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Apr 7, 2020
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TIP-137: add the link #144

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add the link
Federico2014 Apr 3, 2020
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Merge remote-tracking branch 'origin/feature/verify_proofs' into feat…
Federico2014 Apr 7, 2020
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31 changes: 16 additions & 15 deletions tip-137.md
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@@ -1,7 +1,7 @@
---
```
tip: 137
title: Zero-knowledeg Proof Verification functions
title: Zero-knowledge Proof Verification functions
author: federico<federico.zhen@tron.network>
discussions-to: https://github.com/tronprotocol/tips/issues/137
status: draft
Expand All @@ -12,32 +12,32 @@ created: 2020-03-09

## Simple Summary

The TIP provides the zero-knowledge proof verification functions in shielded contract, which can be used in shielded token transactions.
The TIP provides the zero-knowledge proof verification functions in the shielded contract ([TIP-135](https://github.com/tronprotocol/tips/blob/master/tip-135.md)), which can be used in shielded token transactions.

## Abstract

The TIP introduces three new functions: `verifyMintProof`, `verifyTransferProof`, and `verifyBurnProof`, which are implemented in the form of precompiled contract, and can accelerate the zero-knowledge verification for the `mint`, `transfer` and `burn` operations in shielded token contract.
The TIP introduces three new functions: `verifyMintProof`, `verifyTransferProof`, and `verifyBurnProof`, which are implemented in the form of the precompiled contract, and can accelerate the zero-knowledge verification for the `mint`, `transfer` and `burn` operations in the shielded token contract.

## Motivation

In order to implement shielded transaction for [TRC-20](https://github.com/tronprotocol/TIPs/blob/master/tip-20.md) token, We have developed the shielded token contract. The contract has three core modules: `mint`, `transfer` and `burn`. `mint` is used to transform the public TRC-20 tokens into shielded tokens. `transfer` is used for shielded token transactions. `burn` is used to transform the shielded tokens back to public TRC-20 tokens. The shielded contract is implemented based on zero-knowledge proof, so it needs the complex zero-knowledge proof verification in `mint`, `transfer` and `burn` methods. In order to accelerate the speed, we will make use of the new functions in the contract to implement the verification process.
To implement the shielded transactions for [TRC-20](https://github.com/tronprotocol/TIPs/blob/master/tip-20.md) token, We have developed the shielded token contract ([TIP-135](https://github.com/tronprotocol/tips/blob/master/tip-135.md)). The contract has three core modules: `mint`, `transfer` and `burn`. `mint` is used to transform the public TRC-20 tokens into shielded tokens. `transfer` is used for shielded token transactions. `burn` is used to transform the shielded tokens back to public TRC-20 tokens. The shielded contract is implemented based on zero-knowledge proof, so it needs the complex zero-knowledge proof verification in `mint`, `transfer` and `burn` methods. To accelerate the speed, we will make use of the new functions in the contract to implement the verification process.

## Specification

The following define the methods implementation for shielded token contract.
The following defines the implementation of the methods for the shielded token contract.

### Preliminaries
**NoteCommitment**

The TRC-20 token is tranformed into shielded token in the form of commitment by cryptographic method, which is defined as:
The TRC-20 token is transformed into shielded token in the form of commitment by cryptographic method, which is defined as:

*note<sub>-</sub>commitment = NoteCommitment<sub>r</sub>(v)*

The `v` value is hided by `note_commitment` with the blinding factor `r`.
The `v` value is hidden by `note_commitment` with the blinding factor `r`.

**SpendDescription**

The `SpendDescription` includes zk-SNARK proof related data, which is used as the input of shielded token transaction.
The `SpendDescription` includes zk-SNARK proof related data, which is used as the input of the shielded token transaction.

```text
message SpendDescription {
Expand All @@ -52,7 +52,7 @@ message SpendDescription {

**ReceiveDescription**

The `ReceiveDescrion` also includes zk-SNARK proof related data, which is used as the output of shielded token transaction.
The `ReceiveDescrion` also includes zk-SNARK proof related data, which is used as the output of the shielded token transaction.

```text
message ReceiveDescription {
Expand Down Expand Up @@ -117,32 +117,32 @@ The total input length of `verifyTransferProof` is variable. According to the in
[320 bytes for input][288 bytes for output][64 bytes for spend_authority_signature]
```

The total input lengh of `verifyTransferProof` is 1856 bytes.
The total input length of `verifyTransferProof` is 1856 bytes.

- one input and two output

```
[320 bytes for input][576 bytes for output][64 bytes for spend_authority_signature]
```
The total input lengh of `verifyTransferProof` is 2144 bytes.
The total input length of `verifyTransferProof` is 2144 bytes.

- two input and one output

```
[640 bytes for input][288 bytes for output][128 bytes for spend_authority_signature]
```

The total input lengh of `verifyTransferProof` is 2240 bytes.
The total input length of `verifyTransferProof` is 2240 bytes.

- Two input and two output

```
[640 bytes for input][576 bytes for output][128 bytes for spend_authority_signature]
```

The total input lengh of `verifyTransferProof` is 2528 bytes.
The total input length of `verifyTransferProof` is 2528 bytes.

For the output, `result` is a bool value to indicate whether the proof verification succeeds. The length of `msg` is 66~1058 bytes. , and the other bytes return the node value to construct the Merkle tree. The time cost of `verifyTransferProof` function takes about 10~15ms in parallel mode.
For the output, `result` is a bool value to indicate whether the proof verification succeeds. The length of `msg` is 66 ~ 1058 bytes, which returns the node value to construct the Merkle tree. The time cost of `verifyTransferProof` function takes about 10~15 ms in parallel mode.

（3）`verifyBurnProof`

Expand All @@ -153,7 +153,7 @@ bytes32[10] input = abi.encode(nullifier, anchor, value_commitment, rk, zkproof)
(bool result, bytes memory msg) = verifyBurnProof(abi.encode(input, spend_authority_signature, value, bindingSignature, signHash));
```

- `value` - the amout of shielded tokens to be made public
- `value` - the amount of shielded tokens to be made public

The other parameters are specified as above.

Expand Down Expand Up @@ -276,4 +276,5 @@ Output:
## Implementation

* https://github.com/tronprotocol/java-tron/blob/feature/shielded_TRC20_contract/actuator/src/main/java/org/tron/core/vm/PrecompiledContracts.java
* https://github.com/tronprotocol/java-tron/blob/feature/shieldedUSDT/deploy/PrivateUSDT.sol