ConfidentialWallet.js

import assert from "assert"
import { fromJS, Map, List, Set } from "immutable"
import { PrivateKey, PublicKey, Aes, brainKey, hash, key } from "@graphene/ecc"
import { fetchChain, config, chain_types, Apis, TransactionBuilder, number_utils } from "@graphene/chain"
import { ops, Serializer } from "@graphene/serializer"
import AddressIndex from "./AddressIndex"
import ByteBuffer from "bytebuffer"

var bs58 = require("bs58")
let { stealth_memo_data, stealth_confirmation, blind_transfer, transfer_from_blind } = ops
let { toImpliedDecimal } = number_utils
let Long = ByteBuffer.Long

/** This class is used for stealth transfers.

    Anytime you send to an external stealth address, you will need to capture the `confirmation_receipt` hex in the returned promise.  This must be sent to the recipient so they may claim their balance.   
    
    separated out change_receipts and confirmation receipts.  So, only if your sending to another blind address do you need to grab the 1 and only "confirmation_receipt" .. The wallet should store everything so you normally would not need any change_receipts.

    Serilizable persisterent state (JSON serilizable types only)..  This is the data used by this class and kept in walletStorage.wallet_object:

    ```js
    const empty_wallet = fromJS({
        blind_receipts: [ see this.receiveBlindTransfer()  ],
        keys: {
            "pubkey": {
                //  No two keys can have the same label, no two labels can have the same key
                label: t.maybe(t.Str),
                import_account_names: t.maybe(t.Arr),
                brainkey_sequence: t.maybe(t.Num),
                private_wif: t.Str, // was: encrypted_key: t.Str
                index_address: undefined|true // Mark legacy keys for address indexing (addresses are calculated outside of this wallet backup)  
            }
        }
    })
    ```
 */
export default class ConfidentialWallet {
    
    constructor( walletStorage ) {
        // The walletStorage format is documented as comments at the bottom of this file..
        this.wallet = req(walletStorage, "walletStorage")
        
        // Graphene-UI uses a transaction confirmation dialog and will replace this function.
        this.process_transaction = (tr, broadcast, broadcast_confirmed_callback = ()=> Promise.resolve()) =>
            broadcast_confirmed_callback()
            .then(()=> tr.process_transaction(this, null/*signer keys*/, broadcast))
        
        // Convenience functions (ensure friendly return values)
        this.keys = () => this.wallet.wallet_object.getIn(["keys"], Map())
        this.blind_receipts = () => this.wallet.wallet_object.get("blind_receipts", List())
        this.commitments = (receipts = this.blind_receipts()) => receipts
            .reduce( (r, receipt) => r.push(receipt.getIn(["data", "commitment"])), List())
        
        this.labels = (filter = key => true)=> this.keys()
            .reduce( (s, key) => key.has("label") && filter(key) ? s.add(key.get("label")) : s, Set())
        
        // BTS 1.0 addresses for shorts and balance claims
        // Update the index if needed
        // The TransactionBuilder needs this info, it calls this.getPubkeys_having_PrivateKey
        AddressIndex.add( this.keys()
            .reduce( (r, key, pubkey) => key.get("index_address") ? r.push(pubkey) : r, List())
        )
        
        // semi-private methods (outside of this API)
        this.update = update.bind(this)// update the wallet object
        this.assertLogin = assertLogin.bind(this)
        this.getPubkeys_having_PrivateKey = getPubkeys_having_PrivateKey.bind(this)
        this.blind_transfer_help = blind_transfer_help.bind(this)
        this.fetch_blinded_balances = fetch_blinded_balances.bind(this)
        this.send_blind_tr = send_blind_tr.bind(this)
    }
    
    /**
        This method can be used to set or change the label for a public_key.

        This is a one-to-one: one key per label, one label per key.  If there is a conflict, the label is renamed.  A label is optional so their may be any number of unlabeled keys. 

        @arg {PrivateKey|PublicKey|string} key - Key object or public_key string (like: GPHXyz...)
        
        @arg {string} [label = null] - string (like: GPHXyz...).  Required if a private key is not provided.  If provided, must be unique or this method will return false.
        
        @arg {PublicKey|string} public_key - this is provided for performanc gains where it is already known.  A private key object is requred if this is used.  This must be the public_key for the provided private_key although, be cautious, validation can not be performed (without the performance loss).
        
        @return {boolean} false if this label is already assigned, otherwise a wallet update is sent over to the WalletStorage object.
     */
    setKeyLabel( key, label = null, public_key = null ) {
        
        this.assertLogin()
        
        assert( key, "key is required (public key or PrivateKey object)" )
        
        if(typeof key === "string")
            public_key = PublicKey.fromStringOrThrow(key)
        
        let private_key
        if(key.d) {
            private_key = key
        } else {
            if( ! public_key )
                public_key = key
        }
        
        if( ! public_key ) {
            assert( private_key.d, "PrivateKey object is required since public key was not provided")
            public_key = private_key.toPublicKey()
        }
        
        private_key = toString(private_key)
        public_key = toString(public_key)

        if( ! label )
            req(private_key, "Label is required unless a private key is provided")
        
        let keys = this.keys()
        if( label ) {
            let key = keys.find( key => key.get("label") === label )
            if( key != null )
                // this label is already assigned
                return false
        }
        
        this.update(wallet =>
            wallet.updateIn(["keys", public_key], Map(),
                key => key.withMutations( key =>{
                    if( label ) key.set("label", label)
                    
                    if( private_key )
                        key.set("private_wif", private_key)
                    
                    return key
                })
            )
        )
        return true
    }
    
    /**
        @return {string} label or null
    */
    getKeyLabel( public_key ) {
        
        this.assertLogin()
        public_key = toString(req(public_key, "public_key"))
        
        let key = this.keys().get(public_key)
        // let key = this.wallet.wallet_object.getIn(["keys", public_key])
        return key ? key.get("label") : null
    }
    
    /**
        @arg {string} pubkey_or_label
        @return {PublicKey} or null
    */
    getPublicKey( pubkey_or_label ) {
        
        this.assertLogin()
        req(pubkey_or_label, "pubkey_or_label")
        
        if( pubkey_or_label.Q )
            return pubkey_or_label
            
        try {
            return PublicKey.fromStringOrThrow(pubkey_or_label)
        } catch(e) {}
        
        let keys = this.keys()
        let pubkey = keys.findKey( key => key.get("label") === pubkey_or_label )
        if( ! pubkey)
            return null
        
        return PublicKey.fromStringOrThrow( pubkey )
    }
    
    /**
        @arg {PublicKey|string} pubkey_or_label - public key string or object or label
        @return {PrivateKey} or null
    */
    getPrivateKey( pubkey_or_label ) {
        
        this.assertLogin()

        if(! pubkey_or_label)
            return null
        
        let keys = this.keys()
        let priv = pubkey => {
            let key = keys.get( pubkey )
            if( ! key )
                return null
            
            let wif = key.get("private_wif")
            if( ! wif )
                return null
            return PrivateKey.fromWif( wif )
        }
        
        if( pubkey_or_label.Q ) {
            return priv( pubkey_or_label.toString() )
        }
        try {
            PublicKey.fromStringOrThrow( pubkey_or_label )
            return priv(pubkey_or_label)
        } catch(error) {
            // slowest operation last
            let pubkey = this.keys().findKey( key => key.get("label") === pubkey_or_label )
            return pubkey ? priv( pubkey ) : null
        }
    }
    
    
    /**
        Generates a new blind account for the given brain key and assigns it the given label. 
        
        "Stealth accounts" are labeled private keys.  They will also be able to manage "stealth contacts" which are nothing more than labeled public keys.
        
        @throws {Error} [locked|label_exists]
        @arg {string} label
        @arg {string} brain_key
        @return {PublicKey}
    */
    createBlindAccount( label, brain_key  ) {

        this.assertLogin()
        req(label, "label")
        req(brain_key, "brain_key")
        
        brain_key = brainKey.normalize( brain_key )
        let private_key = PrivateKey.fromSeed( brain_key )
        let public_key = private_key.toPublicKey()
        
        if( ! this.setKeyLabel( private_key, label, public_key ))
            throw new Error("label_exists")

        return public_key
    }
    
    /** @return {Map<label, pubkey>} all blind accounts */
    getBlindAccounts() {
        this.assertLogin()
        let keys = this.keys()
        return keys.reduce( (r, key, pubkey) => r.set(key.get("label"), pubkey), Map())
    }
    
    /** @return {Map<label, pubkey>} all blind accounts for which this wallet has the private key */
    getMyBlindAccounts() {
        this.assertLogin()
        let keys = this.keys()
        let reduce = (r, label, pubkey) => ! keys.has(pubkey) ? r : r.set(label, pubkey)
        return keys.reduce( (r, key, pubkey) => reduce(r, key.get("label"), pubkey), Map())
    }
    
    /**
        @arg {string} public key or label
        @return {Promise<Map<asset_id, amount>>} the total balance of all blinded commitments that can be claimed by given account key or label
    */
    getBlindBalances(pubkey_or_label) {
        this.assertLogin()
        let balances = Map().asMutable()
        let p1 = this.fetch_blinded_balances( pubkey_or_label, (bal, receipt)=> {
            let amount = receipt.getIn(["data", "amount"])
            balances.update(amount.get("asset_id"), 0, amt => longAdd(amt, amount.get("amount")).toString() )
        })
        return p1.then(()=> balances.asImmutable())
    }

    /**
        Transfers a public balance from @from to one or more blinded balances using a stealth transfer.
        
        @arg {string} from_account_id_or_name
        @arg {string} asset_symbol
        @arg {array<string, number>} <from_key_or_label, amount> - from key_or_label to amount (destination public_key or key label)
        @arg {boolean} [broadcast = false]
        @return {Promise} reject ["unknown_from_account"|"unknown_asset"] resolve<object> blind_confirmation
    */
    transferToBlind( from_account_id_or_name, asset_symbol, to_amounts, broadcast = false ) {

        this.assertLogin()
        assert.equal(typeof from_account_id_or_name, "string", "from_account_id_or_name")
        assert.equal(typeof asset_symbol, "string", "asset_symbol")
        assert(Array.isArray( to_amounts ), "to_amounts should be an array")

        let idx = 0
        
        let promises = []
        promises.push(fetchChain("getAccount", from_account_id_or_name))
        promises.push(fetchChain("getAsset", asset_symbol))
        
        return Promise.all(promises).then( res =>{
            
            let [ account, asset ] = res
            if( ! account ) return Promise.reject("unknown_from_account")
            if( ! asset ) return Promise.reject("unknown_asset")
            
            // Validate to_amounts, lookup or parse destination public_key or key label (from_key_or_label)
            for( let to_amount of to_amounts) {
                 assert(Array.isArray( to_amount ), 'to_amounts parameter should look like: [["alice",1],["bob",1]]')
                 assert.equal(typeof to_amount[0], "string", 'to_amounts parameter should look like: [["alice",1],["bob",1]]')
                 assert.equal(typeof to_amount[1], "number", 'to_amounts parameter should look like: [["alice",1],["bob",1]]')
                 
                 to_amount[1] = toImpliedDecimal(to_amount[1], asset.get("precision"))
                 
                 let public_key
                 try { public_key = PublicKey.fromStringOrThrow(to_amount[0]) }
                    catch(error) { public_key = this.getPublicKey(to_amount[0]) }
                
                 assert(public_key, "Unknown to_amounts[" + (idx++) + "][0] (from_key_or_label): " + to_amount[0])
                 to_amount[3] = public_key
            }
        
            let promises = []
            let total_amount = 0
            let blinding_factors = []
            let bop = {
                from: account.get("id"),
                outputs: []
            }
            let confirm = {
                outputs: []
            }
            
            for( let to_amount of to_amounts) {
                
                let label = to_amount[0]
                let amount = to_amount[1]
                let to_public = to_amount[3]
                
                let one_time_private = key.get_random_key()
                let secret = one_time_private.get_shared_secret( to_public )
                let child = hash.sha256( secret )
                let nonce = hash.sha256( one_time_private.toBuffer() )
                let blind_factor = hash.sha256( child )
                
                // allows the wallet to store and decrypt the receipt
                // Store ones own receipts (fails in "blind to blind (external)")
                // this.setKeyLabel(one_time_private)
                
                blinding_factors.push( blind_factor.toString("hex") )
                total_amount = longAdd(total_amount, amount)
                
                let out = {}, conf_output
                
                let derived_child = to_public.child( child )
                out.owner = { weight_threshold: 1, key_auths: [[ derived_child.toString(), 1 ]],
                    account_auths: [], address_auths: []}
                
                promises.push( Promise.resolve()
                    .then( ()=> Apis.crypto("blind", blind_factor, amount.toString()))
                    .then( ret =>{ out.commitment = ret })
                    .then( ()=>
                        to_amounts.length > 1 ?
                            Apis
                            .crypto( "range_proof_sign", 0, out.commitment, blind_factor, nonce, 0, 0, amount.toString() )
                            .then( res => out.range_proof = res)
                        :
                            out.range_proof = ""
                    )
                    .then(()=> {
                        conf_output = {
                            label,
                            pub_key: to_public.toString(),
                            decrypted_memo: {
                                amount: { amount: amount.toString(), asset_id: asset.get("id") },
                                blinding_factor: blind_factor.toString("hex"),
                                commitment: out.commitment,
                                check: bufferToNumber(secret.slice(0, 4)),
                                from: one_time_private.toPublicKey().toString()
                            },
                            confirmation: {
                                one_time_key: one_time_private.toPublicKey().toString(),
                                to: to_public.toString(),
                                owner: out.owner, // allows wallet save before broadcasting (durable)
                                external_receipt: true,
                            }
                        }
                        // console.log('4 bufferToNumber', bufferToNumber(secret.slice(0, 4)))
                        let memo = stealth_memo_data.toBuffer( conf_output.decrypted_memo )
                        conf_output.confirmation.encrypted_memo = Aes.fromBuffer(secret).encrypt( memo ).toString("hex")
                        // conf_output.confirmation_receipt = conf_output.confirmation
                        
                        bop.outputs.push( out )
                        confirm.outputs.push( conf_output )
                    })
                    
                )
            }
            
            return Promise.all(promises).then(()=>{
                
                let name = account.get("name")
                let p1
                return Promise.resolve()
                .then( ()=>{ p1 = ()=> this.receiveBlindTransfer( confirm.outputs, "@"+name, "from @"+name ) })
                .then( ()=> Apis.crypto("blind_sum", blinding_factors, blinding_factors.length) )
                .then( res => bop.blinding_factor = res )
                .then( ()=>{
                    
                    bop.amount = { amount: total_amount.toString(), asset_id: asset.get("id") }
                    
                    let tr = new TransactionBuilder()
                    tr.add_type_operation("transfer_to_blind", bop)
                    
                    return this.process_transaction(tr, broadcast, p1).then(()=> {
                        confirm.trx = tr.serialize()
                        confirm.confirmation_receipts = confirmation_receipts(confirm.outputs)
                            .reduce( (r, receipt)=>r.push(bs58.encode(stealth_confirmation.toBuffer(receipt))) , List()).toJS()
                        
                        // console.log("confirm trx2", JSON.stringify(confirm.outputs))
                        return confirm
                    })
                })
                
            })
        })
    }
     
    /**
        @return {List<blind_receipt>} all blind receipts to/form a particular account sorted by date
    */
    blindHistory( pubkey_or_label ) {
        
        this.assertLogin()

        let blind_receipts = null

        if (pubkey_or_label) {
            let public_key = this.getPublicKey(pubkey_or_label)
            assert(public_key, "missing pubkey_or_label " + flipPrefix(pubkey_or_label))
            let pubkey = public_key.toString()
            blind_receipts = this.blind_receipts().filter( receipt => receipt.get("from_key") === pubkey || receipt.get("to_key") === pubkey )
        } else {
            blind_receipts = this.blind_receipts()
        }

        return blind_receipts
            .reduce( (r, receipt) => {
                receipt = receipt.update("from_label", label => flipPrefix(label))
                receipt = receipt.update("to_label", label => flipPrefix(label))
                // console.log("-- receipt -->", receipt.toJS());
                return r.push( receipt )}, List())
            .sort( (a, b) => a.get("date") > b.get("date") )
    }
    
    /**
        Usage:
        ```js
        let receipt = blindHistory("alice").toSeq().first()
        let bs58_encoded_receipt = getEncodedReceipt(receipt.get("conf").toJS())
        ```
        @arg {object} data
        @arg {string|PublicKey} data.encrypted_memo hex
        @arg {string|PublicKey} data.one_time_key
        @arg {string|PublicKey} [data.to = null]
        @return {string} bs58_encoded_receipt
        
    */
    getEncodedReceipt({encrypted_memo, one_time_key, to}) {
        return bs58.encode(stealth_confirmation.toBuffer({encrypted_memo, one_time_key, to}))
    }
    
    /**
        Given a confirmation receipt, this method will parse it for a blinded balance and confirm that it exists in the blockchain.  If it exists then it will save it in the wallet then report the amount received and who sent it.

        Checking the blockchain is optional.  This allows the wallet to save the receipt first before broadcasting.  In that case, confirmation_receipt.owner is provided and the get_blinded_balances API call is skipped.
        
        @arg {string|object|Array<string|object>} confirmation_receipt (HEX or JSON) - serilized stealth_confirmation operation: { to: optional(public_key), one_time_key: public_key, encrypted_memo: hex }
        
        @arg {string} opt_from - optional `from_label` unless the wallet already has a label assigned to the from_key
        @arg {string} opt_memo - optional memo to apply each receipt
        
        @typedef {object} blind_receipt
        @property {object} control_authority: {weight_threshold, ...}
        @property {object} conf: {one_time_key, to, encrypted_memo}
        
        @property {object} data
        @property {object} data.amount: { amount, asset_id }
        @property {string} data.blinding_factor
        @property {string} data.commitment
        @property {number} data.check
        
        @property {string} to_label - alice
        @property {string} to_key - "GPHAbc9Def..."
        @property {string} from_label - "bob" from memo or opt_from
        @property {object} amount - same as data.amount
        @property {string} date - ISO
        @property {string} memo - from opt_memo
        @property {boolean} used - `true` when spent
        
        @return {Promise< array<blind_receipt> >}
    */
    receiveBlindTransfer( confirmation_receipts, opt_from, opt_memo ) {

        // console.log("receiveBlindTransfer confirmation_receipt", confirmation_receipts, opt_from, opt_memo )

        this.assertLogin()
        
        let receipt = conf => {
            
            // console.log('1 conf', JSON.stringify(conf,null,4))
            
            // This conf.from_key -> opt_from in an array allows the receipts to be batched (this triggers a wallet backup). This should only needed if the wallet wants to store its own receipts sent out to external addresses.
            // Store ones own receipts fails, the "from_secret" can't be calculated
            if( conf.from_key && ! opt_from ) {
                //Caller may store the one_time_key in the wallet and provide the public version here
                opt_from = conf.from_key
            }

            if(conf.confirmation)
                conf = conf.confirmation
            
            if( ! conf.to) assert( conf.to, "to is required" )
            
            let result = { conf : fromJS(conf).toJS() }
            
            delete result.conf.owner // not stored, it is provided via get_blinded_balances(commitment)
            
            let to_private = this.getPrivateKey( conf.to )

            assert( typeof conf.encrypted_memo === "string", "Expecting HEX string for confirmation_receipt.encrypted_memo")
            assert( typeof conf.one_time_key === "string", "Expecting Public Key string for confirmation_receipt.one_time_key")
            
            let memo, secret
            function decr(secr) {
                // console.log('d bufferToNumber', bufferToNumber(secr.slice(0, 4)))
                try {
                    let plain_memo = Aes.fromBuffer(secr).decryptHexToText( conf.encrypted_memo )
                    let m = stealth_memo_data.fromBuffer( plain_memo )
                    if(m.check != bufferToNumber(secr.slice(0, 4)))
                        throw "mismatch"
                    memo = stealth_memo_data.toObject(m)
                    secret = secr
                    return true
                } catch(error) {
                    // console.log("wrong key" + (error === " (check mismatch)" ? error : " (parsing error)"))
                    return false
                }
            }
            let from_private
            let to_key = this.getPublicKey( conf.to )
            
            // Turn off parsing error debug, the "check" is inside of the memo so most often we will get debug parsing errors
            // console.log('opt_from,to_key', opt_from, to_key.toString(), !!this.getPrivateKey( opt_from ))
            Serializer.printDebug = false
            if(
                ! (to_private && decr(to_private.get_shared_secret(conf.one_time_key)) )
            &&
                ! ((from_private = this.getPrivateKey( opt_from )) && to_key && decr(from_private.get_shared_secret(to_key)) )
            ) {
                Serializer.printDebug = true
                // Both wallets (the cli_wallet and js wallet) do not save receipts coming from the wallet.  They should save receipts that were sent to a spendable key in the wallet.  The code may play it safe and try to save all receipts.  This error may be commented out after beta.
                // console.log("ConfidentialWallet\tINFO Unable to decrypt memo", JSON.stringify(memo_error))
                throw new Error("Unable to decrypt memo, " + (to_private == null && from_private == null ? "missing key" : "wrong key"))
            }
            
            let child = hash.sha256( secret )
            let child_private = PrivateKey.fromBuffer( child )
            
            if( to_key )
                result.to_key = to_key.toString()
            
            result.to_label = this.getKeyLabel( result.to_key )
            if( memo.from ) {
                result.from_key = memo.from
                result.from_label = this.getKeyLabel( result.from_key )
                if( ! result.from_label ) {
                    result.from_label = opt_from
                    this.wallet.queue_mills = 20*1000
                    this.setKeyLabel( result.from_key, result.from_label )
                }
            } else {
                result.from_label = opt_from
            }
            result.amount = memo.amount
            result.memo = opt_memo
            
            let owner = authority({ key_auths: [[ to_key.child(child).toString(), 1 ]] })
            
            // console.log("memo", JSON.stringify(memo))
            
            // confirm the amount matches the commitment (verify the blinding factor)
            return Apis.crypto("blind", memo.blinding_factor, memo.amount.amount)
            .then( commtiment_test =>
                Apis.crypto("verify_sum", [commtiment_test], [memo.commitment], 0)
                .then( result => assert(result, "verify_sum " + result))
                .then( () => {
                    
                    result.control_authority = owner
                    result.data = memo
                    
                    this.wallet.queue_mills = 20*1000
                    this.setKeyLabel( child_private )
                    result.date = new Date().toISOString()
                    // console.log('2 result', JSON.stringify(result, null, 4))
                    return result
                })
            )
        }

        if( ! Array.isArray( confirmation_receipts ) && ! List.isList(confirmation_receipts))
            confirmation_receipts = [ confirmation_receipts ]
        
        let rp = []
        List(confirmation_receipts).forEach( r =>{
            if( typeof r === 'string' ) {
                r = stealth_confirmation.fromBuffer(new Buffer(bs58.decode(r), "binary"))
                r = stealth_confirmation.toObject(r)
            }
            rp.push(Promise.resolve()

                // combine thrown exceptions and rejected promises
                .then(()=> receipt(r))
                .catch( error => {
                    // Do not re-throw unless fatal
                    // All promises must resolve for the wallet to update
                    
                    // If the receipt does not have a private key, the memo will the only and deciding error
                    if( ! /Unable to decrypt memo/.test(error.toString()) )
                        throw error
                    
                    // external_receipt means: save if the account happens to be in this wallet, don't error if not.
                    if( ! r.confirmation || ! r.confirmation.external_receipt ) throw error
                    
                    console.log( "ConfidentialWallet\tINFO importing external receipt")
                    
                    let from_label = this.getKeyLabel( r.decrypted_memo.from ) || opt_from
                    
                    // The wallet does not want to decrypt external receipts even when the one-time-key is recorded.  This will record them anyways.  This is probably better, decrypting the memo is not required and this saves the over-head of keeping one-time-keys.
                    let external_receipt = {
                        conf: r.confirmation,
                        to_key: r.confirmation.to,
                        to_label: r.label,
                        from_key: r.decrypted_memo.from,
                        from_label,
                        amount: r.decrypted_memo.amount,
                        memo: opt_memo,
                        control_authority: r.confirmation.owner,
                        data: r.decrypted_memo,
                        date: new Date().toISOString(),
                    }
                    // console.log('3 external_receipt', JSON.stringify(external_receipt, null, 4))
                    return external_receipt
                })
            )
        })
        
        let receipts
        return Promise.all(rp)
            // Convert to Immutable.
            // Remove nulls (this wallet did not accept the receipt).
            .then( res => receipts = List(res).reduce( (r, el) => el ? r.push(fromJS(el)) : r, List()) )

            // Update the wallet
            .then(() => console.log( "ConfidentialWallet\tINFO saving " + receipts.size + " receipts" ))
            .then(() => this.update(
                wallet => wallet.update("blind_receipts", List(),
                    // append receipts to blind_receipts
                    blind_receipts => receipts.reduce((r, rr) => r ? r.push(rr) : r, blind_receipts)
                )
            ))
            .then( ()=> receipts )
    }

    /**
        Transfers funds from a set of blinded balances to a public account balance.
        
        @arg {string} from_blind_account_key_or_label
        @arg {string} to_account_id_or_name
        @arg {string} amount
        @arg {string} asset_symbol
        @arg {boolean} [broadcast = false]
        @return blind_confirmation
    */
    transferFromBlind( from_blind_account_key_or_label, to_account_id_or_name, amount, asset_symbol, broadcast = false ){
        
        this.assertLogin()
        
        let promises = []
        promises.push(fetchChain("getAccount", to_account_id_or_name))
        promises.push(fetchChain("getAsset", asset_symbol))
        
        return Promise.all(promises).then( res =>{
            
            let [ to_account, asset ] = res
            if( ! to_account ) return Promise.reject("unknown_to_account")
            if( ! asset ) return Promise.reject("unknown_asset")
            
            amount = toImpliedDecimal(amount, asset.get("precision"))
            
            let from_blind_fee
            return Promise.resolve()
            
            .then( () => get_blind_transfer_fee(asset.get("id"), 0) )
            .then( fee => from_blind_fee = fee )
            
            .then( () => longAdd(from_blind_fee.amount, amount))
            
            .then( amount_with_fee =>
                this.blind_transfer_help(
                    from_blind_account_key_or_label, from_blind_account_key_or_label,
                    amount_with_fee, asset_symbol, false/*broadcast*/, true/*to_temp*/
                )
            )
            .then( conf => {
    
                assert( conf.outputs, "outputs are required" )
                
                // Sender's change address
                let last_output = conf.outputs[conf.outputs.length - 1]
                
                let from_blind = {
                    fee: from_blind_fee,
                    amount: { amount: amount.toString(), asset_id: asset.get("id") },
                    to: to_account.get("id"),
                    blinding_factor: last_output.decrypted_memo.blinding_factor,
                    inputs: [{
                        commitment: last_output.decrypted_memo.commitment,
                        owner: authority(),
                        // one_time_key added for signing
                        // one_time_key: last_output.confirmation.one_time_key
                    }]
                }
                
                let operations = conf.trx.operations
                operations.push( from_blind )
                
                let p1
                let has_change = conf.outputs.length === 2
                if( has_change ) {
                    let change_out = conf.outputs[0]
                    let cr = { // confirmation_receipt
                        // { to, one_time_key, encrypted_memo, [owner = null] } 
                        to: this.getPublicKey(from_blind_account_key_or_label).toString(),
                        one_time_key: change_out.confirmation.one_time_key,
                        encrypted_memo: change_out.confirmation.encrypted_memo
                    }
                    // make sure the change is stored before broadcasting (durable)
                    p1 = ()=> this.receiveBlindTransfer(cr, from_blind_account_key_or_label, "to " + to_account.get("name"))
                }
                    
                // console.log("conf.trx", JSON.stringify(conf.trx))
                return this.send_blind_tr(
                    operations,
                    from_blind_account_key_or_label,
                    broadcast,
                    conf.one_time_keys,
                    p1
                ).then( tr => {
                    conf.trx = tr
                    if( has_change )
                        conf.change_receipt = conf.confirmation_receipts[0]
                    
                    delete conf.confirmation_receipts
                    return conf
                })
            })
        })
    }

    /**
        Used to transfer from one set of blinded balances to another.
        
        @arg {string} from_key_or_label
        @arg {string} to_key_or_label
        @arg {string} amount
        @arg {string} asset_symbol
        @arg {boolean} [broadcast = false]
        @return blind_confirmation
    */
    blindTransfer( from_key_or_label, to_key_or_label, amount, asset_symbol, broadcast = false) {
        
        this.assertLogin()
        
        return Promise.resolve()
        .then( ()=> fetchChain("getAsset", asset_symbol) )
        .then( asset => {
            if( ! asset ) return Promise.reject("unknown_asset")
            amount = toImpliedDecimal(amount, asset.get("precision"))
            return this.blind_transfer_help(from_key_or_label, to_key_or_label, amount, asset_symbol, broadcast)
            .then( conf =>{
                // Their may or may not be a change receipt.  Always return the last receipt
                let cs = conf.confirmation_receipts
                if(cs.length === 2)
                    conf.change_receipt = cs[0]
                
                conf.confirmation_receipt = cs[ cs.length - 1 ] // the last one
                delete conf.confirmation_receipts
                return conf
            })
        })
        
    }
    
    /**
        @arg {number|string} asset_symbol_or_id
        @return {object} like { asset_id: "1.3.0", amount: 2000000 }
    */
    getFeeToAccount(asset_symbol_or_id = "1.3.0") {
        let f1, f2, asset
        return Promise.resolve()
        
        .then(()=> fetchChain("getAsset", asset_symbol_or_id)).then(_asset=> asset = _asset)
        .then(()=> console.log(asset))
        
        .then(()=> get_blind_transfer_fee(asset.get("id"), 0)).then(_fee=> f1 = _fee)
        .then(()=> get_blind_transfer_fee(asset.get("id"), 2)).then(_fee=> f2 = _fee)
        .then(()=> assert(f1.asset_id, f2.asset_id, `Fee asset type mismatch, f1 ${f1}, f2 ${f2}`))
        
        .then(()=>({ asset_id: f1.asset_id, amount: parseInt(f1.amount) + parseInt(f2.amount) }) ) 
    }
    
    /**
        @arg {number|string} asset_symbol_or_id
        @return {object} like { asset_id: "1.3.0", amount: 2000000 }
    */
    getFeeToBlind(asset_symbol_or_id = "1.3.0") {
        let f1, asset
        return Promise.resolve()
        
        .then(()=> fetchChain("getAsset", asset_symbol_or_id)).then(_asset=> asset = _asset)
        .then(()=> assert(asset, "Asset not found: " + asset_symbol_or_id))
        
        .then(()=> get_blind_transfer_fee(asset.get("id"), 2)).then(_fee=> f1 = _fee)
        
        .then(()=>({ asset_id: f1.asset_id, amount: parseInt(f1.amount) }) ) 
    }

}

function fetch_blinded_balances(pubkey_or_label, callback) {
    
    let public_key = this.getPublicKey( pubkey_or_label )
    assert( public_key, "missing pubkey_or_label " + pubkey_or_label)
    
    let pubkey = public_key.toString()

    let receipts = this.blind_receipts()
        .filter( r => r.get("to_key") === pubkey)
        // .filterNot( r => r.get("used") === true )// just for testing
    
    let used = Set()
    let commitments = this.commitments(receipts)
    
    let p1 = Apis.db("get_blinded_balances", commitments.toJS()).then( bbal => {
        
        // if( ! bbal.length )
        //     console.log("INFO\tConfidentialWallet\tno blinded balances", pubkey_or_label, commitments.toJS())
        
        let bbalMap = List(bbal).reduce( (r, bal)=> r.set(bal.commitment, bal), Map())
        
        receipts.forEach( receipt => {
            let commitment = receipt.getIn(["data", "commitment"])
            let bal = bbalMap.get(commitment)
            
            // console.log("used", ! bal, receipt.get('amount'), '\t', pubkey_or_label)
            
            if( ! bal ) {
                used = used.add(commitment)
                return
            }
            let ret = callback(bal, receipt, commitment)
            if( ret === false )
                return false
        })
    })
    
    // update "used" in the wallet after the API call finishes
    return p1.then(()=> {
        
        if( used.size ) return this.update(wallet => wallet
            .update("blind_receipts", receipts => receipts.reduce( (r, receipt) =>
                used.has( receipt.getIn(["data", "commitment"]) ) ?
                    r.push(receipt.set("used", true)) :
                    r.push(receipt)
                , List()
            ))
        )
        
    })
}

/**
    Short method to help form and send a blind transfer..
    
    @arg {string} from_key_or_label
    @arg {string} to_key_or_label
    @arg {string} amount - The implied decimal places amount
    @arg {string} asset_symbol
    @arg {boolean} broadcast
    @arg {boolean} to_temp
    
    @typedef {object} ret
    @property {object} outputs
    @property {object} outputs.decrypted_memo: {from, amount, blinding_factor, commitment, check}
    @property {object} outputs.confirmation: {one_time_key, to, owner, encrypted_memo}
    @property {string} outputs.label - "alice"
    @property {string} outputs.pub_key: "GPHAbc9Def..."
    @property {object} outputs.auth: {weight_threshold, ...}
    
    @property {object} fee: {amount, asset_id}
    @property {object} trx: {ref_block_num, ...}
    @property {array<string>} one_time_keys - for signing
    
    @return {Promise<ret>} 
*/
function blind_transfer_help(
    from_key_or_label, to_key_or_label,
    amount, asset_symbol, broadcast = false, to_temp = false
) {
    this.assertLogin()
    
    // assert digits (for implied decimal format)
    assert(isDigits(amount), "expecting only digits in amount " + amount) //not prefect, but would catch some invalid calls
    
    let confirm = {
        outputs: []
    }
    
    let from_key = this.getPublicKey(from_key_or_label)
    let to_key = this.getPublicKey(to_key_or_label)
    
    assert(from_key, "missing from_key_or_label: " + from_key_or_label)
    assert(to_key, "missing to_key_or_label: " + to_key_or_label)
    
    let promises = []
    promises.push(fetchChain("getAsset", asset_symbol))

    return Promise.all(promises).then( res =>{
        
        let [ asset ] = res
        if( ! asset ) return Promise.reject("unknown_asset")
        
        let blind_tr = {
            outputs: [],
            inputs: []
        }
        let one_time_keys = Set()
        let available_amount = Long.ZERO
        let blinding_factors = []
        
        let used = []
        let amount_with_fee
        
        return Promise.resolve()
        
        .then( ()=> get_blind_transfer_fee( asset.get("id")) )
        .then( fee =>{
            blind_tr.fee = fee
            confirm.fee = fee
        })
        
        .then( ()=>{ amount_with_fee = longAdd(amount, blind_tr.fee.amount) })
        .then( ()=> this.fetch_blinded_balances(from_key_or_label, (bal, receipt, commitment) =>{
            
            let control_authority = receipt.get("control_authority")
            
            let one_time_key = receipt.get("conf").get("one_time_key")
            //for signing
            one_time_keys = one_time_keys.add( one_time_key )
            
            blind_tr.inputs.push({ commitment,
                owner: control_authority.toJS(), one_time_key })
            
            blinding_factors.push( receipt.get("data").get("blinding_factor") )
            
            available_amount = longAdd(available_amount, receipt.get("amount").get("amount"))
            
            // return false to "break"
            // Break if the available_amount total is >= amount_with_fee
            // Being over is fine, change will be provided...
            return longCmp(available_amount, amount_with_fee) < 0
            
        }) )
        .then(()=> {
            
            assert( longCmp(available_amount, amount_with_fee) >= 0,
                `Insufficent Balance, available ${available_amount.toString()}, transfer amount plus fees ${amount_with_fee.toString()}`)
            
            let one_time_private = key.get_random_key()
            let secret = one_time_private.get_shared_secret( to_key )
            let child = hash.sha256( secret )
            let nonce = hash.sha256( one_time_private.toBuffer() )
            let blind_factor
            
            // Saving this one_time_key may allow the wallet to decrypt sent receipt memos (this is probably not requied).  Also extra backup overhead here...
            // (did not store in unit test: "blind to blind (external)")
            // this.setKeyLabel( one_time_private )
            
            let from_secret = one_time_private.get_shared_secret( from_key )
            let from_child = hash.sha256( from_secret )
            let from_nonce = hash.sha256( nonce )
            
            let change = longSub(longSub(available_amount, amount), blind_tr.fee.amount)
            let change_blind_factor
            
            let has_change = longCmp(change, 0) > 0
            
            let bf_promise
            if( has_change ) {
                blind_factor = hash.sha256( child )
                blinding_factors.push( blind_factor.toString("hex") )
                bf_promise = Apis
                    .crypto("blind_sum", blinding_factors, blinding_factors.length - 1)
                    .then( bf => change_blind_factor = bf )
            } else {
                bf_promise = Apis
                    .crypto("blind_sum", blinding_factors, blinding_factors.length )
                    .then( bf => blind_factor = bf )
                    .then( () => blinding_factors.push( blind_factor.toString("hex") ))
            }
            
            return bf_promise.then(()=> {
                
                let to_out = { }

                let derived_child = to_key.child( child )
                to_out.owner = to_temp ? authority() :
                    authority({ key_auths: [[ derived_child.toString(), 1 ]] })
                
                return Promise.resolve()
                .then( ()=> Apis.crypto("blind", blind_factor, amount.toString()))
                .then( ret => to_out.commitment = ret )
                
                .then( ()=>{
                    
                    let rp_promise
                    
                    if( ! has_change ) {
                        
                       rp_promise = Promise.resolve()
                       to_out.range_proof = ""
                       
                   } else {
                        
                        let change_out = {}
                        let derived_child = from_key.child( from_child )
                        change_out.owner =
                            authority({ key_auths: [[ derived_child.toString(), 1 ]] })
                        
                        rp_promise = Apis.crypto(
                            "range_proof_sign",
                            0, to_out.commitment, blind_factor,
                            nonce, 0, 0, amount.toString()
                        )
                        .then( res => to_out.range_proof = res)
                        
                        .then( ()=> Apis.crypto("blind", change_blind_factor, change) )
                        .then( res => change_out.commitment = res )
                        
                        .then( ()=> Apis.crypto(
                            "range_proof_sign",
                            0, change_out.commitment, change_blind_factor,
                            from_nonce, 0, 0, change
                        ))
                        .then( res => change_out.range_proof = res )
                        
                        .then( ()=>{
                            
                            blind_tr.outputs[1] = change_out
                            
                            let conf_output = {
                                decrypted_memo: {},
                                confirmation: {}
                            }
                            
                            conf_output.label = from_key_or_label
                            conf_output.pub_key = from_key.toString()
                            // conf_output.from_key = one_time_private.toPublicKey().toString()//trying to save "from blind" receipt 
                            conf_output.decrypted_memo.from = from_key.toString()
                            conf_output.decrypted_memo.amount = { amount: change.toString(), asset_id: asset.get("id") }
                            conf_output.decrypted_memo.blinding_factor = change_blind_factor.toString("hex")
                            conf_output.decrypted_memo.commitment = change_out.commitment
                            conf_output.decrypted_memo.check = bufferToNumber(from_secret.slice(0, 4))
                            conf_output.confirmation.one_time_key = one_time_private.toPublicKey().toString()
                            conf_output.confirmation.to = from_key.toString()
                            conf_output.confirmation.owner = change_out.owner
                            // console.log('b bufferToNumber', bufferToNumber(from_secret.slice(0, 4)))
                            
                            let from_aes = Aes.fromBuffer(from_secret)
                            let memo = stealth_memo_data.toBuffer( conf_output.decrypted_memo )
                            conf_output.confirmation.encrypted_memo = from_aes.encrypt( memo ).toString("hex")
                            
                            conf_output.auth = change_out.owner
                            conf_output.confirmation_receipt = conf_output.confirmation
                        
                            confirm.outputs.push( conf_output )
                        })
                    }
                    
                    return rp_promise.then(()=>{
                        
                        blind_tr.outputs[0] = to_out
                        
                        let conf_output = {
                            decrypted_memo: {},
                            confirmation: {}
                        }
                        
                        conf_output.label = to_key_or_label
                        conf_output.pub_key = to_key.toString()
                        conf_output.decrypted_memo.from = from_key.toString()
                        conf_output.decrypted_memo.amount = { amount: amount.toString(), asset_id: asset.get("id") }
                        conf_output.decrypted_memo.blinding_factor = blind_factor.toString("hex")
                        conf_output.decrypted_memo.commitment = to_out.commitment
                        conf_output.decrypted_memo.check = bufferToNumber(secret.slice(0, 4))
                        // console.log('2 bufferToNumber', bufferToNumber(from_secret.slice(0, 4)))
                        conf_output.confirmation.one_time_key = one_time_private.toPublicKey().toString()
                        conf_output.confirmation.to = to_key.toString()
                        conf_output.confirmation.owner = to_out.owner
                        conf_output.confirmation.external_receipt = true
                        
                        let aes = Aes.fromBuffer(secret)
                        let memo = stealth_memo_data.toBuffer( conf_output.decrypted_memo )
                        conf_output.confirmation.encrypted_memo = aes.encrypt( memo ).toString("hex")
                        
                        conf_output.auth = to_out.owner
                        // conf_output.confirmation_receipt = conf_output.confirmation
                        
                        // transferFromBlind needs to_out as last
                        confirm.outputs.push( conf_output )
                        let p1
                        if( ! to_temp ) {
                            // make sure the receipts are stored first before broadcasting
                            p1 = ()=> this.receiveBlindTransfer(confirm.outputs, from_key_or_label)
                        }
                        return this.send_blind_tr([blind_tr], from_key_or_label, broadcast, null, p1, to_temp)
                        .then( tr => {
                            confirm.trx = tr
                            confirm.one_time_keys = one_time_keys.toJS()
                            confirm.confirmation_receipts = confirmation_receipts(confirm.outputs)
                                .reduce( (r, receipt)=>
                                    r.push(bs58.encode(stealth_confirmation.toBuffer(receipt))) , List()).toJS()
                            
                            return confirm
                        })
                    })
                })
            })
        })
    })
}

// required
function req(data, field_name) {
    if( data == null ) throw new Error("Missing required field: " + field_name)
    return data
}

/** @return {Promise} */
function update(callback) {
    let wallet = callback(this.wallet.wallet_object)
    return this.wallet.setState(wallet)
    .catch( error =>{
        console.error("ERROR\tConfidentialWallet\tupdate", error, "stack", error.stack)
        throw error
    })
}

let confirmation_receipts = outputs => List(outputs)
    .reduce( (r, out)=>{
        assert(out.confirmation, "confirmation required")
        return r.push(out.confirmation)
    }, List())

function send_blind_tr(ops, from_key_or_label, broadcast, one_time_keys, broadcast_confirmed_callback, to_temp = false) {
    
    let tr = new TransactionBuilder()

    for(let op of ops) {

        if( Array.isArray(op) ) {
            op = op[1]
        }
        
        assert(op.inputs, "inputs are required")
        let op_name = op.outputs ? "blind_transfer" : "transfer_from_blind"
        tr.add_type_operation(op_name, op)
        {
            let signer
            let sign = one_time_key => {
                
                if( ! signer) {
                    signer = this.getPrivateKey(from_key_or_label)
                }

                if( ! signer )
                    throw new Error("Missing private key for: " + from_key_or_label)
                
                let secret = signer.get_shared_secret( one_time_key )
                let child = hash.sha256( secret )
                tr.add_signer(signer.child(child))
            }
            
            for(let input of op.inputs)
                if( input.one_time_key )
                    sign( input.one_time_key )
            
            if( one_time_keys )
                for(let one_time_key of one_time_keys)
                    sign( one_time_key )
        }
    }
    if(to_temp)
        // don't trigger the confirmation dialog
        return tr.process_transaction(this, null/*signer keys*/, false/*broadcast*/).then(()=> tr)
    else
        // confirmation dialog
        return this.process_transaction(tr, broadcast, broadcast_confirmed_callback).then(()=> tr)
}

/** Feeds need to be obtained in advance before calculating inputs and outputs. */
function get_blind_transfer_fee(asset_id, output_count = 2) {
    
    // Create an empty but serilizable operation to send to the server
    let op = output_count === 0 ? transfer_from_blind : blind_transfer
    let object = op.toObject({}, {use_default: true})
    
    for(let i = 1; i < output_count; i++)
        object.outputs.push( object.outputs[0] )
    
    let tr = new TransactionBuilder()
    tr.add_type_operation(op.operation_name, object)
    return tr.set_required_fees(asset_id).then(()=>{
        let fee = tr.operations[0][1].fee
        assert.equal( asset_id, fee.asset_id, "expecting fee asset_id to match" )
        // console.log("output_count, blind transfer fee", output_count, fee)
        return fee
    })
}

let isDigits = value => value === "numeric" || /^[0-9]+$/.test(value)

function assertLogin() {
    if( ! this.wallet.private_key )
        throw new Error("Wallet is locked")
}

var flipPrefix = label =>
    ! label ? label :
    /^@/.test(label) ? label.substring(1) :
    "~" + label

var toString = data => data == null ? data :
    data["toWif"] ? data.toWif() : // Case for PrivateKey.toWif()
    data["toString"] ? data.toString() : // Case for PublicKey.toString()
    data

let bufferToNumber = (buf, type = "Uint32") => 
    ByteBuffer.fromBinary(buf.toString("binary"), ByteBuffer.LITTLE_ENDIAN)["read" + type]()

// let indexableKeys = keys => keys
//     .reduce( (r, key, pubkey) => key.get("index_address") ? r.push(pubkey) : r, List())

function getPubkeys_having_PrivateKey( pubkeys, addys = null ) {
    let return_pubkeys = []
    let keys = this.keys()
    if(pubkeys) {
        for(let pubkey of pubkeys) {
            let key = keys.get(pubkey)
            if(key && key.has("private_wif")) {
                return_pubkeys.push(pubkey)
            }
        }
    }
    if(addys) {
        for (let addy of addys) {
            let pubkey = AddressIndex.getPubkey(addy)
            return_pubkeys.push(pubkey)
        }
    }
    return return_pubkeys
}

let long = (operation, arg1, arg2) => new Long(arg1)[operation]( new Long(arg2) )
let longAdd = (a, b) => long("add", a, b)
let longMul = (a, b) => long("multiply", a, b)
let longCmp = (a, b) => long("compare", a, b)
let longSub = (a, b) => long("subtract", a, b)

let authority = (data, weight_threshold = data ? 1 : 0)  =>
    fromJS({ weight_threshold, key_auths: [], account_auths: [], address_auths: [] })
    .merge(data).toJS()