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arnaucube 4 years ago
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      README.md
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README.md

@ -2,10 +2,13 @@
*From Esperanto, **miksi** (miks·i): to mingle, to blend, to mix, to shuffle* *From Esperanto, **miksi** (miks·i): to mingle, to blend, to mix, to shuffle*
![](miksi-logo00-small.png)
Ethereum mixer where all the computation & constructions are done offchain and then proved inside a zkSNARK to the Smart Contract (for the *deposit* and for the *withdraw*).
This means that the client builds a MerkleTree and makes all the needed computation, and then generates a zk-proof where proves that all the offchain computation is done following all the rules (no leaf deletion, only one leaf addition, correct leaf format).
This allows to use only `~325.000 gas` for the *deposit*, and `~308.000 gas` for the withdraw.
![](miksi-logo00-small.png)
**Warning:** This repository is in a very early stage.
**Warning:** This repository is in a very early stage. The current version works, but is not finished and there are some improvements to be added.
WebApp to use miksi-core can be found at https://github.com/arnaucube/miksi-app WebApp to use miksi-core can be found at https://github.com/arnaucube/miksi-app
@ -27,8 +30,10 @@ npm run test-sc
## Spec draft ## Spec draft
**Note:** The spec & code is a work in progress, there are some pending works & improvements planned to do, and some diagrams for better explanation.
### Deposit ### Deposit
*All computation & constructions are done offchain and then proved inside a zkSNARK to the Smart Contract*
- user generates a random `secret` & `nullifier` - user generates a random `secret` & `nullifier`
- computes the `commitment`, which is the Poseidon hash: `commitment = H(coinCode, amount, secret, nullifier)`, where: - computes the `commitment`, which is the Poseidon hash: `commitment = H(coinCode, amount, secret, nullifier)`, where:
- `coinCode`: code that specifies which currency is being used (`0`==ETH) - `coinCode`: code that specifies which currency is being used (`0`==ETH)
@ -39,16 +44,18 @@ npm run test-sc
- build the MerkleTree with the getted commitments - build the MerkleTree with the getted commitments
- add the new computed `commitment` into the MerkleTree - add the new computed `commitment` into the MerkleTree
- generate zkSNARK proof, where is proving: - generate zkSNARK proof, where is proving:
- prover knows the `secret` & `nullifier` for the `commitment`
- the transition from `RootOld` (the current one in the Smart Contract) to `RootNew` has been done following the rules (only one addition, no deletion)
- prover knows the `secret` & `nullifier` for the `commitment` which is in a leaf in the merkletree
- the transition from `RootOld` (the current one in the Smart Contract) to `RootNew` has been done following the rules (only one leaf addition, no leaf deletion, correct leaf format, etc)
- user sends ETH to the smart contract `deposit` call, together with the zkProof data - user sends ETH to the smart contract `deposit` call, together with the zkProof data
- smart contract verifies the zkProof of the deposit, and if everything is ok stores the commitment & the new root
Deposit circuit can be found [here](https://github.com/miksi-labs/miksi-core/blob/master/circuits/deposit.circom). Deposit circuit can be found [here](https://github.com/miksi-labs/miksi-core/blob/master/circuits/deposit.circom).
### Withdraw ### Withdraw
*All computation & constructions are done offchain and then proved inside a zkSNARK to the Smart Contract*
- user gets all the commitments from the SmartContract - user gets all the commitments from the SmartContract
- build the MerkleTree with the getted commitments - build the MerkleTree with the getted commitments
- generate the siblings for the `commitment` of which the user knows the `secret` & `nullifier`
- generate the siblings (merkle proof) for the `commitment` of which the user knows the `secret` & `nullifier`
- generate zkSNARK proof, where is proving: - generate zkSNARK proof, where is proving:
- user knows a `secret` for a public `nullifier` - user knows a `secret` for a public `nullifier`
- which `commitment` is in the MerkleTree - which `commitment` is in the MerkleTree
@ -57,3 +64,6 @@ Deposit circuit can be found [here](https://github.com/miksi-labs/miksi-core/blo
Withdraw circuit can be found [here](https://github.com/miksi-labs/miksi-core/blob/master/circuits/withdraw.circom). Withdraw circuit can be found [here](https://github.com/miksi-labs/miksi-core/blob/master/circuits/withdraw.circom).
# Thanks
Miksi is possible thanks to [circom](https://github.com/iden3/circom), [circomlib](https://github.com/iden3/circomlib), [wasmsnark](https://github.com/iden3/wasmsnark), and thanks to the ideas about offchain computation validated with a zkSNARK in the [Zexe paper](https://eprint.iacr.org/2018/962.pdf).

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circuits/deposit.circom

@ -55,7 +55,11 @@ template Deposit(nLevels) {
comCheck.in[1] <== commitment; comCheck.in[1] <== commitment;
comCheck.out === 1; comCheck.out === 1;
// TODO instead of 2 siblings input, get siblingsOld from siblingsNew[len-1]
// TODO instead of 2 siblings input, get siblingsOld from
// siblingsNew[len-1] both siblingsOld & siblingsNew have same values
// except for one, can be merged into one, to ensure that the circuit
// checks that the leaf non existing under rootOld is in the same
// position than the check that the leaf exists under the rootNew
// check that nLevels-1 siblings match from siblingsOld & siblingsNew // check that nLevels-1 siblings match from siblingsOld & siblingsNew
component siblEq[nLevels]; component siblEq[nLevels];

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test/contracts/miksi.test.ts

@ -94,7 +94,7 @@ contract("miksi", (accounts) => {
commitmentsArray[0] = res[0]; commitmentsArray[0] = res[0];
currKey = res[2]; currKey = res[2];
}); });
it("Rebuild the tree from sc commitments", async () => { it("Rebuild the tree from sc commitments", async () => {
let treeTmp = await smt.newMemEmptyTrie(); let treeTmp = await smt.newMemEmptyTrie();
await treeTmp.insert(0, 0); await treeTmp.insert(0, 0);

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