Updated details [ZEC] ZCASH + Announcing Zcash Cloud Mining



  • Zcash and Jaxx Announce ZEC approved and live on iOS Appstore

    Toronto, ON – April 12, 2017 – Today marks another historic day for Zcash as the privacy-oriented cryptocurrency announces its approval on the App Store via Jaxx’s iOS platform.

    The team behind Zcash includes some of the leading scientists behind the advanced zero-knowledge technology used in the protocol. Together with expert engineers, they are continuously researching and developing improvements to the infrastructure and usability for users and third-party services like Jaxx.

    Zooko Wilcox, CEO of the company behind Zcash development, Zerocoin Electric Coin Company, said, “Jaxx is a very simple, easy-to-use wallet and the team behind it has been a pleasure to work with. I’m delighted that thanks to them, hundreds of millions of iPhone users can, for the first time send and receive Zcash from their phones.”

    Jaxx was the first wallet to integrate Zcash following its mainnet launch on October 28, 2016, and is thrilled to now have Zcash available on its iOS platform. Apple has a rigorous approval process, especially for allowing cryptocurrencies onto the App Store, and their approval is a clear indication that Zcash is a fast growing and well respected technology.

    Anthony Diiorio, CEO of Jaxx, said, “The privacy aspect of their technology meshes really well with Jaxx’s philosophies. We’ve been working on a Zcash-integrated iOS version for a long time and we’re over the moon that Zcash has been approved on the App Store.”

    Jaxx also confirmed today that they are in talks with Zcash on the possibility of supporting ZEC shielded addresses. Currently, Jaxx supports transparent addresses which behave similarly to Bitcoin, publishing transaction data publicly to the blockchain. While the mere use of shielded addresses by others provide greater privacy for transparent addresses compared to Bitcoin, official support for shielded addresses in Jaxx will significantly enhance capabilities for users.

    “Zcash is a very well run project and it’s been an absolute pleasure to work with Zooko and team. We look forward to continuous collaboration between our two projects, especially for when we implement Zcash’s shielded addresses,” said Diiorio.

    In addition to being integrated on all of Jaxx’s platforms, Zcash also announced its integration on a second wallet, SmartWallet, a Brazilian money application.

    Jaxx’s iOS version with Zcash is now available for download via jaxx.io or on the Apple App Store.

    Zcash CEO Zooko Wilcox and Jaxx CEO Anthony Diiorio are available for interview.

    About Zcash:

    The Zcash Company is a science-driven team; a combination of academic expertise in computer science and cryptography with security software engineering talent. We are developing the next generation of secure digital currency and blockchain technology through the use of zero-knowledge proofs, to guarantee privacy and confidentiality. We aim to set a new standard for privacy. The Zcash protocol is a decentralized and open-source cryptocurrency offering total payment confidentiality. Unlike Bitcoin, Zcash transactions automatically hide the sender, recipient, and value of all transactions on the blockchain. It is based on peer-reviewed cryptographic research, and built by a world-class, security-focused engineering team. However, as with any new technology, there is risk involved. Currently the team is focused on building and maintaining an open, permissionless system that is viable, robust, and justifiably reliable and secure for users.

    About Jaxx:

    Jaxx is a multi-token blockchain wallet that provides a unified experience across 9 platforms and devices, including Windows, Apple and Linux desktops, Apple and Android mobile devices and tablets, as well as Google Chrome and Firefox extensions. The Jaxx wallet enables crypto-to-crypto exchange with frictionless in-wallet conversion via Shapeshift. Users are always in control of their keys and Jaxx neither holds nor has access to customer funds. Design and user experience driven, and built with simplicity in mind, Jaxx’s mission is to become the interface to the blockchain world.

    To learn more, visit jaxx.io

    Jaxx Press Contact

    Annie Lee



  • Zcash (ZEC) Pre Release  v1.0.8-1

    Download



  • Security Announcement 2017-04-13

    Synopsis: A bug related to transaction priority handling may allow an attacker to crash Zcash nodes (DoS) via a specially crafted transaction. A fix is implemented in zcashd release 1.0.8-1.

    There is a separate release post documenting the included changes.

    ZcashCo, and several exchanges, wallet vendors, and miners have already deployed a mitigation as well as detectors for this attack vector. No attacks have been detected.

    Who is at Risk: Users are at risk who rely on zcashd releases starting with 1.0.4 up to and including 1.0.8.

    We have collaborated with major exchanges, wallet providers, and miners and they have already mitigated this issue for their services.

    Who is not at Risk: Users who have upgraded to zcashd 1.0.8-1, or rely on a service which has done so are not at risk.

    How can at-risk users protect themselves?

    1. Upgrading to zcashd release 1.0.8-1 is the most certain protection.
    2. For users of third party services (such as exchanges, wallets, or mining pools), check if the service has announced upgrading to zcashd 1.0.8-1.

    How can I tell if an attack is occurring? ZcashCo and several large exchanges, wallet providers, and miners have deployed sensors which detect attacks against this vector. In the event that an attack is detected, the ZcashCo will take the following actions:

    Note: The major exchanges, wallet vendors, and miners we are in communication with are already protected against such an attack.

    Impact: If an attack transaction is successfully executed then only the users running vulnerable clients which have accepted the transaction in their mempool will be vulnerable. Accepting an attacker's transaction with an old client may cause the Zcash client to crash.

    Technical Background: Zcash, like Bitcoin, assigns a priority to transactions in order to decide whether they should be accepted into a node's mempool. In practice the current transaction volume for Zcash is sufficiently low that this rarely has an effect, but the mechanism is still enabled. In Zcash 1.0.4, a change was made to this calculation to boost the priority of shielded transactions. However, an error in this code can –in circumstances that are normally rare, but can be forced by an attacker– result in an out-of-bounds memory access, which causes a segmentation fault.

    Followup Announcements:

    • See the security notifications page for further updates on this issue, and any future security issue.
    • Continue to check this blog.


  • Zcash Announces Apple App Store Approval on Jaxx’s iOS Platform

    An exciting update for the Zcash ecosystem comes from the Jaxx team. Jaxx were one of the very first wallets to support Zcash, implementing it into their Android and desktop wallets only days after the Zcash launch on October 28th.

    In their initial statement announcing integration with Zcash, they indicated upcoming support in their iOS wallet and today, Zcash on Jaxx for iOS is live!

    Anthony Di Iorio, CEO of Jaxx, says, "The privacy aspect of their technology meshes really well with Jaxx’s philosophies. We’ve been working on a Zcash integrated iOS version for a long time and we’re over the moon that Zcash has been approved on the App Store."

    Jaxx for iOS has 32,000 users and growing. With the inclusion of Zcash, now hundreds of millions of users have the ability to send and receive Zcash from their iPhones.

    Jaxx has additionally confirmed their interest in supporting shielded addresses in the future. As more wallets with easy-to-use interfaces introduce shielded addresses into their software, not only will the users of those applications gain enhanced privacy for transactions they send and receive but also, the ecosystem as a whole will become more private.

    We are excited about the expansion of Zcash into additional operating systems and hope to see this trigger more support for Zcash in iOS moving forward.

    Jaxx for iOS joins a growing list of third-party GUI applications supporting Zcash 

    Wallets considering adding Zcash support should reach out to us in emailcommunity chat, we'd be happy to help!

    For more details, see the full press release from Jaxx.



  • Zcash [ZEC] 1.0.9 Postponed

    We have decided to postpone the Zcash Sprout 1.0.9 release from today's planned release date to mid-May.

    We have been planning a transition in May of our release process and policies to improve our collaborations with community and industry partners, to improve safety, and to prepare for our Sapling protocol upgrade. Due to the v1.0.8-1 hotfix release last week, it makes the most sense to postpone 1.0.9 until the new process is in place.

    We'll post an announcement of the new release process and policies ahead of the 1.0.9 release. We have exciting features and collaborations underway. Stay tuned!



  • ZCASH [ ZEC] Payment Contexts & Reusing Shielded Addresses

    The privacy provided in Zcash allows users to disclose a shielded
    payment address publicly or to multiple individuals without the worry of
    transactions sent to that address becoming linked in the blockchain.
    When sending to or from a shielded address, the data involved in that
    side of the transaction is encrypted (regardless if receiving from or
    sending to a transparent address).








    Distinct Payment Contexts

    While shielded addresses are encrypted, the scope of the payment address is something to consider.

    If Alice has a small business she runs out of her home, any business mail sent to her home address provides a clear link between her personal life and business even if the details of the correspondences are secured in envelopes. In a similar fashion, if Alice has a business which accepts Zcash for services or products and personal blog which she posts the same Zcash address for accepting donations to, it is possible for a third-party to correlate the business and blog.

    It is therefore recommended for Alice to use separate payment addresses for her business and blog, similar to having a separate business address (such as a private mailbox) for receiving business correspondence.

    Reusing Shielded Addresses

    Note that it is advisable to reuse shielded addresses for receiving payments within the same context. While it has become standard practice for generating a new address for each receiving transaction in most cryptocurrencies, that is not a problem when using shielded addresses. In fact, it saves the extra hassle of tracking many different addresses and reduces the number of outputs consumed when creating a new transaction. This reduction makes overall transaction size smaller and requires less resources for generating a zero-knowledge proof.

    A great example of this distinction can be seen on the donations page for the non-profit Riseup.net. When a supporter goes to make a bitcoin donation, they're provided with a newly generated address but when a supporter makes a Zcash donation, the same shielded address is provided for everyone!

    One Shielded Address Per Purpose

    We encourage folks to follow suit and reuse shielded addresses for accepting Zcash payments within the same context. For contexts which should remain unassociated, however, make sure to keep the shielded addresses unassociated as well.

    For more user privacy considerations, see the Privacy & Security Recommendations.






  • ZCASH [ZEC] - Dev update April 21, 2017

    At the beginning of the week, we had the first of our regularly scheduled (once a month) meetings about the pre-Sapling hard fork (HF0) in which we narrowed down tickets into a select group using the tag HF0 wishlist. These tickets address the meta goal of making HF0 and future hard forks safer and simpler.

    We also had a topical meeting around revamping the release lifecycle and policy An overview of which will be released as a blog post in the very near future. We also touched on the concept of development environments but did not come to a final resolution on their implementation across the areas in which they aim to be used.

    Work on other process-related concepts like roadmapping and security incident procedure were also discussed more this week with the goal of
    releasing public documents outlining them coming in the near future.

    And with last week’s securityincident engineering timesync behind us, regular work on pull-request review and pre-Sapling features (payment disclosure, payment offloading and XCAT) were back in full swing this week.


    We also continued work on the block observatory and testnet faucet mentioned in last week’s update.

    A handful of new FAQs  were added to the website this week and next week, keep an eye out for the initial version of our zk-SNARK section in addition to the newest in the explaining zk-SNARK blog series.

    We’ve also planned a Google hangout and livestream with Zcash engineers to discuss and explain zk-SNARKs in two weeks on May 6th at 16:00 UTC. Those interested can request an invite to join the hangout or post questions as comments in the video beforehand and/or questions in the chat box when the session is live.

    As a reminder, check out the working groups wiki page if you’re interested in becoming more involved in Zcash core development and ecosystem maintenance and growth. Also, don’t forget to ping us if you’d like to be invited to one of our future topical meetings, we’d love to include those from the greater community who are interested!



  • Zcash- Explaining SNARKs Part V: From Computations to Polynomials

    << Part IV

    In the three previous parts, we developed a certain machinery for dealing with polynomials. In this part, we show how to translate statements we would like to prove and verify to the language of polynomials. The idea of using polynomials in this way goes back to the groundbreaking work of Lund, Fortnow, Karloff and Nisan.

    In 2013, another breakthrough work of Gennaro, Gentry, Parno and Raykova defined an extremely useful translation of computations into polynomials called a Quadratic Arithmetic Program (QAP). QAPs have become the basis for modern zk-SNARK constructions, in particular those used by Zcash.

    In this post we explain the translation into QAPs by example. Even when focusing on a small example rather than the general definition, it is unavoidable that it is a lot to digest at first, so be prepared for a certain mental effort :).

    Suppose Alice wants to prove to Bob she knows c1,c2,c3∈Fp" role="presentation">c1,c2,c3∈F###i

    /i###

    such that
    (c1⋅c2)⋅(c1+c3)=7" role="presentation">(c1⋅c2)⋅(c1+c3)=7.
    The first step is to present the expression computed from c1,c2,c3" role="presentation">c1,c2,c3 as an arithmetic circuit.

    Arithmetic circuits

    An arithmetic circuit consists of gates computing arithmetic operations like addition and multiplication, with wires connecting the gates. In our case, the circuit looks like this:


    The bottom wires are the input wires, and the top wire is the output wire giving the result of the circuit computation on the inputs.

    As can be seen in the picture, we label the wires and gates of the circuit in a very particular way, that is needed for the next step of translating the circuit into a QAP:

    • When the same outgoing wire goes into more than one gate, we still think of it as one wire - like w1" role="presentation">w1
  • in the example.
  • We assume multiplication gates have exactly two input wires, which we call the left wire and right wire.
  • We don't label the wires going from an addition to multiplication
    gate, nor the addition gate; we think of the inputs of the addition gate
    as going directly into the multiplication gate. So in the example we
    think of w1" role="presentation">w1
  • and w3" role="presentation">w3 as both being right inputs of g2" role="presentation">g2
    • .

    A legal assignment for the circuit, is an assignment of values to the labeled wires where the output value of each multiplication gate is indeed the product of the corresponding inputs.

    So for our circuit, a legal assignment is of the form: (c1,…,c5)" role="presentation">(c1,…,c5)

    where c4=c1⋅c2" role="presentation">c4=c1⋅c2 and c5=c4⋅(c1+c3)" role="presentation">c5=c4⋅(c1+c3)

    .

    In this terminology, what Alice wants to prove is that she knows a legal assignment (c1,…,c5)" role="presentation">(c1,…,c5)

    such that c5=7" role="presentation">c5=7

    . The next step is to translate this statement into one about polynomials using QAPs.

    Reduction to a QAP

    We associate each multiplication gate with a field element: g1" role="presentation">g1

    will be associated with 1∈Fp" role="presentation">1∈F###i

    /i### and g2" role="presentation">g2 with 2∈Fp" role="presentation">2∈F###i

    /i###. We call the points {1,2}" role="presentation">{1,2} our target points. Now we need to define a set of "left wire polynomials" L1,…,L5" role="presentation">L1,…,L5, "right wire polynomials" R1,…,R5" role="presentation">R1,…,R5 and "output wire polynomials" O1,…,O5" role="presentation">O1,…,O5

    .

    The idea for the definition is that the polynomials will usually be zero on the target points, except the ones involved in the target point's corresponding multiplication gate.

    Concretely, as w1,w2,w4" role="presentation">w1,w2,w4

    are, respectively, the left, right and output wire of g1" role="presentation">g1;
    we define L1=R2=O4=2−X" role="presentation">L1=R2=O4=2−X, as the polynomial 2−X" role="presentation">2−X is one on the point 1" role="presentation">1 corresponding to g1" role="presentation">g1 and zero on the point 2" role="presentation">2 corresponding to g2" role="presentation">g2

    .

    Note that w1" role="presentation">w1

    and w3" role="presentation">w3 are both right inputs of g2" role="presentation">g2.
    Therefore, we define similarly L4=R1=R3=O5=X−1" role="presentation">L4=R1=R3=O5=X−1 - as X−1" role="presentation">X−1 is one on the target point 2" role="presentation">2 corresponding to g2" role="presentation">g2

    and zero on the other target point.

    We set the rest of the polynomials to be the zero polynomial.

    Given fixed values (c1,…,c5)" role="presentation">(c1,…,c5)

    we use them as coefficients to define a left, right, and output "sum" polynomials. That is, we define

    L:=∑i=15ci⋅Li,R:=∑i=15ci⋅Ri,O:=∑i=15ci⋅Oi" role="presentation">L:=∑5i=1ciLi,R:=∑5i=1ciRi,O:=∑5i=1ciOi

    ,

    and then we define the polynomial P:=L⋅R−O" role="presentation">###i

    /i###:=LRO

    .

    Now, after all these definitions, the central point is this: (c1,…,c5)" role="presentation">(c1,…,c5)

    is a legal assignment to the circuit if and only if P" role="presentation">###i

    /i###

    vanishes on all the target points.

    Let's examine this using our example. Suppose we defined L,R,O,P" role="presentation">L,R,O,###i

    /i###

    as above given some c1,…,c5" role="presentation">c1,…,c5.
    Let's evaluate all these polynomials at the target point 1" role="presentation">1

    :

    Out of all the Li" role="presentation">Li

    's only L1" role="presentation">L1 is non-zero on 1" role="presentation">1.
    So we have L(1)=c1⋅L1(1)=c1" role="presentation">L(1)=c1⋅L1(1)=c1.
    Similarly, we get R(1)=c2" role="presentation">R(1)=c2 and O(1)=c4" role="presentation">O(1)=c4

    .

    Therefore, P(1)=c1⋅c2−c4" role="presentation">###i

    /i###(1)=c1⋅c2−c4

    .
    A similar calculation shows P(2)=c4⋅(c1+c3)−c5" role="presentation">###i

    /i###(2)=c4⋅(c1+c3)−c5

    .

    In other words, P" role="presentation">###i

    /i###

    vanishes on the target points if and only if (c1,…,c5)" role="presentation">(c1,…,c5)

    is a legal assignment.

    Now, we use the following algebraic fact: For a polynomial P" role="presentation">###i

    /i###

    and a point a∈Fp" role="presentation">a∈F###i

    /i###, we have P(a)=0" role="presentation">###i

    /i###(a)=0 if and only if the polynomial X−a" role="presentation">Xa divides P" role="presentation">###i

    /i###, i.e. P=(X−a)⋅H" role="presentation">###i

    /i###=(Xa)⋅H for some polynomial H" role="presentation">H

    .

    Defining the target polynomial T(X):=(X−1)⋅(X−2)" role="presentation">T(X):=(X−1)⋅(X−2)

    , we thus have that T" role="presentation">T divides P" role="presentation">###i

    /i### if and only if (c1,…,c5)" role="presentation">(c1,…,c5)

    is a legal assignment.

    Following the above discussion, we define a QAP as follows:

    A Quadratic Arithmetic Program Q" role="presentation">Q

    of degree d" role="presentation">d and size m" role="presentation">m consists of polynomials L1,…,Lm" role="presentation">L1,…,Lm, R1,…,Rm" role="presentation">R1,…,Rm, O1,…,Om" role="presentation">O1,…,Om and a target polynomial T" role="presentation">T of degree d" role="presentation">d

    .

    An assignment (c1,…,cm)" role="presentation">(c1,…,cm)

    satisfies Q" role="presentation">Q if, defining L:=∑i=1mci⋅Li,R:=∑i=1mci⋅Ri,O:=∑i=1mci⋅Oi" role="presentation">L:=∑mi=1ciLi,R:=∑mi=1ciRi,O:=∑mi=1ciOi and P:=L⋅R−O" role="presentation">###i

    /i###:=LRO, we have that T" role="presentation">T divides P" role="presentation">###i

    /i###

    .

    In this terminology, Alice wants to prove she knows an assignment (c1,…,c5)" role="presentation">(c1,…,c5)

    satisfying the QAP described above with c5=7" role="presentation">c5=7

    .

    To summarize, we have seen how a statement such as "I know c1,c2,c3" role="presentation">c1,c2,c3

    such that (c1⋅c2)⋅(c1+c3)=7" role="presentation">(c1⋅c2)⋅(c1+c3)=7

    " can be translated into an equivalent statement about polynomials using QAPs. In the next part, we will see an efficient protocol for proving knowledge of a satisfying assignment to a QAP.

    [1]excellent post for more details on the transformation from a program to a QAP.


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