geth mining not working without --allow-insecure-unlock (geth 1.9.16-stable-ea3b00ad)

Question

I am running a private ethereum blockchain with POA

geth --port 3000 --networkid 42 --datadir=./blkchain --maxpeers=5  --rpc --rpcport 8543 --rpcaddr 127.0.0.1 --rpccorsdomain "*" --rpcapi "eth,net,web3,personal,miner" --allow-insecure-unlock  2>>eth.log

Then send transactions using Web3js

    let tx = {from:accounts[targetAccount],to:accounts[targetAccount],value: 0,gas: 100000, data:web3.utils.toHex(targetAccount)};
    web3.eth.accounts.signTransaction(tx, keys[targetAccount]).then(signed => {
       var tran = web3.eth.sendSignedTransaction(signed.rawTransaction);

       tran.on('transactionHash', hash => {
         console.log('write blockchain ', hash);
       });

       tran.on('error', console.error);
   });

Then miner.start() from geth console

Everything works fine.

But when I start geth again without --allow-insecure-unlock there are pending transactions: (eth.pendingTransactions.length > 0) and sendTransaction always return: Error: Returned error: already known.

I don't want to use this param: --allow-insecure-unlock. Any hints for this? Many thanks!!

(If i start geth again with --allow-insecure-unlock, it seems to work again)

Answer 1

Try specifying explicitly your private network informations such as in this example from the web3js documentation :

web3.eth.accounts.signTransaction({
to: '0xF0109fC8DF283027b6285cc889F5aA624EaC1F55',
value: '1000000000',
gas: 2000000
common: {
  baseChain: 'mainnet',
  hardfork: 'petersburg',
  customChain: {
    name: 'custom-chain',
    chainId: 1,
    networkId: 1
  }
}
}, '0x4c0883a69102937d6231471b5dbb6204fe5129617082792ae468d01a3f362318')
.then(console.log);

Replace the parameters of the common object by those of your private blockchain.

Also, some remarks :

• your "from" and "to" parameters are the same. Furthermore, according to the doc, the tx object used with accounts.signTransaction has no parameter "from".
• your data is not correct, you have to use the "encodeAbi()" method on your smart contract function : https://web3js.readthedocs.io/en/v1.2.7/web3-eth-contract.html#methods-mymethod-encodeabi .
• you should never stock in clear your private keys in your code.
• Ethereumjs-tx is a good, well known alternative to web3 to sign transactions.