11

Lets say I have a transaction like below:

var tx =     { transaction_id: 
'111ee28e5deca69e54dadf751eba8fae181f0ceafc601dcab92700f5200abef8',
      broadcast: false,
      transaction: 
       { compression: 'none',
         transaction: 
          { expiration: '2018-05-09T13:00:16',
            region: 0,
            ref_block_num: 19637,
            ref_block_prefix: 1895049749,
            max_net_usage_words: 0,
            max_kcpu_usage: 0,
            delay_sec: 0,
            context_free_actions: [],
            actions: [Array] },
         signatures: [] } }

Let's say const privateKey = 5KBwtUpu6qMKysaUXswjQr1b3Rhdza2EftAUFQPi6wZpUdkcY13

What is the specific process for signing this transaction? How are the fields encoded and what data is included in the transaction signature?

8

You can use eosjs-ecc for signing easily.

If you want to sign a hash:

ecc.Signature.signHash(sha256hash, privateKey).toString()

If you want to sign something that isn't a hash:

ecc.sign(Buffer.from(someData, 'utf8'), privateKey)

Edit: The transaction itself will have to be serialized based on the ABI, packed and then signed. eosjs uses fcbuffer for that.

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  • Great! Thanks. I will try this as soon as I get home. :)) – cookiekid May 9 '18 at 22:29
  • But for signing an EOS Transaction, what is the input to the sign function? – John Haager May 9 '18 at 22:35
  • 1
    @JohnHaager so that's a bit more in-depth. The transaction itself will have to be serialized based on the ABI, packed and then signed. eosjs uses fcbuffer for that. – nsjames May 9 '18 at 22:41
  • 1
    @nsjames That's good info. You should add it to your answer as it will help those who end up needing to implement transaction signing in languages other than JS. – John Haager May 9 '18 at 23:18
  • @nsjames wait... so this will not generate a valid signature so that the transaction can be pushed to the blockchain with the produced signature? Sorry, I can't try this for myself atm since I'm not at home. – cookiekid May 9 '18 at 23:19
2

To sign a transaction offline you can use eosjs. There is a configuration option

broadcast [boolean=true] - post the transaction to the blockchain. Use false to obtain a fully signed transaction.

If you want to translate it to another language you need to convert the code from

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0

I normally use it like this and eosjs signs it automatically.

eos.contract('currency').then(currency => {
 currency.transaction(cur => {
  cur.transfer('inita', 'initb', '1 CUR', '')
 })
})

If you want to sign it yourself i guess you should use eosjs-ecc

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  • 1
    This still uses a third party api. I need to do it manually. I have seen eosjs-ecc but I am still unsure of what data actually needs to be signed. You can't sign an object unless it is converted to a string, buffer etc. – cookiekid May 9 '18 at 13:41
  • 1
    To do that manually I would check the EOSRPC Wallet sign_transaction endpoint. But I suggest you to have an instance of keosd and let it handle your keys, you could just call the sign_transaction out-of-the-box! – Leo Ribeiro May 9 '18 at 14:22
  • 2
    "This still uses a third party api". Does this mean you want to sign without using any existing library? If so maybe you should drop "eosjs" from the title. – Todd Fleming May 9 '18 at 19:17
  • No, sorry for confusion. I mean that using nanonano's method requires that you connect to a node. It has to be done without needing to. – cookiekid May 9 '18 at 19:54

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