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```
val requiredWeight = valTotalWeight * 2 / 3;
assert(accWeight >= requiredWeight) throw ERR_NOT_ENOUGH_WEIGHT;
```
While checking signature:
- division is used - it's a bad idea for a smart contract;
- `accWeight` must be strictly bigger than `requiredWeight`;
- the hash of data is recalculated each iteration, but it is possible to do it once.
val requiredWeight = valTotalWeight * 2 / 3;
assert(accWeight >= requiredWeight) throw ERR_NOT_ENOUGH_WEIGHT;
```
While checking signature:
- division is used - it's a bad idea for a smart contract;
- `accWeight` must be strictly bigger than `requiredWeight`;
- the hash of data is recalculated each iteration, but it is possible to do it once.
Solid implementation of lite-client and tx-checker, but "hints"-based tx-search in proof (insecure). Quite a lot additional functionality for UX improvement. For instance shard-optimization and attempt to implement shard-transaction checks (unfortunately too simplified to work in production).
More info on issues: https://contest.com/docs/TrustlessBridgeChallengeAssessment
More info on issues: https://contest.com/docs/TrustlessBridgeChallengeAssessment
Division with round down is a problem and it's not helping at all. You just lowering required weight by doing that, and allowing invalid block to be accepted by smart contract.
Here is snippet you can insert in browser console and see that comparison with division returns TRUE where valid calculation should return FALSE.
var signedWeight = 3;
var totalWeight = 5;
var isEnough_usingDiv = signedWeight >= Math.floor((totalWeight * 2 / 3));
var isEnough_usingMul = signedWeight * 3 >= totalWeight * 2;
console.log(isEnough_usingDiv, isEnough_usingMul);
Here is snippet you can insert in browser console and see that comparison with division returns TRUE where valid calculation should return FALSE.
var signedWeight = 3;
var totalWeight = 5;
var isEnough_usingDiv = signedWeight >= Math.floor((totalWeight * 2 / 3));
var isEnough_usingMul = signedWeight * 3 >= totalWeight * 2;
console.log(isEnough_usingDiv, isEnough_usingMul);
Good job on the submission! The code looks solid and the comments make it clear it's well thought through!
I think it's OK security-wise. Couple of notes:
1. I do think the pedantic mode is required, because when verifying a block in a future epoch, the stored validator weights are not valid anymore and it's impossible to know if the signatures add up to a majority in that future block's epoch
2. I wouldn't send a merkle proof with just a single pruned branch. From a security perspective, it doesn't do more than sending the same hash twice
3. I wonder why tracking state in a hashmap would be "morally forbidden"? Is it not possible to create this without leaks through limits, bounced messages and gas checking?
I think it's OK security-wise. Couple of notes:
1. I do think the pedantic mode is required, because when verifying a block in a future epoch, the stored validator weights are not valid anymore and it's impossible to know if the signatures add up to a majority in that future block's epoch
2. I wouldn't send a merkle proof with just a single pruned branch. From a security perspective, it doesn't do more than sending the same hash twice
3. I wonder why tracking state in a hashmap would be "morally forbidden"? Is it not possible to create this without leaks through limits, bounced messages and gas checking?
Nobody added any issues yet...