How to sign raw transaction with eosjs?

Question

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?

Answer 1

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.

Answer 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

• eos.transaction (https://github.com/EOSIO/eosjs/blob/5107933dff1863a86a112889a1f65429b7537a07/src/write-api.js#L490),

• FcBuffer (as metioned already in some answers) and

• defaultSignProvider using ecc (https://github.com/EOSIO/eosjs/blob/745603a982ded9781721c46a1209d98640527928/src/index.js#L192)

Answer 3

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