Stratum Mining Protocol for Sia

This is the official documentation of the Stratum mining protocol for Sia developed by SiaMining.

If you're looking for mining software compatibility, please go to the compatibility section.


Previous attempts at adapting the Stratum protocol so that it could be used for mining cryptocurrencies which, like Sia, show significant differences from Bitcoin took an approach that could be described as “getwork over Stratum”, or “getwork over TCP”. What this means is that they sent the same header data that would be sent by the old getwork-style protocol, only packed inside the fields of the original Stratum protocol, which were meant to carry different data. Such an approach retains of course the advantage of removing the overhead of HTTP, but has also clear downsides when compared to the original Stratum protocol:

For the above reasons, decided to develop a true Stratum protocol for Sia.

One of the main objectives was to stay as close as possible to the original Stratum protocol. This makes the implementation easier and allows for better software compatibility.


Unless otherwise specified, everything works in the same way as described by the Stratum mining protocol specification for Bitcoin. In particular, the names and parameter counts remain the same for all methods and notifications.


All hexadecimally-encoded data is serialized as specified by the Sia protocol. No endianness conversion is performed.




    "params": [
        [ "356464cda3f7a83a350aeb3ae5101ff56799cd68ad48b475426141540876bd31", "9cb176ec5b06898ef40f0e73242e0b0ff9d34ece67a241d529f2c18c67c73803" ],
    "id": null,
    "method": "mining.notify"

Building the Arbitrary Transaction

Due to the differences between the Bitcoin block format and the Sia block format, the coinbase transaction is replaced here by a so-called arbitrary transaction. This transaction is built in the same way the coinbase transaction is: by concatenating coinb1, extranonce1, extranonce2, and coinb2.

What is different is how this transaction must be hashed: you have to prepend a null byte to the transaction, and then apply the same blake2b hashing function used by Sia.

You can consider the following Python snippet as a reference:

import binascii
from pyblake2 import blake2b

arbtx_hash_bin = blake2b('\x00' + binascii.unhexlify(arbtx), digest_size=32).digest()

Computing the Merkle Root

The arbitrary transaction hash is the rightmost leaf of the Merkle tree rather than the leftmost.

For each of the merkle_branch hashes, prepend a single byte with a value of 1, and append the hash resulting from the previous iteration (or the hash of the arbitrary transaction for the first iteration). Apply blake2b to this 65-byte buffer.

The following Python snippet illustrates the process:

def build_merkle_root(merkle_branch, arbtx_hash_bin):
    merkle_root = arbtx_hash_bin
    for h in merkle_branch:
        merkle_root = blake2b('\x01' + binascii.unhexlify(h) + merkle_root, digest_size=32).digest()
    return merkle_root

Building the Header

The 80-byte header is built by concatenating prevhash (32 bytes), a nonce (8 bytes), ntime (8 bytes), and the Merkle root (32 bytes).


The only difference is that the 4th and 5th parameters (ntime and nonce) are 64-bit values, and must be 16 characters long.


    "params": [
    "id": 4,
    "method": "mining.submit"


No changes here: we retain the same definition of difficulty used by Bitcoin and by the original Stratum protocol. Note that Sia uses a different (and more intuitive) definition of difficulty, and the two differ by a factor of about 4,295,032,833, which is slightly over 232.

For Stratum, difficulty 1 corresponds to the target


while for Sia the difficulty-1 target is


Please note that Stratum difficulties do not have to be integer numbers. For instance, it is common for pools to use targets like


which corresponds to a Stratum difficulty of about 0.99998474121094105.

Compatible Software


SiaMining's OpenCL and Cuda miner, Marlin, supports the Stratum protocol for Sia natively.


We made a fork of sgminer that implements the Stratum protocol for Sia described in this document. It can be used as follows:

sgminer --algorithm=sia --url=stratum+tcp:// --userpass=YourAddress.YourWorker -I 28

A Windows binary is available.


KlausT's ccminer supports the Stratum protocol for Sia described in this document. It can be used as follows:

ccminer -a sia -e --url=stratum+tcp:// -u YourAddress.YourWorker -i 28

Windows binaries are available.

Stratum Mining Proxy

For all miners supporting the Sia HTTP protocol you can use our Stratum mining proxy running locally on one of your computers. One mining proxy can handle an almost unlimited number of connected miners. By default the proxy connects to SiaMining's Stratum server and listens locally on ports 9980 (HTTP) and 3333 (Stratum), so you don't usually need to specify any options when running it. You then connect your miners in the usual way but specifying the address of the proxy instead of that of the pool.

If your HTTP miner does not support specifying a payout address, you can pass the --custom-user=YourAddress option to the proxy. This will override any username or payout address specified by the miners connecting to it.

Note how the Stratum proxy allows you to handle many miners while keeping only one network connection to the pool.