ARPA is a Secure Computation Network Compatible With Blockchains They propose a blockchain-based secure computation network of Multi-party Computation (MPC). ARPA cryptographically enables private smart contract, unprecedented data-at-use privacy protection, as well as scalable computational sharding.
DEMOS comes from ancient Greek, meaning democracy, and also means collective. DEMOS is mainly to provide help for more and more public chains. In the process of helping, they gather public chains.