Diamond (DMD) is a Proof-of-Stake coin focused on scarcity. Their marketing materials emphasize the limited circulation of the coin, and the benefits of the network's incentivized cloud mining system, which rewards users for contributing their computing resources.

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.

Decred (DCR) is a decentralized currency with an emphasis on community based governance. Decred is led by several early adopters of Bitcoin and is designed to implement many of the goals of early Bitcoin idealists. Decred is highly focused on community contribution and governance. Users that contribute to the community can receive compensation for their work and anybody can submit a proposal ti make an improvement to the platform.
Decred has a hybrid Proof-of-Activity (PAC) consensus algorithm that combines the mining of Proof-of-Work (PoW) with the stake verifying model of Proof-of-Stake (PoS). It's designed to incentivize the community to participate and to reward both miners and stake verifiers. When DCR is mined, PoW miners receives 60% of the coins, PoS voters receive 30%, and 10% goes towards the development of the Decred platform.

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