Data Notarization without Blockchain

The process of data notarization plays an important role in multiple application contexts. Data notarization is typically implemented by leveraging blockchain technologies. In certain cases, the adoption of blockchain in real-life applications could be not adequate, due to the cost of transactions, in the case of public blockchains, or the complexity of the solution, in the case of permissioned blockchains. Therefore, it is interesting to explore possible alternatives to blockchain. This paper proposes a notarization scheme leveraging existing social networks. The scheme allows multiple notarizations on the same data and, due to the socialnetwork paradigm which it relies on, it is strongly oriented to cooperative work and information-sharingbased applications