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Dev Update – Checkpointing


The next large milestone for GRAFT is implementing checkpointing (a way to achieve finality and avoid various double spend exploits between the layers of the multi-layer blockchain).

We have been looking at checkpointing solutions from Dash, LOKI, and Ethereum Casper. All of them use slightly different approaches for validator quorum selection, conflicting checkpoints resolution, revision attacks, catastrophic crashes, etc. Our goal is to pick the best model for GRAFT by leveraging the work that’s been done on these other platforms.

Here’s a high-level checkpointing solutions analysis:

Quorum selection

  • Dash: set of active large (320-400) quorums, own communication protocol
  • Loki: 2 quorums (10 members)
  • Casper: 2 set of validators. Size of each set isn’t specified, supposed to be dynamic

Checkpointing frequency

  • Dash: every block
  • Loki: every 4 blocks
  • Casper: 100s (links)

Slashing

  • Dash: scoring, collateral not slashed but masternode could be banned
  • Loki: none, only deregistration from being active service node
  • Casper: “gradual” (incremental) for lack of responsiveness, harsher for incorrect result

Conflicting checkpoints (fork choice)

Double Spend

Over the next couple of weeks we will be working on putting together a proof-of-concept for GRAFT checkpointing, at which point we will publish the design to collect comments and proceed with full implementation.

References:

Lyra DAG Development

As you may know, Slava has stepped away from day-to-day at GRAFT.
One of the community devs who was working alongisde with Slava for a while however, has stepped up to continue Lyra work and has already built an impressive showcase application and a roadmap. Little too early to “count the chickens”, but looking quite promising that Lyra development will continue.


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