I read that sometimes a pool will report a "Low difficulty share" error if the solution indeed did not match the specified difficulty but it could also be reported if someone had already found a nonce that hashed the block and you were too late submitting yours. So for example, my pool sent me


I then submitted


to which I got the response

{"id":"c018e089ab7e70a54232623d","jsonrpc":"2.0","error":{"code":-1,"message":"Low difficulty share"}}

I'm pretty bad with the calculations. How can I tell if my share (based on the information I've provided here) indeed didn't match the difficulty target or is it possible that someone else already submitted a nonce that hashed the block?


You can find the difficulty of a submitted hash (which is just a big endian hex encoded string) by dividing the base difficulty (2^256-1) by your hash.

As such, nodejs-pool (the most common pool software), checks your submitted hash difficulty as follows:

let hashArray = hash.toByteArray().reverse();
let hashNum = bignum.fromBuffer(new Buffer(hashArray));
let hashDiff = baseDiff.div(hashNum);

if (hashDiff.ge(blockTemplate.difficulty)) {
    // valid here against block, so mined a block
} else if (hashDiff.lt(job.difficulty)) {
    // invalid here (this is where you are failing the test)
} else {
    // valid, record share

Using your supplied hash and target (which is also BE encoded hex string) you would yield:

job.difficulty = 4294967
hashDiff = 472

Hence it is of low difficulty (thus an invalid, low difficulty, share).

  • Hey a quick clarification on the base difficulty -- you listed it as (2^256-1), which would be "FFFFFFFFFFFFFFFF" in hex, is that right? The code you listed defines the base difficulty as "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" , which seems substantially greater. – Dave Jun 6 '18 at 16:26
  • 2^256-1 is 32 bytes (64 characters) which is what is used in the code. Your calculation of 2^256-1 is incorrect. – jtgrassie Jun 6 '18 at 18:52

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