feat: merkle tree verification #31
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Thank you for the PR! Great work.
Can you provide a test suite for this? Like it's done in SolidityByExample, to demonstrate how to use this contract in practice?
src/ch01-02-merkle_tree.md
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| A Merkle tree is a hash-based data structure that is a generalization of the hash list. It is a tree structure in which each leaf node is a hash of a block of data, and each non-leaf node is a hash of its children. Typically, Merkle trees have a branching factor of 2, meaning that each node has up to 2 children. | ||
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| If you are familiar with developing whitelists, Merkle trees actively used. In Solidity we use Keccak256 for hashing leaves. As felt252 range is not able to fit a keccak256 hash, we use Pedersen as hash function in this example. |
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As felt252 range is not able to fit a keccak256 hash, we use Pedersen as hash function in this example.
That is true, however I don't think that's a good reason as we could just use u256s and hash these u256s with keccak together.
I think what matters here is that pedersen is cheaper than keccak, and as you mentioned we can make it work with felts instead of uints
| root::write(_root); | ||
| } | ||
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| // Checks is merkle proof verified or not. |
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// Verifies the given Merkle proof
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| fn _verify(root:felt252, leaf: felt252, ref proof: Array::<felt252>) -> bool { | ||
| let proof_len = proof.len(); | ||
| let calc_root = _verify_body(leaf, ref proof, proof_len, 0_u32); |
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Instead of having verify_body as a recursive function, can you make it as a loop instead?
| } | ||
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| fn _verify_body( | ||
| leaf: felt252, ref proof: Array::<felt252>, proof_len: u32, index: u32 |
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proof_len is an unrequired argument here as you can simply use proof.len().
also, instead of increasing the index by 1, and decreasing the proof len by 1, you could just call proof.pop_front() on the proof (passed as a Span). and simply pass the proof.
| // Checks is merkle proof verified or not. | ||
| #[view] | ||
| fn verify(account: ContractAddress, mut proof: Array::<felt252>) -> bool { | ||
| let account_as_felt: felt252 = account.into(); |
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account is transformed into a felt252 here, and the destination type is explicit. You can just shadow the previous type of account, the type identifier in the variable name is not required.
let account: felt252 = account.into();
| fn _verify(root:felt252, leaf: felt252, ref proof: Array::<felt252>) -> bool { | ||
| let proof_len = proof.len(); | ||
| let calc_root = _verify_body(leaf, ref proof, proof_len, 0_u32); | ||
| if (calc_root == root) { |
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you can simplify it to return calc_root == root;
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@ermvrs What is the state of this PR? |
Here is an example of how to use Merkle Trees with pedersen hash.