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Frequently Asked Questions

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Using

Zcash Ecosystem

How can I acquire Zcash (ZEC)?

You can buy ZEC from participating online exchanges/markets with another cryptocurrency or fiat currency (depending on which exchange you use). We put together a list of exchanges supporting Zcash trades at launch here but these are just a few of the first exchanges and wallets that supported Zcash at launch. There have been many more that have come into existence. We encourage the community to host their own lists and repositories of successful providers such as in this Zcash community blog. You might also have luck finding someone to buy Zcash from in-person or offering services/products to be paid for in Zcash. And of course, you are highly encouraged to run a Zcash mining node to earn tokens for taking part in securing the decentralized network!
You can get more info on installing a node and sending ZEC in our 1.0 Guide.

How do I install a Zcash wallet?

There are already a variety of third-party options for storing and sending ZEC, in addition to the officially supported core client, zcashd. Many of these third-party wallets have limitations in their support for Zcash; in particular including shielded addresses in a transaction requires a large amount of computer memory and most wallets (both hardware and web-based) have yet to integrate this feature.
You can browse a list we put together of third-party support at launch here. As mentioned in the above question, these are a few of the first exchanges and wallets that supported Zcash at launch. There have been many more that have come into existence. We encourage the community to host their own lists and repositories of successful providers such as in this Zcash community blog.

What is the difference between addresses that start with "t" and addresses that start with "z"?

Zcash is built upon and extends the Bitcoin protocol. Addresses which start with "t" behave exactly like Bitcoin, including their globally public properties and we refer to these as "transparent addresses". Addresses which start with "z" include the privacy enhancements provided by zero-knowledge proofs (see FAQ: what is a zero-knowledge proof?) and we refer to these as "shielded addresses". It is possible to send ZEC between these two address types.

Does Zcash have multi-signature transactions?

Yes, but not with privacy. Zcash supports all of the same kinds of transactions that Bitcoin supports, such as multi-signature transactions, but all of those don't have any added privacy — they have the same privacy properties as in Bitcoin, i.e. global transparency. You can see the difference between single-signature and multi-signature transparent addresses with their starting characters: "t1" and "t3" respectively.
Note that it's possible to sandwich any transaction using transparent addresses — e.g. a multi-signature transaction — between private Zcash spends. For example, do a private Zcash spend to yourself, then do a globally transparent transaction (which could be a multi-signature transaction), and then the new holder of the funds (possibly you or possibly someone else) does another private Zcash spend to themselves.
Some privacy benefits may be preserved from that technique. We would caution against assuming this gives blanket privacy in general for any use, though, so this is an area for future study.

What is the difference between Zcash and Bitcoin?

Zcash is a fork of the bitcoin protocol, the first and most widely used blockchain cryptocurrency. This means it maintains it's own blockchain and currency token. Zcash builds on the existing work from the Bitcoin core team to enable privacy preserving transaction data using zero-knowledge proofs (see FAQ: what is a zero-knowledge proof?). It also includes some non-privacy changes to bitcoin, including its proof of work algorithm (see FAQ: "What are you changing from Bitcoin's Design? What parts of the Bitcoin network remain?" for more detail on technical differences).

Zcash Client (zcashd)

How should I run Zcash?

To join the network, the 1.0 Guide is the best place to start. Keep updated with the information we post on our blog to know the current phase and stay updated on zcashd, the core Zcash client.

Is there a version for Windows, Mac, Android, or iOS?

The Zcash company has official support for only Linux. While we have no intentions to officially support other operating systems, a third-party has already ported the client for MacOS and you can keep an eye on our community forum for future third-party Windows and mobile support. Since we cannot endorse software we do not build ourselves, we encourage users to do due diligence on the legitimacy and safety of software built by third-parties before downloading and installing.

How do I mine ZEC?

Check out the 1.0 Guide for instructions to install and run a node on the Zcash test network. Our mining guide can assist in setting up your node to mine.

General

Business

What is the mission of Zcash?

Our mission is to create an open financial technology platform that everyone in the world can use.
We believe that personal privacy is necessary for core human values like dignity, intimacy, and ethics. Companies need privacy in order to conduct their business; and we believe that privacy strengthens social ties and social institutions, protects societies against their enemies, and helps societies to be more peaceful and more prosperous. Finally, in an open and programmable financial system, privacy is the only way to ensure fungibility.
We are a science-driven team. We are the discoverers of the underlying scientific techniques and the designers of the protocol; we are not the controllers or the power-holders. We believe in the value of decentralization, which promotes security and fairness. Every user of Zcash is a part of the network, and helps protect it against failure and corruption. We created Zcash, but its ultimate destiny lies not in our hands, but in yours.

When did Zcash launch?

The Zcash block chain launched on October 28, 2016, bringing into existence the first Zcash monetary units. This software release and the initial phase of the block chain is called ‘Sprout’ to emphasize that it is a young, budding block chain with great potential to grow.
Please read our launch blog post for more details.

Who are your investors? How is Zcash funded?

A full list of Zcash investors can be found on our team page.
Zcash has raised capital in a non-traditional way; there have not been the same clearly delineated “Series A” or “Seed” round nominations like other similar technology companies. The first public investors included: Pantera Capital, Digital Currency Group, Fenbushi Capital, London Trust Media, Evolve VC, Naval Ravikant, Niraj Mehta, David Dacus, Roger Ver, Alan Fairless, Ben Davenport, Brian Cartmell, James Nicholas, Jonathan Perlow, Charlie Songhurst, Adam Ludwin, Devon Gundry, Ryan Smith, and Rop Gonggrijp.
In the summer of 2016 there was a private raise that included the following new and already established funders: Aaron Grieshaber, Branson Bollinger, Maple Ventures (Amir Chetrit and Steven Nerayoff), Brian Cartmell, Vlad Zamfir, Roger Ver, Digital Currency Group, Barry Silbert, Charles Songhurst, Fenbushi, Shapeshift, Erik Voorhees, David Lee Kuo Chuen, Fred Ehrsam, Sebastian Serrano, and Li Xiaolai.
There will not be a crowdfunding round.

Who is the Zcash team?

Our team includes the scientists who invented the Zerocash protocol, engineers and communicators with a specialized track record in open privacy technology, advisors who are leaders in the Bitcoin, Ethereum, and academic communities, and well-regarded investors. See our team page for details.

What is the Zcash Foundation?

The Zcash Foundation is a non-profit entity for maintaining and improving the Zcash protocol in the interests of all users, present and future. It will receive 1.44% of the monetary base (over four years) to support this work, thanks to pledges from some of the stakeholders to donate part of their share of the Founders’ Reward.

If the Zcash cryptocurrency provides transactional privacy, won’t bad people use it?

Yes, but bad guys will use anything. Bad guys use cars, bad guys use the Internet, bad guys use cash, bad guys use the current banking system. Our goal is not to invent something that bad guys can't use, it is to invent something that can empower and uplift the billions of good people on this planet.
For more context about our values, see the Hello World blog post.

Economics

What are the economics of Zcash? Is there going to be a fixed monetary base?

Zcash's monetary base will be the same as Bitcoin's — 21 million Zcash currency units (ZEC, or ⓩ) will be mined over time. It is a scarce token just like Bitcoin which can be transferred globally and exchanged to/from other cryptocurrencies or fiat currencies via online exchanges, in-person transactions, etc.
10% of the mining reward will be distributed to the stakeholders in the Zcash Company — founders, investors, employees, and advisors. We call this the “Founders’ Reward”.

Since the value sent between shielded addresses is private, how can we determine the number ZEC in circulation?

Currently, we know that every miner validates every transaction, and each transaction comes with a zero-knowledge proof that it doesn't violate conservation-of-money (i.e. a proof that the money coming out of the transaction is ≤ the money going into the transaction).
This reasoning depends on the soundness of the zero-knowledge proofs. If someone could get the miners to accept a transaction that created new money — if you could somehow forge a zero-knowledge proof or defeat the zero-knowledge-proof-verifier software in the miners — then you could counterfeit money.
We are investigating options for the future which would enable accounting for all ZEC in existance. Stay tuned to our blog for any proposals on this matter.

What is the Founders’ Reward?

10% of the eventual monetary base goes to the founders. The Founders’ Reward is distributed incrementally over the first four years of mining, so that there is continued incentive and continued resources for the founders to improve the value of the coin. Unlike a pre-mine or an Initial Coin Offering, this structure offers little or no opportunity for the founders to pump-and-dump.
After four years, the Founders’ Reward ends and all of the mining rewards after that go to the miners.
Read more in the blog post Funding, Incentives, and Governance.

Who will receive the Founders’ Reward?

The investors who funded the creation of Zcash will collectively receive 1.65% of the ultimate Zcash monetary base. The founders, employees, and advisors will collectively get 5.72%.
The two biggest single beneficiaries of the Founders' Reward are the “Zcash Company strategic reserve” receiving 1.19% and the non-profit Zcash Foundation receiving 1.44%. The strategic reserve fund will go towards new projects to increase the value of the Zcash Company and the Foundation fund will benefit the maintenance and evolution of the Zcash protocol in the interests of all users, present and future.
Read more in Continued Funding and Transparency.

Is the Founders' Reward a pre-mine?

I (Zooko) don’t call it that because it’s not “pre”. (And it’s not mining.) Also, unlike a typical “pre-mine”, the Zcash Founders' Reward is transparent and it aligns the incentives of the creators and the users of the system.

What markets are supporting Zcash?

Many markets and exchanges have decided to support Zcash. See our blog post on third party support at launch for a preliminary list and this community maintained page of exchanges which support ZEC.

Community

Are there online Zcash communities?

There are! Particularly our offical community forum and the community-run developer chat.

Are there any local Zcash communities? How do I find local Zcash enthusiasts and traders?

You might find some Zcash enthusiasts and traders at local cryptocurrency meetups. Get in touch if you’re thinking about or interested in starting a Zcash meetup in your community, we’d love to hear from you! info@z.cash

Technical

Overview

Simply put, what is a zero-knowledge proof? How does Zcash integrate it?

Zero knowledge proofs are a scientific breakthrough in the field of cryptography: they allow you to prove knowledge of some facts about hidden information without revealing that information. The property of allowing both verifiability and privacy of data makes for a strong use case in all kinds of transactions, and we’re integrating this concept into a block chain for encrypting the sender address, the recipient address, and the amount. A block chain that encrypts transaction data (making it private) and lacks zero-knowledge proofs also lacks the assurance that all the transactions are valid. This is because the nodes in the network can’t determine whether the sender really had that money or whether they previously sent it to someone else, or never had it in the first place. The encrypted data becomes unverifiable by network nodes.
In Zcash, we use a particular type of zero-knowledge proof called zk-SNARKs (or “zero-knowledge succinct non-interactive arguments of knowledge”). Within a Zcash transaction, there may exist a string of data that the sender of a transaction provides –the “zero-knowledge proof”– along with the encrypted transaction data which proves properties of the encrypted data cryptographically, including that the sender couldn’t have generated that string unless they had ownership over the spending key and unless the input and output values are equal. The proof also guarantees creation of a unique nullifier which is used to mark tokens as spent, when they are, in fact spent. This allows for verification that the transaction is valid, while preserving privacy of the transaction details.

What is the difference between Zerocoin, Zerocash, Zcash and ZEC?

Zerocoin is a cryptographic currency protocol invented by Ian Miers, Christina Garman, Matthew Green, and Aviel D. Rubin in 2013. Zerocash is an improved cryptographic currency protocol invented by Eli Ben-Sasson, Alessandro Chiesa, Christina Garman, Matthew Green, Ian Miers, Eran Tromer, and Madars Virza in 2014. Zcash is an implementation of the Zerocash protocol, with certain improvements as described in our protocol specification (all of the scientists who designed the Zerocash protocol are members of the Zcash team). We have adopted ZEC as the informal three letter currency code for the Zcash currency, and ⓩ as its currency symbol.

Does Zcash offer complete anonymity for transactions?

Zcash enhances privacy for users by encrypting sender, amount and recipient data within single-signature transactions published to its public block chain ledger.
Zcash does not: encrypt data for multisignature, protect against correlations made with public transactions (for example, when Zcash is traded to/from another cryptocurrency) or obfuscate IP addresses. It is possible to use it in conjunction with an anonymizing network such as Tor, in order to obtain protection against network eavesdropping which is complementary to transaction privacy.
It should be noted that while Zcash facilitates anonymization for its users amongst a wide pool of individuals, we align more with the term “privacy” to describe what Zcash technology aims to provide. While related in scope, the terms have subtle differences. Anonymity relates to removing personal identifiers linked to potentially public data such as sending an anonymous tip to law enforcement or wearing a mask during a protest. Privacy considers the data itself in need of protection such as a discussion during a private meeting and more relevant, the encryption of information - whether for keeping personally or sharing with a select number of others. Anonymity methods can enhance privacy goals, such as defending against targeted attacks on private data, and vice versa if the protected data relates to personally identifiable information. The encryption of data in private Zcash transactions aligns with the latter as it is foremost a tool for financial privacy with the added benefit of increased anonymity.
For more information on anonymity properties in Zcash, see How does Zcash compare to other cryptocurrencies with anonymizing properties?

Will Zcash contain a backdoor?

Neither Zcash nor any other cryptographic algorithms or software we've made contains a backdoor, and they never will.

Is Zcash peer reviewed?

Yes. Zcash is based on the peer-reviewed Zerocash protocol, which was published in the IEEE Security & Privacy conference in 2014. The Zerocash paper provides a detailed technical overview of the specification. Our changes to the protocol are not (yet) peer-reviewed, but they are described and justified comprehensively in our protocol specification. Those changes are also in the process of being subjected to several independent security audits.

Is Zcash built on the Bitcoin block chain?

No. Zcash is its own separate block chain.

Have you considered sidechains, Ethereum, or embedding into the Bitcoin protocol?

Yes, we've explored all of those ideas in varying degrees. What we're doing right now is the simplest thing that can make Zcash a real, live, permanent medium of exchange and store of value, and that is to create a separate block chain.

What are you changing from Bitcoin's Design? What parts of the Bitcoin network remain?

We're following a general principle of "conservative innovation". Aside from the Zerocash privacy protocol (itself already a massive technological achievement), we wish to avoid making changes from Bitcoin's design without a strong rationale.
We’ve decided to make a number of relatively conservative changes to Bitcoin’s consensus rules:

  • We’ve adopted a “smooth” difficulty adjustment algorithm, based on DigiShield v3.
  • We’ve adopted a memory-hard proof of work, Equihash, which involves adding a memory-hard problem to be solved in valid blocks.
  • We’ve changed the block interval target from 10 minutes to 2.5 minutes, and modified other constants in order to preserve the monetary base of roughly 21 million coins and halving interval of 4 years.
  • We’ve increased the block size limit to 2MB.
  • We require coinbase transactions to contain an output to our Founders’ Reward P2SH address during the first 4 years before the first halving.
  • We require transactions spending coinbase outputs to contain no “transparent” outputs (vout should be empty).
  • We’ve removed activation rules for softforks in Bitcoin and made them enabled by default.

Zcash embeds a confidential value transfer scheme alongside the traditional Bitcoin infrastructure; for most purposes, it simply adds additional behavior to the existing primitives.
For further detail, see the 'Consensus Changes from Bitcoin' section of our protocol specification.

How does Zcash compare to other cryptocurrencies with anonymizing properties?

All anonymity is not created equal: you're better off if we can only figure out that one out of 6 billion people bought a Nickelback album, then if we know it was either you or one guy in Tristan da Cunha. The size of your anonymity set matters and the mixing strategies which other cryptocurrencies use for anonymity provides a rather small one in comparison to Zcash. This is not to say these other methods are worthless, there are tradeoffs between the two, but Zcash has a distinct advantage in terms of anonymity and we think it matters.
If you are worried about maintaining privacy given repeated interactions with merchants or others who already have some partial information about you, the size of the anonymity set matters considerably. Long term intersectional attacks are a major problem with anonymity systems. The smaller the set you mix with on any given transaction, the easier it is for some third party to use outside information to eliminate everyone else in the mixing set (e.g because she knows no one else in the set was online at the time of the transaction or was in your approximate geographic area), and determine the true spender. One of the few effective defenses we have for this is to simply include as many people as possible in the anonymity set. If you want to avoid companies building financial profiles of users from the block chain, this is precisely the type of attack you need to thwart. When you perform a transaction in Zcash, you effectively mix with all transactions ever performed (except those where the sender chose to be transparent).

What are SNARK public parameters? How is Zcash generating its SNARK parameters securely?

A set of public parameters are required for generating the proofs required to validated private transactions. The process of generating these public parameters (commonly referred to as “paramgen”) also produces a by-product (which we have nicknamed the “toxic waste”) that could be used to subvert the block chain by creating fake coins that are indistinguishable from real ones (the relationship between the public parameters and this toxic waste is similar to that between a public key and a private key). It is therefore important that this toxic waste be securely destroyed.
We have designed a process whereby the job of generating the public parameters is split between a number of people, each of whom generate a piece of the parameters. These pieces can then be brought together and combined to create the public parameters. As long as one of the people involved in generating the parameters destroys their portion of the “toxic waste”, there is no way to subvert the parameters.
For technical details on these parameters, see Zcash Parameters and How They Will Be Generated.

Mining

How will Zcash be created?

Like Bitcoin, Zcash is a mined cryptocurrency, which means that new ZEC will be created each time a block is added to the Zcash block chain. New blocks will be created roughly every 150 seconds (2.5 minutes). The monetary supply curve will mirror Bitcoin’s, except that, because Zcash’s blocks will be mined 4 times as frequently as Bitcoin’s, the number of ZEC created per Zcash block will be a quarter the number of BTC created per Bitcoin block. The first weeks after Zcash launch will be in a “slow-start” mining period.

Is Zcash proof-of-work? What mining algorithm do you use? Is it ASIC resistant?

Yes, since launch, Zcash has been based on proof-of-work. Maybe the community will choose to change it to proof-of-stake or something someday. We cannot predict what the community or communities will ultimately decide about such things but are very much open to improvement and evolution.
We are currently using Equihash as the proof-of-work for block mining in Zcash. Equihash is a proof-of-work algorithm devised by Alex Biryukov and Dmitry Khovratovich. It is based on a computer science and cryptography concept called the Generalized Birthday Problem. Please read the Why Equihash blog post for more details.
The algorithm is currently not economically implementable in ASIC. We’re still evaluating whether we think it will resist custom hardware (“ASIC”) implementation long-term.

What will the average block time be?

2.5 minutes (150 seconds)

How many ZEC will be made per block?

After the slow-start period, 12.5 ZEC will be mined per block. Each 4 year period (or 840,000 mined blocks), the ZEC creation amount will halve (from 12.5 to 6.25 to 3.125 to 1.5625 and so on).
See the question What is slow-start mining? for details on the slow-start period.

What is the maximum block size?

2MB

What is slow-start mining?

While we have taken every precaution (and subjected the code to security audits), we are unable to guarantee that the Zcash code is 100% free from bugs and security vulnerabilities. In order to minimize the impact of any unforeseen problems during the launch of Zcash, the amount of ZEC each time a block is mined will start at zero and gradually ramp up to 12.5 ZEC after 34 days. The slow-start period ended on December 1st, 2016.

Where should I ask a question that is not answered on this page?

The best place to ask questions is our community forum. We'll add more common questions to this document as we become aware of them.