wownero-puddle/stratum-ss.md

Stratum mode self-select

One major concern of pool mining has been that of pool centralization. A malicious pool operator, controlling a pool with a significant portion of the total network hash-rate (e.g. 51% or more), has the ability to perform various attacks. This is made possible due to the fact miners have no visibility into what block template they are actually mining on. This leads to another concern - censorship of transactions. Again, as miners have no visibility of the block template they are mining, they also have no visibility of the transactions included in the block template. This enables a malicious pool be selective as to which transactions get included (or not) into a block.

To address these concerns, I've implemented a new, experimental and optional mode to this pool, which enables miners to select their own block template to mine on.

What follows are the instructions to test this new mode and the changes made to the stratum messages. For a miner to test against the pool, there is a very simple miner, monero-powpy (stratum-ss-miner.py), and also a hastily cobbled together branch of XMRig.

Building

The only variation to the standard build instructions in the README, is that you'll first need to fetch and compile the latest Monero master branch.

Running

Start your newly compiled monerod and monero-wallet-rpc. For example, in one shell:

cd "$MONERO_ROOT"/build/Linux/master/release/bin
./monerod --testnet

And in another shell:

cd "$MONERO_ROOT"/build/Linux/master/release/bin
./monero-wallet-rpc --testnet --rpc-bind-port 28084 --disable-rpc-login \
    --password "" --wallet-file ~/testnet-pool-wallet

Next, in a third shell, run monero-pool. Instructions per the README.

Lastly you'll need to run a miner that supports this new stratum mode (see above):

• If using monero-powpy, install the requirements per the projects README, then just run the stratum-ss-miner.py miner, optionally editing the parameters first.

• If using XMRig, edit your pool object in your config.json file setting the algo field to "algo": "cryptonight/r" and setting the self-select field to your daemon address (e.g. "self-select": "localhost:28081").

Specification

What follows are the stratum message and flow changes required to enable pool miners to mine on miner created block templates.

(1) The miner logs into the pool with an additional mode parameter:

{
    "method": "login",
    "params": {
        "login": "wallet address",
        "pass": "password",
        "agent": "user-agent/0.1",
        "mode": "self-select" /* new field */
    },
    "jsonrpc": "2.0",
    "id":1
}

(2) The pool responds with a result job which includes the pool wallet address and an extra nonce:

{
    "result": {
        "job": {
            "pool_wallet": "pool wallet address", /* new field */
            "extra_nonce": "extra nonce hex", /* new field */
            "target": "target hex",
            "job_id": "job id"
        },
        "id": "client id",
        "status": "OK"
    },
    "jsonrpc": "2.0",
    "id":1
}

(3) The miner can now call the daemons RPC method get_block_template with parameters extra_nonce: extra_nonce (implemented in pull request #5728), and wallet_address: pool_wallet.

The miner now informs the pool of the resulting block template it will use for the job:

{
    "method":"block_template", /* new method */
    "params": {
        "id": "client id",
        "job_id": "job id",
        "blob": "block template hex",
        "height": N,
        "difficulty": N,
        "prev_hash": "prev hash hex"
    },
    "jsonrpc": "2.0",
    "id":1
}

(4) The pool validates and caches the supplied block template and responds with a status:

{
    "result": {
        "status": "OK",
        "error", null
    },
    "jsonrpc": "2.0",
    "id":1
}

(5) The miner submits results. No changes here:

{
    "method":"submit",
    "params": {
        "id": "client id",
        "job_id": "job id",
        "nonce": "deadbeef",
        "result": "hash hex"
    },
    "jsonrpc": "2.0",
    "id":1
}

(6) The pool responds to job submissions. No changes here:

{
    "result": {
        "status": "OK",
        "error", null
    },
    "jsonrpc": "2.0",
    "id":1
}

(7) The pool asks the miner to start a new job:

{
    "method": "job",
    "params": {
        "pool_wallet": "pool wallet address", /* new field */
        "extra_nonce": "extra nonce hex", /* new field */
        "target": "target hex",
        "job_id": "job id"
    },
    "jsonrpc": "2.0",
    "id":1
}

The miner now repeats from step #3.