Peercoin is the first Proof-of-Stake (PoS) cryptocurrency. It was created in 2012 and is one of the oldest and most reliable cryptocurrency networks in the crypto sector. The protocol was developed by Sunny King and Scott Nadel, both of whom are anonymous. Sunny King also created Primecoin and VEE.
Peercoin’s PoS consensus mechanism is now widely used in the blockchain space, and allows every network participant to be both a miner or an owner. The project is focused on creating a cryptocurrency platform that will be stable, secure, energy efficient, and distributed fairly.

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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ICON (ICX) is unique compared to most other digital currrencies. ICON's primary objective is to establish a unifying system to integrate an unlimited numbers of blockchains. This would allow numerous blockchains to work together and incorporate aspects of all of them. ICON is powered by a unique system called loopchain, that can adopt different features, rules, and consensus systems. The loopchain has different circles, with nodes that connect it. There are community nodes and individual nodes that are all connected to the ICON Republic, which is the entire ecosystem. These nodes can connect in countless ways and results in unlimited applications. The network has an innovative consensus mechanism called Delegated Proof-of-Contribution (DPoC).