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Use UInt64 instead of Decimal when calculating proof of work.

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Fix target calculations in proof of work.
Fix incorrect greater than comparison between UInt8 arrays.
This commit is contained in:
Mikunj 2019-05-02 12:40:42 +10:00
parent d3f1ba5c8e
commit 1eed630af8
1 changed files with 46 additions and 70 deletions
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116
LokiKit/ProofOfWork.swift
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@ -1,63 +1,40 @@
import CryptoSwift
private extension Int {
private extension UInt64 {
init(_ decimal: Decimal) {
let double = NSDecimalNumber(decimal: decimal).doubleValue
self.init(double)
}
}
private extension UInt8 {
init(_ decimal: Decimal) {
self.init(Int(decimal))
}
}
private extension Decimal {
/// Get the remainder of a Decimal
static func %(lhs: Decimal, rhs: Int) -> Decimal {
return Decimal(Int(lhs) % rhs)
}
/// Divide a Decimal by an Int
static func /(lhs: Decimal, rhs: Int) -> Decimal {
return lhs / Decimal(rhs)
}
/// Convert a Decimal to a UInt8 array of a given length
func toArray(ofLength length: Int) -> [UInt8] {
return (0..<length).map { i in
let n = length - (i + 1)
// 256 ** n is the value of one bit in arr[i], modulus to carry over
// (self / 256**n) % 256;
let denominator = pow(256, n)
let fraction = self / denominator
// fraction % 256
let remainder = fraction % 256
return UInt8(remainder)
}
self.init(truncating: decimal as NSDecimalNumber)
}
}
// UInt8 Array specific stuff we need
private extension Array where Element == UInt8 {
// Convert a UInt64 into an array
init(_ uint64: UInt64) {
let array = stride(from: 0, to: 64, by: 8).reversed().map {
UInt8(uint64 >> $0 & 0x000000FF)
}
self.init(array)
}
/// Compare if lhs array is greater than rhs array
static func >(lhs: [UInt8], rhs: [UInt8]) -> Bool {
guard lhs.count == rhs.count else { return false }
// lhs is greater than rhs if any value in lhs is greater than the corresponding value in the rhs
return zip(lhs, rhs).contains { $0 > $1 }
for i in (0..<lhs.count) {
// If the values are the same then move onto the next pair
if (lhs[i] == rhs[i]) { continue }
return lhs[i] > rhs[i]
}
return false
}
/// Increment the UInt8 array by a given amount
///
/// - Parameter amount: The amount to increment by
/// - Returns: The incrememnted array
func increment(by amount: Int) -> [UInt8] {
var newNonce = [UInt8](self)
var newNonce = self
var increment = amount
for i in (0..<newNonce.count).reversed() {
guard increment > 0 else { break }
@ -77,26 +54,27 @@ private extension Array where Element == UInt8 {
*/
public enum ProofOfWork {
static let nonceLength = 8
// If this changes then we also have to use something other than UInt64 to support the new length
private static let nonceLength = 8
// Modify this value for difficulty scaling
enum NonceTrials {
private enum NonceTrials {
static let development = 10
static let production = 100
}
public struct Configuration {
struct Configuration {
var pubKey: String
var data: String
var timestamp: Date
var ttl: UInt
var ttl: Int
var isDevelopment = false
func getPayload() -> [UInt8] {
let timestampString = String(timestamp.timeIntervalSince1970)
var payload: [UInt8] {
let timestampString = String(Int(timestamp.timeIntervalSince1970))
let ttlString = String(ttl)
let payloadString = timestampString + ttlString + pubKey + data
return [UInt8](payloadString.utf8)
return payloadString.bytes
}
}
@ -107,16 +85,16 @@ public enum ProofOfWork {
///
/// - Parameter config: The configuration data
/// - Returns: A nonce string or nil if it failed
public static func calculate(with config: Configuration) -> String? {
let payload = config.getPayload()
static func calculate(with config: Configuration) -> String? {
let payload = config.payload
let nonceTrials = config.isDevelopment ? NonceTrials.development : NonceTrials.production
let target = calcTarget(ttl: config.ttl, payloadLength: payload.count, nonceTrials: nonceTrials)
// Ref: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER
let maxSafeInteger = pow(2, 53) - 1
var trialValue = maxSafeInteger.toArray(ofLength: nonceLength)
let maxSafeInteger = UInt64(pow(2, 53) - 1)
var trialValue = [UInt8](maxSafeInteger)
let initialHash = [UInt8](config.data.sha512().utf8)
let initialHash = payload.sha512()
var nonce = [UInt8](repeating: 0, count: nonceLength)
while trialValue > target {
@ -132,25 +110,23 @@ public enum ProofOfWork {
}
/// Calculate the UInt8 target we need to reach
private static func calcTarget(ttl: UInt, payloadLength: Int, nonceTrials: Int) -> [UInt8] {
let decimalTTL = Decimal(ttl)
let decimalPayloadLength = Decimal(payloadLength)
let decimalNonceTrials = Decimal(nonceTrials)
let decimalTwo16 = pow(2, 16) - 1
let decimalTwo64 = pow(2, 64) - 1
private static func calcTarget(ttl: Int, payloadLength: Int, nonceTrials: Int) -> [UInt8] {
let two16 = UInt64(pow(2, 16) - 1)
let two64 = UInt64(pow(2, 64) - 1)
// ttl converted to seconds
let ttlSeconds = decimalTTL / 1000
// Do all the calculations
let totalLength = decimalPayloadLength + Decimal(nonceLength)
let ttlMult = ttlSeconds * totalLength
let innerFrac = ttlMult / decimalTwo16
let lenPlusInnerFrac = totalLength + innerFrac
let denominator = decimalNonceTrials * lenPlusInnerFrac
let targetNum = decimalTwo64 / Int(denominator)
let ttlSeconds = ttl / 1000
return targetNum.toArray(ofLength: nonceLength)
// Do all the calculations
let totalLength = UInt64(payloadLength + nonceLength)
let ttlMult = UInt64(ttlSeconds) * totalLength
// UInt64 values
let innerFrac = ttlMult / two16
let lenPlusInnerFrac = totalLength + innerFrac
let denominator = UInt64(nonceTrials) * lenPlusInnerFrac
let targetNum = two64 / denominator
return [UInt8](targetNum)
}
}