Facebook的Libra區(qū)塊鏈?zhǔn)侨绾芜\作的

Facebook的Libra區(qū)塊鏈?zhǔn)侨绾芜\作的，針對這個問題，這篇文章詳細(xì)介紹了相對應(yīng)的分析和解答，希望可以幫助更多想解決這個問題的小伙伴找到更簡單易行的方法。

摘要

The Libra protocol allows a set of replicas—referred to as validators—from different authorities to jointly maintain a database of programmable resources.

換句話說，也就是這個系統(tǒng)需要由一組權(quán)威機(jī)構(gòu)以自上而下的方式進(jìn)行控制。然而，請注意，該數(shù)據(jù)庫是為維護(hù)“可編程資源”而不僅僅是維護(hù)數(shù)字貨幣的。

These resources are owned by different user accounts authenticated by public key cryptography and adhere to custom rules specified by the developers of these resources.

使用諸如“資源”（resources）之類的通用詞匯使我懷疑這里不僅僅是指一種穩(wěn)定幣。

Transactions are based on predefined and, in future versions, user-defined smart contracts in a new programming language called Move. We use Move to define the core mechanisms of the blockchain, such as the currency and validator membership.

好了，這個有意思了。使用專門的智能契約語言會導(dǎo)致很多問題，比如該語言的功能豐富度，以及延伸到該系統(tǒng)對對抗性契約的健壯性有多強(qiáng)的問題。還有一些關(guān)于開發(fā)人員友好性以及Libra如何保護(hù)智能合約開發(fā)人員不受影響的問題都是需要明晰的。

These core mechanisms enable the creation of a unique governance mechanism that builds on the stability and reputation of existing institutions in the early days but transitions to a fully open system over time.

關(guān)于開發(fā)人員友好性以及Libra如何保護(hù)智能合約開發(fā)人員不受影響，這仍是問題。

1.簡介

This ecosystem will offer a new global currency—the Libra coin—which will be fully backed with a basket of bank deposits and treasuries from high-quality central banks.

Libra是一種通用的加密資產(chǎn)協(xié)議，第一個資產(chǎn)將是一種穩(wěn)定幣。

Over time, membership eligibility will shift to become completely open and based only on the member’s holdings of Libra.

聽起來很像股權(quán)證明。顯然，計劃是在五年后開放會員資格，并希望他們當(dāng)時能夠找到股份證明——盡管我預(yù)計它們會遇到與Ethereum相同的問題。

The association has published reports outlining … the roadmap for the shift toward a permissionless system.

我很確定這將是分布式網(wǎng)絡(luò)首次從許可型轉(zhuǎn)換為非許可型。也許整個網(wǎng)絡(luò)可以轉(zhuǎn)換為股權(quán)證明，但為了穩(wěn)定幣/籃子，一些實體必須保持對傳統(tǒng)金融系統(tǒng)的開放。這將是通過Libra協(xié)會長期集中控制的重點。

Validators take turns driving the process of accepting transactions. When a validator acts as a leader, it proposes transactions, both those directly submitted to it by clients and those indirectly submitted through other validators, to the other validators. All validators execute the transactions and form an authenticated data structure that contains the new ledger history. The validators vote on the authenticator for this data structure as part of the consensus protocol.

這聽起來像Practical Byzantine Fault Tolerance(實用拜占庭容錯算法)，這是一個很好理解的發(fā)展了20年的算法，盡管他們可能做了一些調(diào)整。我們在白皮書的第5節(jié)中了解到它被稱為LibraBFT，它是HotStuff共識協(xié)議的變體。

As part of committing a transaction T i at version i, the consensus protocol outputs a signature on the full state of the database at version i—including its entire history—to authenticate responses to queries from clients.

這是值得注意的，主要是因為它意味著新的驗證者應(yīng)該能夠加入網(wǎng)絡(luò)并快速同步，而不必回溯區(qū)塊鏈的整個歷史記錄，前提是它們信任現(xiàn)有的驗證者。
這種帳戶模型是有可能的，因為Facebook不太可能關(guān)注隱私，而它確實對智能合約感興趣。

2.邏輯數(shù)據(jù)模型

The Libra protocol uses an account-based data model to encode the ledger state.

從數(shù)據(jù)結(jié)構(gòu)的角度來看，Libra更像Ethereum或Ripple，而不是比特幣。UTXO模型有優(yōu)點也有缺點——由于基于輸出的歷史記錄的簡單性，它具有更好的私密性和更健壯的事務(wù)歷史記錄——但是處理復(fù)雜的智能合約可能更困難。因此，賬戶模式是有意義的，因為Facebook不太可能關(guān)注隱私，盡管聽起來它對智能合同很感興趣。

The Libra protocol does not link accounts to a real-world identity. A user is free to create multiple accounts by generating multiple key-pairs. Accounts controlled by the same user have no inherent link to each other. This scheme follows the example of Bitcoin and Ethereum in that it provides pseudonymity for users.

這聽起來好得驚人，但我想知道Libra coin是否也是這種情況。對于那些想要開發(fā)一些更能保護(hù)隱私的應(yīng)用程序的開發(fā)人員來說，觀察這個系統(tǒng)的開放程度將是一件很有趣的事情。

Every resource has a type declared by a module. Resource types are nominal types that consist of the name of the type and the name and address of the resource’s declaring module.

看起來你可以生成一個地址，只要每個資產(chǎn)都有唯一的名稱，該地址就可以分配任意數(shù)量的資產(chǎn)。

Executing a transaction T i produces a new ledger state S i as well as the execution status code, gas usage, and event list.

好了，現(xiàn)在我們知道了如何保護(hù)系統(tǒng)免受資源耗盡攻擊，大概是利用類似于Ethereum的資源成本系統(tǒng)。

There is no concept of a block of transactions in the ledger history.

有趣。Libra協(xié)議中沒有實際的區(qū)塊鏈數(shù)據(jù)結(jié)構(gòu)——塊更像是一個虛擬的邏輯結(jié)構(gòu)，驗證者使用它來協(xié)調(diào)系統(tǒng)狀態(tài)的確認(rèn)快照?；剡^頭來看，這一節(jié)的第一句話現(xiàn)在有了更多的意義:

All data in the Libra Blockchain is stored in a single versioned database. A version number is an unsigned 64-bit integer that corresponds to the number of transactions the system has executed.

我所熟悉的每個加密資產(chǎn)網(wǎng)絡(luò)都以相同的方式在非常高的層次上工作：首先存在一個系統(tǒng)狀態(tài)，然后執(zhí)行一個事務(wù)，實際上是一個狀態(tài)轉(zhuǎn)換函數(shù)，接著新的系統(tǒng)狀態(tài)就出現(xiàn)了。

將批量事務(wù)放入容器或塊中的目的是為了對它們進(jìn)行排序和加時間戳。這對于無許可網(wǎng)絡(luò)非常重要，在這種網(wǎng)絡(luò)中，數(shù)據(jù)通過動態(tài)多方成員簽名進(jìn)行身份驗證，驗證者可以自由地加入和離開網(wǎng)絡(luò)。因為Libra運行一個經(jīng)過許可的系統(tǒng)，所以它可以使用一個更有效的協(xié)商一致算法，而不需要批處理事務(wù)，因為事務(wù)歷史記錄被重寫的可能性要小得多。

In the initial version of the Libra protocol, only a limited subset of Move’s functionality is available to users. While Move is used to define core system concepts, such as the Libra currency, users are unable to publish custom modules that declare their own resource types. This approach allows the Move language and toolchain to mature—informed by the experience in implementing the core system components—before being exposed to users. The approach also defers scalability challenges in transaction execution and data storage that are inherent to a general-purpose smart contract platform.

這聽起來非常類似于前面提到的“open validator membership（開放驗證者成員資格）”計劃。似乎Facebook還沒有解決任何一個Ethereum多年來一直在努力解決的重大問題。

In order to manage demand for compute capacity, the Libra protocol charges transaction fees, denominated in Libra coins.

Libra coins實際上是協(xié)議的原生單位，就像ETH是Ethereum的原生單位。這就引出了另一個關(guān)于Libra匿名性質(zhì)的問題：你可以在沒有AML / KYC的情況下獲得幣嗎？如果不能，那么您似乎無法匿名地使用系統(tǒng)的任何功能。查閱Calibra錢包，它將需要AML / KYC。所以我想知道最終是否會有一些進(jìn)入系統(tǒng)的方式?jīng)]有受到嚴(yán)格控制。

The system is designed to have low fees during normal operation, when sufficient capacity is available.

這確實很模糊，并引發(fā)了許多問題：什么是低收費？什么是正常操作？什么是足夠的容量？

3.執(zhí)行交易

Many parts of the core logic of the blockchain are defined using Move, including the deduction of gas fees. To avoid circularity, the VM disables the metering of gas during the execution of these core components.

這聽起來很危險，但該文檔的作者指出，核心組件必須以防御性方式編寫以防止DoS攻擊。

The key feature of Move is the ability to define custom resource types … the Move type system provides special safety guarantees for resources. A resource can never be copied, only moved. These guarantees are enforced statically by the Move VM. This allows us to represent Libra coins as a resource type in the Move language.

這就澄清了之前的問題：Libra coins是否像ETH或BTC一樣是本地資產(chǎn)。我希望這些幣只是系統(tǒng)啟動時默認(rèn)的或唯一允許的資源類型，其他資源將在未來提供。

Move’s stack-based bytecode has fewer instructions than a higher-level source language would. In addition, each instruction has simple semantics that can be expressed via an even smaller number of atomic steps. This reduces the specification footprint of the Libra protocol and makes it easier to spot implementation mistakes.

這聽起來像是經(jīng)過深思熟慮的; 希望這意味著他們的腳本語言的安全性將比Ethereum更好。

我們看到“Libra區(qū)塊鏈” 實際上并不是區(qū)塊鏈。

4.已驗證的數(shù)據(jù)結(jié)構(gòu)和存儲

The Libra protocol uses a single Merkle tree to provide an authenticated data structure for the ledger history … specifically, the ledger history uses the Merkle tree accumulator approach to form Merkle trees, which also provides efficient append operations.

我們再一次看到“Libra區(qū)塊鏈”實際上并不是區(qū)塊鏈。這個協(xié)議似乎設(shè)計得非常好，但是奇怪的是，當(dāng)賬戶歷史的數(shù)據(jù)結(jié)構(gòu)是一組有簽名的賬戶狀態(tài)時，它們?nèi)匀环Q它為區(qū)塊鏈。驗證者正在為每個賬戶狀態(tài)做出承諾，并且所有歷史帳戶狀態(tài)也都在Merkle樹中承諾，但我還沒有真正看到形成鏈的任何反向鏈接數(shù)據(jù)列表——更不用說形成塊鏈了。

The authenticator of an account is the hash of this serialized representation.
Note that this representation requires recomputing the authenticator over the full account after any modification to the account. The cost of this operation is O(n), where n is the length of the byte representation of the full account.

嗯，如果沒有對給定帳戶存儲的數(shù)據(jù)量進(jìn)行限制，這聽起來像是DoS攻擊的開端。

We anticipate that as the system is used, eventually storage growth associated with accounts may become a problem. Just as gas encourages responsible use of computation resources, we expect that a similar rent-based mechanism may be needed for storage. We are assessing a wide range of approaches for a rent-based mechanism that best suits the ecosystem.

另一個未解決的問題。迫不及待地想說“租金太高了！”

The voting power must remain honest both during the epoch as well as for a period of time after the epoch in order to allow clients to synchronize to the new configuration. A client that is offline for longer than this period needs to resynchronize using some external source of truth to acquire a checkpoint that they trust.

哎。目前尚不清楚這個“時間段”有多長，但如果一個epoch不到一天，那么我猜測指定的“時間段”也是如此。看起來這個共識協(xié)議不夠強(qiáng)大，參與者可能會隨意離開并重新加入網(wǎng)絡(luò)。

5.拜占庭容錯共識

LibraBFT assumes that a set of 3f + 1 votes is distributed among a set of validators that may be honest, or Byzantine. LibraBFT remains safe, preventing attacks such as double spends and forks when at most f votes are controlled by Byzantine validators.

就像PBFT一樣，這種一致性算法可以容忍33％的驗證者是不誠實的。HotStuff的修改聽起來很合理：
通過使驗證者簽署塊的狀態(tài)（而不僅僅是事務(wù)序列）來抵制非確定性錯誤。

一個發(fā)出明確超時信號的起搏器，驗證者依賴于這些超時信號的仲裁集來進(jìn)入下一輪 - 這應(yīng)該可以提高活性。
不可預(yù)知的領(lǐng)導(dǎo)者選舉機(jī)制，以限制針對領(lǐng)導(dǎo)者的DoS攻擊。
聚合簽名以便保存那些簽署了仲裁集證書來為塊接受投票的身份驗證者。

6.網(wǎng)絡(luò)

Each validator in the Libra protocol maintains a full membership view of the system and connects directly to any validator it needs to communicate with. A validator that cannot be connected to directly is assumed to fall within the quota of Byzantine faults tolerated by the system.

這將需要大量工作才能將系統(tǒng)擴(kuò)展到數(shù)百個驗證者。

7. Libra核心實施內(nèi)容

The security of the Libra Blockchain rests on the correct implementation of validators, Move programs, and the Move VM. Addressing these issues in Libra Core is a work in progress.

這部分內(nèi)容已經(jīng)基本總結(jié)完畢，盡管他們在Rust中編寫了實現(xiàn)，這對性能和安全性來說似乎是一個良好的開端。

8.表現(xiàn)

We anticipate the initial launch of Libra protocol to support 1,000 payment transactions per second with a 10-second finality time between a transaction being submitted and committed.

由于只有100個左右的驗證者，并且它們都相互直接連接的，所以10秒的塊時間聽起來是可行的。

最低節(jié)點要求：

• 40 Mbps網(wǎng)絡(luò)連接

• 1個商品CPU

• 16 TB SSD

前面有一些關(guān)于保持驗證人從頭執(zhí)行初始同步的能力，而不是信任來自其他驗證人簽名狀態(tài)的參考文獻(xiàn)。我預(yù)計，如果Libra得到充分使用，那么執(zhí)行這樣的同步將很快變得非常不切實際，因此，節(jié)點安全模型將高度依賴于信任驗證者。

9.用Move實現(xiàn)Libra生態(tài)系統(tǒng)策略

The [Libra coin] reserve is the key mechanism for achieving value preservation. Through the reserve, each coin is fully backed with a set of stable and liquid assets. The Libra coin contract allows the association to mint new coins when demand increases and destroy them when the demand contracts. The association does not set a monetary policy. It can only mint and burn coins in response to demand from authorized resellers. Users do not need to worry about the association introducing inflation into the system or debasing the currency: For new coins to be minted, there must be a commensurate fiat deposit in the reserve.

好的，但現(xiàn)在我們討論的是網(wǎng)絡(luò)外部的事件。如白皮書前面所述，網(wǎng)絡(luò)無法執(zhí)行使用網(wǎng)絡(luò)狀態(tài)外部數(shù)據(jù)輸入的腳本。因此，上述代碼片段中的“can”和“must”修飾語肯定是指網(wǎng)絡(luò)并不知道的Libra Association政策或合同義務(wù)。

The consensus algorithm relies on the validator-set management Move module to maintain the current set of validators and manage the allocation of votes among the validators. Initially, the Libra Blockchain only grants votes to Founding Members.

假設(shè)驗證者對驗證者集的更改進(jìn)行投票，聽起來這會導(dǎo)致與我們在股權(quán)證明系統(tǒng)中看到的類似問題——遠(yuǎn)程攻擊。如果創(chuàng)始成員的密匙的重要閾值受到損害，攻擊者是否可以從源頭寫入新的賬戶歷史記錄？如果是這樣，其他節(jié)點會接受嗎？目前尚不清楚共識協(xié)議是否允許重寫舊狀態(tài)還是僅僅允許追加狀態(tài)。

We plan to gradually transition to a proof-of-stake.

如果他們能解決尚未解決的問題。

未解決的問題

如何進(jìn)行管理？

我們可以看到Libra Association是一個由成員組成的委員會，需要2/3的絕對多數(shù)通過才能做出改變的決策。他們是唯一有資格鑄造或銷毀Libra coin的人，但如果有足夠的共識，他們可以做出任何他們想要的改變。

是否需要AML / KYC？

顯然，協(xié)議級別不需要它，但Calibra錢包聲明所有用戶都將通過政府頒發(fā)的ID進(jìn)行驗證。聽起來Calibra錢包將是在一段時間內(nèi)唯一可用的錢包，所以目前還不清楚開發(fā)人員和用戶是否可以在Libra網(wǎng)絡(luò)上運行不遵守與Calibra相同標(biāo)準(zhǔn)的應(yīng)用程序。
什么是低收費？什么是正常操作？什么是足夠的容量？
CALIBRA錢包FAQ承諾低收費，但這似乎與在高負(fù)載時底層協(xié)議的操作相沖突。

Transaction fees will be low-cost and transparent, especially if you’re sending money internationally. Calibra will cut fees to help people keep more of their money.

Libra真的會對開發(fā)者開放嗎？

根據(jù)實現(xiàn)無許可共識的計劃：

The Libra Blockchain will be open to everyone—any consumer, developer, or business can use the Libra network, build products on top of it, and add value through their services. Open access ensures low barriers to entry and innovation and encourages healthy competition that benefits consumers.

我懷疑開發(fā)人員是否能夠在這個平臺上運行他們所想像的任何技術(shù)上有效的應(yīng)用程序。我沒有讀到任何讓我相信這個系統(tǒng)會抵制審查制度的內(nèi)容，但只有時間會告訴我們答案！

關(guān)于Facebook的Libra區(qū)塊鏈?zhǔn)侨绾芜\作的問題的解答就分享到這里了，希望以上內(nèi)容可以對大家有一定的幫助，如果你還有很多疑惑沒有解開，可以關(guān)注億速云行業(yè)資訊頻道了解更多相關(guān)知識。