What is Zcash?

Launching this fall (2016)

Zcash is a decentralized and open-source cryptocurrency that offers  privacy and selective transparency of transactions using advanced  cryptography. Zcash payments are published on a public blockchain, but  the sender, recipient, and amount of a transaction remain private. Zcash software is available in an alpha release for experimentation  and software development, but the real currency doesn't yet exist and  will not until the official launch this fall. Download the Tech Preview  release here, or get started with our Public Alpha Guide.   

Transaction metadata

Bitcoin transactions work using triple-entry accounting: transactions  combine the "outputs" of previous transactions and split into new  outputs of arbitrary value. The spend-authority of the "inputs" of a  transaction, as well as the balance of the transaction, are checked  manually by all nodes. This means that all unspent outputs must be kept  by all fully verifying nodes, but also, that all nodes are aware of all  values and parties involved in transactions.   

Zero-knowledge proofs

Our zero-knowledge proving scheme makes it possible to hide values  and other identifying information from the public. Using advanced  cryptographic techniques, users simply prove that the values balance and  that they are authorized to spend such value. (And that they have not  spent it before.)   

Performance

The proofs that we use in our scheme, called zk-SNARKs, are short and  take very little time to verify. Transaction "outputs" in our protocol  are not retained by full nodes, as they are entered into a finite-size  accumulator. Only the spendability of an output is retained. As a  result, nearly all components of a transaction can be pruned by fully  validating nodes.   

Further Information

We're working to provide more in-depth technical specification. You can find further details on our developer wiki's specification page.  

https://z.cash

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