425 research outputs found

    Decentralized Anonymous Micropayments

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    Micropayments (payments worth a few pennies) have numerous potential applications. A challenge in achieving them is that payment networks charge fees that are high compared to “micro” sums of money. Wheeler (1996) and Rivest (1997) proposed probabilistic payments as a technique to achieve micropayments: a merchant receives a macro-value payment with a given probability so that, in expectation, he receives a micro-value payment. Despite much research and trial deployment, micropayment schemes have not seen adoption, partly because a trusted party is required to process payments and resolve disputes. The widespread adoption of decentralized currencies such as Bitcoin (2009) suggests that decentralized micropayment schemes are easier to deploy. Pass and Shelat (2015) proposed several micropayment schemes for Bitcoin, but their schemes provide no more privacy guarantees than Bitcoin itself, whose transactions are recorded in plaintext in a public ledger. We formulate and construct *decentralized anonymous micropayment* (DAM) schemes, which enable parties with access to a ledger to conduct offline probabilistic payments with one another, directly and privately. Our techniques extend those of Zerocash (2014) with a new probabilistic payment scheme; we further provide an efficient instantiation based on a new fractional message transfer protocol. Double spending in our setting cannot be prevented. Our second contribution is an economic analysis that bounds the additional utility gain of any cheating strategy, and applies to virtually any probabilistic payment scheme with offline validation. In our construction, this bound allows us to deter double spending by way of advance deposits that are revoked when cheating is detected

    SHAREDWEALTH: A CRYPTOCURRENCY TO REWARD MINERS EVENLY

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    Bitcoin [19] is a decentralized cryptocurrency that has recently gained popularity and has emerged as a popular medium of exchange. The total market capitalization is around 1.5 billion US dollars as of October 2013 [28]. All the operations of Bitcoin are maintained in a distributed public global ledger known as a block chain which consists of all the successful transactions that have ever taken place. The security of a block chain is maintained by a chain of cryptographic puzzles solved by participants called miners, who in return are rewarded with bitcoins. To be successful, the miner has to put in his resources to solve the cryptographic puzzle (also known as a proof of work). The reward structure is an incentive for miners to contribute their computational resources and is also essential to the currency\u27s decentralized nature. One disadvantage of the reward structure is that the payment system is uneven. The reward is always given to one person. Hence people form mining pools where every member of the pool solves the same cryptographic puzzle and irrespective of the person who solved it, the reward is shared evenly among all the members of the pool. The Bitcoin protocol assumes that the miners are honest and they follow the Bitcoin protocol as prescribed. If group of selfish miners comes to lead by forming pools, the currency stops being decentralized and comes under the control of the selfish miners. Such miners can control the whole Bitcoin network [29]. Our goal is to address this problem by creating a distinct peer-to-peer protocol that reduces the incentives for the miners to join large mining pools. The central idea is to pay the “runners-up” who come close to finding a proof, thereby creating a less volatile payout situation. The work done by the “runners-up” can be used by other miners to find the solution of proof of work by building upon their work. Once they find the actual solution they have to include the solution of the other miner in order to get rewarded. The benefit of this protocol is that not only the miners save their computational resources but also the reward is distributed among the miners

    Enhancing the Privacy of Decentralized Identifiers with Ring Signatures

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    Most identifiers used today, such as OpenID Connect, are controlled by third parties, which can track how the identifier is used. To overcome this, self-sovereign identifiers, such as Decentralized Identifiers (DIDs), which are entirely owned and managed by the user, have been developed. However, in some cases even DIDs alone do not sufficiently protect the user's privacy. For example, if a service can be accessed at multiple fixed locations, using the same identifier repeatedly for each location may over time also reveal the user's location. One of the techniques to hide the exact service identifiers are ring signatures, which enable the generation of anonymous signatures where the real signer's identity is hidden in a set of possible signers. This thesis takes the use case of electric vehicle charging, where the electric vehicle location may be revealed if static identifiers are used by the electric vehicles and charging stations. A previous solution uses a new ephemeral DID for every interaction, but this requires the creation of a large number of DIDs. This thesis examines an alternative approach of using ring signatures to achieve better privacy with a lower number of DIDs. The major outcomes of this thesis include how to implement ring signatures for anonymous authentication, comparison of resource consumption with respect to the previous solution, and the applicability of ring signature technology on a broader scale such as in constrained devices. The performance of the new solution was compared with the existing solution by implementing prototypes on Android phones, which communicate over Bluetooth. An assumption on the number of charging events was made based on real data for the country of Norway. The results show that ring signatures are easy to implement and provide slightly better privacy but they are significantly more resource-intensive in terms of storage (about 2 times more) and processing (about 9 times slower). Therefore, large scale implementation of ring signatures on the constrained devices is challenging

    The Architecture of Coupon-Based, Semi-off-Line, Anonymous Micropayment System for Internet of Things

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    Part 6: Computational Systems ApplicationsInternational audienceIn the Internet of Things a lot of business opportunities may be identified. The devices in IoT may create ad-hoc temporary networks to provide services or share some resources. Such services are characterized by a great economical potential, especially while provided at mass-scale and for incidental users. However, the development of paid services or resources in IoT is hampered by relatively big transaction costs of payment operations. To deal with this problem, we propose a novel architecture of coupon based, semi off line, anonymous micropayment system to enable transactions in the scope of Internet of Things. User anonymity and security is assured by the usage of standard cryptographic techniques together with novel architectural design of the payment processes. Utilization of a hash function allows generating and verifying electronic coins in computationally efficient way, so as to be executed even in hardware- and software-restricted environment such as Internet of Things
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