Zcash upgraded to Sapling at block height 419200 (approximately October 29)

The next major update to Zcash, codenamed Sapling, is scheduled to activate on October 29, 2018, at block 419,200.

Sapling represents cryptographic breakthroughs in protocol design and engineering over the past two years that will improve the performance and functionality of shielded (encrypted) transactions. Today, most Zcash transactions still use transparent addresses, in much the same way as Bitcoin. This is largely due to the enormous computational overhead required to prove the validity of shielded transactions. With Sapling, we can take a (significant) step toward making shielded addresses more common.

Sapling’s performance in shielded transactions

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Currently, if you create a new z-address, it looks like this:

 zcA6qngiR3U7HxYopyTWkaDLwYBd83D5MT7Jb9gpgTzPLMZytzRbtdPP1Syv4RvRgHeoZrJWSask3DyfwXG9DGPMWMvX7aC 

This is called a Sprout stealth address because it was introduced when the original version of Zcash, “Sprout,” was released. This address starts with “zc.”

After Sapling is activated, the generated stealth address will look like this:

 zs1z7rejlpsa98s2rrrfkwmaxu53e4ue0ulcrw0h4x5g8jl04tak0d3mm47vdtahatqrlkngh9sly 

This new shorter address will start with "zs" and is called a Sapling shielded address. The legacy Sprout shielded addresses will still work after Sapling is activated, but will be deprecated in favor of this new type of address.

Influence

Payments using the new Sapling shielded addresses can be constructed in seconds and take up only 40MB of memory. Exchanges, mobile wallets, vendors, small traders, and other third parties will be able to support shielded transactions.

The increasing usage of hidden addresses will improve the privacy protection efficiency of the entire network.

Decoupling payment authorization

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All shielded transactions require the creation of a zero-knowledge proof . Currently, the hardware that builds the proof must hold the spending keys to authorize the transaction. Sapling changes this, and the hardware that builds the proof can now be independent of the hardware that signs the transaction.

Influence

Entrepreneurs can run the cheap signing step in a trusted environment and have another computer that does not have access to the spending key generate the proof. In addition, hardware wallets can also support stealth addresses by allowing the connected computer to generate zero-knowledge proofs without exposing the spending key to the connected computer.

Key strengthening

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Shielded addresses currently support Incoming Observation Keys . Holders of an Incoming Observation Key for a shielded address can see the value and memo fields of incoming transactions to that address. However, they cannot see the addresses from which transactions were sent, nor can they spend funds.

Sapling extends the viewing key capabilities to include the ability to see transactions being sent from shielded addresses. Visibility includes transaction value, memo field, and destination address.

Influence

The observation key allows the owner of the shielded address to directly inspect the transaction details without exposing the private key (spend key). In addition, the observation private key can also be shared with a trusted third party for commitment, auditing or other purposes. Currently, only incoming transactions are visible to the observation key.

Efficient wallet using many stealth addresses

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Sapling shielded addresses have a feature that billions of addresses can receive payments at the same time without any additional cost to the receiver. And all these addresses are unlinkable.

Influence

Currently, exchanges and merchants must pay a computing resource “penalty” to receive a large number of shielded address transactions. The new Sapling shielded addresses allow these merchants to create a large number of distinct and unlinkable shielded addresses for their clients.

Follow our progress

We’re really excited about the potential of the Sapling update and can’t believe how exciting it is to make shielded payments faster and easier for users! We’ll continue to update here with information about the activation date and provide users with resources and tips for handling this update.

Sapling upgrade time: https://z.cash/upgrade/sapling