# Repeat-Authenticate Scheme for Multicasting of Blockchain Information in IoT Systems

## TL;DR

This paper introduces a multicast-based authentication scheme for blockchain information dissemination in IoT systems, reducing communication overhead and exploiting blockchain structure for efficient, reliable, and timely authentication over wireless channels.

## Contribution

It proposes a novel multicast authentication scheme with time-amortized signatures and redundancy coding, improving efficiency and reliability in blockchain IoT communication.

## Key findings

- Multicast approach reduces communication resources compared to unicast.
- Time-amortized signatures enable delayed authentication, saving bandwidth.
- Redundant coding improves reliability over unreliable wireless channels.

## Abstract

We study the problem of efficiently disseminating authenticated blockchain information from blockchain nodes (servers) to Internet of Things (IoT) devices, through a wireless base station (BS). In existing blockchain protocols, upon generation of a new block, each IoT device receives a copy of the block header, authenticated via digital signature by one or more trusted servers. Since it relies on unicast transmissions, the required communication resources grow linearly with the number of IoT devices. We propose a more efficient scheme, in which a single copy of each block header is multicasted, together with the signatures of servers. In addition, if IoT devices tolerate a delay, we exploit the blockchain structure to amortize the authentication in time, by transmitting only a subset of signature in each block period. Finally, the BS sends redundant information, via a repetition code, to deal with the unreliable wireless channel, with the aim of decreasing the amount of feedback required from IoT devices. Our analysis shows the trade-off between timely authentication of blocks and reliability of the communication, depending on the packet loss rate offered by the channel. The numerical results show that the performance benefits of the proposed scheme makes it a viable starting point for designing new lightweight protocols for blockchains.