BitcoinDark is a fork of Bitcoin with a poorly defined purpose and use case. BitcoinDark is based on the InstantDEX protocol, a decentralized exchange for BitcoinDark and other cryptocurrencies supported by the project. The platform is also supposed to include a Pegged Asset Exchange (PAX) to allow users to buy and sell pegged assets – including fiat currencies, commodities, ETFs, and stocks.
BitcoinDark is a Proof-of-Stake (PoS) currency that has gained a significant market cap, but the project has failed to show how its vision will be implemented or how it will add value compared to other blockchain projects.

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.

PascalCoin is the first blockchain that can be deleted, and reduces the dependency of the entire blockchain history to verify transactions. It is a Proof-of-Work (PoW) cryptocurrency that places a strong emphasis on achieving the same level of scalability as credit card networks such as VISA. Pascal's architecture is based on an innovative cryptographic structure called the SafeBox. It facilitates faster transactions by storing account balances separately from the blockchain. The SafeBox only uses the last 100 blocks on the chain to update transaction history. This allows the network nodes to synchronize much faster while preserving the security of the blockchain, and reducing the computing resources needed to maintain it.
PascalCoin also enables simplified account naming to make it easier to transfer funds.