English Chinese (Simplified)
a new kind of range proofs replacing RingCT in transactions to obfuscate the amounts sent
["bulletproofs", "bulletproof"]
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The Basics 基础知识
@RingCT was introduced to obfuscate transaction amounts. One goal of @RingCT was to prove the sum of inputs - outputs in the @transaction was equal to 0, and all outputs were positive numbers.
To accomplish this, two kind of ring signatures were constructed: One ring signature for the whole transaction (to prove the sum is 0), and a set of ring signatures for the subsets of transaction bits (to prove the outputs are positive numbers), then combined together using originally Schnorr signatures (and later replaced by Borromean ring signature).
为了实现这个目标,构建了两种环签名:一个环签名为整个交易(证明输出之和为0);另一组环签名为交易单位的子集(为了证明所有输出都是正数),然后组合在一起,最初使用 Schnorr 签名(后来被 Borromean 环签名所取代)。
While it was doing the job, a big drawback was the huge size of such a ringCT transaction. 当它运行的时候,存在一个很大的缺点就是这种环机密交易的尺寸太大。
Where it comes to bulletproofs 涉及到防弹协议
Back in 2017, a [Standford applied crypto group](https://crypto.stanford.edu/bulletproofs/) wrote a [paper](https://eprint.iacr.org/2017/1066.pdf) presenting a new kind of range proofs, called bulletproofs.
> Bulletproofs are short non-interactive zero-knowledge proofs that require no trusted setup.
> 防弹证明是一种短的非交互式零知识证明,不需要可信的设置。
Bulletproofs, unlike Borromean or Schnorr signatures, are very efficient as range proofs. Proving a big set of data only generates a small proof, and the size of this proofs grows logarithmically with the size of the data being proved.
与 Borromean 或 Schnorr 签名不同,防弹协议作为范围证明非常高效。要证明一个大的数据集只需产生一个小的证明,而且这个证明的尺寸随着被证明数据的规模大小呈对数增长。
It means that increasing the number of outputs in a transaction will, with bulletproofs only slightly increase the size of the proof.
Bulletproofs also have the advantage to allow to prove that multiple committed amounts are in the desired range at once. No need to prove each output to each destination in separate proofs; the whole transaction amounts could be proven in one bigger (but still very small) bulletproof. 防弹协议还具有这样一些优势,可以同时证明多个提交的数量在所需范围内。不需要分别证明每个输出到每个目标;整个交易金额可以被证明在一个更大的(但仍然非常小)防弹协议中。
Thorough audit process and implementation 彻底的审核过程及执行
As bulletproofs were really new, and the initial implementation made by the group, while thoroughly done, needed a rewrite focused on our specific use-case, implementing bulletproof in Monero was not a simple thing.
The code has been written and rewritten to follow the new version of bulletproofs which was still being developed, but once this Monero implementation was finalized, the resulting deployment should be taken with extreme care.
Therefore, the community started an auditing process. Researchers reached out to Benedikt Bünz, lead author of the Bulletproofs paper, and to [OSTIF](https://ostif.org/) an organization which helps open source technologies to improve and secure themselves.
OSTIF directed the group to several organizations with the skills required to perform the audit. While one of them asked to be kept unnamed and was therefore put away from the process that needed to be public, two others (QuarksLab & Kudelski Security) were choosen to conduct the audit.
Our 3 auditors were funded by the community to ensure that the implementation did not contain any critical bugs or exploits. The final reports were released during the summer of 2018, with several useful corrections and fixes suggested, and the final bulletproof implementation has been added first to Monero Stagenet, and then to the main Monero network during the October 2018 network upgrade.
Since the bulletproofs deployment, the size of an average transaction has dropped by at least 80%, as well as the transaction fees. 自从防弹协议部署以来,平均交易尺寸已经下降了至少80%,交易费用也因而大幅下降。