diff --git a/libsignal-protocol-dotnet/DecryptionCallback.cs b/libsignal-protocol-dotnet/DecryptionCallback.cs
index b72b20d..d974872 100644
--- a/libsignal-protocol-dotnet/DecryptionCallback.cs
+++ b/libsignal-protocol-dotnet/DecryptionCallback.cs
@@ -1,24 +1,25 @@
-/** 
- * Copyright (C) 2016 smndtrl, langboost
- * 
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- * 
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
+using libsignal.state;
+using System.Threading.Tasks;
+/** 
+* Copyright (C) 2016 smndtrl, langboost
+* 
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+* 
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
 namespace libsignal
 {
     public interface DecryptionCallback
     {
-        void handlePlaintext(byte[] plaintext);
+        Task handlePlaintext(byte[] plaintext, SessionRecord sessionRecord);
     }
 }
diff --git a/libsignal-protocol-dotnet/SessionCipher.cs b/libsignal-protocol-dotnet/SessionCipher.cs
index 36f9977..c4edef1 100644
--- a/libsignal-protocol-dotnet/SessionCipher.cs
+++ b/libsignal-protocol-dotnet/SessionCipher.cs
@@ -24,6 +24,7 @@
 using Strilanc.Value;
 using System;
 using System.Collections.Generic;
+using System.Threading.Tasks;
 
 namespace libsignal
 {
@@ -141,7 +142,9 @@ public CiphertextMessage encrypt(byte[] paddedMessage)
          */
         public byte[] decrypt(PreKeySignalMessage ciphertext)
         {
-            return decrypt(ciphertext, new NullDecryptionCallback());
+            var tsk = (decrypt(ciphertext, new NullDecryptionCallback()));
+            tsk.Wait();
+            return tsk.Result;
         }
 
         /**
@@ -165,7 +168,7 @@ public byte[] decrypt(PreKeySignalMessage ciphertext)
          * @throws InvalidKeyException when the message is formatted incorrectly.
          * @throws UntrustedIdentityException when the {@link IdentityKey} of the sender is untrusted.
          */
-        public byte[] decrypt(PreKeySignalMessage ciphertext, DecryptionCallback callback)
+        public Task<byte[]> decrypt(PreKeySignalMessage ciphertext, DecryptionCallback callback)
         {
             lock (SESSION_LOCK)
             {
@@ -175,7 +178,7 @@ public byte[] decrypt(PreKeySignalMessage ciphertext, DecryptionCallback callbac
 
                 identityKeyStore.SaveIdentity(remoteAddress, sessionRecord.getSessionState().getRemoteIdentityKey());
 
-                callback.handlePlaintext(plaintext);
+                callback.handlePlaintext(plaintext, sessionRecord).Wait();
 
                 sessionStore.StoreSession(remoteAddress, sessionRecord);
 
@@ -184,7 +187,7 @@ public byte[] decrypt(PreKeySignalMessage ciphertext, DecryptionCallback callbac
                     preKeyStore.RemovePreKey(unsignedPreKeyId.ForceGetValue());
                 }
 
-                return plaintext;
+                return Task.FromResult(plaintext);
             }
         }
 
@@ -202,7 +205,9 @@ public byte[] decrypt(PreKeySignalMessage ciphertext, DecryptionCallback callbac
          */
         public byte[] decrypt(SignalMessage ciphertext)
         {
-            return decrypt(ciphertext, new NullDecryptionCallback());
+            var tsk = decrypt(ciphertext, new NullDecryptionCallback());
+            tsk.Wait();
+            return tsk.Result;
         }
 
         /**
@@ -223,7 +228,7 @@ public byte[] decrypt(SignalMessage ciphertext)
          *                                is no longer supported.
          * @throws NoSessionException if there is no established session for this contact.
          */
-        public byte[] decrypt(SignalMessage ciphertext, DecryptionCallback callback)
+        public Task<byte[]> decrypt(SignalMessage ciphertext, DecryptionCallback callback)
         {
             lock (SESSION_LOCK)
             {
@@ -241,11 +246,11 @@ public byte[] decrypt(SignalMessage ciphertext, DecryptionCallback callback)
                     throw new UntrustedIdentityException(remoteAddress.Name, sessionRecord.getSessionState().getRemoteIdentityKey());
                 }
 
-                callback.handlePlaintext(plaintext);
+                callback.handlePlaintext(plaintext, sessionRecord).Wait();//no async in a lock
 
                 sessionStore.StoreSession(remoteAddress, sessionRecord);
 
-                return plaintext;
+                return Task.FromResult(plaintext);
             }
         }
 
@@ -425,7 +430,7 @@ private byte[] getPlaintext(MessageKeys messageKeys, byte[] cipherText)
         private class NullDecryptionCallback : DecryptionCallback
         {
 
-            public void handlePlaintext(byte[] plaintext) { }
+            public Task handlePlaintext(byte[] plaintext, SessionRecord sessionRecord) => Task.CompletedTask;
         }
     }
 }
diff --git a/libsignal-protocol-dotnet/groups/GroupCipher.cs b/libsignal-protocol-dotnet/groups/GroupCipher.cs
index 8c0f977..f7de31d 100644
--- a/libsignal-protocol-dotnet/groups/GroupCipher.cs
+++ b/libsignal-protocol-dotnet/groups/GroupCipher.cs
@@ -18,8 +18,10 @@
 using libsignal.groups.ratchet;
 using libsignal.groups.state;
 using libsignal.protocol;
+using libsignal.state;
 using libsignal.util;
 using System;
+using System.Threading.Tasks;
 
 namespace libsignal.groups
 {
@@ -134,7 +136,7 @@ public byte[] decrypt(byte[] senderKeyMessageBytes, DecryptionCallback callback)
 
                     byte[] plaintext = getPlainText(senderKey.getIv(), senderKey.getCipherKey(), senderKeyMessage.getCipherText());
 
-                    callback.handlePlaintext(plaintext);
+                    callback.handlePlaintext(plaintext, null).Wait();
 
                     senderKeyStore.storeSenderKey(senderKeyId, record);
 
@@ -217,8 +219,9 @@ private byte[] getCipherText(byte[] iv, byte[] key, byte[] plaintext)
 
         private  class NullDecryptionCallback : DecryptionCallback
         {
-            public void handlePlaintext(byte[] plaintext) { }
-        }
+			public Task handlePlaintext(byte[] plaintext, SessionRecord sessionRecord) => Task.CompletedTask;
+
+		}
 
     }
 }