PRCYJS

NodeJS library for making PRCY privacy transactions

API Call List:

Request					Response
Descriptions	Verb	URI Prefix	Method	Params
Requests API to scan for utxos and return them	post	wallet	scan	viewkey:${viewkey} spendpub:${pubspenkey} sinceblock: ${sinceblock} filterspents: true/false => true means only return unspent utxos	"scanning": false, "scannedheight": 477302, "utxos": [keyimage],"txes": { "keyimage": { "vin": [], "vout": [], "blockindex": 476098, "blocktime": 1592551400, "txfee": 1.496, "ringsize": 13, "_id": "5eec67d9824cf9f9a0195dd8", "txid": "keyimage", "__v": 0, "blockhash": "36540454e15e8a4fc20311feff8e4084e14fb532a855a70a43cbb2beeaca5e76", "type": "standard" } },
Requests the last scanned height for the key pair	post	wallet	getscannedheight	viewkey:${viewkey} spendpub:${pubspenkey}
	get	api	keyimages	${keyimages}	{"spents":[],"unspents":["13a3caf5416c349f362735b70b6a2f63c2f94fca9ce2bbfb70848d3f102cb054"]}
Get the latest API block height	get	api	blockcount
Get decoys from the API	get	api	decoys	$(number)
Generates the bulletproof for the given params	get	api	bulletproofs	${bpinputSerializedHex}
Broadcasts the raw transaction	post	api	broadcasttx	${rawSignedTx}
server public key for encrypting view key and spend public key	get	api	getencryptionkey
Allows utxo's to be added to the API	post	wallet	addutxos	viewkey:${viewkey} spendpub:${pubspenkey} scannedheight: ${scannedheight} utxos: string in format txid-index:txid-index...
Marks the given utxos as spent in the API	Post	wallet	markspents	viewkey:${viewkey} spendpub:${pubspenkey} spents: string in format txid-index:txid-index...

Note: You must obtain API info and Server Encryption Key from the PRCY team to be able to access the API. These are placed in the src/prcylib/config.js.

Usage

• Create a wallet object from mnemonics

const Wallet = require('prcyjs').Wallet;
const config = require('prcyjs').Constants;
var walletObject = new Wallet({mnemonics: mnemonics.mnemonics}, config.PRCY_SERVER, config.PRCYCHAIN, "Bitcoin seed");

Once wallet object created, then it will automatically send requests to the RPC server to scan for all transactions belonging to the wallet.

• Get wallet balances: wallet balances are only available (and correct) if and only if the transaction scanning is finished.

function getBalance(wl) {
   if (wl.isScanning) return 'wallet is scanning';
   return {spendable: wl.spendable, immature: wl.immature, pending: wl.pending}
}

Note that wl.isScanning should be always false, except if the user is logging-in the wallet, which might take from 5 second to 1 minute to finishn scanning, depending whether the user log-in the wallet previously or not.

Wallet will periodically send request to the server every minute to scan for new wallet transactions.

For third-party integration, nothing needs to be done except initialize the wallet object and uses it to show information on the apps of the third-parties.

• Get the current block height:

wl.currentBlockHeight

• Create transaction and broadcast it:

walletObject.sendTo(destination, amount, function(ret) {
  if (ret.success) {
    state.txCreateResult = {success: true, message: "Successfully create transaction " + ret.txid + " sending " + input.amount + " to " + input.destination};
  } else {
    state.txCreateResult = {success: false, message: "Error:" + ret.reason};
  }
  walletObject.recomputeBalance();
})

** destination: the receiver address ** amount: amount to send. Amount should be in decimal string

It is worth noting that the wallet object will manage and recompute balances so that third-parties only need to inject the wallet object in their app.

API "sinceblock" Parameter Usage

• Server has already seen the key:
  • sinceBlock = XXX => Server scans from the scanned height stored in the server and return all utxos in block > XXX
• Server has never seen the key:
  • sinceBlock = 0 => Server scans the entire chain and returns all utxos found
  • sinceBlock = XXX => Server scan all blocks > XXX and returns all utxos included in blocks > XXX

If it’s a new wallet, you would only need to set sinceBlock = the currentBlock height => done!

EncryptedViewKey and EncryptedSpendPub

• Call getencryptionkey from API to get the public key of the server to encrypt view key and public spend key => EncryptionKey
• Encryption:
  • Generate random r (32 bytes), compute R = r*G
  • Compute ECDH = Hash(r*EncryptionKey)
  • Compute encryptedviewkey = viewkey + ECDH
  • Compute encryptedspendpub
    • X = X of public spend key
    • EncryptedX = X + ECDH
    • encryptedspendpub = EncryptedX|| (03|02)
• Send to server: {method=.., encryptedviewkey=encryptedviewkey, encryptedspendpub=encryptedspendpub, encrypted=true}

Note: r in the request sent to server is R in the formulae

PRCYJS Statuses / Status Values (currentStatus/currentStatusVal)

Statuses have been added to keep the user up to date as to what the wallet is currently doing. Each status also has a corresponding currentStatusVal integer that can be accessed as well.

• Idle - 1 - Starting state
• Scanning - 2 - When the wallet is scanning for UTXOs belonging to a restored phrase
• Processing UTXOs - 3 - Taking the UTXOs that were scanned and processing them all
• Generating transaction history - 4 - Creation of the transaction history from scanned UTXOs
• Recomputing wallet balance - 5 - Recomputing wallet balance
• Complete - 6 - The process is complete

Get the current Status:

wl.currentStatus

Get the current StatusVal:

wl.currentStatusValue

View Path/Spend Path

Get the current View Path:

wl.getViewPath

Get the current Spend Path:

wl.getSpendPath

Set the current View Path:

wl.setViewPath(path)

Set the current Spend Path:

wl.setSpendPath(path)

Default View Paths:

• prcycoin seed: "m/44'/" + coinType + "'/0'/0/0"
• Bitcoin seed: "m/44'/" + coinType + "'/0'/0/0"

Default Spend Paths:

• prcycoin seed: "m/44'/" + coinType + "'/1'/0/0"
• Bitcoin seed: "m/44'/" + coinType + "'/0'/0/0"

Basic Test

Requires

• node.js
• Mnemonic Recovery Phrase
• PRCY

Start Testing

1. Create a new wallet
2. Write down the Mnemonic Recovery Phrase
3. Send some coins (minimum 1 PRCY recommended)
4. Add the Mnemonic Recovery Phrase on \tests\wallet\createwallet.js
5. Edit the amount of PRCY to send on \tests\wallet\createwallet.js
6. Run npm install
7. Edit src/prcylib/config.js with the required information
8. Run npm run tests