mirror of https://github.com/oxen-io/session-ios
[Merge] Proof of Work
Niels Andriesse
6 years ago
committed by
GitHub
commit
3ce721f069
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import CryptoSwift
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private extension UInt64 {
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init(_ decimal: Decimal) {
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self.init(truncating: decimal as NSDecimalNumber)
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}
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}
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// UInt8 Array specific stuff we need
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private extension Array where Element == UInt8 {
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// Convert a UInt64 into an array of size 8
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init(_ uint64: UInt64) {
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let array = stride(from: 0, to: 64, by: 8).reversed().map {
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UInt8(uint64 >> $0 & 0x000000FF)
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}
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self.init(array)
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}
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/// Compare if lhs array is greater than rhs array
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static func >(lhs: [UInt8], rhs: [UInt8]) -> Bool {
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guard lhs.count == rhs.count else { return false }
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for i in (0..<lhs.count) {
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// If the values are the same then move onto the next pair
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if (lhs[i] == rhs[i]) { continue }
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return lhs[i] > rhs[i]
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}
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return false
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}
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/// Increment the UInt8 array by a given amount
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///
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/// - Parameter amount: The amount to increment by
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/// - Returns: The incrememnted array
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func increment(by amount: Int) -> [UInt8] {
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var newNonce = self
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var increment = amount
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for i in (0..<newNonce.count).reversed() {
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guard increment > 0 else { break }
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let sum = Int(newNonce[i]) + increment
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newNonce[i] = UInt8(sum % 256)
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increment = sum / 256
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}
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return newNonce
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}
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}
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/**
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* The main logic which handles proof of work.
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*
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* This was copied from the messenger desktop.
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* Ref: libloki/proof-of-work.js
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*/
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public enum ProofOfWork {
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// If this changes then we also have to use something other than UInt64 to support the new length
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private static let nonceLength = 8
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// Modify this value for difficulty scaling
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private enum NonceTrials {
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static let development = 10
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static let production = 100
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}
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struct Configuration {
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var pubKey: String
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var data: String
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var timestamp: Date
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var ttl: Int
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var isDevelopment = false
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var payload: [UInt8] {
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let timestampString = String(Int(timestamp.timeIntervalSince1970))
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let ttlString = String(ttl)
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let payloadString = timestampString + ttlString + pubKey + data
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return payloadString.bytes
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}
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}
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/// Calculate a proof of work for the given configuration
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///
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/// Ref: https://bitmessage.org/wiki/Proof_of_work
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///
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/// - Parameter config: The configuration data
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/// - Returns: A nonce string or nil if it failed
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static func calculate(with config: Configuration) -> String? {
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let payload = config.payload
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let nonceTrials = config.isDevelopment ? NonceTrials.development : NonceTrials.production
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let target = calcTarget(ttl: config.ttl, payloadLength: payload.count, nonceTrials: nonceTrials)
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// Start with most the max value we can
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var trialValue = [UInt8](repeating: UInt8.max, count: nonceLength)
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let initialHash = payload.sha512()
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var nonce = [UInt8](repeating: 0, count: nonceLength)
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while trialValue > target {
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nonce = nonce.increment(by: 1)
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// This is different to the bitmessage pow
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// resultHash = hash(nonce + hash(data)) ==> hash(nonce + initialHash)
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let resultHash = (nonce + initialHash).sha512()
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trialValue = Array(resultHash[0..<8])
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}
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return nonce.toBase64()
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}
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/// Calculate the UInt8 target we need to reach
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private static func calcTarget(ttl: Int, payloadLength: Int, nonceTrials: Int) -> [UInt8] {
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let two16 = UInt64(pow(2, 16) - 1)
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let two64 = UInt64(pow(2, 64) - 1)
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// ttl converted to seconds
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let ttlSeconds = ttl / 1000
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// Do all the calculations
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let totalLength = UInt64(payloadLength + nonceLength)
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let ttlMult = UInt64(ttlSeconds) * totalLength
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// UInt64 values
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let innerFrac = ttlMult / two16
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let lenPlusInnerFrac = totalLength + innerFrac
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let denominator = UInt64(nonceTrials) * lenPlusInnerFrac
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let targetNum = two64 / denominator
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return [UInt8](targetNum)
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}
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}
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@ -1 +1 @@
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Subproject commit aed207f026696cbb76066748fba6689a9c04194e
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Subproject commit 34ae9f4f2dd47c4d66de7525fbe1054f4f573512
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