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The blockchain ecosystem has evolved into a multi-chain world with various blockchains vying for use. Although each blockchain may have its own native cryptocurrency or digital assets, there are use cases to transfer these assets between blockchains. Systems that bring these digital assets across blockchains are called bridges, and have become important parts of the ecosystem. The designs of bridges vary and range from quite primitive to extremely complex. However, they typically consist of smart contracts holding and releasing digital assets, as well as nodes that help facilitate user interactions between chains. In this paper, we first provide a high level breakdown of components in a bridge and the different processes for some bridge designs. In doing this, we identify risks associated with bridge components. Then we analyse past exploits in the blockchain ecosystem that specifically targeted bridges., Comment: 37 pages, 15 figures

In order to secure the communication in Internet of Things era, a low overhead power analysis countermeasure called uniform distribution random power generator is proposed for stream ciphers. To alter the power signature of protected circuit, ring oscillators, which act as unit power generators, are grouped in a systematic approach to generate additional power with uniform probability distribution. Experiments from the proposed evaluation framework demonstrate that the secret key of unprotected device can be disclosed within 103 power traces with standard differential power analysis attack, whereas the same attack mounted on the proposed scheme cannot be disclosed even after 106 measurements. Moreover, the area and the power overhead are reduced by at least 29% and 22% compared with the state-of-the-art works, respectively.