One of blockchain’s main selling points is that all of its transactions are public. Even in private blockchains, transactions can be public to all of the participants in that network.
An Estonia-based startup is now out with a possible solution. Lightstreams has launched a blockchain network with a new Permissioned Block protocol that employs smart contracts to grant, block or revoke access to content for specific users.
“The blockchain is broken at the moment in terms of privacy,” said Lightstreams CEO/founder Michael Smolenski in a statement. “It’s simply too public.”
His company’s solution is a modification of the popular Ethereum blockchain protocol. With Permissioned Blocks, users who have been granted access by a smart contract’s author can share content or transactional info with other users with similar access. Or the smart contract’s owner can determine which users get access to attached content, or under what conditions they will get access, such as after making a payment.
In other words, Lightstreams breaks the blockchain into zones of controlled access. In addition to privacy issues for financial and other sensitive data, Lightstreams points to the upcoming General Data Protection Regulation (GDPR), which requires privacy of personal data as the default. Personal data made widely public on a blockchain would seem to violate that requirement.
While this ability to granularly control access is a key selling point for his company’s blockchain network, Smolenski also points to two other features: speed and decentralized storage.
Instead of the labor-intensive, consensus-based and slow “mining” used in Ethereum to add blocks of data, Lightstreams employs the Tendermint proof-of-authority, which achieves a similar kind of consensus to add data blocks but without human-controlled mining. The result, Smolenski told me, is a transactional speed that is “an order of magnitude” faster than Ethereum.
The data is stored in a decentralized storage network, with the blockchain acting as an access control and pointer.
Because blocks written to a blockchain are essentially immutable, Lightstreams stores the data separately to facilitate erasure (such as for GDPR’s right to be forgotten) and data sharing in a peer-to-peer distributed file system.
In Lightstreams, a document is attached to a smart contract whose author defines conditions for access. For instance, the document might be a video, and the author might decide to charge one Photon token for each viewing. Photon is the name of Lightstreams’ cryptocurrency.
The entire video could be stored within a Lightstreams node on the author’s own computer, wrapped inside a smart contract security layer and played only when someone in the network pays one Photon.
But the video can also be broken into segments and stored across the Lightstreams network, with each segment bearing a reference number so the video is played back in sequence and each segment in a secure node that controls access according to the terms of the smart contract. This allows the video to be played back on a peer-to-peer basis, so that the larger the network of users, the more storage locations there are to ensure capacity.
Here’s Lightstreams’ video explanation of the above:
Smolenski also suggests a use case where a network user wants to grant access for her medical record to her specialist. The record itself could reside on several people’s computers, but the smart contract limits access to, say, the specialist.
This allows the network user to control her own medical information, securely. The record remains stored as segments on the computers in the network, viewed by the specialist in its entirety but not transferred to the specialist.
When I asked if having sensitive data in so many distributed locations creates more opportunities for vulnerabilities, Smolenski pointed out that the smart contract provides a security layer for each location of data. Additionally, each storage location — that is, each computer in the network — would only have an incomplete portion of the document.
But, he added, “If you want to make it 100 percent secure, you put [data] behind a firewall,” which, of course, limits access.