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.

Quantum Resistant Ledger is developing an enterprise blockchain platform that is designed to be secure against an attack from quantum computers. The Quantum Resistant Ledger (QRL) implements a more secure type of cryptographic signatures call XMSS. The network has a Proof of Stake consensus mechanism.

Bitcoin Cash SV is a cryptocurrency that was created as a result of a hard fork of the Bitcoin Cash blockchain that occurred on November 15, 2018. The central issue that led to the hard fork of Bitcoin Cash was a debate among prominent members of the Bitcoin Cash community regarding block size. A larger block size can improve transaction times, but also lead to greater network centralization. Roger Ver, an influential cryptocurrency advocate, was one of the central figures in favor of keeping the smaller 32 MB block size, while Craig Wright, the chief scientist at nChain, favored a larger 128 MB block size. The division between these two factions led to the hard fork that created Bitcoin Cash ABC and Bitcoin Cash SV.