dav. Txawm li cas los xij, cov neeg siv khoom thiab cov neeg siv khoom tau txhawb nqa tsis muaj zog "export" cryptography rau xyoo vim yog tib yam inertia uas tswj kev txhawb nqa rau txhua qhov txheej txheem qub txeeg qub teg. Cov neeg siv khoom ntseeg tias lawv yuav ntsib lub server uas tsis txhawb lwm yam. Cov servers tau ua tib yam. Tau kawg, SSL raws tu qauv hais tias cov neeg siv khoom thiab cov servers yuav tsum tsis txhob siv cov txheej txheem tsis muaj zog thaum muaj qhov zoo dua. Tab sis tib lub ntsiab lus siv rau Tressler thiab nws lub txhab nyiaj.

Qhov kev xav no pom nws txoj hauv kev mus rau ob qhov kev tawm tsam siab uas cuam tshuam kev ruaj ntseg ntawm SSL raws tu qauv hauv 2015, ob qho tib si tshawb pom los ntawm Microsoft cov kws tshawb fawb thiab INRIA. Ua ntej, cov ntsiab lus ntawm FREAK nres tau tshaj tawm thaum Lub Ob Hlis, ua raws li peb lub hlis tom qab los ntawm lwm qhov kev tawm tsam zoo sib xws hu ua Logjam, uas peb yuav tham txog ntau yam ntxiv thaum peb txav mus rau kev tawm tsam ntawm pej xeem cov ntaub ntawv tseem ceeb.

Cryptographic attacks: piav qhia rau lub siab tsis meej pemKom txhob raug FREAK (tseem hu ua "Smack TLS") tau tshwm sim thaum cov kws tshawb fawb tau soj ntsuam TLS tus neeg siv khoom / server siv thiab pom cov kab mob xav paub. Nyob rau hauv cov kev siv no, yog tias tus neeg siv tsis txawm hais kom siv tsis muaj zog xa tawm crypto txiaj, tab sis tus neeg rau zaub mov tseem teb nrog cov yuam sij no, tus neeg siv hais tias "Huag zoo" thiab hloov mus rau qhov tsis muaj zog cipher suite.

Thaum lub sij hawm, export cryptography yog dav suav hais tias yog outdated thiab off-txoj kev, yog li qhov kev tawm tsam tuaj ua ib qho kev poob siab thiab cuam tshuam ntau yam tseem ceeb, suav nrog Tsev Dawb, IRS, thiab NSA qhov chaw. Txawm li cas los xij, nws hloov tawm tias ntau lub servers tsis zoo tau ua kom zoo dua los ntawm kev rov siv cov yuam sij qub dua li tsim cov tshiab rau txhua qhov kev sib tham. Qhov no ua rau nws ua tau, tom qab txo qis cov txheej txheem, ua kom muaj kev tawm tsam ua ntej: kev tawg ib qho tseem ceeb tseem kim heev ($ 100 thiab 12 teev thaum lub sijhawm tshaj tawm), tab sis tus nqi tsim nyog ntawm kev tawm tsam kev sib txuas tau txo qis. Nws yog txaus los xaiv tus yuam sij server ib zaug thiab tawg qhov encryption rau tag nrho cov kev sib txuas tom ntej los ntawm lub sijhawm ntawd.

Thiab ua ntej peb tsiv mus, muaj ib qho kev tawm tsam siab heev uas yuav tsum tau hais ...

Oracle nres

Cryptographic attacks: piav qhia rau lub siab tsis meej pemMoxie Marlinspike zoo tshaj plaws hu ua leej txiv ntawm tus ntoo khaub lig-platform crypto messaging app Signal; tab sis peb tus kheej nyiam ib qho ntawm nws qhov kev tsim kho tshiab tsawg dua - lub hauv paus ntsiab lus ntawm cryptographic doom (Cryptographic Doom Txoj Cai). Txhawm rau piav me ntsis, peb tuaj yeem hais qhov no: “Yog tias txoj cai ua tiav txhua yam ua haujlwm cryptographic ntawm cov lus los ntawm qhov muaj peev xwm ua phem thiab coj txawv txawv nyob ntawm qhov tshwm sim, nws yuav raug puas tsuaj. " Los yog hauv daim ntawv ntse dua: "Tsis txhob muab cov ntaub ntawv los ntawm tus yeeb ncuab rau kev ua, thiab yog tias koj yuav tsum tau, ces tsawg kawg tsis txhob qhia qhov tshwm sim."

Cia peb tso tseg tsis pub dhau, hais kom txhaj tshuaj, thiab lwm yam; lawv dhau qhov kev sib tham no. Kev ua txhaum cai ntawm "doom txoj cai" ua rau muaj kev cuam tshuam crypto loj heev vim qhov tseeb tias cov txheej txheem coj raws nraim li qhov xav tau.

Raws li ib qho piv txwv, cia peb coj tus qauv tsim tsis tseeb nrog rau qhov tsis zoo hloov pauv cipher, thiab tom qab ntawd ua kom pom qhov muaj peev xwm tawm tsam. Thaum peb twb tau pom qhov kev tawm tsam ntawm kev hloov pauv cipher siv qhov ntsuas zaus, nws tsis yog "lwm txoj hauv kev los rhuav tshem tib lub cipher." Ntawm qhov tsis sib xws, kev tawm tsam oracle yog qhov kev tsim kho tshiab ntau dua, siv tau rau ntau qhov xwm txheej uas qhov kev soj ntsuam zaus ua tsis tiav, thiab peb yuav pom qhov ua qauv qhia ntawm qhov no hauv ntu tom ntej. Ntawm no qhov yooj yim cipher tsuas yog xaiv los ua tus piv txwv kom meej.

Yog li Alice thiab Bob sib txuas lus siv qhov yooj yim hloov pauv cipher siv tus yuam sij paub tsuas yog rau lawv. Lawv nruj heev txog qhov ntev ntawm cov lus: lawv muaj raws nraim 20 cim ntev. Yog li lawv tau pom zoo tias yog ib tus neeg xav xa cov lus luv dua, lawv yuav tsum ntxiv qee cov ntawv sau rau qhov kawg ntawm cov lus kom ua tau raws nraim 20 cim. Tom qab qee qhov kev sib tham, lawv txiav txim siab tias lawv tsuas lees txais cov ntawv hauv qab no dummy: a, bb, ccc, dddd thiab lwm yam. Yog li, cov ntawv nyeem dummy ntawm txhua qhov ntev yuav tsum paub.

Thaum Alice los yog Bob tau txais cov lus, lawv thawj zaug xyuas tias cov lus yog qhov ntev (20 cim) thiab cov lus xaus yog cov ntawv nyeem tsis raug. Yog tias qhov no tsis yog, ces lawv teb nrog cov lus yuam kev tsim nyog. Yog tias cov ntawv nyeem ntev thiab cov ntawv dummy zoo, tus neeg tau txais kev nyeem cov lus nws tus kheej thiab xa cov lus teb encrypted.

Thaum lub sij hawm tawm tsam, tus neeg tawm tsam impersonates Bob thiab xa cov lus cuav rau Alice. Cov lus tsis muaj tseeb - tus neeg tawm tsam tsis muaj tus yuam sij, thiab yog li tsis tuaj yeem tsim cov lus muaj txiaj ntsig. Tab sis txij li cov txheej txheem ua txhaum txoj cai doom, tus neeg tawm tsam tseem tuaj yeem ntes Alice kom nthuav tawm cov ntaub ntawv tseem ceeb, raws li qhia hauv qab no.

Tub sab: PREWF ZHJKL MMMN. LA

Alice: Invalid dummy ntawv.

Tub sab: PREWF ZHJKL MMMN. LB

Alice: Invalid dummy ntawv.

Tub sab: PREWF ZHJKL MMMN. LC

Alice: ILCT? TLCT RUWO PUT KCAW CPS OWPOW!

Tus tub sab tsis paub dab tsi Alice nyuam qhuav hais, tab sis sau tseg tias lub cim C yuav tsum sib phim a, txij li thaum Alice lees txais cov ntawv dummy.

Tub sab: REWF ZHJKL MMMN. LAA

Alice: Invalid dummy ntawv.

Tub sab: REWF ZHJKL MMMN. LBB

Alice: Invalid dummy ntawv.

Tom qab ntau qhov kev sim ...

Tub sab: REWF ZHJKL MMMN. LGG

Alice: Invalid dummy ntawv.

Tub sab: REWF ZHJKL MMMN. LHH

Alice: TLQO JWCRO FQAW SUY LCR C OWQXYJW. IW PWWR TU TCFA CHUYT TLQO JWFCTQUPOLQZ.

Ntxiv dua thiab, tus neeg tawm tsam tsis paub tias Alice nyuam qhuav hais li cas, tab sis sau tseg tias H yuav tsum sib phim b txij li Alice txais cov ntawv dummy.

Thiab yog li ntawd mus txog thaum tus neeg tawm tsam paub lub ntsiab lus ntawm txhua tus cwj pwm.

Thaum xub thawj siab ib muag, txoj kev zoo li ib tug xaiv plaintext nres. Thaum kawg, tus neeg tawm tsam xaiv cov ntawv ciphertexts, thiab cov neeg rau zaub mov mloog lus ua lawv. Qhov sib txawv tseem ceeb uas ua rau cov kev tawm tsam no tuaj yeem siv tau hauv lub ntiaj teb tiag tiag yog tias tus neeg tawm tsam tsis tas yuav nkag mus rau cov ntawv teev lus tseeb - cov lus teb rau cov neeg rau zaub mov, txawm tias ib qho tsis muaj txiaj ntsig li "Cov ntawv tsis raug cai," txaus.

Thaum qhov kev tawm tsam tshwj xeeb no yog kev qhia, tsis txhob daig rau ntawm qhov tshwj xeeb ntawm "dummy text" tswvyim, qhov tshwj xeeb cryptosystem siv, lossis cov kab lus tseeb ntawm cov lus xa los ntawm tus neeg tawm tsam. Lub tswv yim yooj yim yog li cas Alice reacts txawv raws li cov khoom ntawm cov ntawv dawb, thiab ua li ntawd yam tsis tau lees paub tias cov ntawv ciphertext sib raug tau los ntawm ib tog neeg ntseeg. Yog li, Alice tso cai rau tus neeg tawm tsam los nyem cov ntaub ntawv zais tawm ntawm nws cov lus teb.

Muaj ntau yam uas tuaj yeem hloov pauv hauv qhov xwm txheej no. Cov cim uas Alice ua rau, lossis qhov sib txawv ntawm nws tus cwj pwm, lossis txawm tias siv cryptosystem. Tab sis lub hauv paus ntsiab lus yuav nyob twj ywm tib yam, thiab kev tawm tsam tag nrho yuav nyob twj ywm hauv ib daim ntawv lossis lwm qhov. Qhov kev siv yooj yim ntawm qhov kev tawm tsam no tau pab nthuav tawm ntau yam kab mob kev nyab xeeb, uas peb yuav saib sai sai; tab sis ua ntej muaj qee qhov kev kawm theoretical yuav tsum tau kawm. Yuav ua li cas siv qhov tsis tseeb "Alice tsab ntawv" nyob rau hauv qhov kev tawm tsam uas tuaj yeem ua haujlwm ntawm lub cipher niaj hnub no? Puas yog qhov no ua tau, txawm tias hauv kev xav?

Xyoo 1998, Swiss cryptographer Daniel Bleichenbacher teb cov lus nug no hauv qhov kev lees paub. Nws tau nthuav tawm qhov kev tawm tsam oracle ntawm kev siv dav dav rau pej xeem tus lej cryptosystem RSA, siv cov phiaj xwm tshwj xeeb. Hauv qee qhov kev siv RSA, tus neeg rau zaub mov teb nrog cov lus yuam kev sib txawv nyob ntawm seb cov ntawv nyeem puas phim cov tswv yim lossis tsis; qhov no yog txaus los ua tawm tsam.

Plaub xyoos tom qab ntawd, xyoo 2002, tus kws sau ntawv Fabkis txoj Serge Vaudenay tau qhia txog qhov kev tawm tsam ntawm kev tawm tsam yuav luag zoo ib yam li ib qho uas tau piav qhia hauv Alice qhov xwm txheej saum toj no - tshwj tsis yog tias es tsis txhob siv cov ntawv cuav, nws tau tsoo tag nrho cov chav kawm ntawm cov ciphers niaj hnub uas tib neeg siv tiag tiag. Tshwj xeeb, Vaudenay's attack aims fixed input size ciphers ("block ciphers") thaum lawv siv nyob rau hauv thiaj li hu ua "CBC encryption hom" thiab nrog ib tug tej yam nrov padding tswvyim, yeej sib npaug rau ib tug nyob rau hauv lub Alice scenario.

Tsis tas li ntawd nyob rau hauv 2002, American cryptographer John Kelsey - co-sau Tw - tau npaj ntau yam kev tawm tsam ntawm cov kab ke uas nthuav cov lus thiab tom qab ntawd nkag mus rau lawv. Qhov tseem ceeb tshaj plaws ntawm cov no yog qhov kev tawm tsam uas tau coj kom zoo dua qhov tseeb tias feem ntau muaj peev xwm ua kom pom qhov ntev ntawm cov ntawv dawb los ntawm qhov ntev ntawm cov ntawv ciphertext. Hauv txoj kev xav, qhov no tso cai rau kev tawm tsam oracle uas rov qab los ntawm cov ntsiab lus qub.

Hauv qab no peb muab cov lus piav qhia ntxaws ntxiv ntawm Vaudenay thiab Kelsey tawm tsam (peb yuav muab cov lus piav qhia ntxaws ntxiv ntawm Bleichenbacher nres thaum peb txav mus rau kev tawm tsam ntawm pej xeem cov ntsiab lus cryptography). Txawm hais tias peb siv zog ua haujlwm zoo tshaj plaws, cov ntawv nyeem dhau los ua ib qho txuj ci; yog li yog tias cov saum toj no txaus rau koj, hla ob ntu tom ntej.

Vodene kev tawm tsam

Yuav kom nkag siab txog Vaudenay nres, peb thawj zaug yuav tsum tham me ntsis ntxiv txog kev thaiv ciphers thiab hom encryption. Ib tug "block cipher" yog, raws li tau hais, ib tug cipher uas siv ib tug yuam sij thiab ib tug input ntawm ib tug ntev ntev ("block length") thiab tsim ib tug encrypted block ntawm tib ntev. Block ciphers tau siv dav thiab suav tias muaj kev nyab xeeb. Tam sim no so haujlwm DES, suav tias yog thawj tus lej niaj hnub no, yog qhov thaiv cipher. Raws li tau hais los saum no, tib yam muaj tseeb rau AES, uas tau siv dav rau niaj hnub no.

Hmoov tsis zoo, thaiv ciphers muaj ib qho tsis muaj zog. Qhov loj block loj yog 128 khoom, lossis 16 cim. Obviously, niaj hnub cryptography yuav tsum tau ua hauj lwm nrog loj input cov ntaub ntawv, thiab qhov no yog qhov twg encryption hom tuaj rau hauv kev ua si. Encryption hom yog qhov tseem ceeb ntawm kev hack: nws yog ib txoj hauv kev siv lub thaiv cipher uas tsuas yog lees txais cov tswv yim ntawm qee qhov loj rau kev nkag siab ntawm qhov ntev.

Vodene qhov kev tawm tsam yog tsom rau qhov nrov CBC (Cipher Block Chaining) hom kev ua haujlwm. Qhov kev tawm tsam kho lub hauv paus block cipher raws li ib tug tej yam yees siv, impregnable dub lub thawv thiab tag nrho bypasses nws kev ruaj ntseg.

Nov yog daim duab qhia tias CBC hom ua haujlwm li cas:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Lub voj voog ntxiv qhia txog XOR (tsuas yog OR) ua haujlwm. Piv txwv li, qhov thib ob block ntawm ciphertext tau txais:

  1. Los ntawm kev ua haujlwm XOR ntawm qhov thib ob plaintext block nrog thawj ciphertext block.
  2. Encrypting lub resulting block nrog ib tug thaiv cipher siv tus yuam sij.

Txij li thaum CBC ua rau kev siv hnyav ntawm kev ua haujlwm binary XOR, cia peb siv sijhawm los nco qab qee yam ntawm nws cov khoom:

  • Idempotency: Cryptographic attacks: piav qhia rau lub siab tsis meej pem
  • Kev sib txuas lus: Cryptographic attacks: piav qhia rau lub siab tsis meej pem
  • Associativity: Cryptographic attacks: piav qhia rau lub siab tsis meej pem
  • Self-reversibility: Cryptographic attacks: piav qhia rau lub siab tsis meej pem
  • Byte loj: byte n ntawm Cryptographic attacks: piav qhia rau lub siab tsis meej pem = (byte n Cryptographic attacks: piav qhia rau lub siab tsis meej pem) Cryptographic attacks: piav qhia rau lub siab tsis meej pem (byte n Cryptographic attacks: piav qhia rau lub siab tsis meej pem)

Feem ntau, cov khoom no txhais tau tias yog tias peb muaj qhov sib npaug nrog XOR cov haujlwm thiab ib qho tsis paub, nws tuaj yeem daws tau. Piv txwv li, yog peb paub li ntawd Cryptographic attacks: piav qhia rau lub siab tsis meej pem nrog tus tsis paub Cryptographic attacks: piav qhia rau lub siab tsis meej pem thiab nto moo Cryptographic attacks: piav qhia rau lub siab tsis meej pem и Cryptographic attacks: piav qhia rau lub siab tsis meej pem, ces peb tuaj yeem tso siab rau cov khoom hais saum toj no los daws qhov sib npaug rau Cryptographic attacks: piav qhia rau lub siab tsis meej pem. Los ntawm kev thov XOR ntawm ob sab ntawm qhov sib npaug nrog Cryptographic attacks: piav qhia rau lub siab tsis meej pem, peb tau Cryptographic attacks: piav qhia rau lub siab tsis meej pem. Qhov no txhua yam yuav dhau los ua qhov tseem ceeb hauv ib pliag.

Muaj ob qhov sib txawv me me thiab qhov sib txawv loj ntawm peb qhov xwm txheej Alice thiab Vaudenay qhov kev tawm tsam. Ob tug me me:

  • Nyob rau hauv tsab ntawv, Alice xav kom cov ntawv nyeem kom xaus nrog cov cim a, bb, ccc thiab lwm yam. Hauv kev tawm tsam Wodene, tus neeg raug tsim txom xav kom cov ntsiab lus xaus N lub sij hawm nrog N byte (uas yog, hexadecimal 01 lossis 02 02, lossis 03 03 03, thiab lwm yam). Qhov no yog qhov sib txawv ntawm cov tshuaj pleev ib ce.
  • Hauv Alice scenario, nws yooj yim los qhia seb Alice puas tau txais cov lus los ntawm cov lus teb "Cov ntawv sau tsis raug." Hauv Vodene qhov kev tawm tsam, kev tshuaj xyuas ntau dua yog xav tau thiab kev ua kom meej meej ntawm tus neeg raug tsim txom yog qhov tseem ceeb; tab sis rau lub hom phiaj ntawm brevity, cia peb coj nws raws li qhov muab tias qhov kev tshuaj ntsuam no tseem ua tau.

Qhov txawv tseem ceeb:

  • Txij li thaum peb tsis siv tib lub cryptosystem, kev sib raug zoo ntawm tus neeg tawm tsam-tswj ciphertext bytes thiab cov lus zais (qhov tseem ceeb thiab cov ntawv dawb) yuav pom tseeb txawv. Yog li ntawd, tus neeg tawm tsam yuav tau siv lub tswv yim sib txawv thaum tsim cov ntawv ciphertexts thiab txhais cov lus teb rau cov neeg rau zaub mov.

Qhov sib txawv loj no yog qhov kawg ntawm qhov kev sib tw kom nkag siab txog Vaudenay nres, yog li cia peb siv sijhawm los xav txog vim li cas thiab yuav ua li cas lub oracle nres ntawm CBC tuaj yeem raug teeb tsa hauv thawj qhov chaw.

Piv txwv tias peb tau txais CBC ciphertext ntawm 247 blocks, thiab peb xav decrypt nws. Peb tuaj yeem xa cov lus cuav rau lub server, ib yam li peb tuaj yeem xa cov lus cuav rau Alice ua ntej. Tus neeg rau zaub mov yuav decrypt cov lus rau peb, tab sis yuav tsis qhia lub decryption - hloov, dua, raws li nrog Alice, tus neeg rau zaub mov yuav qhia ib me ntsis ntawm cov ntaub ntawv: seb lub plaintext puas siv tau padding los yog tsis.

Xav txog tias hauv Alice qhov xwm txheej peb muaj kev sib raug zoo hauv qab no:

$$display$$text{SIMPLE_SUBSTITUTION}(text{ciphertext},text{key}) = text{plaintext}$$display$$

Cia peb hu qhov no "Alice's equation." Peb tswj cov ntawv ciphertext; tus neeg rau zaub mov (Alice) tau xau cov ntaub ntawv tsis meej txog cov ntawv tau txais; thiab qhov no tau tso cai rau peb txiav txim siab cov ntaub ntawv hais txog qhov kawg ntawm qhov tseem ceeb - qhov tseem ceeb. Los ntawm kev sib piv, yog tias peb tuaj yeem pom qhov kev sib txuas rau CBC tsab ntawv, peb yuav tuaj yeem rho tawm qee cov ntaub ntawv zais cia rau ntawd thiab.

Luckily, muaj tiag tiag kev sib raug zoo tawm muaj uas peb siv tau. Xav txog qhov tso zis ntawm qhov kawg hu rau decrypt ib block cipher thiab qhia qhov tso zis no li Cryptographic attacks: piav qhia rau lub siab tsis meej pem. Peb kuj qhia txog cov blocks ntawm cov ntawv dawb Cryptographic attacks: piav qhia rau lub siab tsis meej pem thiab ciphertext blocks Cryptographic attacks: piav qhia rau lub siab tsis meej pem. Ua tib zoo saib ntawm daim duab CBC thiab pom tias muaj dab tsi tshwm sim:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Cia peb hu qhov no "CBC equation."

Hauv Alice's scenario, los ntawm kev saib xyuas cov ntawv ciphertext thiab saib cov ntaub ntawv sib xws, peb tuaj yeem txhim kho qhov kev tawm tsam uas tau rov qab los rau lub sijhawm thib peb hauv qhov sib npaug - tus yuam sij. Hauv qhov xwm txheej CBC, peb kuj saib xyuas cov ntawv ciphertext thiab saib xyuas cov ntaub ntawv xau ntawm cov ntsiab lus sib thooj. Yog tias qhov piv txwv tuav, peb tuaj yeem tau txais cov ntaub ntawv hais txog Cryptographic attacks: piav qhia rau lub siab tsis meej pem.

Cia peb xav tias peb rov qab los tiag tiag Cryptographic attacks: piav qhia rau lub siab tsis meej pem, yog li cas? Zoo, tom qab ntawd peb tuaj yeem luam tag nrho cov ntawv kawg ntawm cov ntawv nyeem ib zaug (Cryptographic attacks: piav qhia rau lub siab tsis meej pem), tsuas yog nkag mus Cryptographic attacks: piav qhia rau lub siab tsis meej pem (uas peb muaj) thiab
tau txais Cryptographic attacks: piav qhia rau lub siab tsis meej pem nyob rau hauv qhov sib npaug ntawm CBC.

Tam sim no peb muaj kev cia siab rau tag nrho cov phiaj xwm kev tawm tsam, nws yog lub sijhawm los ua kom tiav cov ntsiab lus. Thov ua tib zoo saib raws nraim li cas cov ntaub ntawv plaintext tau leaked ntawm lub server. Hauv Alice tsab ntawv, qhov xau tshwm sim vim Alice tsuas yog teb nrog cov lus raug yog tias $inline$text{SIMPLE_SUBSTITUTION}(text{ciphertext}, ntawv nyeem{key})$inline$ xaus nrog kab a (los yog bb, thiab lwm yam, tab sis qhov muaj feem ntawm cov mob no tshwm sim los ntawm lub caij nyoog tsawg heev). Zoo ib yam li CBC, tus neeg rau zaub mov lees txais cov padding yog thiab tsuas yog yog tias Cryptographic attacks: piav qhia rau lub siab tsis meej pem xaus rau hauv hexadecimal 01. Yog li cia peb sim tib qhov ua kom yuam kev: xa cov ntawv ciphertexts cuav nrog peb tus kheej tus nqi cuav Cryptographic attacks: piav qhia rau lub siab tsis meej pemkom txog thaum tus neeg rau zaub mov lees txais qhov sau.

Thaum tus neeg rau zaub mov lees txais qhov padding rau ib qho ntawm peb cov lus cuav, nws txhais tau tias:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Tam sim no peb siv cov cuab yeej byte-byte XOR:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Peb paub cov lus thawj thiab thib peb. Thiab peb twb tau pom tias qhov no tso cai rau peb rov qab tau lub sij hawm ntxiv - qhov kawg byte los ntawm Cryptographic attacks: piav qhia rau lub siab tsis meej pem:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Qhov no kuj muab peb cov byte kawg ntawm qhov kawg plaintext thaiv ntawm CBC kab zauv thiab cov cuab yeej byte-by-byte.

Peb tuaj yeem tso nws ntawm qhov ntawd thiab txaus siab tias peb tau ua qhov kev tawm tsam ntawm qhov muaj zog theoretically cipher. Tab sis qhov tseeb peb tuaj yeem ua ntau ntxiv: peb tuaj yeem rov qab tau tag nrho cov ntawv. Qhov no yuav tsum tau ua kom yuam kev uas tsis nyob hauv Alice tus thawj tsab ntawv thiab tsis tas yuav tsum muaj kev tawm tsam oracle, tab sis nws tseem tsim nyog kawm.

Txhawm rau kom nkag siab nws, ua ntej nco ntsoov tias qhov tshwm sim ntawm kev tso tawm tus nqi raug ntawm cov byte kawg yog Cryptographic attacks: piav qhia rau lub siab tsis meej pem peb muaj peev xwm tshiab. Tam sim no, thaum forging ciphertexts, peb tuaj yeem tswj hwm qhov kawg byte ntawm cov ntsiab lus sib thooj. Ib zaug ntxiv, qhov no muaj feem xyuam rau CBC kab zauv thiab cov cuab yeej byte-by-byte:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Txij li tam sim no peb paub lub sij hawm thib ob, peb tuaj yeem siv peb txoj kev tswj hwm thawj zaug los tswj lub thib peb. Peb tsuas yog xam:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Peb tsis tuaj yeem ua qhov no ua ntej vim tias peb tsis muaj qhov kawg byte tsis tau Cryptographic attacks: piav qhia rau lub siab tsis meej pem.

Qhov no yuav pab tau peb li cas? Piv txwv tias peb tam sim no tsim tag nrho cov ntawv ciphertexts xws li nyob rau hauv cov ntaub ntawv sib raug zoo kawg byte yog sib npaug. 02. Tam sim no tus neeg rau zaub mov tsuas yog lees txais padding yog tias cov ntawv sau xaus nrog 02 02. Txij li thaum peb tau kho qhov kawg byte, qhov no tsuas yog tshwm sim yog tias penultimate byte ntawm cov ntawv dawb kuj tseem yog 02. Peb tseem xa cov ntawv cuav ciphertext blocks, hloov cov penultimate byte, kom txog thaum lub server lees txais padding rau ib qho ntawm lawv. Hauv qhov no peb tau txais:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Thiab peb restore lub penultimate byte Cryptographic attacks: piav qhia rau lub siab tsis meej pem ib yam li lub xeem dhau los. Peb txuas ntxiv mus rau tib lub siab: peb kho qhov kawg ntawm ob bytes ntawm cov ntawv nyeem rau 03 03, peb rov ua qhov kev tawm tsam no rau qhov thib peb byte ntawm qhov kawg thiab lwm yam, thaum kawg rov ua kom tiav Cryptographic attacks: piav qhia rau lub siab tsis meej pem.

Yuav ua li cas txog cov ntawv nyeem? Thov nco ntsoov tias tus nqi Cryptographic attacks: piav qhia rau lub siab tsis meej pem yog tiag $inline$text{BLOCK_DECRYPT}(text{key},C_{247})$inline$. Peb tuaj yeem muab lwm qhov thaiv Cryptographic attacks: piav qhia rau lub siab tsis meej pem, thiab kev tawm tsam tseem yuav ua tiav. Qhov tseeb, peb tuaj yeem hais kom tus neeg rau zaub mov ua $inline$text{BLOCK_DECRYPT}$inline$ rau txhua yam ntaub ntawv. Thaum lub sijhawm no, nws yog qhov kev ua si dhau - peb tuaj yeem txiav txim siab ib qho ciphertext (saib lwm qhov CBC decryption daim duab pom qhov no; thiab nco ntsoov tias IV yog pej xeem).

Txoj kev tshwj xeeb no ua lub luag haujlwm tseem ceeb hauv kev tawm tsam oracle uas peb yuav ntsib tom qab.

Kelsey qhov kev tawm tsam

Peb lub koom haum John Kelsey tau tso tawm cov hauv paus ntsiab lus ntawm ntau qhov kev tawm tsam, tsis yog cov ntsiab lus ntawm kev tawm tsam tshwj xeeb ntawm ib qho cipher. Nws 2002 kab lus ntawm lub xyoo yog kev kawm txog kev tawm tsam ntawm cov ntaub ntawv encrypted compressed. Koj puas xav tias cov ntaub ntawv uas cov ntaub ntawv raug compressed ua ntej encryption tsis txaus los tawm tsam? Nws hloov tawm tias txaus.

Qhov kev xav tsis thoob no yog vim muaj ob lub hauv paus ntsiab lus. Ua ntej, muaj kev sib raug zoo ntawm qhov ntev ntawm cov ntawv dawb thiab qhov ntev ntawm cov ntawv ciphertext; rau ntau tus lej ciphers tseeb sib npaug. Thib ob, thaum compression ua tiav, kuj tseem muaj kev sib raug zoo ntawm qhov ntev ntawm cov lus compressed thiab qib ntawm "noisiness" ntawm cov ntawv dawb, uas yog, qhov feem pua ​​​​ntawm cov cim tsis rov ua dua (lub ntsiab lus yog "siab entropy"). ).

Txhawm rau pom lub hauv paus ntsiab lus ntawm kev nqis tes ua, xav txog ob lub ntsiab lus:

Plaintext 1: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

Plaintext 2: ATVXCAGTRSVPTVVULSJQHGEYCMQPCRQBGCYIXCFJGJ

Cia peb xav tias ob qho tib si plaintexts yog compressed thiab ces encrypted. Koj tau txais ob qhov txiaj ntsig ciphertexts thiab yuav tsum twv seb qhov twg ciphertext ntais ntawv twg:

Ciphertext 1: PVOVEYBPJDPVANEAWVGCIUWAABCIYIKOOURMYDTA

Ciphertext 2: DWKJZXYU

Cov lus teb yog qhov tseeb. Ntawm cov plaintexts, tsuas yog plaintext 1 tuaj yeem muab tso rau hauv qhov ntev meager ntawm qhov thib ob ciphertext. Peb xam qhov no tsis paub dab tsi txog compression algorithm, tus yuam sij encryption, lossis txawm tias tus lej cim nws tus kheej. Piv nrog rau cov hierarchy ntawm qhov ua tau cryptographic tawm tsam, qhov no yog hom vwm.

Kelsey hais ntxiv tias nyob rau hauv qee qhov xwm txheej txawv txav no kuj tseem tuaj yeem siv los ua kev tawm tsam oracle. Tshwj xeeb, nws piav qhia txog yuav ua li cas tus neeg tawm tsam tuaj yeem rov qab tau cov ntaub ntawv zais cia yog tias nws tuaj yeem yuam tus neeg rau zaub mov kom encrypt cov ntaub ntawv (cov ntawv sau ua raws li. Cryptographic attacks: piav qhia rau lub siab tsis meej pemthaum nws tswj tau Cryptographic attacks: piav qhia rau lub siab tsis meej pem thiab tuaj yeem tshawb xyuas qhov ntev ntawm cov txiaj ntsig encrypted.

Ib zaug ntxiv, zoo li lwm qhov kev tawm tsam oracle, peb muaj kev sib raug zoo:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Ntxiv dua thiab, peb tswj ib lub sijhawm (Cryptographic attacks: piav qhia rau lub siab tsis meej pem), peb pom qhov xau me me ntawm cov ntaub ntawv hais txog lwm tus tswv cuab (ciphertext) thiab sim rov qab qhov kawg (plaintext). Txawm hais tias muaj kev sib piv, qhov no yog qhov xwm txheej txawv me ntsis piv rau lwm qhov kev tawm tsam oracle peb tau pom.

Txhawm rau qhia seb qhov kev tawm tsam no yuav ua haujlwm li cas, cia peb siv lub tswv yim tsis tseeb compression uas peb nyuam qhuav tuaj nrog: TOYZIP. Nws saib cov kab ntawv uas tau tshwm sim yav dhau los hauv cov ntawv nyeem thiab hloov lawv nrog peb qhov chaw nyob bytes uas qhia qhov twg yuav pom qhov piv txwv ua ntej ntawm kab thiab pes tsawg zaus nws tshwm nyob ntawd. Piv txwv li, kab helloworldhello tuaj yeem compressed rau hauv helloworld[00][00][05] 13 bytes ntev piv rau thawj 15 bytes.

Xav tias tus neeg tawm tsam sim rov qab cov ntsiab lus ntawm ib daim ntawv password=..., qhov twg tus password nws tus kheej tsis paub. Raws li Kelsey tus qauv kev tawm tsam, tus neeg tawm tsam tuaj yeem nug tus neeg rau zaub mov kom nthuav tawm thiab tom qab ntawd nkag mus rau hauv daim ntawv cov lus (plaintext ua raws li. Cryptographic attacks: piav qhia rau lub siab tsis meej pem), qhov twg Cryptographic attacks: piav qhia rau lub siab tsis meej pem - ntawv nyeem dawb. Thaum tus neeg rau zaub mov tau ua tiav lawm, nws qhia qhov ntev ntawm qhov tshwm sim. Kev tawm tsam mus zoo li no:

Tub sab: Thov compress thiab encrypt cov plaintext yam tsis muaj padding.

Server: Cov txiaj ntsig ntev 14.

Tub sab: Thov compress thiab encrypt cov plaintext uas yog ntxiv rau password=a.

Server: Cov txiaj ntsig ntev 18.

Lub cracker sau: [thawj 14] + [peb bytes uas hloov password=] + a

Tub sab: Thov compress thiab encrypt cov plaintext uas tau ntxiv password=b.

Server: Cov txiaj ntsig ntev 18.

Tub sab: Thov compress thiab encrypt cov plaintext uas tau ntxiv password=с.

Server: Cov txiaj ntsig ntev 17.

Lub cracker sau: [thawj 14] + [peb bytes uas hloov password=c]. Qhov no xav tias tus thawj plaintext muaj cov hlua password=c. Ntawd yog, tus password pib nrog tsab ntawv c

Tub sab: Thov compress thiab encrypt cov plaintext uas tau ntxiv password=сa.

Server: Cov txiaj ntsig ntev 18.

Lub cracker sau: [thawj 14] + [peb bytes uas hloov password=с] + a

Tub sab: Thov compress thiab encrypt cov plaintext uas tau ntxiv password=сb.

Server: Cov txiaj ntsig ntev 18.

(… Qee lub sij hawm tom qab…)

Tub sab: Thov compress thiab encrypt cov plaintext uas tau ntxiv password=со.

Server: Cov txiaj ntsig ntev 17.

Lub cracker sau: [thawj 14] + [peb bytes uas hloov password=co]. Siv tib lub logic, tus neeg tawm tsam xaus lus tias tus password pib nrog cov ntawv co

Thiab yog li ntawd kom txog thaum tag nrho tus password rov qab.

Tus nyeem ntawv yuav raug zam txim rau qhov xav tias qhov no yog ib qho kev qhia ua haujlwm nkaus xwb thiab qhov xwm txheej zoo li no yuav tsis tshwm sim hauv ntiaj teb tiag. Alas, raws li peb yuav pom sai sai no, nws yog qhov zoo dua tsis txhob muab tso rau hauv cryptography.

Hom vulnerabilities: CRIME, POODLE, DROWN

Thaum kawg, tom qab kawm txoj kev xav kom ntxaws, peb tuaj yeem pom tias cov tswv yim no tau siv li cas hauv kev tawm tsam cryptographic tiag tiag.

HLOOV

Cryptographic attacks: piav qhia rau lub siab tsis meej pemYog tias qhov kev tawm tsam yog tsom rau tus neeg raug tsim txom browser thiab network, qee qhov yuav yooj yim dua thiab qee qhov yuav nyuaj dua. Piv txwv li, nws yooj yim pom tus neeg raug tsim txom cov tsheb khiav: tsuas yog zaum nrog nws hauv tib lub tsev noj mov nrog WiFi. Vim li no, cov neeg raug tsim txom (piv txwv li txhua tus) feem ntau qhia kom siv kev sib txuas encrypted. Nws yuav nyuaj dua, tab sis tseem ua tau, ua HTTP thov sawv cev ntawm tus neeg raug tsim txom rau qee qhov chaw thib peb (piv txwv li, Google). Tus neeg tawm tsam yuav tsum ntxias tus neeg raug tsim txom mus rau nplooj ntawv siab phem nrog ib tsab ntawv uas ua rau qhov kev thov. Lub web browser yuav cia li muab cov ncuav qab zib sib kho kom haum.

Qhov no zoo li amazing. Yog Bob mus evil.com, tuaj yeem tsab ntawv ntawm lub xaib no tsuas yog nug Google kom email Bob tus password rau [email protected]? Zoo, hauv txoj kev xav yog, tab sis qhov tseeb tsis muaj. Qhov xwm txheej no yog hu ua cross-site thov forgery attack (Hla-Site Request Forgery, CSRF), thiab nws tau nrov nyob ib ncig ntawm nruab nrab-90s. Hnub no yog evil.com sim ua kom yuam kev no, Google (lossis ib lub vev xaib hwm tus kheej) feem ntau yuav teb nrog, "Zoo, tab sis koj CSRF token rau qhov kev pauv no yuav yog ... um ... три триллиона и семь. Thov rov ua tus lej no." Cov browsers niaj hnub no muaj qee yam hu ua "ib txoj cai hauv keeb kwm" uas cov ntawv sau rau ntawm qhov chaw A tsis muaj kev nkag mus rau cov ntaub ntawv xa los ntawm lub vev xaib B. Yog li tsab ntawv ntawm evil.com tuaj yeem xa cov lus thov rau google.com, tab sis tsis tuaj yeem nyeem cov lus teb lossis ua tiav qhov kev hloov pauv.

Peb yuav tsum hais meej tias tshwj tsis yog Bob siv kev sib txuas encrypted, tag nrho cov kev tiv thaiv no tsis muaj qab hau. Tus neeg tawm tsam tuaj yeem nyeem Bob txoj kev khiav tsheb thiab rov qab tau Google cov khoom qab zib sib kho. Nrog rau cov ncuav qab zib no, nws yuav tsuas qhib Google tab tshiab yam tsis tau tawm ntawm nws tus kheej browser thiab ua tus Bob yam tsis tau ntsib pesky tib txoj cai. Tab sis, hmoov tsis rau ib tug tub sab, qhov no tau dhau los ua tsawg thiab tsawg dua. Hauv Is Taws Nem tag nrho tau tshaj tawm ntev txog kev ua tsov rog ntawm kev sib txuas uas tsis muaj kev sib txuas, thiab Bob txoj kev tawm mus yog tej zaum yuav encrypted, txawm nws nyiam los tsis nyiam. Tsis tas li ntawd, txij thaum pib ntawm kev ua raws li txoj cai, kev khiav tsheb kuj yog poob qis ua ntej encryption; qhov no yog ib qho kev coj ua los txo latency.

Qhov no yog qhov uas nws los rau hauv kev ua si HLOOV (Compression Ratio Infoleak Ua Yooj Yim, yooj yim to los ntawm compression piv). Qhov teeb meem tau tshwm sim thaum lub Cuaj Hlis 2012 los ntawm cov kws tshawb fawb txog kev ruaj ntseg Juliano Rizzo thiab Thai Duong. Peb twb tau tshuaj xyuas tag nrho theoretical hauv paus, uas tso cai rau peb nkag siab tias lawv tau ua dab tsi thiab yuav ua li cas. Tus neeg tawm tsam tuaj yeem yuam Bob tus browser xa cov lus thov mus rau Google thiab tom qab ntawd mloog cov lus teb ntawm lub network hauv zos hauv daim ntawv compressed, encrypted. Yog li ntawd peb muaj:

Cryptographic attacks: piav qhia rau lub siab tsis meej pem

Ntawm no tus neeg tawm tsam tswj qhov kev thov thiab muaj kev nkag mus rau cov tsheb sniffer, suav nrog cov pob ntawv loj. Kelsey qhov xwm txheej tsis tseeb tau tshwm sim.

Nkag siab txog txoj kev xav, cov kws sau ntawv ntawm CRIME tau tsim ib qho kev siv uas tuaj yeem nyiag cov ncuav qab zib sib tham rau ntau qhov chaw, suav nrog Gmail, Twitter, Dropbox thiab Github. Qhov tsis zoo cuam tshuam rau feem ntau cov web browsers niaj hnub no, ua rau thaj tsam raug tso tawm uas ntsiag to faus lub compression feature hauv SSL kom nws yuav tsis siv txhua. Tsuas yog ib qho kev tiv thaiv los ntawm qhov tsis zoo yog qhov muaj txiaj ntsig Internet Explorer, uas tsis tau siv SSL compression txhua.

POODLE

Cryptographic attacks: piav qhia rau lub siab tsis meej pemThaum Lub Kaum Hli 2014, Google pab neeg ruaj ntseg tau ua nthwv dej hauv zej zog kev ruaj ntseg. Lawv muaj peev xwm siv tau qhov tsis zoo nyob rau hauv SSL raws tu qauv uas tau patched ntau tshaj kaum xyoo dhau los.

Nws hloov tawm hais tias thaum lub servers tab tom khiav lub ci tshiab TLSv1.2, ntau tus tau tso kev txhawb nqa rau cov cuab yeej cuab tam SSLv3 rau kev rov qab sib raug zoo nrog Internet Explorer 6. Peb twb tau tham txog kev tawm tsam downgrade, yog li koj tuaj yeem xav txog dab tsi tshwm sim. Ib qho zoo-orchestrated sabotage ntawm kev tuav tes raws tu qauv thiab cov servers tau npaj rov qab mus rau qhov qub SSLv3, qhov tseem ceeb undoing 15 xyoo dhau los ntawm kev tshawb fawb kev ruaj ntseg.

Rau cov ntsiab lus keeb kwm, Nov yog cov ntsiab lus luv luv ntawm keeb kwm ntawm SSL mus txog rau version 2 los ntawm Matthew Green:

Transport Layer Security (TLS) yog qhov tseem ceeb tshaj plaws kev ruaj ntseg raws tu qauv hauv Internet. [..] yuav luag txhua qhov kev sib pauv koj ua hauv Is Taws Nem yog nyob ntawm TLS. [..] Tab sis TLS tsis yog TLS ib txwm. Cov txheej txheem pib nws lub neej nyob rau hauv Netscape Kev Sib Txuas Lus hu ua "Secure Sockets Layer" lossis SSL. Cov lus xaiv muaj nws tias thawj version ntawm SSL yog qhov txaus ntshai heev uas cov neeg tsim khoom tau sau tag nrho cov ntawv luam tawm ntawm cov lej thiab muab faus rau hauv qhov chaw zais cia hauv New Mexico. Raws li qhov tshwm sim, thawj qhov kev tshaj tawm ntawm SSL yog qhov tseeb version SSL 2. Nws zoo nkauj txaus ntshai, thiab [..] nws yog ib yam khoom ntawm nruab nrab-90s, uas niaj hnub cryptographers suav hais tias yog "lub hnub nyoog tsaus nti ntawm crypto txiaj" Ntau qhov kev tawm tsam cryptographic uas phem tshaj plaws uas peb paub txog niaj hnub no tseem tsis tau pom. Raws li qhov tshwm sim, cov neeg tsim khoom ntawm SSLv2 raws tu qauv tau raug tso tseg kom fumble lawv txoj hauv kev tsaus ntuj, thiab lawv tau ntsib. ntau yam txaus ntshai monsters - rau lawv chagrin thiab peb cov txiaj ntsig, txij li kev tawm tsam ntawm SSLv2 tau tso cov tshooj lus tseem ceeb rau tiam tom ntej ntawm cov txheej txheem.

Ua raws li cov xwm txheej no, xyoo 1996, kev ntxhov siab Netscape rov tsim kho SSL raws tu qauv los ntawm kos. Qhov tshwm sim yog SSL version 3, uas kho ob peb paub txog kev ruaj ntseg teeb meem ntawm nws cov thawj.

Hmoov zoo rau cov tub sab, "ob peb" tsis txhais hais tias "tag nrho." Zuag qhia tag nrho, SSLv3 muab tag nrho cov tsev tsim nyog los tua Vodene nres. Cov txheej txheem siv CBC hom thaiv cipher thiab cov txheej txheem padding tsis ruaj ntseg (qhov no tau raug kho hauv TLS; yog li qhov xav tau rau kev tawm tsam qis). Yog tias koj nco qab cov tswv yim padding hauv peb cov lus piav qhia thawj zaug ntawm Vaudenay nres, SSLv3 tswv yim zoo sib xws.

Tab sis, hmoov tsis zoo rau cov tub sab, "zoo ib yam" tsis txhais hais tias "zoo tib yam." SSLv3 padding tswvyim yog "N random bytes ua raws li tus naj npawb N". Sim, nyob rau hauv cov xwm txheej no, xaiv ib qho kev xav ntawm cov ntawv ciphertext thiab mus dhau tag nrho cov kauj ruam ntawm Vaudene lub tswv yim qub: koj yuav pom tias qhov kev tawm tsam tau ua tiav qhov kawg byte los ntawm cov ntawv sib txuas ntawm cov ntawv dawb, tab sis tsis mus ntxiv. Decrypting txhua 16th byte ntawm lub ciphertext yog qhov ua kom yuam kev zoo, tab sis nws tsis yog yeej.

Tau ntsib nrog kev ua tsis tiav, pab pawg Google tau hloov mus rau qhov chaw kawg: lawv hloov mus rau tus qauv kev hem thawj muaj zog dua - ib qho siv hauv CRIME. Piv txwv tias tus attacker yog ib tsab ntawv khiav hauv tus neeg raug tsim txom lub browser tab thiab tuaj yeem rho tawm cov ncuav qab zib sib tham, qhov kev tawm tsam tseem yog qhov tseem ceeb. Txawm hais tias tus qauv kev hem thawj dav dav tsis tshua muaj tseeb, peb pom hauv ntu dhau los tias tus qauv tshwj xeeb no ua tau.

Muab qhov muaj peev xwm tawm tsam muaj zog dua no, kev tawm tsam tam sim no tuaj yeem txuas ntxiv mus. Nco ntsoov tias tus neeg tawm tsam paub qhov twg cov khoom qab zib encrypted tshwm nyob rau hauv header thiab tswj qhov ntev ntawm HTTP thov ua ntej nws. Yog li ntawd, nws muaj peev xwm tswj hwm qhov kev thov HTTP kom qhov kawg byte ntawm cov kua nplaum uas tau ua raws li qhov kawg ntawm qhov thaiv. Tam sim no cov byte no haum rau decryption. Koj tuaj yeem ntxiv ib tus cim rau qhov kev thov, thiab qhov kawg ntawm byte ntawm cov ncuav qab zib yuav nyob twj ywm hauv tib qhov chaw thiab tsim nyog rau kev xaiv siv tib txoj kev. Qhov kev tawm tsam txuas ntxiv ua qhov no kom txog thaum cov ntaub ntawv ncuav qab zib rov qab tag nrho. Nws hu ua POODLE: Padding Oracle ntawm Downgraded Legacy Encryption.

DUA

Cryptographic attacks: piav qhia rau lub siab tsis meej pemRaws li peb tau hais, SSLv3 muaj nws qhov tsis zoo, tab sis nws yog qhov txawv ntawm nws cov thawj coj, txij li cov leaky SSLv2 yog ib yam khoom ntawm lub sijhawm sib txawv. Muaj koj tuaj yeem cuam tshuam cov lus hauv nruab nrab: соглашусь на это только через мой труп tig mus rau hauv соглашусь на это; tus neeg siv khoom thiab cov neeg rau zaub mov tuaj yeem ntsib hauv online, tsim kev ntseeg siab thiab sib pauv cov lus zais nyob rau hauv pem hauv ntej ntawm tus neeg tawm tsam, uas tuaj yeem ua rau ob qho tib si yooj yim. Kuj tseem muaj qhov teeb meem nrog kev xa tawm crypto txiaj, uas peb tau hais thaum xav txog FREAK. Cov no yog cryptographic Sodom thiab Gomorrah.

Thaum Lub Peb Hlis 2016, ib pab neeg tshawb fawb los ntawm ntau qhov chaw sib txawv tau tuaj ua ke thiab ua qhov kev tshawb pom tsis txaus ntseeg: SSLv2 tseem siv hauv kev ruaj ntseg. Yog lawm, cov neeg tawm tsam tsis tuaj yeem txo qis TLS niaj hnub ntu rau SSLv2 txij li lub qhov ntawd raug kaw tom qab FREAK thiab POODLE, tab sis lawv tseem tuaj yeem txuas rau servers thiab pib SSLv2 ntu lawv tus kheej.

Tej zaum koj yuav nug, vim li cas peb mob siab rau qhov lawv ua nyob ntawd? Lawv muaj kev sib kho tsis zoo, tab sis nws yuav tsum tsis txhob cuam tshuam rau lwm qhov kev sib tham lossis kev ruaj ntseg ntawm server - txoj cai? Zoo, tsis heev. Yog, qhov ntawd yog li cas nws yuav tsum nyob hauv txoj kev xav. Tab sis tsis yog - vim tias tsim cov ntawv pov thawj SSL ua rau muaj lub nra hnyav, ua rau ntau lub servers siv tib daim ntawv pov thawj thiab, vim li ntawd, tib lub RSA yuam sij rau TLS thiab SSLv2 kev sib txuas. Txhawm rau ua qhov teeb meem loj dua, vim muaj kab laum OpenSSL, "Disable SSLv2" kev xaiv hauv qhov kev siv SSL nrov no tsis ua haujlwm tiag.

Qhov no ua rau muaj kev cuam tshuam kev sib tw ntawm TLS, hu ua DUA (Decrypting RSA nrog Obsolete thiab Weakened eNcryption, decrypting RSA nrog tsis siv lawm thiab tsis muaj zog encryption). Nco qab tias qhov no tsis zoo ib yam li kev tawm tsam luv luv; tus neeg tawm tsam tsis tas yuav ua "tus txiv neej hauv nruab nrab" thiab tsis tas yuav koom nrog tus neeg siv khoom los koom nrog kev sib tham tsis ruaj ntseg. Cov neeg tawm tsam tsuas yog pib qhov kev sib tham tsis ruaj ntseg SSLv2 nrog cov neeg rau zaub mov lawv tus kheej, tawm tsam cov txheej txheem tsis muaj zog, thiab rov qab tau tus neeg rau zaub mov RSA tus yuam sij ntiag tug. Tus yuam sij no kuj siv tau rau TLS kev sib txuas, thiab txij li qhov no mus, tsis muaj TLS kev ruaj ntseg yuav tiv thaiv nws los ntawm kev cuam tshuam.

Tab sis txhawm rau txhawm rau nws, koj xav tau kev tawm tsam ua haujlwm tawm tsam SSLv2, uas tso cai rau koj kom rov qab tsis tau tsuas yog cov tsheb khiav, tab sis kuj tseem zais RSA server yuam sij. Txawm hais tias qhov no yog kev teeb tsa nyuaj, cov kws tshawb fawb tuaj yeem xaiv txhua qhov tsis zoo uas raug kaw tag nrho tom qab SSLv2. Lawv thaum kawg pom ib qho kev xaiv tsim nyog: Bleichenbacher nres, uas peb tau hais ua ntej thiab qhov uas peb yuav piav qhia meej hauv tsab xov xwm tom ntej. SSL thiab TLS raug tiv thaiv los ntawm qhov kev tawm tsam no, tab sis qee qhov kev sib txawv ntawm SSL, ua ke nrog cov yuam sij luv luv hauv kev xa tawm qib cryptography, ua rau nws ua tau. ib qho kev siv tshwj xeeb ntawm DROWN.

Thaum lub sijhawm tshaj tawm, 25% ntawm Is Taws Nem cov vev xaib sab saum toj tau cuam tshuam los ntawm DROWN qhov tsis muaj peev xwm, thiab qhov kev tawm tsam tuaj yeem ua nrog cov peev txheej me me uas muaj rau txawm tias tus neeg tsis zoo ib leeg hackers. Retrieving tus neeg rau zaub mov tus yuam sij RSA yuav tsum tau yim teev ntawm kev xam thiab $440, thiab SSLv2 tau los ntawm kev siv tsis tau mus rau xov tooj cua.

Tos, ua li cas txog Heartbleed?

Qhov no tsis yog kev tawm tsam cryptographic hauv qhov kev xav tau piav qhia saum toj no; Qhov no yog ib qho tsis txaus.

Cia peb so

Peb pib nrog qee cov tswv yim yooj yim: brute force, interpolation, downgrading, cross-protocol, thiab precomputation. Tom qab ntawd peb saib ntawm ib qho txheej txheem siab heev, tej zaum lub ntsiab lus tseem ceeb ntawm kev tawm tsam cryptographic niaj hnub: kev tawm tsam oracle. Peb tau siv sijhawm ntau los txheeb xyuas nws - thiab nkag siab tsis yog hauv paus ntsiab lus xwb, tab sis kuj tseem muaj cov ntsiab lus ntawm ob qhov kev siv tshwj xeeb: Vaudenay nres ntawm CBC encryption hom thiab Kelsey nres ntawm pre-compression encryption raws tu qauv.

Hauv kev tshuaj xyuas kev txo qis thiab kev tawm tsam ua ntej, peb tau piav qhia luv luv ntawm FREAK nres, uas siv ob txoj hauv kev los ntawm kev muaj lub hom phiaj txo qis rau cov yuam sij tsis muaj zog thiab tom qab ntawd rov siv tib cov yuam sij. Rau tsab xov xwm tom ntej, peb yuav txuag tau qhov (zoo sib xws) Logjam nres, uas yog lub hom phiaj tseem ceeb ntawm pej xeem algorithms.

Tom qab ntawd peb saib peb qhov piv txwv ntxiv ntawm kev siv cov ntsiab cai no. Ua ntej, kev ua txhaum cai thiab POODLE: ob qhov kev tawm tsam uas tso siab rau tus neeg tawm tsam lub peev xwm los txhaj cov lus tsis txaus ntseeg ntawm ib sab ntawm lub hom phiaj plaintext, tom qab ntawd tshuaj xyuas cov neeg rau zaub mov cov lus teb thiab ces, siv oracle attack methodology, exploit no sparse information to, part of recover the plaintext. CRIME tau mus rau txoj hauv kev ntawm Kelsey qhov kev tawm tsam ntawm SSL compression, thaum POODLE es tsis txhob siv qhov sib txawv ntawm Vaudenay qhov kev tawm tsam ntawm CBC nrog cov nyhuv tib yam.

Peb mam li tig peb lub siab rau tus ntoo khaub lig-txoj cai DROWN nres, uas tsim kev sib txuas rau cov neeg rau zaub mov siv cov txheej txheem SSLv2 qub thiab tom qab ntawd rov qab cov neeg rau zaub mov cov yuam sij zais cia siv Bleichenbacher nres. Peb tau hla cov lus qhia txog kev tawm tsam tam sim no; zoo li Logjam, nws yuav tsum tau tos kom txog thaum peb muaj kev nkag siab zoo ntawm pej xeem cov ntsiab lus cryptosystems thiab lawv qhov tsis zoo.

Hauv tsab xov xwm tom ntej no peb yuav tham txog kev tawm tsam siab tshaj xws li kev sib ntsib hauv nruab nrab, sib txawv cryptanalysis thiab kev tawm tsam hnub yug. Cia wb mus nrawm nrawm rau hauv kev tawm tsam sab-channel, thiab tom qab ntawd txav mus rau qhov lom zem: pej xeem qhov tseem ceeb cryptosystems.

Tau qhov twg los: www.hab.com

Ntxiv ib saib