Release 4.0 has implemented the shielded TRC-20 contract, which can hide the source address, destination address, and the token amount for TRC-20 transactions and provide users with better privacy. The shielded TRC-20 contract has three core functions: mint, transfer and burn. mint is used to transform the public TRC-20 token to shielded token; transfer is used for shielded token transactions; burn is used to transform the shielded token back to the public TRC-20 token. To support the shielded TRC-20 contract, four new zero-knowledge instructions (verifyMintProof, verifyTransferProof, verifyBurnProof and pedersenHash) are added in TVM, which make it convenient to provide privacy for arbitrary TRC-20 contract.

Notices

Forced upgrade

New features

• Add 4 new instructions (verifyMintProof, verifyTransferProof, verifyBurnProof and pedersenHash) in TVM to support TRC20 shielded transactions based on zk-SNARKs (#3172).

  • verifyMintProof: used to validate the zero-knowledge proof for mint function.
  • verifyTransferProof: used to validate the zero-knowledge proof for transfer function.
  • verifyBurnProof: used to validate the zero-knowledge proof for burn function.
  • pedersenHash: used to compute the Pedersen hash.

• Update the initial parameters of zk-SNARKs scheme generated by the MPC Torch (#3210).

• Add the APIs to support shielded TRC-20 contract transaction (#3172).

  1. Create shielded contract parameters

  rpc CreateShieldedContractParameters (PrivateShieldedTRC20Parameters) returns (ShieldedTRC20Parameters) {}

  2. Create shielded contract parameters without ask

  rpc CreateShieldedContractParametersWithoutAsk (PrivateShieldedTRC20ParametersWithoutAsk) returns (ShieldedTRC20Parameters) {}

  3. Scan shielded TRC20 notes by ivk

  rpc ScanShieldedTRC20NotesByIvk (IvkDecryptTRC20Parameters) returns (DecryptNotesTRC20) {}

  4. Scan shielded TRC20 notes by ovk

  rpc ScanShieldedTRC20NotesByOvk (OvkDecryptTRC20Parameters) returns (DecryptNotesTRC20) {}

  5. Check if the shielded TRC20 note is spent

  rpc IsShieldedTRC20ContractNoteSpent (NfTRC20Parameters) returns (NullifierResult) {}

  6. Get the trigger input for the shielded TRC20 contract

    rpc GetTriggerInputForShieldedTRC20Contract (ShieldedTRC20TriggerContractParameters) returns (BytesMessage) {}

• Support the ovk to scan the transparent output of burn transaction (#3203).

• Support the burn transaction with zero or one shielded output (#3224).

• Add data field in transaction log trigger class for future memo note (#3200).

The following TIPs are implemented in this release:

• TIP-135: Shielded TRC-20 contract standards, guarantee the privacy of the shielded transfer of TRC-20 tokens.
• TIP-137: Implements three zero-knowledge proof instructions in TVM to support the shielded TRC-20 contract (#3172).
• TIP-138: Implements the Pedersen hash computation instruction in TVM to support the shielded TRC-20 contract (#3172).

Changes

• Check if null before getInstance when get transaction info from DB to fix exception of getTransactioninfoByBlkNum (#3165).