More Like this

1. Cross-chain Transactions

   https://doi.org/10.1109/ICBC48266.2020.9169477  

   Shadab, Narges ; Houshmand, Farzin ; Lesani, Mohsen ( May 2020 , 2020 IEEE International Conference on Blockchain and Cryptocurrency (ICBC))

   null (Ed.)

   The value of cryptocurrencies is highly volatile and investors require fast and reliable exchange systems. In cross-chain transactions, multiple parties exchange assets across multiple blockchains which can be represented as a directed graph with vertexes V as parties and edges E as asset transfers. In a simple form, cross-chain transactions are cross-chain swaps where each edge e transfers an asset that the head of e already owns. However, in general, a cross-chain transaction includes a sequence of exchanges at each blockchain. Further, transactions may have off-chain steps and hence may not be strongly connected. Given a transaction, protocols are desired that guarantee the following property called uniformity. If all parties conform to the protocol, all the assets should be transferred. Further, if any party deviates from the protocol, the conforming parties should not experience any loss. Previous work introduced a uniform protocol for strongly connected cross-chain swaps and showed that no uniform protocol exists for transactions that are not strongly connected. We present a uniform protocol for general cross-chain transactions with sequenced and off-chain steps when a few certain parties are conforming. Further, we prove a new property called end-to-end that guarantees that if the source parties pay, the sink parties are paid. We present a synthesis tool called XCHAIN that given a high-level description of a cross-transaction can automatically generate smart contracts in Solidity for all the parties. 

   more » « less
2. Privacy-Preserving Cross-Chain Atomic Swaps

   https://doi.org/10.1007/978-3-030-54455-3_38  

   Deshpande A., Herlihy M ( August 2020 , Lecture notes in computer science)

   null (Ed.)

   Recently, there has been a lot of interest in studying the transfer of assets across different blockchains in the form of cross-chain atomic swaps. Unfortunately, the current candidates of atomic swaps (hash-lock time contracts) offer no privacy; the identities as well as the exact trade that happened between any two parties is publicly visible. In this work, we explore the different notions of privacy that we can hope for in an atomic swap protocol. Concretely, we define an atomic swap as a two-party protocol and formalize the different notions of privacy in the form of anonymity, confidentiality and indistinguishability of swap transactions. As a building block, we abstract out the primitive of Atomic Release of Secrets ( ARS ) which captures atomic exchange of a secret for a pre-decided transaction. We then show how ARS can be used to build privacy-preserving cross-chain swaps. We also show that the recently introduced notion of adapter signatures [Poe18, War17] is a concrete instantiation of ARS under the framework of Schnorr signatures [Sch91] and thus, construct a private cross-chain swap using Schnorr signatures. 

   more » « less
3. DLSAG: Non-Interactive Refund Transactions For Interoperable Payment Channels in Monero

   Moreno-Sanchez, Pedro ; Blue, Arthur ; Le, Duc V ; Noether, Sarang ; Goodell, Brandon ; Kate, Aniket. ( February 2020 , 24th International Conference on Financial Cryptography and Data Security (FC 2020))

   Monero has emerged as one of the leading cryptocurrencies with privacy by design. However, this comes at the price of reduced expressiveness and interoperability as well as severe scalability issues. First, Monero is restricted to coin exchanges among individual addresses and no further functionality is supported. Second, transactions are authorized by linkable ring signatures, a digital signature scheme used in Monero, hindering thereby the interoperability with virtually all the rest of cryptocurrencies that support different digital signature schemes. Third, Monero transactions require an on-chain footprint larger than other cryptocurrencies, leading to rapid ledger growth and thus scalability issues. This work extends Monero expressiveness and interoperability while mitigating its scalability issues. We present Dual Linkable Spontaneous Anonymous Group Signature for Ad Hoc Groups (DLSAG), a linkable ring signature scheme that enables for the first time non-interactive refund transactions natively in Monero: DLSAG can seamlessly be implemented along with other cryptographic tools already available in Monero such as commitments and range proofs. We formally prove that DLSAG provides the same security and privacy notions introduced in the original linkable ring signature [31] namely, unforgeability, signer ambiguity, and linkability. We have evaluated DLSAG and showed that it imposes even slightly lower computation and similar communication overhead than the current digital signature scheme in Monero, demonstrating its practicality. We further show how to leverage DLSAG to enable off-chain scalability solutions in Monero such as payment channels and payment-channel networks as well as atomic swaps and interoperable payments with virtually all cryptocurrencies available today. DLSAG is currently being discussed within the Monero community as an option for adoption as a key building block for expressiveness, interoperability, and scalability. 

   more » « less
4. Speculative urbanism and the urban-financial conjuncture: Interrogating the afterlives of the financial crisis

   https://doi.org/10.1177/0308518X211016003  

   Goldman, Michael ( April 2021 , Environment and Planning A: Economy and Space)

   This article proposes an analytical–methodological approach to understand this historical conjuncture of speculative urbanism in which global finance capital plays an increasingly important role in urban transformation. Whereas the scholarship on urban financialization makes sharp distinctions between what occurs in the global North and the South, portraying the process in the South as one of subordination or peripheralization and in the North as mature and stable (although volatile), this article seeks to demonstrate that the North–South divide is less effective as an explanatory power. Instead, it presents an analytical approach that is attuned to the relentless dynamism and inter-scalar hyper-mobility of finance capital working across the postcolonial map—in other words, a relational–conjunctural approach. The article suggests the method of “following the financial strategy” by analyzing urban forms and projects as processes constituted by the nexus of practices in finance and city planning. It looks closely at finance’s use of inter-scalar financial tools (such as arbitrage, interest rate swaps, collateralized debt obligations, and currency hedges) across borders, sectors, infrastructures, and conditions, as mediated by national and international state actors. The value of this analytical–methodological approach will be illustrated through notable financial transactions occurring in and across cities to emphasize their speculative and financial characteristics—specifically highlighting investments traversing cities of Spain, the USA, and India. The focus here is on financial strategies emerging from the detritus of the 2008 global financial crisis and shaped by the expanding discursive-material formation of speculative urbanism. 

   more » « less
5. Fides: Managing Data on Untrusted Infrastructure

   https://doi.org/10.1109/ICDCS47774.2020.00053  

   Maiyya, Sujaya ; Bum Cho, Danny Hyun ; Agrawal, Divyakant ; El Abbadi, Amr ( November 2020 , IEEE International Conference on Distributed Computing Systems)

   null (Ed.)

   Significant amounts of data are currently being stored and managed on third-party servers. It is impractical for many small scale enterprises to own their private datacenters, hence renting third-party servers is a viable solution for such businesses. But the increasing number of malicious attacks, both internal and external, as well as buggy software on third-party servers is causing clients to loose their trust in these external infrastructures. While small enterprises cannot avoid using external infrastructures, they need the right set of protocols to manage their data on untrusted infrastructures. In this paper, we propose TFCommit, a novel atomic commitment protocol that executes transactions on data stored across multiple untrusted servers. To our knowledge, TFCommit is the first atomic commitment protocol to execute transactions in an untrusted environment without using expensive Byzantine replication. Using TFCommit, we propose an auditable data management system, Fides, residing completely on untrustworthy infrastructure. As an auditable system, Fides guarantees the detection of potentially malicious failures occurring on untrusted servers using tamper-resistant logs with the support of cryptographic techniques. The experimental evaluation demonstrates the scalability of our approach and the relatively low overhead of executing transactions on untrusted infrastructure. 

   more » « less