I have investigated and played with corda-settler project. Following the recommendations within the documentation, I have created a custom ethereum module (with an outline similar to the ripple module), providing the option to settle obligations using off-ledger payments in ETH. The implementation (https://github.com/vladichhh/corda-settler)
consists of the following significant pieces:
flows
MakeEthPayment
services
ETHClient
ETHService
types
EthPayment
EthSettlement
token
registered DigitalCurrency for ETH
oracle
added logic for ETH payment verification
MakeEthPayment.kt
@Suspendable
override fun makePayment(obligation: Obligation<*>, amount: Amount<T>): EthPayment<T> {
// get ETHService client
val ethClient = serviceHub.cordaService(ETHService::class.java).client
val recipient = obligation.settlementMethod?.accountToPay.toString()
val amountToSend = amount.quantity.toString()
// trigger ETH transfer
val txHash = ethClient.sendEth(recipient, amountToSend)
// return the payment
return EthPayment(txHash, amount, PaymentStatus.SENT)
}
ETHClient.kt
fun sendEth(recipient: String, amount: String): String {
val weiAmount: BigInteger = Convert.toWei(amount, Convert.Unit.GWEI).toBigInteger()
val credentials: Credentials = WalletUtils.loadCredentials(walletPassword, walletFile)
val transactionReceipt: TransactionReceipt = Transfer
.sendFunds(web3j, credentials, recipient, BigDecimal(weiAmount), Convert.Unit.WEI)
.send()
return transactionReceipt.transactionHash
}
In order to send the required ETH amount to the specified recipient account, we have to do some Ethereum specific stuff:
- we are connecting to Ethereum public blockchain environment, using “web3j” library
- in order to trigger am Etherem transaction and transfer specified ETH amount, "web3j" requires an access to the file, containing encrypted sender's wallet
- thus we have to provide password (to decrypt wallet) and location of the file, containing encrypted sender's wallet
And here are the issues:
- I got the exception that the file could not be found, no matter where I am putting it. I have checked even the “swift” implementation and tried to use the class loader to load my file, but without success.
- I suppose, the file with encrypted sender’s wallet should be located on one of the following places:
corda-settler/ethereum/src/main/resources/file.tmp
corda-settler/cordapp/src/main/resources/file.tmp
- Finally I have hardcoded the location in that way:
/Users/vladimirhristov/WebstormProjects/Corda/corda-settler/cordapp/src/main/resources/file.tmp
and seems that the file was found but got another exception:
java.lang.OutOfMemoryError - screenshot
Seems that the operation of wallet decryption is highly consuming, which breaks maybe the flow. There is an option to reduce the algorithm complexity of the wallet generation, which will reflect in lower resources required to decrypt the same wallet at the next step, but this will reduce the security as well.
And here are my three basic questions ...
- How could I specify (location/mechanism) and make flow to find successfully my file, containing the sender’s encrypted wallet ?
- How could I access a files in the flow, or if there is another mechanism to attach only the file with encrypted wallet and pass the decryption to core Corda ?
- Do I need just to increase node resources (tuning JVM params increasing -Xms/-Xmx) in order to avoid OutOfMemoryError ?
Content of the file (containing encrypted sender’s wallet):
file.tmp
{"version":3,"id":"ecb51768-8564-498a-bb11-3a5a5c8dc0bb","address":"2bafc482bd227dfd5ba250521a00be3a4cc88bbd","crypto":{"ciphertext":"e0511415792dfa7221ba1b8f32b8ec98e1410f45e612e2100df1aceddfdb22bd","cipherparams":{"iv":"7ffa2af08f502c63d57e62440ad77539"},"cipher":"aes-128-ctr","kdf":"scrypt","kdfparams":{"dklen":32,"salt":"8051a5df1c02eb3eba81d2920fbb84b76b948a1248bbba62ffff684e733948cf","n":131072,"r":8,"p":1},"mac":"be23fe0e261ba38892581d80afd0c86563748377b5cc702b6ed3285a13cceff6"}}
I will appreciate any help! Thanks in advance :)