Re-add proof of work

Podfile

@@ -99,6 +99,7 @@ target 'SignalMessaging' do
 end
 
 target 'SessionMessagingKit' do
+  pod 'CryptoSwift', :inhibit_warnings => true
   pod 'PromiseKit', :inhibit_warnings => true
   pod 'SwiftProtobuf', '~> 1.5.0', :inhibit_warnings => true
 end

Podfile.lock

@@ -332,6 +332,6 @@ SPEC CHECKSUMS:
   YYImage: 6db68da66f20d9f169ceb94dfb9947c3867b9665
   ZXingObjC: fdbb269f25dd2032da343e06f10224d62f537bdb
 
-PODFILE CHECKSUM: 58acf63b2164dadf743187b6a52154721c1c01dd
+PODFILE CHECKSUM: 4d6ed1d0ef2a98ce221ebfffc9ae860d4703ec47
 
 COCOAPODS: 1.10.0.rc.1

Pods

@@ -1 +1 @@
-Subproject commit 03a39c064860412e9e69b99f19dd85cd5a9b8aad
+Subproject commit 855baeb2e72e3f90eb0cdcbc682162175db2bec8

SessionMessagingKit/Pipelines/SendingPipeline.swift

@@ -13,11 +13,13 @@ public enum SendingPipeline {
     public enum Error : LocalizedError {
         case protoConversionFailed
         case protoSerializationFailed
+        case proofOfWorkCalculationFailed
 
         public var errorDescription: String? {
             switch self {
             case .protoConversionFailed: return "Couldn't convert message to proto."
             case .protoSerializationFailed: return "Couldn't serialize proto."
+            case .proofOfWorkCalculationFailed: return "Proof of work calculation failed."
             }
         }
     }
@@ -35,8 +37,10 @@ public enum SendingPipeline {
         let recipient = ""
         let base64EncodedData = data.base64EncodedString()
         let ttl: UInt64 = 2 * 24 * 60 * 60 * 1000
-        let timestamp: UInt64 = 0
+        guard let (timestamp, nonce) = ProofOfWork.calculate(ttl: ttl, publicKey: recipient, data: base64EncodedData) else {
-        let nonce = ""
+            SNLog("Proof of work calculation failed.")
+            return Promise(error: Error.proofOfWorkCalculationFailed)
+        }
         let snodeMessage = SnodeMessage(recipient: recipient, data: base64EncodedData, ttl: ttl, timestamp: timestamp, nonce: nonce)
         let _ = SnodeAPI.sendMessage(snodeMessage)
         return Promise.value(())

SessionMessagingKit/Utilities/FixedWidthInteger+BigEndian.swift

@@ -0,0 +1,13 @@
+
+
+internal extension FixedWidthInteger {
+
+    init?(fromBigEndianBytes bytes: [UInt8]) {
+        guard bytes.count == MemoryLayout<Self>.size else { return nil }
+        self = bytes.reduce(0) { ($0 << 8) | Self($1) }
+    }
+
+    var bigEndianBytes: [UInt8] {
+        return withUnsafeBytes(of: bigEndian) { [UInt8]($0) }
+    }
+}

SessionMessagingKit/Utilities/ProofOfWork.swift

@@ -0,0 +1,36 @@
+import SessionUtilities
+import SessionSnodeKit
+
+enum ProofOfWork {
+
+    /// A modified version of [Bitmessage's Proof of Work Implementation](https://bitmessage.org/wiki/Proof_of_work).
+    static func calculate(ttl: UInt64, publicKey: String, data: String) -> (timestamp: UInt64, base64EncodedNonce: String)? {
+        let nonceSize = MemoryLayout<UInt64>.size
+        // Get millisecond timestamp
+        let timestamp = NSDate.millisecondTimestamp()
+        // Construct payload
+        let payloadAsString = String(timestamp) + String(ttl) + publicKey + data
+        let payload = payloadAsString.bytes
+        // Calculate target
+        let numerator = UInt64.max
+        let difficulty = UInt64(SnodeAPI.powDifficulty)
+        let totalSize = UInt64(payload.count + nonceSize)
+        let ttlInSeconds = ttl / 1000
+        let denominator = difficulty * (totalSize + (ttlInSeconds * totalSize) / UInt64(UInt16.max))
+        let target = numerator / denominator
+        // Calculate proof of work
+        var value = UInt64.max
+        let payloadHash = payload.sha512()
+        var nonce = UInt64(0)
+        while value > target {
+            nonce = nonce &+ 1
+            let hash = (nonce.bigEndianBytes + payloadHash).sha512()
+            guard let newValue = UInt64(fromBigEndianBytes: [UInt8](hash[0..<nonceSize])) else { return nil }
+            value = newValue
+        }
+        // Encode as base 64
+        let base64EncodedNonce = nonce.bigEndianBytes.toBase64()!
+        // Return
+        return (timestamp, base64EncodedNonce)
+    }
+}

SessionSnodeKit/SnodeAPI.swift

@@ -18,10 +18,11 @@ public enum SnodeAPI {
     private static let snodeFailureThreshold = 4
     private static let targetSwarmSnodeCount = 2
 
-    internal static var powDifficulty: UInt = 1
     /// - Note: Changing this on the fly is not recommended.
     internal static var useOnionRequests = true
 
+    public static var powDifficulty: UInt = 1
+    
     // MARK: Error
     public enum Error : LocalizedError {
         case clockOutOfSync

Signal.xcodeproj/project.pbxproj

@@ -618,6 +618,8 @@
 		C3BBE0A82554D4DE0050F1E3 /* JSON.swift in Sources */ = {isa = PBXBuildFile; fileRef = C3C2A5D92553860B00C340D1 /* JSON.swift */; };
 		C3BBE0A92554D4DE0050F1E3 /* HTTP.swift in Sources */ = {isa = PBXBuildFile; fileRef = C3C2A5BC255385EE00C340D1 /* HTTP.swift */; };
 		C3BBE0AA2554D4DE0050F1E3 /* Dictionary+Description.swift in Sources */ = {isa = PBXBuildFile; fileRef = C3C2A5D52553860A00C340D1 /* Dictionary+Description.swift */; };
+		C3BBE0B52554F0E10050F1E3 /* ProofOfWork.swift in Sources */ = {isa = PBXBuildFile; fileRef = C3BBE0B42554F0E10050F1E3 /* ProofOfWork.swift */; };
+		C3BBE0C72554F1570050F1E3 /* FixedWidthInteger+BigEndian.swift in Sources */ = {isa = PBXBuildFile; fileRef = C3BBE0C62554F1570050F1E3 /* FixedWidthInteger+BigEndian.swift */; };
 		C3C2A5A3255385C100C340D1 /* SessionSnodeKit.h in Headers */ = {isa = PBXBuildFile; fileRef = C3C2A5A1255385C100C340D1 /* SessionSnodeKit.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		C3C2A5A6255385C100C340D1 /* SessionSnodeKit.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = C3C2A59F255385C100C340D1 /* SessionSnodeKit.framework */; };
 		C3C2A5A7255385C100C340D1 /* SessionSnodeKit.framework in Embed Frameworks */ = {isa = PBXBuildFile; fileRef = C3C2A59F255385C100C340D1 /* SessionSnodeKit.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
@@ -1609,6 +1611,8 @@
 		C3AECBEA24EF5244005743DE /* fa */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = fa; path = translations/fa.lproj/Localizable.strings; sourceTree = "<group>"; };
 		C3BBE0752554CDA60050F1E3 /* Configuration.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Configuration.swift; sourceTree = "<group>"; };
 		C3BBE07F2554CDD70050F1E3 /* Storage.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Storage.swift; sourceTree = "<group>"; };
+		C3BBE0B42554F0E10050F1E3 /* ProofOfWork.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ProofOfWork.swift; sourceTree = "<group>"; };
+		C3BBE0C62554F1570050F1E3 /* FixedWidthInteger+BigEndian.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "FixedWidthInteger+BigEndian.swift"; sourceTree = "<group>"; };
 		C3C2A59F255385C100C340D1 /* SessionSnodeKit.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = SessionSnodeKit.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		C3C2A5A1255385C100C340D1 /* SessionSnodeKit.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = SessionSnodeKit.h; sourceTree = "<group>"; };
 		C3C2A5A2255385C100C340D1 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
@@ -3243,6 +3247,15 @@
 			path = SwiftCSV;
 			sourceTree = "<group>";
 		};
+		C3BBE0B32554F0D30050F1E3 /* Utilities */ = {
+			isa = PBXGroup;
+			children = (
+				C3BBE0C62554F1570050F1E3 /* FixedWidthInteger+BigEndian.swift */,
+				C3BBE0B42554F0E10050F1E3 /* ProofOfWork.swift */,
+			);
+			path = Utilities;
+			sourceTree = "<group>";
+		};
 		C3C2A5A0255385C100C340D1 /* SessionSnodeKit */ = {
 			isa = PBXGroup;
 			children = (
@@ -3319,6 +3332,7 @@
 				C3BBE07F2554CDD70050F1E3 /* Storage.swift */,
 				C300A5BB2554AFFB00555489 /* Messages */,
 				C300A5F02554B08500555489 /* Pipelines */,
+				C3BBE0B32554F0D30050F1E3 /* Utilities */,
 			);
 			path = SessionMessagingKit;
 			sourceTree = "<group>";
@@ -4878,6 +4892,7 @@
 				C3C2A74D2553A39700C340D1 /* VisibleMessage.swift in Sources */,
 				C3C2A7562553A3AB00C340D1 /* VisibleMessage+Quote.swift in Sources */,
 				C300A5FC2554B0A000555489 /* ReceivingPipeline.swift in Sources */,
+				C3BBE0B52554F0E10050F1E3 /* ProofOfWork.swift in Sources */,
 				C3BBE0802554CDD70050F1E3 /* Storage.swift in Sources */,
 				C3C2A7842553AAF300C340D1 /* SNProto.swift in Sources */,
 				C3C2A7682553A3D900C340D1 /* VisibleMessage+Contact.swift in Sources */,
@@ -4890,6 +4905,7 @@
 				C3C2A75F2553A3C500C340D1 /* VisibleMessage+LinkPreview.swift in Sources */,
 				C3C2A74425539EB700C340D1 /* Message.swift in Sources */,
 				C300A5C92554B04E00555489 /* SessionRequest.swift in Sources */,
+				C3BBE0C72554F1570050F1E3 /* FixedWidthInteger+BigEndian.swift in Sources */,
 				C300A5B22554AF9800555489 /* VisibleMessage+Profile.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;