diff --git a/SignalServiceKit/src/Loki/API/LokiGroupChatAPI.swift b/SignalServiceKit/src/Loki/API/LokiGroupChatAPI.swift
index 5309235d9..b2b73a98f 100644
--- a/SignalServiceKit/src/Loki/API/LokiGroupChatAPI.swift
+++ b/SignalServiceKit/src/Loki/API/LokiGroupChatAPI.swift
@@ -13,25 +13,41 @@ public final class LokiGroupChatAPI : NSObject {
         return SSKEnvironment.shared.contactsManager.displayName(forPhoneIdentifier: userHexEncodedPublicKey) ?? "Anonymous"
     }
     
+    internal static var identityKeyPair: ECKeyPair {
+        return OWSIdentityManager.shared().identityKeyPair()!
+    }
+    
     private static var userHexEncodedPublicKey: String {
-        return OWSIdentityManager.shared().identityKeyPair()!.hexEncodedPublicKey
+        return identityKeyPair.hexEncodedPublicKey
     }
     
+    
     public enum Error : Swift.Error {
-        case tokenParsingFailed, messageParsingFailed
+        case tokenParsingFailed, tokenDecryptionFailed, messageParsingFailed
     }
     
-    public static func getEncryptedToken() -> Promise<String> {
+    public static func fetchToken() -> Promise<String> {
         print("[Loki] Getting group chat auth token.")
-        let url = URL(string: "\(serverURL)/loki/v1/getToken")!
-        let parameters = [ "pubKey" : userHexEncodedPublicKey ]
-        let request = TSRequest(url: url, method: "POST", parameters: parameters)
+        let url = URL(string: "\(serverURL)/loki/v1/get_challenge?pubKey=\(userHexEncodedPublicKey)")!
+        let request = TSRequest(url: url)
         return TSNetworkManager.shared().makePromise(request: request).map { $0.responseObject }.map { rawResponse in
-            guard let json = rawResponse as? JSON, let encryptedToken = json["cipherText64"] as? String else { throw Error.tokenParsingFailed }
-            return encryptedToken
+            guard let json = rawResponse as? JSON, let cipherText64 = json["cipherText64"] as? String, let nonce64 = json["nonce64"] as? String, let serverPubKey64 = json["serverPubKey64"] as? String, let cipherText = Data(base64Encoded: cipherText64), let nonce = Data(base64Encoded: nonce64), let serverPubKey = Data(base64Encoded: serverPubKey64) else { throw Error.tokenParsingFailed }
+            
+            let ivAndCipher = nonce + cipherText
+            guard let tokenData = try? DiffieHellman.decrypt(cipherText: ivAndCipher, publicKey: serverPubKey, privateKey: identityKeyPair.privateKey) else { throw Error.tokenDecryptionFailed }
+            
+            return tokenData.base64EncodedString()
         }
     }
     
+    public static func submitToken(_ token: String) -> Promise<Void> {
+        print("[Loki] Submitting group chat auth token.")
+        let url = URL(string: "\(serverURL)/loki/v1/submit_challenge")!
+        let parameters = [ "pubKey" : userHexEncodedPublicKey, "token" : token ]
+        let request = TSRequest(url: url, method: "POST", parameters: parameters)
+        return TSNetworkManager.shared().makePromise(request: request).asVoid()
+    }
+    
     public static func getMessages(for group: UInt) -> Promise<[LokiGroupMessage]> {
         print("[Loki] Getting messages for group chat with ID: \(group).")
         let queryParameters = "include_annotations=1&count=-\(batchCount)"
diff --git a/SignalServiceKit/src/Loki/Crypto/FallbackSessionCipher.swift b/SignalServiceKit/src/Loki/Crypto/FallbackSessionCipher.swift
index 336bdc4a6..e1d92c587 100644
--- a/SignalServiceKit/src/Loki/Crypto/FallbackSessionCipher.swift
+++ b/SignalServiceKit/src/Loki/Crypto/FallbackSessionCipher.swift
@@ -72,7 +72,7 @@ private extension String {
     @objc public func encrypt(message: Data) -> Data? {
         guard let symmetricKey = symmetricKey else { return nil }
         do {
-            return try diffieHellmanEncrypt(plainText: message, symmetricKey: symmetricKey)
+            return try DiffieHellman.encrypt(plainText: message, symmetricKey: symmetricKey)
         } catch {
             Logger.warn("FallBackSessionCipher: Failed to encrypt message")
             return nil
@@ -86,38 +86,10 @@ private extension String {
     @objc public func decrypt(message: Data) -> Data? {
         guard let symmetricKey = symmetricKey else { return nil }
         do {
-            return try diffieHellmanDecrypt(cipherText: message, symmetricKey: symmetricKey)
+            return try DiffieHellman.decrypt(cipherText: message, symmetricKey: symmetricKey)
         } catch {
             Logger.warn("FallBackSessionCipher: Failed to decrypt message")
             return nil
         }
     }
-    
-    // Encypt the message with the symmetric key and a 16 bit iv
-    private func diffieHellmanEncrypt(plainText: Data, symmetricKey: Data) throws -> Data {
-        let iv = Randomness.generateRandomBytes(ivLength)!
-        let ivBytes = [UInt8](iv)
-        
-        let symmetricKeyBytes = [UInt8](symmetricKey)
-        let messageBytes = [UInt8](plainText)
-        
-        let blockMode = CBC(iv: ivBytes)
-        let aes = try AES(key: symmetricKeyBytes, blockMode: blockMode)
-        let cipherText = try aes.encrypt(messageBytes)
-        let ivAndCipher = ivBytes + cipherText
-        return Data(bytes: ivAndCipher, count: ivAndCipher.count)
-    }
-    
-    // Decrypt the message with the symmetric key
-    private func diffieHellmanDecrypt(cipherText: Data, symmetricKey: Data) throws -> Data {
-        let symmetricKeyBytes = [UInt8](symmetricKey)
-        let ivBytes = [UInt8](cipherText[..<ivLength])
-        let cipherBytes = [UInt8](cipherText[ivLength...])
-        
-        let blockMode = CBC(iv: ivBytes)
-        let aes = try AES(key: symmetricKeyBytes, blockMode: blockMode)
-        let decrypted = try aes.decrypt(cipherBytes)
-        
-        return Data(bytes: decrypted, count: decrypted.count)
-    }
 }