The Aztec Protocol is an efficient zero-knowledge privacy protocol designed to enable private transactions on the Ethereum blocckhain. Their zero-knowledge proofs enable private transactions that can facilitate a variety of inter-operable financial applications on Ethereum. Aztec is a ConsenSys portfolio company.

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The Dusk Network is a privacy-oriented blockchain protocol that is designed for creating programmable and confidential securities. Dusk places a strong focus on privacy and aims to make it easier for developers to create digital securities and zero-knowledge DApps. The network is currently powered by the Ethereum based DUSK token.

Ubiq is an Ethereum fork that aims to create a more stable smart contract platform for building DApps. Ubiq's protocol currently uses a Proof-of-Work (PoW) consensus mechanism, but will switch to Proof-of-Stake in 2019. The network is powered by the UBQ coin.
Ubiq's goal is to create a reliable and stable platform for developing DApps by modifying Ethereum's code base with important changes that will make it more secure and reduce instability. Consensus is based on their Flux Difficulty Algorithm, which is designed to constantly adjust the hash rate to protect against network attacks.