Instructor: Mr. Ben77
On August 23, CKB released its Lightning Network Fiber Network light paper. Recently, I have been studying the Lightning Network knowledge in depth and have gained some knowledge, so I did some research on Fiber as soon as possible and wrote this article.
1. Improvements of Fiber
Compared with the Lightning Network on BTC, Fiber has its own considerations in design. At the same time, due to the characteristics of eUTXO and CKB networks, it also brings some unique technical points.
1. Asset transfer within the channel
Since Lightning Labs developed Taproot asset, the Lightning Network has finally expanded its asset issuance capabilities. However, the implementation logic of Taproot asset transfer in a general Lightning Channel is as follows:
Taproot assets enter and leave the channel through "exchange rate conversion" on both sides of the channel, and BTC is actually flowing in the channel. If you want to realize that Taproot assets flow in the channel, you need to improve the channel into a "Taproot Channel", which may need to be solved in a form similar to sidechain.
In Fiber, assets are transferred directly within the channel. The conceptual diagram of its implementation is as follows:
2. Adoption of PTLC
The lightning network on BTC uses HTLC technology. HTLC is actually good enough in actual use, but it still has the possibility of destroying the privacy of the lightning network in multi-hop links.
In terms of technology, HTLC uses the same preimage throughout the "multi-hop" path. At the same time, given that the preimage is randomly generated by the payee, it is unlikely that two different payments use the same preimage. Therefore, if an entity (individual, company, etc.) controls multiple nodes on a payment path, it can obtain complete transaction information based on the input obtained by a node and the output of another node. Then, this entity can use some heuristic method (based on the path length or node type) to guess which node in the path is the payer and which node is the payee. The efforts made by onion routing in terms of privacy will be destroyed.
With PTLC, each hop in the path uses a different secret value. In this way, the privacy achieved through onion routing is protected. Fiber uses PTLC technology.
For more details on this technical point, please refer to the following article:
What is a Point Time Lock Contract (PTLC)?
(https://www.btcstudy.org/2022/01/27/breaking-down-the-bitcoin-lightning-network-eltoo/)
3. Alleviated the problems encountered by BTC Lightning Network
The overall design of Fiber is derived from BTC’s Lightning Network, so some of the current problems of the Lightning Network are also “inherited”, such as the very important “liquidity management” problem.
In the BTC lightning network, the management of channel liquidity is a very troublesome thing, but because the entry and collection of payments require liquidity, we inevitably have to adjust the channel liquidity scenario. The current solutions, whether it is "submarine swap", "JIT" or "channel splicing", will involve the problem of requiring users to conduct 1-2 transactions on the main network. The BTC main network has slow confirmation and may have high gas, which will make people confused or have a bad experience.
In Fiber, the currently revealed "LSP+Submarine Swap" solution does not get rid of the problems of this liquidity solution, but the cost of submitting a ckb transaction is very low and the waiting time is very short, which will provide a much better user experience.
4. Interoperability with BTC Lightning Network
Fiber is not limited to the CKB network. It can achieve 1:1 conversion between BTC and CCBTC through the "intermediate acceptor" model. This method is somewhat similar to building "a lightning bridge", and this solution can be made decentralized, that is, ordinary people who have such assets can also participate in providing this service and act as "acceptors."
If we think further, BTC can be directly swapped for other assets in the CKB network in this way, just by accepting the exchange rate quote from the public Oracle.
Of course, this is currently in the conceptual design stage and we still need to observe the actual development situation.
2. Problems with Fiber
In addition to the problems that need to be faced together due to "inheritance", Fiber also has some issues worth discussing.
1. Necessity
The development of BTC's Lightning Network was born out of "small block limits" and "extremely high confirmation time on the main network". The goal is to improve these problems in the payment field, achieve a significant reduction in fees and a significant increase in TPS.
As for the CKB network, through testing, the current transfer fee is about 0.0000183ckb. Combined with the current price of ckb (~0.01U), the fee is about 0.000000183U, which is already very, very, very low. Even if we consider that the price of ckb increases 10 times and the ckb network is 10 times more congested, the fee of a transaction is only 0.0000183U, which is still very low. Therefore, the necessity of the Lightning Network is obviously insufficient compared to the BTC network.
At the same time, considering that lightning payment still has problems such as [difficulty in operating and maintaining nodes], [requires both parties to pay online], and [insufficient capital utilization], although there are certain means to improve it, the necessity does not seem to be that strong.
Of course, we can also look at this issue from several angles:
1) From the perspective of payment speed, the block time of the CKB network is 8~48s, and the lightning network is basically close to "instant payment", which improves the payment speed;
2) From the perspective of technological development, the CKB network itself has its own ecosystem. The development of the Lightning Network will help the development and expansion of the entire ecological technology map. Other technologies such as ZK may also be introduced in the future, which can also be viewed from this perspective.
2. Lightning Model Problem
The lightning model used by Fiber is based on "Daric", which is a traditional P2P model. However, judging from the recent market development of the BTC lightning network, the P2P model has encountered great problems. The entire market is turning to LSP custody. The closure of Mutiny wallet also confirms this. The announcement of the suspension of operations by LSP under Mutiny also casts a shadow on whether the LSP custody solution can be maintained.
I think we need to keep a close eye on future changes to the Lightning model.
3. Outlook for Fiber
I have always respected the development team of CKB. I have said the reason before, that is, I respect the team that is still willing to explore and develop, especially the Eastern team, regardless of success or failure. Therefore, I have expectations for Fiber, and I have thought about the possible directions to look forward to or think about, and I would like to share them here.
1. How to leverage the advantages of ckb network to innovate
The CKB network introduced a new architecture at the beginning of its design, so whether it can make use of its network characteristics to make more innovations on the lightning network is a direction I am looking forward to. For example:
1) How to perfectly solve the problem of offline payment?
2) Can liquidity management issues be addressed from a fundamental design framework?
3) Can the difficulty of interaction in multi-person channels be fundamentally solved?
4）……
Innovation is always the primary productive force and also the treasure trove of this market!
2. Build more lightning demand scenarios
There is a universal problem with the Lightning Network, that is, where exactly should the Lightning Network be used? We have millions of TPS, but in what situations in reality are there such strong interactive needs? Or what scenarios are very necessary or can only be solved by the Lightning Network?
I have considered "paid streaming" and "game", and also derived "LAPP", but these types of projects on the market either have not taken off or are already "dead", so the scene should be left there, and Fiber will also encounter such a problem.
I hope that Fiber can explore and even "build" more lightning demand scenarios. Technology can only reflect its value when it is put into practice. Otherwise, it will easily become a "geek's toy". However, in my conversations with relevant personnel, I learned that the CKB team attaches great importance to this and I hope to see their continuous progress in this regard.
