5月16日的Project PAI 技术路线直播快照：Chuck Ng（左上），Mark Harvilla博士（右上），Yongzheng Jia博士（左下）和 Nikhil Jain（右下）
重要公告
01
感谢大家参加周六上午的直播。这是一次非常成功的分享会，我们非常感谢大家一直以来的支持。您可以扫描下面二维码或者点击链接查看直播中的内容展示：
Project PAI贡献者会在将来进行更多的直播分享，着重于有关项目的具体技术细节分享，例如有用工作量证明等。敬请期待更多讯息！
PAI Coin Pool 促销活动正在进行中！只要满足质押至少1,000个PAI币权益并达到3个月，就可以获得10个PAI币奖励。你也可以通过挖掘40,000个幸运哈希来赚取奖励。该促销活动将于北京时间5月22日星期五晚上11点截止。
常见问题（持续更新）
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PAI 混合共识：什么是投票服务提供商（VSP）？
基于工作量证明（PoW）的加密货币依靠矿工硬件的强大哈希功能来定期向区块链中添加新区块。当PoW挖掘需要专用硬件（例如，专用集成电路（ASIC）或图形处理单元（GPU））时，其成本可能非常昂贵。这些成本严重限制了低预算实体（例如个人和小公司）的采矿机会。为了缓解这种情况，某些加密货币使用权益证明（PoS）机制，矿工必须抵押一些加密货币才能获得奖励。这消除了对特殊硬件和高电费的需求，但是它本身对其他类型的攻击会敏感。
通过混合共识协议将PoW和PoS组合在一起，可大大减少PoW或PoS单独使用时的缺点。在PAI 币的混合解决方案中，PoW矿工必须包含前一个区块的投票。这些投票由先前通过购买门票表示有意参与的随机投票组成。由于该过程是自动进行的，因此选民必须至少拥有一台永久在线的计算机并可以进行投票。这与仅基于PoW的加密货币硬件要求可能还存在很大的距离，对于想要参与的个人而言也依旧是个问题。因为即使桌面用户可以永久将计算机保持在线状态，但对于移动钱包用户来说实际上是不可能的。
这便是投票服务提供商（VSP）可以发挥作用的地方。VSP是具有高可用性系统的第三方实体，可以代表购票者进行投票。买票时，参与者可以将投票权委派给VSP。
从技术上讲，我们可以通过创建具有两个贡献输出的票务交易来完成表决权的委托：一个具有参与者的地址，一个具有指定参与者地址和VSP地址构建的二对一的多重签名地址。当选定投票后，VSP会以一种规定的投票方式进行投票，所获得的奖励将在参与者地址和多重签名地址之间按比例分配。这样，VSP就可以在不改变参与者奖励的情况下花费其自己的奖励。VSP奖励也称为VSP费用。投票交易的正确性会由共识规则来强制执行。
这种方法对于参与者和VSP都是安全的。因为参与者对通过其地址贡献的奖励份额享有专有权。VSP是无法使用这部分奖励，因为它无法访问相应的秘钥。但是，VSP可以访问通过多重签名地址贡献的奖励份额。
在非常小的概率下才可能会产生VSP在需要时不投票的情况，若发生，参与者可以赎回包括VSP费用在内的全部初始股份，因为其具有多重签名地址之一。出于同样的原因，即使在选择票证后，用户也可以直接投票，但唯一无法退回的是购票交易费。
总而言之，VSP是混合加密货币生态系统的重要组成部分，即使用户智能手机上的移动钱包余额很少，它也可以帮助该用户参与投票过程和奖励共享。它们在去中心化的加密货币挖矿和奖励共享中发挥着非常重要的作用。
有用工作量证明：什么是有用工作量证明？
有用工作量证明（PoUW）是由Project PAI核心贡献者研究和开发的共识协议，旨在：
● 扩展PoW共识的效用；
● 促进任意的”链上”计算；
● 减少能源的浪费支出
工作量证明就像是彩票：每个参与活动的矿工都有机会因开采新区块而赢得区块奖励，这可以激发更多用户参与采矿。参与的人越多，加密货币网络的去中心化程度就越高，但是任何单个矿工获得区块奖励的可能性就越小——除非他购买更多的彩票赌注。”购买更多赌注”的唯一方法是以更高的哈希率进行开采，这将需要花费更多的成本去维持并消耗更多的电力。
由于这场无止境的争夺更多彩票赌注的竞争——拥有更高的哈希率——比特币网络目前每年消耗超过66兆瓦时的电力，约等于一个拥有1000万人口国家的能源消耗。而且，由于PAI币本身也是基于PoW的，因此它可能会走上同一条道路。
这些事实促使一些Project PAI贡献者决定对PoW协议进行修改，该修改将依据于”有用工作量”的概念，即第三方需完成某些”工作”。
当彩票赌注投入比特币的PoW共识，它会需要一个随机数（字面上），而投入PAI币PoUW共识的彩票赌注需要一个与有用工作量单元相关联的数字。因此，尽管与PAI币PoUW相关的能耗可能仍然很大，但仍将可能用于其他地方（例如：云计算平台、服务器场、台式计算机等）。
大多数加密货币只有一种类型的用户——交易者，即那些以交易或出售其他物品来交换货币的加密货币。相反，PAI 币PoUW将具有两种类型的用户：交易者和请求者。请求者是将数据和计算工作请求提交给PAI 币网络并收费的请求者。例如，一家公司可能会提交一个请求来挖掘客户评论数据；学术人员可能会提交一份工作来训练机器学习模型；或者流行病学家可能会提交一份工作来模拟病毒在人群中的传播。这里存在着无数种可能性。
通过重新考虑工作量证明机制中彩票赌注的来源，有用工作量证明旨在促进这些任意链上的计算，从而扩展传统工作量证明共识的效用，并减少能源的浪费支出。
请注意——如果你想知道更多其他内容，欢迎前往PAI论坛提问！
每周更新
03
PAI Coin Pool
上周，推荐和促销奖励系统已成功启动！现在你就可以通过推荐朋友、家人和其他人来赚取额外的PAI币。操作十分容易——只需复制自己的推荐链接（可在您的PCP个人资料中找到）并将其发送给认识的人。你可以通过根据你分享的推荐链接注册账号的用户活动获得第一等级推荐奖励，也有机会进一步获得第二层被推荐人的用户活动产生的第二等级推荐奖励。
本周，我们将发布更新版的GUI ，如上图所示，用户可以准确地看到自己在正在进行的促销活动中获得了多少奖励。
此外，在北京时间5月22日星期五晚上11点之前，锁定至少1,000个PAI币权益并且达到3个月或以上的时间，即可获得10 PAI币奖励！
PAI 混合共识
下面是我们开发人员在上周的一些提交/ 更新：
● 单元和功能测试
https://github.com/projectpai/paicoin/pull/301
● 权益版本更新
https://github.com/projectpai/paicoin/issues/302
● 代替用户自动投票
https://github.com/projectpai/paicoin/pull/303
PAI 论坛 & PAI Pass
目前具有PAI Pass集成的PAI论坛在测试中一直稳定。团队一直努力优化用户体验和改善后端基础结构，将在本周正式上线。此外，我们也一直在测试某些地理区域存在的可访问权限问题，以确定版本解决方案。待延迟问题和可访问权限解决后，我们将上线全新的具有PAI Pass集成的论坛从而代替现有的PAI论坛。
欢迎在此查看PAI Pass白皮书了解更多相关信息：
https://projectpai.com/pai-whitepaper/
问题和建议
04
有问题或者建议？
欢迎来 PAI 论坛 发表!
感谢您一直以来的支持！
PAI News – May 18, 2020
Announcements
Thank you everyone for joining the Livestream presentation last Saturday morning. It was a huge success and we appreciate your ongoing support. You can find the slides here:
https://www.paiforum.com/post/a-look-back-on-the-516-pai-ama-livestream-10528382
The Project PAI Contributors will do additional livestreams in the future focused on specific technical details of projects like Proof of Useful Work. Stay tuned for more information!
The PAI Coin Pool promotion is ongoing! Stake 1,000 PAI Coin or more for at least 3 months and earn a 10 PAI Coin bonus. You can also earn the bonus by mining 40,000 Lucky Hashes. The promotion expires on Friday, May 22 at 11 PM Beijing Time.
Frequently Asked Questions
PAI Hybrid Consensus:What is a Voting Service Provider (VSP)?
Proof-of-Work (PoW)-based cryptocurrencies rely on the massive hashing power of miners’ hardware to regularly keep adding new blocks to the blockchain. PoW mining can be very expensive when it requires dedicated hardware like Application Specific Integrated Circuits (ASICs) or Graphics Processing Units (GPUs). These costs severely limit the access of low-budget entities, like individuals and small companies, to mining. To mitigate this, some cryptocurrencies use a Proof-of-Stake (PoS) mechanism, whereby a miner must stake some cryptocoins to receive a reward. This eliminates the need for special hardware and high electricity costs, but is itself sensitive to other kinds of attacks.
Combining PoW and PoS via a Hybrid Consensus protocol significantly reduces the individual drawbacks of PoW or PoS when used alone. In PAI Coin’s Hybrid solution, PoW miners must include votes for the previous block. These votes are cast by randomly selected entities that previously expressed their intention to participate by purchasing tickets. Since the process is automated, voters must have at least one computer permanently online and ready to vote. While this is not even close to the hardware requirements for PoW-only cryptocurrencies, it might still be an issue for individuals wanting to participate. Even if it might be acceptable for desktop users to leave their computer permanently online, it’s practically impossible for Mobile Wallet users.
This is where Voting Service Providers (VSPs) come into play. VSPs are third-party entities with high availability systems for voting on behalf of a ticket buyer. When buying a ticket, a participant can delegate the voting rights to a VSP.
Technically, the delegation of voting rights is done by creating a ticket purchase transaction with two contribution outputs: one having the participant’s address and one specifying a 1-of-2 multiple signature (multisig) address built from an address of the participant and an address of the VSP. When the ticket is selected to vote, the VSP creates the vote in such a way that the reward is split proportionally between the participant’s address and the multisig address. The VSP will then be able to spend its reward, while not touching the participant’s reward. The VSP reward is also known as the VSP fee. The correctness of the vote transaction is enforced by the consensus rules.
This approach is safe for both the participant and the VSP for several reasons. The participant has exclusive rights to the share of the reward that is contributed to with his/her address. The VSP cannot spend this part of the reward because it does not have access to the corresponding private keys. The VSP, however, has access to the share of the reward that is contributed to with the multisig address.
In the highly improbable case that the VSP does not vote when needed, the participant can redeem the entire initial stake, including the VSP fee, because he/she has one of the multisig address components. For the same reason, the user can even vote directly when the ticket is selected. The only funds that cannot be restored are the ticket purchase transaction fees.
In conclusion, VSPs are an important component of a Hybrid cryptocurrency ecosystem that facilitate the participation of virtually any user in the voting process and the reward sharing, with as little as a mobile wallet on a smartphone. They play an important role in the complete decentralization of cryptocurrency mining and reward sharing.
Proof of Useful Work: What is Proof of Useful Work?
Proof of Useful Work (PoUW) is a consensus protocol being researched and developed by Project PAI Core Contributors, in an effort to:
●Extend the utility of PoW consensus;
●Facilitate arbitrary “on-chain” computations;
●Reduce wasteful energy expenditure
Proof of Work is like a lottery: Every participating miner has a chance to win the block reward for mining a new block, and this motivates many users to participate in mining. The more people that participate, the more decentralized the cryptocurrency network becomes, but the less likely it is for any individual miner to win the block reward—unless he or she buys more entries into the lottery. The only way to “buy more entries” is to mine at a higher hash rate, which costs more money to maintain, and expends more electricity.
Because of this never-ending race for more lottery entries—higher hash rate—the Bitcoin network currently consumes over 66 Terawatt-Hours of electricity per year, roughly equivalent to the energy consumption of a nation of 10 million people. And, because it’s inherently PoW based, PAI Coin could be on the same path.
Such facts motivated some Project PAI Contributors to investigate changes to the PoW protocol which would rely on the notion of “Useful Work,” i.e., any “work” that a third party has requested to be completed.
While lottery entries to Bitcoin’s PoW consensus simply require a random number (literally), lottery entries to PAI Coin’s PoUW consensus require a number which is provably associated with a unit of Useful Work. So, while the energy consumption associated with PAI Coin PoUW may well still be quite large, it would be spent on calculations that would presumably be done anyway and elsewhere (e.g., on a cloud computing platform, in a server farm, on a desktop computer, etc.).
Most cryptocurrencies only have one type of user—transactors, i.e., those who exchange the cryptocoin as a currency, whether for sale or trade or in exchange for other items for purchase. PAI Coin PoUW, instead, would have two types of users: transactors, but also… requestors. Requestors are those who submit data and computational job requests to the PAI Coin network for a fee. For example, a corporation might submit a request to mine customer review data; an academic might submit a job to train a Machine Learning model; or an epidemiologist might submit a job to simulate the spread of a virus in a population. The possibilities are endless.
By rethinking the origin of lottery entries in the Proof of Work mechanism, Proof of Useful Work aims to facilitate these arbitrary on-chain computations, thereby expanding the utility of traditional Proof-of-Work consensus, and reducing wasteful energy expenditure.
Remember — If there’s something else you want to know, just ask on PAI Forum!
PAI Weekly Updates
PAI Coin Pool
Last week, the Referral and Promotional Bonus systems [+mark@lanier.ai do we have any stats on how many folks been using it after launch? If they look impressive, then maybe mention it?
_Assigned to Mark Harvilla_]were successfully launched! You can now earn extra PAI Coin by referring your friends, family, and followers. It’s easy — just copy your Referral Link (available in your PCP profile) and send it to everyone you know. You can earn Tier 1 Referral Rewards based on the activity of anyone who signs up with your link… and Tier 2 Referral Rewards based on the activity of anyone who signs up using theirs.
This week, an updated GUI ?, previewed above, will be released allowing you to see exactly how much progress you’ve made toward an ongoing promotion.
Speaking of which…
Stake 1,000 PAI Coin for 3 months or longer before Friday, May 22, 11 PM Beijing Time and earn a 10 PAI Coin Bonus! You can also earn the bonus by mining 40,000 Lucky Hashes before the end date.
PAI Hybrid Consensus
Here’s a snapshot of some of the commits / PRs by our developers last week:
●Unit & Functional tests
https://github.com/projectpai/paicoin/pull/301
●Stake versioning
https://github.com/projectpai/paicoin/issues/302
●Automatic voting on behalf of user
https://github.com/projectpai/paicoin/pull/303
PAI Forum & PAI Pass
The PAI Forum with PAI Pass integration has been stable in testing. The team has been making updates to the user experience and backend infrastructure. Those changes will go live this week. In addition, it became clear that accessibility was a concern for some geographic regions — so testing has been ongoing to determine a production release hosting solution. Once latency and accessibility issues have been resolved, the forum with PAI Pass integration will be made available to the community in place of the existing Paiforum.
You can also find more information about PAI Pass on the PAI Pass Whitepaper here:
https://projectpai.com/pai-whitepaper/
Questions? Comments? Feedback?
Sound off on PAI Forum!
Thank you for your support!
来源：PAI
