## Description
ADR to address the process for proving an amnesia attack (as a form of global evidence) from `PotentialAmnesiaEvidence` detected by light clients
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For contributor use:
- [ ] Wrote tests
- [ ] Updated CHANGELOG_PENDING.md
- [ ] Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
- [ ] Updated relevant documentation (`docs/`) and code comments
- [ ] Re-reviewed `Files changed` in the Github PR explorer
Closes: #4546
The algorithm uses an array to store the headers and validators and populates it at every bisection (which is an unsuccessful verification). When a successful verification finally occurs it updates the new trusted header, trims that header from the cache (the array) and sets the depth pointer back to 0. Instead of retrieving new headers it will use the cached headers, incrementing in depth until it reaches the end of the cache which by then it will start to retrieve new headers from the provider.
Mathematically, this method doesn't properly bisect after the first round but it will always choose a pivot header that is within 1/8th of the upper header's height. I.e. if we are trying to jump 128 headers, the maximum offset from bisection height (64) is 64 + 16(128/8) = 80, therefore a better heuristic would be to obtain the new pivot header height as the middle of these two numbers which would therefore mean to multiply it by 9/16ths instead of 1/2 (sorry this might be a bit more complicated in writing but I can try better explain if someone is interested). Therefore I would also, upon consensus, propose that we change the pivot height to 9/16th's of the previous height
