@sismo-core/kv-merkle-tree

Key Value Merkle tree

Merkle tree implementation used in Sismo protocol

Made by Sismo

A KV Merkle tree is a key-value store enhanced with a merkle tree. The merkle tree stores in its leaves the following data: hash(key, value).

Merkle tree used in the Sismo Hydra s1 proving scheme to build accounts and registry trees.

Find here more informations on how KV Merkle trees are used for the Sismo Protocol.

Generate your Merkle tree

From data

With the constructor you will be able to instanciate a KVMerkleTree from MerkleTreeData.

In the default beaviour this will create a tree where the leaves will be hash(key,value).

For example if we take the use case of an airdrop, this could allow you to store the amount of token (the value) associated to a user Ethereum account (the key) in the Merkle tree.

const merkleTree = new KVMerkleTree({
  "0xa76f290c490c70f2d816d286efe47fd64a35800a": 1,
  "0x0085560b24769daa4ed057f1b2ae40746aa9aab6": 1,
  "0x0294350d7cf2c145446358b6461c161a927b3a87": 1,
  "0x4f9c798553a207536b79e886b54f169264a7a155": 1,
  "0xa1b04c9cbb449d13c4fca9c7e6be1f810e6f35e9": 1,
}, poseidonHash);

Params	Default	Type	Description
data	null	MerkleTreeData	Data used to generate your Merkle tree.
hashFunction	null	HashFunction	Hash function used to generate your Merkle tree.
forceHeight	null	number	Force the number of levels in your Merkle tree.
hashLeaves	true	boolean	Define if your leaf will be hashed or not.

The rest of params in the constructor are due to technicals needs, do not add them.

From leaves

const merkleTree = KVMerkleTree.fromLeaves([
  "0x1b1f552ecfaccc27b98bee59c3d6a05b7d0577878a16e596af333d92d30cddf3",
  "0x2b7f0fee9c5d6d14439ecbb8b957ad7bb47aed55e4b2ffeaa6a8837f97ac22e0",
  "0x19ba655c7d77f8ece9dceee1b3540c06424a067eba896dbcc706087860e28d95",
  "0x1ce55db377a85fe5bd4b876faa9abce3df63db2e5661db52736d5a60ec8223f0",
  "0x1f01ca4d7306f30daac2d5117eae0fff0daabfd020b51fc66e4c1625044733d0",
    ...
]);

Params	Default	Type	Description
leaves	string[]	MerkleTreeData	Leaves used to generate your Merkle tree.
hashFunction	null	HashFunction	hash function used to generate your Merkle tree.
forceHeight	null	number	Force the height of your merkle tree.
hashLeaves	false	boolean	Define if your leaf will be hashed or not.

Usages

Functions	Description
getHeight(): number	Return the height of your Merkle tree.
getRoot(): BigNumber	Return the root of your Merkle tree.
getValue(key: string): BigNumber	Return the value associated to a key. Not available in a Merkle tree create from leaves.
getMerklePathFromLeaf(leaf: string): MerklePath	Return MerklePath of a leaf.
getMerklePathFromKey(key: string): MerklePath	Make the link between key and leaf. This allow you to retrieve the MerklePath without knowing the value associated to a key. Not available in a Merkle tree create from leaves.
toJson(): JsonMerkleTree	Export your Merkle tree in json format
KVMerkleTree.fromJson(jsonMerkleTree: JsonMerkleTree): KVMerkleTree	Import your Merkle tree from json format.

Types

JsonMerkleTree

type JsonMerkleTree = {
    root: string,
    height: number,
    pointers?:
      [key: string]: {
        leafValue: string,
        value: number | null
      }
    }
    tree: {
      [nodeValue: string]: { 
        p?: string,
        r?: string,
        l?: string
      }
    }
}

	Description
root	Merkle root or "top hash" of the Merkle tree (see more)
height	Number of level of the Merkle tree
pointers	Key store that allow you to retrieve a leaf from a key without knowing the value. For example in an airdrop, the user will be able to retrieve his leaf from his Ethereum account without knowing the amount of token he deserve
tree	Merkle tree where p is the parent of the current node, r the right child and l the left child

MerklePath

interface MerklePath {
    path: [BigNumber](https://docs.ethers.io/v5/api/utils/bignumber/)[]; 
    indices: number[]; // 0 if the has is on left, 1 if the has is on the right
}

	Description
path[]	List of nodes to get the Merkle root from a leaf
indices[]	0 if the node is on left, 1 if the node is on the right

MerkleTreeData

type MerkleTreeData = { [key: string]: number | null };

HashFunction

type HashFunction = (inputs: any[]) => BigNumber

License

Distributed under the MIT License.

Contribute

Please, feel free to open issues, PRs or simply provide feedback!

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