How to sign offline?

[KiyoCao]

How to sign offline?

[croath]

Hi @MaoxinCao , did you mean signing transaction? All transactions are signed offline with SwiftyEOS. Try to make a token transfer like the README file described: Using Currency.transferCurrency.

But some params are needed to be fetched from an eos endpoint (block prefix and/or block number).

[croath]

Hi @MaoxinCao , did you solve the problem?

[zhenghongchuan]

I have the same question..

[zhenghongchuan]

how to sign to like this:

{
  "signatures": [
    "SIG_K1_KdRNkKSDNFUb7gU45UZcySykeGRGp4ESzEZj4pyJwWsuDVkRcHjREViyF1qQmci8981zib3zGebD64YAXgsNQkzAa7jftK"
  ],
  "compression": "none",
  "packed_context_free_data": "",
  "packed_trx": "a4f38c5b390282247889000000000100a6823403ea3055000000572d3ccdcd01104260d33d364dc300000000a8ed323241104260d33d364dc3204260d33d364dc31027000000000000044a554e474c45002054657374206279207368616e676a696e67202e2020323031383039303330303200"
}

[croath]

@zhenghongchuan it's a signed transaction, right?

I'll make it clear by posting an example. I have a transaction to make, it's a token-transfer transaction:

1. Account agoodaccount wants to transfer 1 EOS to account gq3dinztgage. The first step is to have a transaction action like this:

{  
         "account":"eosio.token",
         "name":"transfer",
         "authorization":[  
            {  
               "actor":"agoodaccount",
               "permission":"active"
            }
         ],
         "data":{  
            "from":"agoodaccount",
            "to":"gq3dinztgage",
            "quantity":"1.0000 EOS"
         }
      }

2. With the raw transaction action, the next step is to pack it, by converting this key-value based structure(json) to hex representation with the contract's ABI. After packing, the whole trasaction will be something like you've posted:

a4f38c5b390282247889000000000100a6823403ea3055000000572d3ccdcd01104260d33d364dc300000000a8ed323241104260d33d364dc3204260d33d364dc31027000000000000044a554e474c45002054657374206279207368616e676a696e67202e2020323031383039303330303200

(It's the string I just copied from your code.

3. After that, the final thing is signing. Using EOS's standard signing method, and your private key, to sign this hex string to a signature:

SIG_K1_KdRNkKSDNFUb7gU45UZcySykeGRGp4ESzEZj4pyJwWsuDVkRcHjREViyF1qQmci8981zib3zGebD64YAXgsNQkzAa7jftK

4. Then we got the result:

{
  "signatures": [
    "SIG_K1_KdRNkKSDNFUb7gU45UZcySykeGRGp4ESzEZj4pyJwWsuDVkRcHjREViyF1qQmci8981zib3zGebD64YAXgsNQkzAa7jftK"
  ],
  "compression": "none",
  "packed_context_free_data": "",
  "packed_trx": "a4f38c5b390282247889000000000100a6823403ea3055000000572d3ccdcd01104260d33d364dc300000000a8ed323241104260d33d364dc3204260d33d364dc31027000000000000044a554e474c45002054657374206279207368616e676a696e67202e2020323031383039303330303200"
}

The packed transaction, signature, no compression by default, and no context free data. It's ready. Then we can ship this signed transaction http body to one of the EOS RPC endpoint using RPC push_transaction API:

POST http://yourdomainandport/v1/chain/push_transaction

That's all.

With SwiftyEOS, it's much easier to make it happen because you don't need to care about the step 2 and step 3:

var transfer = Transfer()
transfer.from = "agoodaccount"
transfer.to = "gq3dinztgage"
transfer.quantity = "1.0000 EOS"
transfer.memo = "eureka"

Currency.transferCurrency(transfer: transfer, privateKey: importedPk!, completion: { (result, error) in
    if error != nil {
        if (error! as NSError).code == RPCErrorResponse.ErrorCode {
            print("\(((error! as NSError).userInfo[RPCErrorResponse.ErrorKey] as! RPCErrorResponse).errorDescription())")
        } else {
            print("other error: \(String(describing: error?.localizedDescription))")
        }
    } else {
        print("Ok. Txid: \(result!.transactionId)")
    }
})

You can also find the code snippet in the project readme file. It's written in Swift but could be used with Objective-C, too.

[croath]

The crypto signing progress itself is offline. But you can't make the whole process totally offline, because we need to fetch some chain block data and put it together with our transaction, to make a signature.

BTW it's safe to get the abi_json data from an RPC endpoint. Though we could make this step "offline" for the contract we know, it's dangerous because the contract may change anytime.

[KiyoCao]

@croath Thanks Reply.

I am currently doing is multi-signature, so I need to sign offline on multiple terminals. But the signature in SwiftyEOS seems to be put into the transaction.

[zhenghongchuan]

@croath How can I get the privateKey in my currentAccount?

[croath]

@MaoxinCao Sorry that multi-sig is not supported yet.

But I'm sure I could provide a low-level method just for calculating signatures for a given context. Will be ready in next versions.

[croath]

@zhenghongchuan With currentAccount there's no need to take the privateKey, just use SELocalAccount's pushTransaction. Unlock with a password is a safer way in iOS.

[zhenghongchuan]

@croath The point is that can I get the sign json by my currentAccount, and how to do it. And can I create wallet by a account name? Thanks.

[KiyoCao]

let abi = try AbiJson(code: "currency", action: "transfer", json: jsonString) 

EOSRPC.sharedInstance.chainInfo {  (chainInfo, error) in
   EOSRPC.sharedInstance.getBlock(blockNumOrId: "\(chainInfo!.lastIrreversibleBlockNum)" as AnyObject, completion: { (blockInfo, error) in
         EOSRPC.sharedInstance.abiJsonToBin(abi: abi, completion: { (bin, error) in
                                                
                    })
                })
            } 

How to create AbiJson object?  I wrote this, bin is always nil. 

[croath]

@zhenghongchuan

1. Yes and no. There's way you can get the final signed json yourself, read the source file and find the way I do in Transaction.swift.

2. No. A wallet can not be created by just a name. A private key associated with that account is needed.

[croath]

@MaoxinCao Then what the error is?

And are you sure the code you wanna use is currency?

[zhenghongchuan]

@croath Thank you!

[KiyoCao]

@croath It's work...

let abi = try AbiJson(code: "eosio.token", action: "transfer", json: jsonString)

[croath]

🎉