Better, Faster zk-SNARKs: Zcash Developers Release New Privacy Tech

Researchers working on the zcash protocol announced today they've invented a new way to speed up the anonymous cryptocurrency.

Today, zcash, the seventeenth-largest cryptocurrency by market capitalization, uses the bleeding-edge cryptographic technique zk-SNARKs to hide balances and user addresses, but the technique comes with a drawback that's hard to ignore: anonymous transactions are sluggish.

While normal transactions take seconds to create, shielded transactions using zk-SNARKs take one to two minutes. That's why engineers have been exploring ways to cut down the time needed to securely generate shielded transactions.

And now, those efforts appear to be bearing fruit.

Zcash engineer Sean Bowe and cryptographers Matthew Green and Ian Miers (all of whom also work for the for-profit Zcash Company) are releasing a living prototype of a new form of zk-SNARK that could lead to huge improvements in speed.

Meet 'Jubjub'

Called Jubjub, the new type of elliptic curve uses math to slash the time needed to create a transaction.

With the technology, Bowe explains in the announcement blog post, the researchers are claiming "record-breaking performance." According to the post, generating zk-SNARKs transactions will now be roughly five times faster while requiring 98 times less computer memory.

The post explains:

"Fast elliptic-curve cryptography in this context allows us to use more efficient primitives for commitment schemes and collision-resistant hashes."

One advantage of the tech is that it makes possible zcash transactions on a smartphone, which was infeasible before.

Zcash will be rolling out the technology in an upcoming upgrade, Sapling, expected sometime in 2018. The change is scheduled to occur as a hard fork, meaning all users and miners will need to upgrade their software to take advantage of it.

The researchers, though, have also open-sourced the technology so anyone can take advantage of it in their own projects.

Zcash Company user education and community team lead Paige Peterson told CoinDesk:

"Consequently, other projects and companies — both within the cryptocurrency and blockchain world and outside of it — will be able to use these techniques."

Elsewhere in the blockchain world, ethereum's next major upgrade, Metropolis, is already paving the way for zk-SNARKs.

Disclosure: CoinDesk is a subsidiary of Digital Currency Group, which has an ownership in the Zcash Company, developer of zcash.

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