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The decentralized currency network Bitcoin is emerging as a potential new way of performing financial transactions across the globe. Its use of pseudonyms towards protecting users' privacy has been an attractive feature to many of its adopters. Nevertheless, due to the inherent public nature of the Bitcoin transaction ledger, users' privacy is severely(More)
We show that equivocation, i.e., making conflicting statements to others in a distributed protocol, can be monetarily disincentivized by the use of crypto-currencies such as Bitcoin. To this end, we design completely decentralized non-equivocation contracts, which make it possible to penalize an equivocating party by the loss of its money. At the core of(More)
The use of public-key steganography has been proposed for several censorship-resistance systems. However, distribution of the employed public keys presents an availability, scalability, and security challenge in many of these. To mitigate this problem, we introduce the notion of identity-based steganography. In particular, we define identity-based(More)
Dolev-Yao models of cryptographic operations constitute the foundation of many successful verification tools for security protocols, such as the protocol verifier ProVerif. Research over the past decade has shown that many of these symbolic abstractions are computationally sound, i.e., the absence of attacks against the abstraction entails the security of(More)
—Starting with Dining Cryptographers networks (DC-net), several peer-to-peer (P2P) anonymous communication protocols have been proposed. Despite their strong anonymity guarantees none of those has been employed in practice so far: Most fail to simultaneously handle the crucial problems of slot collisions and malicious peers, while the remaining ones handle(More)
Starting with Dining Cryptographers networks (DC-net), several peer-to-peer (P2P) anonymous communication protocols have been proposed. Despite their strong anonymity guarantees none of those has been employed in practice so far: Most fail to simultaneously handle the crucial problems of slot collisions and malicious peers, while the remaining ones handle(More)
—Starting with Dining Cryptographers networks (DC-nets), several peer-to-peer (P2P) anonymous communication protocols have been proposed. However, despite their strong anonymity guarantees, none of them have been employed in practice so far: Most protocols fail to simultaneously address the crucial problems of slot collisions and disruption by malicious(More)
Cryptographic agility is the ability to switch to larger cryptographic parameters or different algorithms in the case of security doubts. This very desirable property of cryptographic systems is inherently difficult to achieve in cryptocurrencies due to their permanent state in the blockchain: for example, if it turns out that the employed signature scheme(More)
We present a generic computational soundness result for interactive cryptographic primitives. Our abstraction of interactive primitives leverages the Universal Composability (UC) framework, and thereby offers strong composability properties for our computational soundness result: given a computationally sound Dolev-Yao model for non-interactive primitives,(More)