ING develops notary service for Corda blockchain

ING said its zero knowledge proof notary service evaluates the validity of a transaction without revealing anything else about it.

Financial services firm ING has announced a "blockchain breakthrough" that it says will improve the privacy and security of transactions made on the open source blockchain platform Corda.

ING's "zero knowledge proof notary service" evaluates the validity of a transaction without revealing anything about it, except that it's valid.

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"Like a notary whose job is to witness the signing of documents to validate them, the 'zero knowledge proof notary' evaluates whether a blockchain transaction is valid or not, but without seeing its contents," ING explained in a statement.

Must read: Blockchain: A cheat sheet (TechRepublic)

Corda's current notary services provide two options: A validating and a non-validating notary.

Although Corda is a recognised distributed ledger technology (DLT) platform, ING said there is a trade-off between a particular security concern and a particular privacy concern. 

"In the case of the validating one, the notary sees the contents of a transaction before it determines if the information is correct, which means participants lose privacy," program director of ING's blockchain team Mariana Gomez de la Villa said.

"A non-validating notary doesn't see a transaction's content, which creates a security risk where the notary could sign off the wrong transaction if a malicious participant builds an invalid transaction. However it protects participants against double-spends, an attack where someone could spend the same asset twice, as does the validating notary."

In a white paper, ING argued the trade-off must be addressed as both concerns may have significant impacts on Corda participants.

ING claims its notary addresses both the privacy and security issue.

The proof of concept is the fourth undertaken by ING's DLT team, with the zero knowledge range proof, launched in 2017, allowing a blockchain network to validate that a secret number is within known limits without disclosing it.

Using a mortgage application as an example, ING said that an applicant could prove their salary sat within a certain range without revealing the exact figure.

See also: Blockchain: Why the revolution is still a decade away

The second proof of concept saw the addition of zero knowledge set memberships, which allowed for other types of information such as locations and names, rather than just numerical data to be validated.

The example ING used for the zero knowledge set memberships was that a bank could validate a new client lives in a country belonging to the European Union, without revealing the country.

The third release, called Bulletproofs, was touted by ING as being faster than the earlier zero knowledge proofs and did not require a trusted setup.

Also this week, Singaporean telco Softbank, alongside IBM and blockchain firm TBCASoft, announced they were working together to enable carriers to leverage blockchain technology through the Carrier Blockchain Study Group (CBSG) Consortium.

TBCASoft has created a cross-carrier blockchain network designed to support industry-specific use cases, such as cross-border payments, digital identity, and telecom supply chain.

The first application to be launched by the CBSG Consortium is the Cross-Carrier Payment System, which will allow travelling mobile subscribers to use their mobile payment app with local merchants while abroad.