Table of Contents
Overview
The following diagram depicts the necessary components needed for merged mining from the Monero application ecosystem.
The following diagram depicts how merged mining with Monero is currently implemented for Tari.
Lastly the following diagram illustrates how pool software interacts with Monero.
Monero Details
Monero Codebase
Serialization and deserialization of a Monero block is needed, this could be reverse engineered from the codebase, however libraries are available to do this. What we do need to know in this regard is that a input blob and block template/block is a hexidecimal representation of the serialization that occurs when interacting with Monero RPC.
It is also important to note that Monero hashes are in little endian format.
The tx_extra tags are found within the coinbase transaction for the monero block [4], the only tag we will be inserting into the monero block template is the merge mining tag.
The input blob for XMRig will need to be calculated after inserting this tag. This is defined by get_block_hashing_blob [1]
in the Monero codebase. This is the result of serializaing the block header, appending the merkle root and the
number of transactions in the block and then converting it to hexidecimal [1].
The merkle root will also need to be calculated when verifying the Monero block. This is defined in the file tree_hash.c, which is an
algorithm from the Monero codebase [2].
RandomX needs to be set up identically to Monero. This is defined by rx_slow_hash in the Monero codebase[2].
The following information hash to be stored in the Tari proof-of-work data to verify (and also calculate the achieved difficulty) of the Monero block: 1) The block header, which is used to calculate the input blob for RandomX. 2) The RandomX key provided with the initial template. This ensures the same result is reached as it would in Monero. Used when calculating the achieved difficulty. 3) The number of transactions in the block (including the coinbase transaction), which is also used to calculate the input blob for RandomX. 4) The merkle root of the block. This is used to verify the block. 5) The transaction hashes which appear in the block (including the coinbase transaction). This is used to both calculate the input blob for RandomX as well as verify the block. 6) The coinbase transaction. This is used to verify the block.
Monero RPC
XMRig calls the following JSON-RPC methods from MoneroD: GET Requests: 1) /get_height - Gets the node’s current height [3]
Example Request:
http://daemon_url:18081/get_height
Response:
{
"height": 1564055,
"status": "OK",
"untrusted": false
}
POST Requests: 1) /get_block_template - Get a block template on which to mine a new block [3]
Example Request
{
"jsonrpc":"2.0",
"id":"0",
"method":"get_block_template",
"params":{
"wallet_address":"44GBHzv6ZyQdJkjqZje6KLZ3xSyN1hBSFAnLP6EAqJtCRVzMzZmeXTC2AHKDS9aEDTRKmo6a6o9r9j86pYfhCWDkKjbtcns",
"reserve_size":60
}
}
Response:
{
"id": "0",
"jsonrpc": "2.0",
"result": {
"blockhashing_blob": "070786a498d705f8dc58791266179087907a2ff4cd883615216749b97d2f12173171c725a6f84a00000000fc751ea4a94c2f840751eaa36138eee66dda15ef554e7d6594395827994e31da10",
"blocktemplate_blob": "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",
"difficulty": 61043624293,
"expected_reward": 4771949057248,
"height": 1561970,
"prev_hash": "f8dc58791266179087907a2ff4cd883615216749b97d2f12173171c725a6f84a",
"reserved_offset": 129,
"status": "OK",
"untrusted": false
}
}
2) /submit_block - Submit a mined block to the network. [3]
Example Request:
{
"jsonrpc":"2.0",
"id":"0",
"method":"submit_block",
"params":["0707e6bdfedc053771512f1bc27c62731ae9e8f2443db64ce742f4e57f5cf8d393de28551e441a0000000002fb830a01ffbf830a018cfe88bee283060274c0aae2ef5730e680308d9c00b6da59187ad0352efe3c71d36eeeb28782f29f2501bd56b952c3ddc3e350c2631d3a5086cac172c56893831228b17de296ff4669de020200000000"]
}
Rejected Response:
{
"id": "0",
"jsonrpc": "2.0",
"error": {
"code": -7,
"message": "Block not accepted"
}
}
Accepted Response:
{
"id": "0",
"jsonrpc": "2.0",
"status": "OK"
"untrusted": false
}
Something to note about the methods is that:
1) With GET methods, the method name is appended to the daemon url.
2) With POST methods, the method name is embedded in the method field of the request body and is sent to the daemon url
appended with /json_rpc.
The Process
The following sequence diagram illustrates the merge mining process across the applications involved [5]
Since the diagram above is quite lengthy and complex the verification criteria of a Monero block in Tari is detailed below: 1) The stored miner transaction contains the merge mining hash of the Tari block. 2) The merkle root in the proof of work is the same as the merkle root calculated from the stored transaction hashes.
References
[1] StackExchange “Format of a block in the Monero Blockchain” [online]. Available: https://monero.stackexchange.com/questions/3958/what-is-the-format-of-a-block-in-the-monero-blockchain. Date accessed: 2020‑10‑21.
[2] Github “Monero Project” [online]. Available https://github.com/monero-project/monero. Date accessed: 2020‑10‑21.
[3] GetMonero “Daemon RPC” [online]. Available: https://web.getmonero.org/resources/developer-guides/daemon-rpc.html. Date accessed: 2020‑10‑21.
[4] StackExchange “How are the various tx-extra types/formats used?” [online]. https://monero.stackexchange.com/questions/1381/how-are-the-various-tx-extra-types-formats-used. Date accessed: 2020‑10‑21.
[5] Github “Monero Project” [online]. Available https://github.com/tari-project. Date accessed: 2020‑10‑21.
