Nakamoto's famous blockchain protocol enables achieving consensus in a so-called \emph{permissionless setting}---anyone can join (or leave) the protocol execution, and the protocol instructions do not depend on the identities of the players. His ingenious protocol prevents ``sybil attacks'' (where an adversary spawns any number of new players) by relying on computational puzzles (a.k.a. ``moderately hard functions'') introduced by Dwork and Naor (Crypto'92). The analysis of the blockchain con...| IACR Cryptology ePrint Archive
Bitcoin is the first and most popular decentralized cryptocurrency to date. In this work, we extract and analyze the core of the Bitcoin protocol, which we term the Bitcoin backbone, and prove two of its fundamental properties which we call common prefix and chain quality in the static setting where the number of players remains fixed. Our proofs hinge on appropriate and novel assumptions on the hashing power of the adversary relative to network synchronicity; we show our results to be tight ...| IACR Cryptology ePrint Archive
We introduced definitions for consensus, Byzantine Broadcast (BB) and Byzantine Agreement (BA), in an earlier post. In this post, we discuss how consensus protocols are used in State Machine Replication (SMR), a fundamental approach in distributed computing for building fault-tolerant systems. We compare and contrast this setting to that of...| decentralizedthoughts.github.io
Post updated in March 2021 Different modeling assumptions under which we construct BFT protocols often make it hard to compare two protocols and understand their relative contributions. In this post we discuss synchronous protocols in the authenticated model (assuming a PKI). A protocol runs in the synchronous model if it...| decentralizedthoughts.github.io
In the standard distributed computing model, the communication uncertainty is captured by an adversary that can control the message delays. The communication model defines the limits to the power of the adversary to delay messages. There are three basic communication models: the Synchronous model, the Asynchronous model, and the Partial...| decentralizedthoughts.github.io
