XCLAIM, Trustless Cross-Chain Communication. XCLAIM is a framework for achieving trustless and efficient cross-chain exchanges using cryptocurrency-backed assets (CbAs). XCLAIM allows to create assets which are 1:1 backed by existing cryptocurrencies, without requiring trust in a central operator. While this approach is applicable to a wide range of cryptocurrencies, we currently focus on implementing Bitcoin-backed tokens on Ethereum, i.e. XCLAIM(BTC,ETH). XCLAIM introduces three protocols to achieve decentralized, transparent, consistent, atomic, and censorship resistant cross-blockchain swaps: Issue: Create Bitcoin-backed tokens on Ethereum. Swap: Swap Bitcoin-backed tokens on Ethereum against Ether or any ERC-20 token. Redeem: Burn Bitcoin-backed tokens on Ethereum and receive the 1:1 amount of Bitcoin in return. The current XCLAIM prototype is compliant with the ERC20 standard. XCLAIM is a research project at the Imperial College London Centre for Cryptocurrency Research and Engineering, in collaboration with SBA Research. This research was co-funded by Blockchain.com, Outlier Ventures, etc.