Author: Steven Goldfeder
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When the cookie meets the blockchain
Cryptocurrencies are portrayed as a more anonymous and less traceable method of payment than credit cards. So if you shop online and pay with Bitcoin or another cryptocurrency, how much privacy do you have? In a new paper, we show just how little. Websites including shopping sites typically have dozens of third-party trackers per site.…
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Breaking, fixing, and extending zero-knowledge contingent payments
The problem of fair exchange arises often in business transactions — especially when those transactions are conducted anonymously over the internet. Alice would like to buy a widget from Bob, but there’s a circular problem: Alice refuses to pay Bob until she receives the widget whereas Bob refuses to send Alice the widget until he…
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How to buy physical goods using Bitcoin with improved security and privacy
Bitcoin has found success as a decentralized digital currency, but it is only one step toward decentralized digital commerce. Indeed, creating decentralized marketplaces and mechanisms is a nascent and active area of research. In a new paper, we present escrow protocols for cryptocurrencies that bring us closer to decentralized commerce. In any online sale of…
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Threshold signatures for Bitcoin wallets are finally here
Today we are pleased to release our paper presenting a new ECDSA threshold signature scheme that is particularly well-suited for securing Bitcoin wallets. We teamed up with cryptographer Rosario Gennaro to build this scheme. Threshold signatures can be thought of as “stealth multi-signatures.”
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Threshold signatures and Bitcoin wallet security: A menu of options
Before Bitcoin can mature as a currency, the security of wallets must be improved. Previously, I motivated the need for sharing Bitcoin wallets using threshold signatures as a means to greatly increase their resilience to theft. For corporate users, threshold signatures enable cryptographically secure access control. For individuals, threshold signatures can be used to build…
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New research: Better wallet security for Bitcoin
[UPDATE (April 3, 2014): We’ve found an error in our paper. In the threshold signature scheme that we used, there are restrictions on the threshold value. In particular if the key is shared over a degree t polynomial, then 2t+1 players (not t+1) are required to to construct a signature. We thought that this could…