Blockchain-based technologies are attractive for security applications because blockchain is innately transparent and highly reliable. While the term 'transparency' generally isn't associated with security, blockchain works because everyone has a copy of the same information. The idea is if an individual attempts to tamper with, or falsify, the information stored in a block, it would be rejected for not matching everyone else's copy.
The problem is when an organization wants to store confidential data on a blockchain, everyone on the blockchain would have a copy of the information.
When it comes to monetary funds, they are secured with a cryptographic key. The problem is, if a key is lost, the funds are often irretrievable. The same goes if a key is stolen; your funds are most likely gone.
That’s where Fujitsu Laboratories come in: they've developed blockchain-based security technology that would not only be able to potentially recover lost or stolen keys, via secret sharing-based keys, they’d also be able to encrypt documents stored on a public blockchain.
These secret sharing-based keys could be split across multiple users so only authorized parties could decrypt confidential data. If two separate users each hold a portion of a key, they would have to cooperate to generate a full key and unlock a confidential document. This same technology would make it possible for large financial transactions to require multi-user authorization, if portions of a key are held by different parties. Secret sharing-based key management could even provide a solution to lost keys. If one user loses their key portion, they’d be able to collaborate with the other authorized user to try and find a solution.
If you're dealing with an issue stemming from a stolen key, Fujitsu has an answer for that as well. They've developed the ability to restrict transactions to pre-established policies. That means that a user could limit transactions to a list of places they're interested in being able to spend their digital currency. Then, if a key is stolen, and the thief attempts to use the funds outside of a pre-specified transaction, the transaction would be denied.
Fujitsu Laboratories have a prototype of this system on Hyperledger, an open source blockchain platform, which would allow integration with Ethereum. They're effectively layering even more security on top of an already secure platform.
Being able to ensure the preservation of the original state of a document, while also being able to keep it confidential, would be a highly useful application of blockchain technology. As far as being able to share a key and requiring cooperation among parties, financial trading applications come to mind. That would make initiating a fraudulent trade that much more difficult. With Ethereum, Fujitsu’s new transaction restriction and document encryption would allow blockchain technology to be applied to a wide variety of fields.