14943

13447

كارشناسي ارشد

مخابرات سيستم

اصفهان : دانشگاه صنعتي اصفهان

1398

چهارده، 137ص. : مصور، جدول، نمودار

محمد دخيل‌عليان

محمدحسن صمداني

حامد نريماني، مسعود عمومي

1398/05/28

كتابنامه

برق

مهندسي برق و كامپيوتر

1398/05/28

2553266

Study and Analysis of Privacy in Bitcoin Shabnam Mirshahzadeh s mirshahzadeh@ec iut ac ir June 19 2019 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Mohammad Dakhilalian mdalian@cc iut ac ir Advisor Dr Mohammad Hasan Samedani mh samadani@ec iut ac ir AbstractBitcoin is the first and most popular currency based on the blockchain Blockchain is a data structurethat records bitcoin transactions publicly and permanently Recent studies have shown that the pri vacy of bitcoin users is severely threatened due to the public nature of the blockchain This affectseven the fungibility a fundamental property required in every payment system so no two coins arecompletely equal As a result there is so much research in these years each of which is somehowenhancing the privacy of users One of the first and most important approaches in this concept is Coin Join transactions where participants merge their transactions and form a final CoinJoin transaction Although this transaction is simple it can improve the privacy level of the participants However ithas the main limitation To prevent the attacker from deriving the original single transactions Coin Join transaction needs to have fixed amounts in the outputs which makes it impossible to use thesetransactions as payments transactions with arbitrary outputs It makes so many transactions whichare merely just for mixing added to the blockchain As a result it greatly affects the scalability ofthe system On the other hand considering the fees of these transactions many users do not join theprocess of mixing In this thesis we propose a framework with eight features for assessing the privacy of cryptocur rencies For each feature quantitative criteria are gathered to measure the privacy of the system interms of that feature Also in this thesis utilizing the Knapsack mixing algorithm and the SecureMulti Party Computation a protocol is proposed that adapts CoinJoin transactions to payment trans actions while protecting privacy not only against blockchain observers but against other transactionparticipants This method by splitting the outputs prevents amount analysis and it does not let thesender and the receiver know each other address directly The security of the proposed protocol isbased on Secure Multi Party Computation functionality and basic cryptographic tools Keywords Bitcoin Cryptocurrency Privacy CoinJoin Transaction Knapsack Mixing

محمد دخيل‌عليان

محمدحسن صمداني

حامد نريماني، مسعود عمومي