ZCoin is a privacy focused cryptocurrency built on Ethereum. The ZCoin protocol enables anonymous transactions with cryptography that utilizes Zero-Knowledge Proofs (ZKP). ZCoin increases privacy on their network by using a coin-mixer contract that wraps transactions in a serial number and destroying wrapped coins once they have been redeemed.
Zcoin was the first cryptocurrency to use a Merkle Tree Proof (MTP) as its proof of work algorithm. Merkle Tree Proofs are an innovative solution to achieving network consensus, and can increase transaction time while reducing the centralizing tendency of ASIC mining.

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.

Digix is digital gold on the blockchain. By combining the historical stability of a valuable physical asset with the advantages of a distributed ledger, Digix allows users to benefit from the advantages of both commodities and digital tokens.
Digix has an innovative Proof of Asset (PoA) protocol that allows it it tokenize a physical asset. The PoA protocol tracks an asset through its chain of custody, and enables anyone to verify its existence without an intermediary. Since every DGX = 1 Gram of gold, their platform can be used as a secure and transparent digital marketplace for gold.
Digix is also behind DigixDAO, a platform that allows users to contribute to building a blockchain-based digital gold payment system. They hope to create a decentralized autonomous organization (DAO) that will participate in creating this platform. Instead of issuing shares, the organization will be run by DigixDAO token holders.