The Coco team shares Richard's view that the distinguishing factor is where the trust boundary exists within the system. In the case of Coco, we assume a lack of trust among consortium participants, but we leverage the attestation and anti-tampering features of Trusted Execution Environments (TEEs) to establish trust between the enclaves: assuming that the TEEs themelves are trustworthy, the TEEs can provide cryptographic proof of the software and configuration running on each enclave. In other words, I don't trust you, but my enclave has decided it can trust your enclave based on mutual attestation exchange and mutual authentication. In other words, we've transitioned from a byzantine failure mode (adversary can replace the expected remote code with arbitrary code at will) to a crash failure mode (adversary can shut the remote enclave down at will, but not alter what runs on it).
Once there is trust between enclaves, Proof of Work seemed inefficient as a consensus mechanism, although it's certainly one choice that is available and that can be used with Coco (in this case Coco would provide governance and confidentiality, but scalability and latency would be limited by PoW). Instead we can use any one of many distributed systems techniques such as Paxos or Raft to achieve consensus.
This is an amazing development for enterprise as it removes the major risk of being cheated after the fact. This is largely why it's so difficult to establish trust between enterprises and had lead to this situation where the best trust is authoritarian centralization.
If we can lose this barrier to establish trust from a human one to a code audit that would be and outstanding achievement for our civilization.
Is there even a difference between a traditional distributed database and a blockchain once you remove proof-of-work? Without proof-of-work, the Bitcoin P2P network would just be a distributed database storing a linked list of blocks (each block pointing to the hash of a previous block), plus some business logic.
And on top of that, it sounds like Microsoft ditched most/all of the proof-of-work, because the nodes are trusted and the proof-of-work increased transaction times. So it sounds like whether Coco is actually a blockchain or a distributed database which has been branded as a blockchain because blockchains are FotM, is debatable.
We tried to address several distinct concerns with Coco: scalability, latency, confidentiality and governance. Scalability and latency are determined largely by the consensus model of the network. Our intent with Coco is to make consensus pluggable so that each network can make its own choices (via the Coco network constitution) about how to run their market.
I agree with you that the branding is tricky, in part because the dominant term "blockchain" is describing a specific data structure. The key point we wanted to convey with Coco is that we are trying to enable secure, performant, multi-party computation. We think there will be many models for this over time as TEEs come into wider use. "Blockchain" is just one of them.
The part of a block depending on the hashes of its ancestors seems very useful for tamper-evidence, which is useful in many applications if you can handle the data model & volume. Being able to definitively say who changed what and when is worth a lot if you have to maintain data which could be used in court and a distributed ledger, Merkle tree, etc. is more predictable and much cheaper to run if you don't have to maintain mining-level infrastructure.
The Coco team shares Richard's view that the distinguishing factor is where the trust boundary exists within the system. In the case of Coco, we assume a lack of trust among consortium participants, but we leverage the attestation and anti-tampering features of Trusted Execution Environments (TEEs) to establish trust between the enclaves: assuming that the TEEs themelves are trustworthy, the TEEs can provide cryptographic proof of the software and configuration running on each enclave. In other words, I don't trust you, but my enclave has decided it can trust your enclave based on mutual attestation exchange and mutual authentication. In other words, we've transitioned from a byzantine failure mode (adversary can replace the expected remote code with arbitrary code at will) to a crash failure mode (adversary can shut the remote enclave down at will, but not alter what runs on it).
Once there is trust between enclaves, Proof of Work seemed inefficient as a consensus mechanism, although it's certainly one choice that is available and that can be used with Coco (in this case Coco would provide governance and confidentiality, but scalability and latency would be limited by PoW). Instead we can use any one of many distributed systems techniques such as Paxos or Raft to achieve consensus.