Primecoin is a cryptocurrency based on finding prime numbers. Identifying prime numbers plays a central role in cryptography. Primecoin's unique Proof-of-Work (PoW) consensus mechanism is able to increase transaction speeds and improve energy efficiency.
The network searches for special prime number chains known as Cunningham chains and bi-twin chains, which are of interest in mathematical research.

Unobtanium is a Proof-of-Work (PoW) cryptocurrency that uses the SHA-256 hashing algorithm. It was designed to serve as a commodity and store of wealth that would be less vulnerable to price fluctuations. The coin's supply is limited to counter inflation, and UNO coins were distributed in a manner that would discourage centralization. UNO can be merge-mined with Bitcoin.

Aurora is developing a blockchain platform that is based on a hybrid dPoS and BFT consensus mechanism. Aurora aims to improve overall blockchain performance with better transaction speeds and security features. Aurora has a multi-chain architecture and an Intelligent App Isolation system that are designed to allow for better smart contract execution. The network is currently powered by the Ethereum-based AOA token.