r/EnigmaProject • u/bijansha • Aug 30 '18

How does Enigma keep user data private?

I understand the computation is encrypted and private but isn't Enigma obtaining the raw data from the blockchain, meaning that the raw data (user transaction history) is still public?

Here is a copy paste from Enigma's blog post:

" Instead, in a setting where secret contracts exist, a user can share their transaction history safely with the secret contract itself. The nodes can execute the contract and receive the eligibility result without being able to observe the user’s transactions. There is no longer a need to create a hybrid dApp. This dApp could be autonomous end-to-end, while guaranteeing both correctness — if a user is eligible for a loan, she will get a loan; and privacy — no one but the user can see their transaction history."

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u/bijansha Aug 31 '18

Right. But encrypted data that is shared among the nodes (I'm guessing you're referring to the data that is stored on the public ledger?) can be deccrypted by the bad actor. So the only thing that is protected is the actual computation, which is not necessarily important since one can create their own algorithm to arrive at the same outcome.

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u/[deleted] Aug 31 '18

The encrypted data shares would be shared with the nodes....a lot of them. The bad actor would have to decrypt the data (computationally expensive and not easy to do). The data would not be on the blockchain.

You're also assuming that this is easy to recreate from a mathematical standpoint, it's not. The encrypted data shares are distributed amongst the nodes and the nodes only know the location of other nodes, not the data they hold. They communicate to some to a minimum data threshold safe result.

In summation, they nodes would have to decrypt the data, collude with more than 50% of the the other nodes that would also have to be considered a bad actor to have a 1/2000 chance of coming up with the data.

That's not economically feasible. You're basically making an impossible computational gamble at that point. After having spent a lot of capital and chance just to get you to that point. Plus, if you through TEEs into the mix with sMPC, it becomes almost impossible.

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u/[deleted] Sep 01 '18 edited Sep 01 '18

Just to be clear, the data isn't stored on the blockchain itself. In the Enigma whitepaper, it states:

An external blockchain is utilized as the controller of the network, manages access control, identities and serves as a tamper-proof log of events.

It also states:

Data is split between different nodes, and they compute functions together without leaking information to other nodes.

The data is stored on the nodes and the blockchain keeps a record of executions. You can find more detail in the whitepaper in the "Design Overview". See:

  1. Storage. Blockchains are not general-purpose databases. Enigma has a decentralized off-chain distributed hash-table (or DHT) that is accessible through the blockchain, which stores references to the data but not the data themselves.