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Updated on October 18, 2021

Privacy marker transactions

You can use privacy marker transactions (PMTs) instead of normal private transactions.

PMTs are public transactions. PMTs each have a corresponding internal private transaction stored in the private transaction manager (Tessera) and only available to participants.

The advantages of using a PMT over a normal private transaction are:

  • The contract address is hidden from public view.
  • The private transaction receipt is only visible to participants of the private transaction.
  • The private transaction itself is stored in the private transaction manager and is only visible to participants.

PMTs use a privacy precompile contract, which retrieves the internal private transaction from Tessera and executes it.

Privacy marker transaction

A PMT is a public transaction with the following parameters:

  • to - privacy precompile contract address
  • input or data - sender address and Tessera hash of the encrypted internal private transaction
  • from - the same signing account as the internal private transaction
  • contractAddress - (in receipt if the PMT is a contract creation transaction) null
  • logs and logsBloom (in receipt) - empty

Example PMT and its receipt

> eth.getTransaction("0x5b7f615e47a8a607ba2b11598f3eccb9be7ac43875f50abd54bdbbcfaeccbb79")
{
  ...
  blockNumber: 121,
  hash: "0x5b7f615e47a8a607ba2b11598f3eccb9be7ac43875f50abd54bdbbcfaeccbb79",
  from: "0xed9d02e382b34818e88b88a309c7fe71e65f419d",
  to: "0x000000000000000000000000000000000000007a",
  input: "0xd174e0b4ddc86936479655ec5c218530c0270afcff1c337caa81e12610f2182d95c642bf297d65592078d7c5509dc0cb0d3c01ea1a5bc4110c004603702d3d8c",
  nonce: 2,
  r: "0x35ea14362403065174863c07d8de5e9f85c365f19ddde7f907f44ebacba6f63a",
  s: "0x1d3c2a8b8342fc086501a9e95361430b221d80e2f4076b6c37f52dac47fff0f0",
  v: "0x38",
  transactionIndex: 0,
  ...
}
> eth.getTransactionReceipt("0x5b7f615e47a8a607ba2b11598f3eccb9be7ac43875f50abd54bdbbcfaeccbb79")
{
  ...
  blockNumber: 121,
  transactionHash: "0x5b7f615e47a8a607ba2b11598f3eccb9be7ac43875f50abd54bdbbcfaeccbb79",
  contractAddress: null,
  from: "0xed9d02e382b34818e88b88a309c7fe71e65f419d",
  to: "0x000000000000000000000000000000000000007a",
  logs: [],
  logsBloom: "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
  status: "0x1",
  transactionIndex: 0,
  ...
}

Internal private transaction

Each PMT has a corresponding internal private transaction. The content of this private transaction is the same as the content of a normal private transaction, except it has the same from and nonce values as the PMT.

Only the hash of the encrypted internal private transaction is stored on chain (as part of the data field of the PMT). The internal private transaction is stored and encrypted in each participant’s Tessera node. As a result, the internal private transaction is only available to participants of the private transaction.

At execution time, GoQuorum retrieves the internal private transaction from Tessera.

Example internal private transaction and its receipt

> eth.getPrivateTransaction("0x5b7f615e47a8a607ba2b11598f3eccb9be7ac43875f50abd54bdbbcfaeccbb79")
{
  ...
  blockNumber: 121,
  hash: "0xbf71ea018f64b6449319b733baa188f5f1e6093306604004cf30d1688c940865",
  from: "0xed9d02e382b34818e88b88a309c7fe71e65f419d",
  to: null,
  input: "0x15b446504790aec35713ebf947490e8674a018958ced63841ebe1ffc447ce52f2c8654f6affb907d5a744606293f6e9f4cf4a210a44041b5ec3696e01d917f3a",
  nonce: 3,
  r: "0x32d982ba0a48083821c0ff013119dce988205a2699485e7a4019911030bddabc",
  s: "0x41870f25243701e4187bb24b69d71b711de6cac742445e0cef501d0705119f1a",
  v: "0x25",
  transactionIndex: 0,
  ...
}
> eth.getPrivateTransactionReceipt("0x5b7f615e47a8a607ba2b11598f3eccb9be7ac43875f50abd54bdbbcfaeccbb79")
{
  blockNumber: 121,
  transactionHash: "0x5b7f615e47a8a607ba2b11598f3eccb9be7ac43875f50abd54bdbbcfaeccbb79",
  contractAddress: "0xd9d64b7dc034fafdba5dc2902875a67b5d586420",
  from: "0xed9d02e382b34818e88b88a309c7fe71e65f419d",
  to: null,
  logs: [{
    ...,
    address: "0xd9d64b7dc034fafdba5dc2902875a67b5d586420",
    blockNumber: 121,
    data: "0x000000000000000000000000000000000000000000000000000000000000000a",
    logIndex: 0,
    topics: ["0x6c2b4666ba8da5a95717621d879a77de725f3d816709b9cbe9f059b8f875e284"],
    transactionHash: "0xbf71ea018f64b6449319b733baa188f5f1e6093306604004cf30d1688c940865",
    transactionIndex: 0,
    ...
  }],
  logsBloom: "0x00000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004000000000000000000000000400000000000000000000000001000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000",
  status: "0x1",
  transactionIndex: 0,
  ...
}

Using privacy marker transactions

To enable PMTs in GoQuorum, set the privacyPrecompileBlock in the GoQuorum genesis file config object to a block where the network is ready to support the privacy precompile. Once the fork block is reached, the node can process and use PMTs. All GoQuorum nodes in the network should be initialized with the same privacyPrecompileBlock value.

Use the --privacymarker.enable command line option when starting GoQuorum to enable PMTs.

Note

Once the privacyPrecompileBlock is reached, a node without the --privacymarker.enable CLI flag can still receive and correctly process PMTs sent from other nodes.

Use the following API methods to interact with PMTs:

Sending unsigned private transactions

To send an unsigned private transaction as a PMT, use the same API methods as with normal private transactions, such as eth_sendTransaction.

If the following conditions are met, the private transaction is created as a PMT and internal private transaction:

  • privateFor is provided.
  • The privacyPrecompileBlock has been reached.
  • The GoQuorum node is started with the --privacymarker.enable option.

Sending signed private transactions

  1. Use eth_fillTransaction or Tessera’s third party /storeraw API to encrypt the private transaction payload.
  2. Create the private transaction, replacing the data value with the hash of the encrypted private transaction payload from Tessera.
  3. Externally sign the private transaction.
  4. Use eth_distributePrivateTransaction to encrypt the signed private transaction and share with all participants.
  5. Create the PMT, with the data value set to the hash returned by eth_distributePrivateTransaction. The from and nonce values must be the same as the private transaction.
  6. Send the PMT using the same APIs as with normal private transactions, such as eth_sendTransaction.
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