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.
Stealthcoin (XST) has been rebranded to Stealth (XST): https://twitter.com/stealthsend/status/993226001101545473 Stealthcoin provides a complete anonymity solution for cryptocurrencies. Stealthcoin has a fair distribution with nearly four hours of low block rewards, a small premine of 1%, and the long-term energy efficiency of proof-of-stake minting.