屏蔽 CSV：比特幣隱私和可擴展性的新時代

今天的比特幣發展主要集中在兩個主要問題：（1）擴容和（2）隱私。對比特幣的通常建議包括添加新的操作碼和腳本工具。

Bitcoin development today focuses on two major issues: (1) scaling and (2) privacy. The usual proposals to Bitcoin involve adding new opcodes and scripting tools. But an old idea is coming back, one that could make transactions more private and peer-to-peer.

今天的比特幣發展主要集中在兩個主要問題：（1）擴容和（2）隱私。對比特幣的通常建議包括添加新的操作碼和腳本工具。但一個古老的想法正在回歸，它可以使交易更加私密和點對點。

Right now, every Bitcoin transaction is broadcast to the entire network for verification. It’s an effective way to prevent double-spending, but it also means more information is exposed than is strictly necessary. This leads to heavier computational demands, higher costs, and a system that struggles to scale.

目前，每筆比特幣交易都會廣播到整個網路進行驗證。這是防止雙重支出的有效方法，但也意味著暴露的資訊超出了嚴格必要的範圍。這導致更重的計算需求、更高的成本以及難以擴展的系統。

But what if moving part of the transaction process client-side didn't just improve efficiency, but also unlocks a whole new era of privacy on Bitcoin?

但是，如果將部分交易流程移至客戶端不僅提高了效率，而且還開啟了比特幣隱私的全新時代，結果會怎麼樣呢？

In our recently published paper, Blockstream, in collaboration with Alpen Labs and ZeroSync, we introduce the Shielded CSV Protocol, an improvement on Client-Side Validation (CSV) that offers truly private transactions. This new protocol is a significant step towards enhancing the privacy of Bitcoin transactions and has the potential to increase transaction capacity from 11 per second to over 100 per second, through some additional measures we’ll cover in this blog post.

在我們最近發表的論文 Blockstream 中，我們與 Alpen Labs 和 ZeroSync 合作，介紹了屏蔽 CSV 協議，這是對客戶端驗證 (CSV) 的改進，可提供真正的私密交易。這個新協議是增強比特幣交易隱私性的重要一步，透過我們將在本部落格文章中介紹的一些額外措施，有可能將交易容量從每秒 11 筆增加到每秒 100 筆以上。

This post offers a high-level overview of the Shielded CSV Protocol, which aims to advance layer one blockchain performance while remaining fully compatible with Bitcoin. Developed by the combined minds of Jonas Nick, Liam Eagen, and Robin Linus. Here’s the backstory on Shielded CSV, and why it has the potential to change everything.

這篇文章對 Shielded CSV 協議進行了高級概述，該協議旨在提高第一層區塊鏈性能，同時保持與比特幣完全相容。由 Jonas Nick、Liam Eagen 和 Robin Linus 共同開發。以下是 Shielded CSV 的背景故事，以及為什麼它有可能改變一切。

Bitcoin Then and Now

比特幣的過去與現在

The Double-Spend Problem: How Bitcoin Solved It

雙花問題：比特幣如何解決它

Before Bitcoin, it was widely believed that creating a reliable digital currency was impossible without a trusted middleman. The double-spend problem meant there was no way to ensure a “digital coin” couldn’t be spent more than once. It was a fundamental flaw that kept digital currency from becoming a reality.

在比特幣出現之前，人們普遍認為，如果沒有可信的中間人，就不可能創造出可靠的數位貨幣。雙重支出問題意味著無法確保「數位貨幣」不會被多次使用。這是一個根本性的缺陷，阻礙了數位貨幣成為現實。

Then, in 2009, Satoshi addressed this problem by introducing the shared public ledger called the blockchain. Instead of relying on a single trusted authority, Bitcoin uses a network of nodes on a shared public ledger, where every transaction is recorded and verified. This system ensures that each coin is unique, making it impossible to spend the same coin twice.

然後，在 2009 年，中本聰透過引入稱為區塊鏈的共享公共分類帳來解決這個問題。比特幣不依賴單一的可信任機構，而是使用共享公共分類帳上的節點網絡，其中每筆交易都被記錄和驗證。該系統確保每個硬幣都是唯一的，因此不可能兩次使用同一個硬幣。

When a Bitcoin transaction is added to the chain, it follows this process:

當比特幣交易添加到鏈上時，它遵循以下過程：

During validation, nodes verify that the coins exist, check the validity of the signature, and enforce the critical double-spend rule—making sure each coin is spent only once.

在驗證過程中，節點驗證硬幣是否存在，檢查簽名的有效性，並執行關鍵的雙花規則——確保每個硬幣僅花費一次。

The whole purpose of this ledger is to maintain order, showing clearly who owns which coins and when they moved.

這個帳本的全部目的是維持秩序，清楚地顯示誰擁有哪些代幣以及它們何時移動。

The purpose of the ledger is to keep transactions in order, making it clear who owns what coins and when they were sent.

分類帳的目的是保持交易有序，明確誰擁有哪些代幣以及何時發送這些代幣。

Since its inception, Bitcoin’s developers keep coming back to the same question: is this really the best and most private way to handle transactions? How can we make this system leaner, more efficient, and more private?

自誕生以來，比特幣的開發人員不斷回到同一個問題：這真的是最好、最私密的交易處理方式嗎？我們要如何讓這個系統更精簡、更有效率、更私密？

A Privacy Problem: Public Transactions

隱私問題：公開交易

Bitcoin's biggest privacy challenge is that bitcoin transactions are out there in the open on the blockchain. Satoshi saw this vulnerability from the beginning. In the original whitepaper, he suggested a straightforward solution: users should create new keys for each transaction and avoid reusing addresses.

比特幣最大的隱私挑戰是比特幣交易在區塊鏈上公開進行。中本聰從一開始就看到了這個漏洞。在最初的白皮書中，他提出了一個簡單的解決方案：使用者應該為每筆交易建立新金鑰並避免重複使用地址。

The idea was to make it harder to link transactions back to a single owner. But in practice, with all the advanced chain analysis methods available today, maintaining privacy is much harder than it seems. Even with new addresses, linking transactions and identifying patterns has become easier for those intent on tracing user activity.

這個想法是為了讓交易更難與單一所有者聯繫起來。但實際上，隨著當今所有先進的鏈分析方法的出現，維護隱私比看起來困難得多。即使使用新地址，對於有意追蹤用戶活動的人來說，連結交易和識別模式也變得更加容易。

In response, privacy-focused protocols like Zcash have introduced novel ways to conceal transaction details using more advanced cryptography and things like zk-SNARKs. But these methods come with significant trade-offs: transactions are larger, making the verification process for nodes more resource-intensive and expensive to verify.

作為回應，Zcash 等注重隱私的協議引入了使用更先進的加密技術和 zk-SNARK 等技術來隱藏交易細節的新方法。但這些方法伴隨著重大的權衡：交易規模更大，使得節點的驗證過程更加資源密集且驗證成本更高。

A Communication Problem: Communication is Inefficient

溝通問題：溝通效率低下

In Bitcoin’s design, mining serves two fundamental purposes: (1) proof-of-publication for transactions and (2) providing a consensus on the order of transactions. However, Bitcoins’ system also intertwines these core functions with less essential tasks, like transaction validation and coin issuance.

在比特幣的設計中，挖礦有兩個基本目的：（1）交易的發布證明；（2）提供交易順序的共識。然而，比特幣的系統也將這些核心功能與較不重要的任務交織在一起，例如交易驗證和硬幣發行。

Across all blockchains, whether it’s Bitcoin, Ethereum, Zcash, or Dogecoin, the transaction process always looks the same: wallets sign transactions, broadcast them to the network, and full nodes validate them. But is validating every transaction directly on the blockchain really necessary?

在所有區塊鏈中，無論是比特幣、以太坊、Zcash 還是狗狗幣，交易過程總是看起來相同：錢包簽署交易，將其廣播到網絡，然後由全節點驗證它們。但直接在區塊鏈上驗證每筆交易真的有必要嗎？

We think there’s a better way. The idea traces back to a 2013 insight, when Peter Todd first mentioned Client-Side Validation. In this mailing list post he asks, ‘Given only proof-of-publication, and a consensus on the order of transactions, can we make a successful crypto-coin system? Surprisingly, the answer is yes!’

我們認為有更好的方法。這個想法可以追溯到 2013 年的見解，當時 Peter Todd 首次提到客戶端驗證。在這篇郵件清單文章中，他問道：“僅考慮發布證明以及對交易順序的共識，我們就能創建一個成功的加密貨幣系統嗎？”令人驚訝的是，答案是肯定的！

Instead of requiring every full node to verify every transaction, CSV allows you to send coins with proof of their validity directly to the recipient

CSV 允許您將帶有有效性證明的代幣直接發送給收件人，而不是要求每個完整節點驗證每筆交易