The cryptonote protocol is an advancement in blockchain technology that employs the concept of ring signatures to share the ownership of a transaction amongst several key holders, despite their disassociation with the transaction. All key holders maintain their dissociation using a proxy signature for their actual address on the blockchain.
The cryptonote protocol's utility is currently limited to smart money, such as the Monero blockchain, and this is primarily due to the opaque blockchain and the computational resources that it demands. The infrastructure for cryptonote is limited and an active area of development.
In September 2016 we assumed stewardship of the Boolberry implementation of the cryptonote protocol. Our research and analysis report can be read here: Boolberry Opportunity & Roadmap