diff --git a/SignalServiceKit/src/Loki/LokiMessage.swift b/SignalServiceKit/src/Loki/LokiMessage.swift
index e937802ef..af065008b 100644
--- a/SignalServiceKit/src/Loki/LokiMessage.swift
+++ b/SignalServiceKit/src/Loki/LokiMessage.swift
@@ -7,12 +7,12 @@ public struct LokiMessage {
     let data: LosslessStringConvertible
     /// The time to live for the message.
     let ttl: UInt64
-    /// When the proof of work was calculated.
-    let timestamp: UInt64
-    /// The base 64 encoded proof of work.
-    let nonce: String
+    /// When the proof of work was calculated, if applicable.
+    let timestamp: UInt64?
+    /// The base 64 encoded proof of work, if applicable.
+    let nonce: String?
     
-    public init(destination: String, data: LosslessStringConvertible, ttl: UInt64, timestamp: UInt64, nonce: String) {
+    public init(destination: String, data: LosslessStringConvertible, ttl: UInt64, timestamp: UInt64?, nonce: String?) {
         self.destination = destination
         self.data = data
         self.ttl = ttl
@@ -20,30 +20,34 @@ public struct LokiMessage {
         self.nonce = nonce
     }
     
-    public static func fromSignalMessage(_ signalMessage: SignalMessage) -> Promise<LokiMessage> {
+    public static func fromSignalMessage(_ signalMessage: SignalMessage, requiringPOW isPOWRequired: Bool) -> Promise<LokiMessage> {
         return Promise<LokiMessage> { seal in
             DispatchQueue.global(qos: .default).async {
                 let destination = signalMessage["destination"]!
                 let data = signalMessage["content"]!
                 let ttl = LokiMessagingAPI.defaultTTL
-                let timestamp = UInt64(Date().timeIntervalSince1970)
-                if let nonce = ProofOfWork.calculate(data: data, pubKey: destination, timestamp: timestamp, ttl: Int(ttl)) {
-                    let result = LokiMessage(destination: destination, data: data, ttl: ttl, timestamp: timestamp, nonce: nonce)
-                    seal.fulfill(result)
+                if isPOWRequired {
+                    let timestamp = UInt64(Date().timeIntervalSince1970)
+                    if let nonce = ProofOfWork.calculate(data: data, pubKey: destination, timestamp: timestamp, ttl: Int(ttl)) {
+                        let result = LokiMessage(destination: destination, data: data, ttl: ttl, timestamp: timestamp, nonce: nonce)
+                        seal.fulfill(result)
+                    } else {
+                        seal.reject(LokiMessagingAPI.Error.proofOfWorkCalculationFailed)
+                    }
                 } else {
-                    seal.reject(LokiMessagingAPI.Error.proofOfWorkCalculationFailed)
+                    let result = LokiMessage(destination: destination, data: data, ttl: ttl, timestamp: nil, nonce: nil)
+                    seal.fulfill(result)
                 }
             }
         }
     }
     
     public func toJSON() -> [String:String] {
-        return [
-            "destination" : destination,
-            "data" : data.description,
-            "ttl" : String(ttl),
-            "timestamp" : String(timestamp),
-            "nonce" : nonce
-        ]
+        var result = [ "destination" : destination, "data" : data.description, "ttl" : String(ttl) ]
+        if let timestamp = timestamp, let nonce = nonce {
+            result["timestamp"] = String(timestamp)
+            result["nonce"] = nonce
+        }
+        return result
     }
 }
diff --git a/SignalServiceKit/src/Loki/LokiMessagingAPI.swift b/SignalServiceKit/src/Loki/LokiMessagingAPI.swift
index 668e31755..e221d785e 100644
--- a/SignalServiceKit/src/Loki/LokiMessagingAPI.swift
+++ b/SignalServiceKit/src/Loki/LokiMessagingAPI.swift
@@ -35,8 +35,8 @@ import PromiseKit
         return TSNetworkManager.shared().makePromise(request: request)
     }
     
-    public static func sendSignalMessage(_ signalMessage: SignalMessage, to destination: String) -> Promise<RawResponse> {
-        return LokiMessage.fromSignalMessage(signalMessage).then(sendMessage)
+    public static func sendSignalMessage(_ signalMessage: SignalMessage, to destination: String, requiringPOW isPOWRequired: Bool) -> Promise<RawResponse> {
+        return LokiMessage.fromSignalMessage(signalMessage, requiringPOW: isPOWRequired).then(sendMessage)
     }
     
     public static func sendMessage(_ lokiMessage: LokiMessage) -> Promise<RawResponse> {
@@ -52,7 +52,7 @@ import PromiseKit
     }
     
     // MARK: Obj-C API
-    @objc public static func sendSignalMessage(_ signalMessage: SignalMessage, to destination: String, completionHandler: @escaping (Any?, NSError?) -> Void) {
-        sendSignalMessage(signalMessage, to: destination).done { completionHandler($0.responseObject, nil) }.catch { completionHandler(nil, $0 as NSError) }
+    @objc public static func sendSignalMessage(_ signalMessage: SignalMessage, to destination: String, requiringPOW isPOWRequired: Bool, completionHandler: @escaping (Any?, NSError?) -> Void) {
+        sendSignalMessage(signalMessage, to: destination, requiringPOW: isPOWRequired).done { completionHandler($0.responseObject, nil) }.catch { completionHandler(nil, $0 as NSError) }
     }
 }