VerSum: Verifiable Computations over Large Public Logs

VERSUM allows lightweight clients to outsource expensive compu- tations over large and frequently changing data structures, such as the Bitcoin or Namecoin blockchains, or a Certificate Transparency log. VERSUM clients ensure that the output is correct by comparing the outputs from multiple servers. VERSUM assumes that at least one server is honest, and crucially, when […]

Reliable peer-to-peer computing system

Paper discuss a heterogeneous, distributed computing system commonly referred as a volunteer computing. Mechanism of determining correctness of results, based on replication and trust modeling, is proposed. In presented solution owners of computational power can flexibly join the network and sell spare machine time. Prototype implementation is based on light virtual machines distributed using BitTorrent […]

Pricing via Processing or Combatting Junk Mail


We present a computational technique for combatting junk mail in particular and controlling access to a shared resource in general. The main idea is to require a user to compute a moderately hard, but not intractable, function in order to gain access to the resource, thus preventing frivolous use. To this end we suggest several […]

How to Use Bitcoin to Incentivize Correct Computations

We study a model of incentivizing correct computations in a variety of cryptographic tasks. For each of these tasks we propose a formal model and design protocols satisfying our model’s constraints in a hybrid model where parties have access to special ideal functionalities that enable monetary transactions. We summarize our results: Verifiable computation. We consider […]