JOURNAL OF SECURITY AND CRIMINAL SCIENCES

Banja Luka, 2019 JOURNAL OF SECURITY AND CRIMINAL SCIENCES

Publisher: University of Faculty of Security Studies Bulevar vojvode Živojina Mišića 10 а 78000 Banja Luka, Phone: +387 51 333 603 https://fbn.unibl.org/

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Managing Editor: Velibor Lalić

Editorial Board: Darko Paspalj (Faculty of Security Studies, University of Banja Luka, Republika Srpska - BiH), Mile Šikman (Ministry of the Interior of the Republika Srpska - BiH ), Milan Lipovac (Faculty of Security, , ), Zana Vrućinić (Faculty of Security Studies, University of Banja Luka, Republika Srpska - BiH) Council of the Journal: Dane Subošić (University of Criminal Investigation and Police Studies, Belgrade, Serbia); Goran Bošković (University of Criminal Investigation and Police Studies, Belgrade, Serbia); Saša Mijalković (University of Criminal Investigation and Police Studies, Belgrade, Serbia); Jasmina Gačić (Faculty of Security, University of Belgrade, Serbia); Božidar Banović (Faculty of Security, University of Belgrade, Serbia); Nenad Putnik (Faculty of Security, University of Belgrade; Milan Gujvica (Faculty of Security Studies, University of Banja Luka, Republika Srpska - BiH); Laurence Armand French (University of New Hampshire, USA); Želimir Kešetović (Faculty of Security, University of Belgrade, Serbia); Sreten Jugović (University of Criminal Investigation and Police Studies, Belgrade, Serbia); Stevo Jaćimovski (University of Criminal Investigation and Police Studies, Belgrade, Serbia)

The Journal Secretariat: Dragana Vasiljević, Milica Sikimić Serbian Proofreader: Slobodanka Vidović Translator: Lidija Nikolić Novaković Print: Grafomark d.o.o Laktaši Circulation: 100 copies ISSN 2637-3076

The journal is published twice a year

The Journal of Security and Criminal Sciences (is registered in the Register of Public Media of the Ministry of Education and Culture of the Republika Srpska under number 688) the fundamentalproblemsarisingfromexecution. principles ofthequantumdistribution of akeyforinformationencryptionand recipient usingthelawsofquantumphysics.Thispaper seekstoaddressthe relatively newfieldensuringsafecommunicationbetween thesenderand particularly cryptography, deals with this issue. Quantum cryptography is a protection inthefieldoftelecommunicationsishighlysignificant.Cryptology, and arevirtuallyimpossibletoprotect.Therefore,theproblemofinformation for thecommunicationlinesthatspanhundredsorthousandsofkilometers physically protectedfromanyonewishingharm,butthisdoesnotholdtrue during transmission.Theunitsfordatastorageandprocessingcanbe industry. However, information isvery susceptible tovarious types ofabuse significant incidents. Telecommunications are thekey information technology technologies issogreatthatomissionsininformationsystemsmayleadto sector oftheeconomy.Thedependencemodernsocietyoninformation part oftheglobaleconomicsystem,acompletelyindependentandsignificant processing, storageandtransmissionofinformation,hasbecomeanintegral information technology(IT).TheITindustry,whichdealswiththeproduction, Institute ofChemistry,TechnologyandMetallurgy,Belgrade Jelena Lamovec Faculty ofSport,UnionUniversity,Belgrade Jovan Setrajcic University ofCriminalInvestigation andPoliceStudies,Belgrade,Serbia Stevo Jacimovski 1 Serbia, Belgrade. E-mail:[email protected] to discloseunauthorizedinformation sharedbyAliceandBob,iscalledEva encryption and decryption are called Alice and Bob. An enemy, who wishes protocols StevoJaćimovski:FullProfessor,University ofCriminalInvestigation andPoliceStudies, Belgrade, DOI 10.7251/ZBKEN1901041J Keywords: Abstract: Inthelatetwentiethcentury,humanraceenterederaof According toAnglo-Saxon tradition, theparticipantsinprocessof ON QUANTUMCRYPTOGRAPHY 1 cryptography, algorithms, encryption, key, quantumphysics, INTRODUCTION COBISS.RS-ID 8274456 UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES UDK 003.26:004.056.55 Review Paper 39 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) 40 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) enemy, (Kilin,Horosko&Nizovcev,2007). manages theprocessofcryptographictransformation, becomes knowntothe encryption system,otherthanthesecretkey,thatis,information formulated arulebywhichthesecurityofkeyisensuredifentire any time.Attheendofnineteenthcentury,DutchscientistKirchhoff is usedtomanagetheencryptionprocessandshouldbeeasilychangeableat of informationcalledakey,ratherthanonthesecrecyanalgorithm.Thekey The securityofmoderncryptosystemsisbasedonthesecrecyasmallitem large computerresources.Therefore,publickeyalgorithmsareusednowadays. security ofthecryptograms,asitisassumedthatEva(theenemy)hasinfinitely encryption algorithm itself cannot, in principle, ensure the unconditional characters intheplaintextandcryptogrammaydiffer.Thesecrecyof into anarbitrary string ofcharacters called acryptogram. The numberof very complex process. If an illegitimate user (Eve) had the secret key, it would secret keysamongtheregularparticipantsininformation exchangeisa the sametimetobothsenderandrecipient.The processofdistributing with thissecret key. Thekeymustbe periodically updated and distributed at secret key(Figure1).Anitemofinformationisalsoencrypted anddecrypted methods, algorithms has unlimitedcomputerresourcesandisfamiliarwiththeuseofcryptographic which isderivedfromeavesdropper(Bennett,1992).Theenemy,itassumed, UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES 4 3 2 particular orderbytwoormoreactors withtheaimofachievingaresult. a resultofinitialdata. Translator’s note: Alice–linkchannel–Bob; secret key; key generator. Aprotocol isaset ofactions(instructions, commands, calculations,algorithms)executedina Analgorithmisaset ofcommands,instructions, actions, calculationsexecutedinorderto achieve The primarytaskofcryptographyistotransformaninitialtext(plaintext) In symmetriccryptosystems,thesenderandrecipient usethesame Figure 1.Structureofsymmetriccryptosystems SYMMETRIC ENCRYPTIONSYSTEM 2 , protocols 3 , andsoon(Dugić,2009). 4 чиков, 2009). key cannotbedeterminedby usingpublickeyencryption(Румянцев&Голуб- Decrypting informationwith thepublickeyisimpossible.Also,decryption is encryptedwiththiskey.Onlytherecipient(Bob)has thesecondsecretkey. public andisavailabletoallusersoftheinformation exchange.Information cryptography. public-key cryptography.Thephysicalwayisrealizedbymeansofquantum The mathematicalmethodisrealizedbyusingatwo-keybasedprotocolor There aretwowaystosolvethekeydistribution:mathematicallyandphysically. flows, this key distribution method has become less acceptable and satisfactory. Therefore, intheconditionsofaconstantincreaseintensityinformation readiness in case of an urgent need for a key transfer is very long and costly. However, thecreationofsuchachannelanditsmaintenanceinoperational – bytransferringthekeytophysicallyprotectedeavesdroppingchannels. algorithm isDESandanimprovedversionof3(Čisar,2015). method ofkeydistribution.Thewell-knownandmostwidespreadsymmetric Therefore, the basic measure of the security of symmetric algorithms is the as long as the key isonly known to thesender and the recipient of the message. (Румянцев, Голубчиков2009). enable theknowledgeofinformationexchangedbetweenAliceandBob 5 Translator’s note: Alice–linkchannelBob; publickey –key exchangecenter–secret key. Asymmetric cryptosystemsusetwokeys–Figure2. Thefirstkeyis The problemhasbeensuccessfullysolvedwithinmoderncryptography. This problemhaspreviouslybeensolvedbyanon-cryptographicmethod Symmetric cryptographicalgorithmsprovideahighlevelofprotection, Figure 2.Structureofasymmetriccryptosystems ASYMMETRIC ENCRYPTIONMETHOD UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES 5 41 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) 42 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) problem ina slightlydifferentway:during aninteraction,twoparticipants distribution ofthekeyover opencommunicationschannelssolvethesame form alongwiththedata. time key,whichisencrypted withatwo-keycipherandistransmittedinthis schemes, whenastringofdata isencryptedwithasymmetriccipheronone- user information.Instead,asymmetricciphersareused aspartofcombined special typesofattacks,suchciphershaveprovedinappropriate toclosedirect due totheextremelylowperformancecharacteristics andexposuretothe key basedprotocol,sothereisnoneedtokeepthesecret keysecure.However, methods istheRSA. The mostfamousalgorithmwithinthegroupofasymmetric cryptographic Diffie–Hellman method isbasedon the complexity of thediscrete logarithm. key, itisenoughtofollowthisprotocol(Jakus,2016): and Hellman,StanfordUniversity.IfAliceBobwanttoestablishasecret computing thediscretelogarithm: same way asAliceor Bob can. The idea is that the calculationAor B requires compute A or B because she can then repeat the computation of the key in the UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES In thesecondcase,inpublic-key cryptography,theschemesfor In thefirstcase,differentkeysareencryptedanddecrypted inthetwo- for which there is no effective way (Stipčević, 2007). The security of the • AlicegeneratesarandomnumberA,computesP=e­­ In 1976,theschemeofasymmetriccryptographywasproposedbyDiffie Then AliceandBobcomputethesecretkey,K,asshowninFigure3. Suppose EvahasPandQ.CanshecomputeK?ToK,must • BobgeneratesarandomnumberB,computesQ=e Figure 3.Diffie–Hellmanprotocol A=lnP,BQ B and sendsQtoAlice. A andsendsPtoBob the lawsofphysics(Jaćimovski&Šetrajčić,2016). The solutionofkeydistributionisrealizedinquantum cryptographybasedon of quantummechanicsforprotection. must besoughtin,colloquiallyspeaking,“hardware”, that is,byusingthelaws about 15-25years. a quantum computer that can break the RSA crypto system will be designed in performs all these divisions, one at each spatial location. According to experts, factorization problem,giventhatonequantumcomputer nowsimultaneously factors. Inthisway,wegetanextremelyrapidaccelerationofthesolutionto configure acomputertoshareournumberwithanothersearchfor simultaneously atdifferentlocations.Ineachoftheselocations,wecan principle. Letusimagineasinglecomputerinsuperposition,whichis simultaneously inmanydifferentstates,asitusesthequantumsuperposition who createdanalgorithmaccordingtowhichaquantumcomputercanexist systems basedonthemathematicalcryptographicmethodscanbecompromised. for which rapidfactoring algorithms have beendeveloped, thecryptographic of themposesasignificantdifficultytoeverymodernclassicalcomputer. or 5times201010.Thenumberoffactorsgrowsrapidlyandfindingall What areitsfactors?Twotimes50equals100.Butthisisalsotruefor425, factor forlargenumbersisadifficultproblem.Letusimaginethenumber100. much computertimeandpowertobreakthecipher(Vedral,2014).Findinga computer-secure, inotherwords,itissecurethesensethatwouldtaketoo the keylength. possible solutions(keys),withanumberofstepsincreasingexponentially believed tobe“tough”inthesensethattheymightsolvedbyguessingall and computingdiscretelogarithmsincertainfinalgroups.Theseproblemsare progress. Their security is based on the problem of factorizing large numbers does notallowtheenemytoobtainkeybyhimselforherself. intercepting informationinachannelduringgeneratingsessionofsuchkey encrypt thedatabeingtransferredusingasymmetriccipher.Furthermore, exchanging informationgenerateasharedsecretkey,whichisthenusedto • • The basicargumentsforthis aretwofold: Therefore, theneedtoprotectcryptosystemshasarisen forotherreasons. It isprecisely for this reasonthatthe idea ofprotecting information The procedureforthiswasdevelopedbyPeterShore(Shor,1994) Nevertheless, with the expected emergence of quantum computers Secrecy inthemodernworldisbasedonideathatsomething The securityoftwo-keycryptosystemsisbasedonaslowtechnical holders) an informationchannel,Eva changesthestatusofinformation non-orthogonal quantum states (inotherwords,whenaccessing Without perturbation,it is impossibletohaveinformationabout It isimpossibletocopyanunknown quantumstate UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES 43 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) 44 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) orthogonal basesareusedin theprotocol:rectangular encode information,fourpolarization statesformingtwointerconnectednon- (Figure 4),althoughitcan beappliedtootherrealizationsofaqubit.To change alongthequantumchannel. noise inagivensituationassumesthatthequantumstate ofparticlesdoesnot absolutely safeifthereisnonoiseinthequantum channel. Theabsenceof whose securityisbasedontheprinciplesofquantum mechanics,makingit protocol forquantumkeydistribution(Kilin,Khoroshko &Nizovtsev,2007), E91protocol. Otherprotocolsofquantumcryptographyarealsoused. encoding ofquantumstates,theso-calledBB84protocol,andelaborates time shifts.Thispaperdemonstratestheprocedureforpolarization cryptography: polarizationencoding,phaseencipheringandencodingusing & Golub,2009). has asmuchinformationaboutthekeyAliceandBobwanthertohave(Picek the remainingbitsareusedtocreatekey.Followingtheseprocedures,Eva level, thentheerrorcorrectionprotocolsandsubsequentcompressionof the errorlevel(usuallyexpressedintermsofpercentages)isbelowcritical each protocolofquantumcryptography,abovewhichsecrecyisnotensured.If does notnecessarilyleadtothelossofsecrecy.Acriticalerrorisdefinedfor occurrence of errors during the transmission and reception of quantum states and thedetectionofEve’sattemptstoenterlinkchannel.Notethat encryption anddecryption. to transmitmessages.Thegeneratedkeycanthusbeusedinacryptosystemfor Quantum cryptographyisonlyusedtogenerateanddistributeakey,ratherthan qubits, thatis,unknownquantumstates,becauseoftheno-cloningtheorem. presence ofthethirdpartytryingtodiscoverkey. established. Twouserswhocommunicatewitheachothercanalwaysdetectthe cannot be eavesdropped without interfering with the transmission can be (Heisenberg, 1974). With quantum physics, a communication channel which during the measuring process, the so-called Heisenberg’s uncertainty principle UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES The BB84protocolisformulatedinthelanguageofindividual photons, The BB84protocol(Bennett&Brassard,1984)isthe historicalfirst Presently, threeformsofquantumstateencryptionareusedin In thisway,quantumcryptography allows forrelativelyfastkeyexchange Also, aneavesdroppercannotcopyunknownquantumbits,theso-called Quantum cryptographyusestheuncertaintyofquantumworld  ↔+ = Example oftheBB84protocol withoutnoise /2 )/ ( 

 ↔− = /2 )/ (

↔ and diagonal 

 both parties. in theeventthatEvadidnotinterceptinformation, shouldbethesamefor the wrongbaseisrejected,soAliceandBobgetso-called sievedkey,which, to AliceandBobnooneelse.Informationaboutthe photonsmeasuredin each ofthesephotonscarriesabitrandominformation, whichisknownonly been establishedintheopencommunicationchannel(stage 8).Inotherwords, encoded inthesephotons,regardlessofthefactthatthis informationhasnever correct base(stages6and7).Afterthat,AliceBob havethesamebitvalues were successfullyobtainedbyBobandwhichofthem weremeasuredinthe To beginwith,AliceandBobdetermine(viaapublic channel) whichphotons parties, butshecannotchangethemorsendnotifications instead ofthem. At thisstage,weassumethatEvacanlistentotheannouncementsbyboth which AliceandBobcanopenlyconveyclassicalinformationtoeachother. in abouthalfthecases(50%),thatis,whenhecorrectlyhitsbase. this way,Bobobtainstheresultscoincidingwithstateofphotonssent turns into the horizontal or vertical line and vice versa, with random results. In the measuringofdiagonalphotoninarectangularbase,itspolarization one (stage 5). Inaccordance with thelawsofquantum mechanics andfollowing interprets theresultofhismeasurementforeachphotonintwoways,asazeroor or diagonal) for each photon and independently of Alice, (stage 4), analogously obtaining aphoton,Bobrandomlyselectsthemeasurementbase(rectangular the states selected stringinthebasecorrespondingtoprimenumberofthatbit,where user (Bob)astringofphotons(stage3)eachwhichencodesonebitfromthe selects aseriesofbits(stage1)andbases2)thensends The nextstageoftheprotocolisrealized via apublic channel, through The essenceoftheBB84protocolisthatoneusers(Alice)randomly ↔

 areencodedinto(0)zero,andthestates Quantum channel–sendingpolarizedphotons Figure 4.TheBB48protocoldemonstration UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES 

into one(1).In ​​ 45 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) 46 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) Table 1.ExampleoftherealizationBB84protocol.States secret key. (stage 11)andtransmission overtheopenchannel. remaining bits properly measured can be used for the secret key encryption the bitscomparedmatch,it isclearthattherewasnoeavesdropping,andthe the properlymeasuredbits sothatthepresenceofEvemustbenoticed.Ifall key. The position of the bits being compared should be a random subset of same information,althoughthesebitscannot,anylonger, beusedforthesecret comparing aportionofbits(stages9and10)forwhich theymusthavethe Bob. Alice and Bob can check if someone is eavesdropping on them by openly if themeasuredphotonoritsreplacementis intheinitialbaseby and isnotincompliancewiththeprobabilitywhich ultimatelyequaltob/2 by thisphoton;anysuchmeasurementgivesbbitsofinformation( b <1/2) performed byEvegivesmorethanonehalfofthebit informationencrypted the sameforAliceandBobiftherewasnoEve.Nomeasurement ofthephotons such awaythatitchangesthebitsofsievedkey, whichwouldhavetobe selection of a rectangular or diagonal base, Eva influences the information in UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES Stage 11 Stage 10 Stage 9 Stage 8 Stage 7 Stage 5 Stage 3 Stage 1 Stage 4 Stage 6 Stage 2 Once thiskeyisused,Alice and Bobrepeattheproceduretocreateanew Suppose Eva is eavesdropping on a quantum channel. Due to the random assessment Sieved key aftererror Alice confirmsit bits Bob discoversaportionof Sieved key their bases are harmonized Аlice tellsBobwhichof Bits receivedbyBob quantum channel distributed alongthe Polarization ofphotons (Alice) Random bittransmission (Bob) Randomly receivedbases the bases ofreception Bob informsAliceabout (Alice) Random bittransmission are indicatedby zero, whilestates

⊗

and by  e ncrypt one(1). ⊗ 0 0 ⊕ ⊕ ⊗ . 0 1 ⊗ ⊕ ⊗ 1 1 1 1 ⊗ ⊗ ⊗ Rectangular anddiagonalbases ↔ 1 0 ⊕ ⊗ ⊕ 1 1 ↕ 1 1 ⊕ ⊕ ⊕

 0 1 ⊗ ⊕ ⊕

 encrypt(0) 0 0 ⊗ ⊕ ⊕ 0 ↔ 0 0 0 ⊕ ⊕ ⊕

the polarizationofonephoton. this schemeisproblematicdue tothelowefficiencyofrecordingandmeasuring identical pseudo-random code sequences.Practically, the implementation of 0 andviceversa.Clearly,in thisway,partners,whenevernecessary,canget receives thevalueofpolarization1,hisorherpartner willregisterthevalue same time,iftheregistrationefficiencyiscloseto unity,whenthesender for himselforherself,andsendstheotheronetohis orherpartner.Atthe a numberoftheAPRphotonpairsandleavesone photonfromeachpair guaranteeing thesecurityofkeytransferandstorage. Thesendergenerates having beenmeasured.BasedontheEPR,Ekertproposed acrypto-scheme of thiseffectisthatthepolarizationphotonsbecomes knownonlyafter are alwaysopposite(thequantuminterferenceeffect). Animportantfeature an unspecifiedpolarization,butduetothesymmetryof theirpolarization,they photons in opposite directions to two observers. The photons are emitted with 1935). TheEPReffectoccurswhenasphericalsymmetric atomradiatestwo using theEinstein-Podolsky-Rosen(EPR)effect(Einstein,Podolsky&Rosen, information leverageandprivacyenhancement. Bob agreeonasmallercryptographickeyinthreephasesviz.errorassessment, distinguished: naturalorartificialsoundslookthesame.Asaresult,Aliceand pertaining to the polarization of photons. These two situations cannot be are likelytooccurduethefactthatEvaisattemptingmeasuredata attempts tomeasurethephotonssentbyAlicebeforetheyreachBob,errors photons accuratelymeasuredislikelytobedetectedincorrectly.Also,ifEva an unknownquantumstateisnotpossibleduetotheno-cloningtheorem. with anumberofdifferentlyorientedpolarizers.However,thereproduction photons. Inthesecondcase,Evawantstoassurepolarizationofphotons of apolarizerwithwhichEvacouldcertaintydistinguishthepolarization uses photonsfromtheconjugatedbases,inotherwords,thereisnoorientation had, soattheendofproceduretheywouldhavesamekey.However,Alice following interventionsonthequantumchannel(Markagić,2012): Further, theimprovementofcryptosystemreliabilitycanbeachieved In thecommunicationprocessbetweenAliceandBob,aportionof In thefirstcase,EvawouldhavesameinformationthatAliceandBob 2. 1. The BB84protocolwouldbethreatenedifEveisabletoperformthe To reproducethephotonssentbyAlice the sameoneandsendittoBob To measurethepolarizationofphotonsentbyAlice,reproduce The securityoftheBB84protocol The Е91protocol (Ekert,1991) UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES 47 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) 48 JOURNAL OF SECURITY AND CRIMINAL SCIENCES • Vol. 1, No. 1 (2019) while theproceduresfor increasing securityshouldbeusedtoreducethe liquid gases.Differentcorrection codesshouldbeusedtofightsystemerrors, that wouldoperateinanormal temperaturerangeandshouldnotbecooledby development ofstablesources ofsinglephotonsandsingle-photondetectors in practice,anumberoftechnical difficultiesneedtobesolved,suchasthe through whichtheinformationistransmittedcannot always becontrolled. is afactorthatcannotpractically be removed,asthequalityofchannel the transmissionofinformationenablinginterception ofsilentdata.This multiphoton pulses.Theuseofstrongphotonpulsesleads tothedampeningof as theattenuationofcommunicationchannelsdueto thenecessityofusing behind whichtheattemptstointerceptinformation canbehidden,aswell transmitted, duetothefactthatthereisafondofitsown errorsinthesystem, communication systemsareunabletoensuretheabsolute secrecyofthedata actual systemsaredifferentfromtheidealones. identify theinterceptionaserrorsoccurringintransmission.However, is impossible,astheparticipantsinexchangeofinformationimmediately the costofsystemimplementation(Ijačić,2014). of relay,practicallimitationssolelyonfiberopticcommunications,aswell participants, theinabilitytoincreasesignalortransmissionthroughatype limited keygenerationspeed,whichdependsdirectlyonthedistanceof is beingactivelyeavesdropped.Themaindisadvantageofthesesystemsthe speed of key generation, with both parties immediately knowing that the line party doesnotleadtotherevealingofasecret,butonlyreduction 150 kilometersinafewseconds.Eavesdroppingoncommunicationsbythird a secret key between two parties connected by optical fibers at distances up to it isalmostpossible,withtheunconditionalsecurity,togenerateanddistribute unconditional securitybasedonthephenomenaofquantummechanics.Today, key distribution technologies. The advantage of these technologies is the of publicandcorporatesecurenetworkcommunicationsusingthequantum there arealreadycommercialdevicesaswelldozensofimplementations are exchangedviatheso-calledquantumchannel,butalsosecretkeys.Today, is toensureasecretkey.Thus,inquantumcryptography,notonlymessages weakest linkinclassicalcryptography.Theonlytaskofquantumcryptography time, thekeyisnotknowntoanyoneelse,evenpotentialenemyEve. Alice andBob)ifthesecretdecryptionkeyisknowntobothparties,atsame traditional methodsthatpracticallyguaranteeasecurecommunication(between UNIVERSITY OFBANJA LUKA - FACULTY OFSECURITY STUDIES However, beforethequantumcommunicationsystems isapplied Unlike theidealquantumcommunicationsystem, actualquantum In idealsystemsofquantumcommunication,theinterceptiondata It isthispresumptionofthesecrecy of the“secretkey”thatis The taskofcryptographyistheexchangesecretmessages.Thereare CONCLUSION Ekart, A. (1991). Quantum cryptography based on Bell’s theorem. Bell’s on based cryptography Quantum (1991). A. Ekart, of description quantum-mechanical Can (1935). Podolsky,N. Rosen, A., B., Einstein, Jaćimovski, S., Šetrajčić,Jaćimovski,S., Physical J.(2016). FundamentalsQuantumCryptography. of Ijačić, S. (2014). Primena kvantne mehanike u kriptografiji, kvantno računarstvo i post- (2009). M. Dugić, Čisar, P(2015).Opšti aspekti kvantne kriptografije. states. twonon-orthogonal any using cryptography Quantum (1992). C. Bennett, Picek, S., Golub, M. (2009). Kvantna kriptografija: razvoj i protokoli. i razvoj kriptografija: Kvantna (2009). M. Golub, S., Picek, kriptografije. kvantne razvoja pravci i Protokoli (2012). M. Markagić, (2007). А.П. Низовцев Д.Б., Хорошко С.Я., Килин Jakuš, M.(2004):Kvantna kriptografija, Faculty ofElectrical Engineeringand Hajzenberg, V. (1974). distribution key Public cryptography: Quantum (1984). G. Brassard, H., C. Bennett, software packageforresearchingphononnanostructures”project. 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