Litecoin MimbleWimble September Summary Update

This update was written and provided by Litecoin MimbleWimble lead developer. David Burkett.

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v0.21 released

I was hoping the v0.21 release would be out already, but I’m waiting for one last developer to review it. A few of us have already run test builds to ensure our environment is set up correctly, so once everyone signs the code we should be able to build and sign a release candidate fairly quickly.

The most notable change in v0.21 is the inclusion of Taproot support. Taproot logic is the same as Bitcoin, but activation is performed differently. We decided to test the bip8 6 mechanism we plan to use for MWEB activation. lockinontimeout set.

Soft fork activation can be difficult to follow because there are a few different ways it can be done (BIP8, BIP9, UASF, etc.) and it happens through multiple steps or “states” in which no activation is performed. It is generally well explained even to non-technical users. To make sure everyone can see what’s going on, let’s take a look at the Taproot activation process.

Activate tabroot

In each block version This is a field that miners can use to “vote” for the soft fork. Miners will use a small portion of it. version This field notifies Taproot activation.

A new “window” starts every 8,064 blocks. At the end of each window, the node aggregates all blocks signaling for the feature, and if the total meets a defined threshold, the feature is “locked” to be activated in the next window. In our case, the threshold is defined as 6,048 blocks, or 75% of the blocks in the window.

Here’s how to find Taproot:

1. Taproot was initially DEFINED Status means it’s a known feature, but you can’t vote on it yet.

2. In block 2,153,088 (early to mid-November) this feature STARTED The status means that upgraded miners can start signaling/voting to activate taproot. After 8,064 blocks (first window), the nodes add up the number of blocks that signaled Taproot activation.

3. The process repeats until one of two conditions is met.

   • A window occurs in at least 6,048 (75%) of the blocks signaling for Taproot.

     • After this window, Taproot switches to: LOCKED_IN situation. Remains LOCKED_IN This gives everyone time to upgrade for the next full window (block 8,064).

     • After becoming LOCKED_IN For one full window, Taproot switches to: ACTIVE. Nodes begin enforcing Taproot consensus rules for every block.

   • Threshold no When we reach block 2,362,752 (November 2022) we will lockinontimeout Previously mentioned options:

     • Taproot switches to: LOCKED_IN, even if it doesn’t meet the benchmark. Miners must initiate signaling to Taproot. Any block that does not send a signal to Taproot will be ignored by the nodes in the network.

     • After becoming LOCKED_IN For one full window, Taproot switches to: ACTIVE. Nodes begin enforcing Taproot consensus rules for every block.

I hope this is easy to understand, but if anything is unclear the full BIP8 specification can be found here 6.

judge

I met with Quarkslab auditors on Wednesday for an interim audit confirmation. They are finalizing their static analysis of the code and have found very few issues so far, which is very encouraging.

We also discussed priorities for the remainder of the audit to ensure the most important aspects were thoroughly covered.

Over the next few weeks, an auditor will focus on manual testing, trying to determine whether it works as expected and, more importantly, whether it can be broken.

Other auditors know a lot about cryptography, so they can compromise key integrity, tx malleability (i.e. someone modifying a transaction they were not the author of), and many other security issues.

We expect the results of the audit to be available within a few weeks.