diff --git a/neo.UnitTests/SDK/UT_RpcClient.cs b/neo.UnitTests/SDK/UT_RpcClient.cs
index 91ec682af5..e76d8d3e2b 100644
--- a/neo.UnitTests/SDK/UT_RpcClient.cs
+++ b/neo.UnitTests/SDK/UT_RpcClient.cs
@@ -438,7 +438,7 @@ public void TestInvokeFunction()
             response["result"] = json;
             MockResponse(response.ToString());
 
-            var result = rpc.InvokeFunction("af7c7328eee5a275a3bcaee2bf0cf662b5e739be", "balanceOf", new[] { new SDK_StackJson { Type = "Hash160", Value = "91b83e96f2a7c4fdf0c1688441ec61986c7cae26" } });
+            var result = rpc.InvokeFunction("af7c7328eee5a275a3bcaee2bf0cf662b5e739be", "balanceOf", new[] { new SDK_Stack { Type = "Hash160", Value = "91b83e96f2a7c4fdf0c1688441ec61986c7cae26" } });
             Assert.AreEqual(json.ToString(), result.ToJson().ToString());
         }
 
diff --git a/neo.UnitTests/UT_FifoSet.cs b/neo.UnitTests/UT_FifoSet.cs
new file mode 100644
index 0000000000..ff5ccf9c27
--- /dev/null
+++ b/neo.UnitTests/UT_FifoSet.cs
@@ -0,0 +1,54 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Neo.IO.Caching;
+using System.Linq;
+
+namespace Neo.UnitTests
+{
+    [TestClass]
+    public class UT_FifoSet
+    {
+        [TestMethod]
+        public void FifoSetTest()
+        {
+            var a = UInt256.Zero;
+            var b = new UInt256();
+            var c = new UInt256(new byte[32] {
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x01
+            });
+
+            var set = new FIFOSet<UInt256>(3);
+
+            Assert.IsTrue(set.Add(a));
+            Assert.IsFalse(set.Add(a));
+            Assert.IsFalse(set.Add(b));
+            Assert.IsTrue(set.Add(c));
+
+            CollectionAssert.AreEqual(set.ToArray(), new UInt256[] { a, c });
+            
+            var d = new UInt256(new byte[32] {
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x02
+            });
+
+            // Testing Fifo max size
+            Assert.IsTrue(set.Add(d));
+            CollectionAssert.AreEqual(set.ToArray(), new UInt256[] { a, c, d });
+
+            var e = new UInt256(new byte[32] {
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+                0x01, 0x03
+            });
+
+            Assert.IsTrue(set.Add(e));
+            Assert.IsFalse(set.Add(e));
+            CollectionAssert.AreEqual(set.ToArray(), new UInt256[] { c, d, e });
+        }
+    }
+}
diff --git a/neo.UnitTests/UT_Transaction.cs b/neo.UnitTests/UT_Transaction.cs
index 18aafb31bb..5b06a816a5 100644
--- a/neo.UnitTests/UT_Transaction.cs
+++ b/neo.UnitTests/UT_Transaction.cs
@@ -12,6 +12,7 @@
 using Neo.VM;
 using Neo.Wallets;
 using Neo.Wallets.NEP6;
+using System.Threading.Tasks;
 
 namespace Neo.UnitTests
 {
@@ -104,8 +105,14 @@ public void FeeIsMultiSigContract()
             using (var unlockA = walletA.Unlock("123"))
             using (var unlockB = walletB.Unlock("123"))
             {
-                var a = walletA.CreateAccount();
-                var b = walletB.CreateAccount();
+                var ta = new Task<WalletAccount>(() => walletA.CreateAccount());
+                var tb = new Task<WalletAccount>(() => walletB.CreateAccount());
+                ta.Start();
+                tb.Start();
+                Task.WaitAll(ta, tb);
+
+                var a = ta.Result;
+                var b = tb.Result;
 
                 var multiSignContract = Contract.CreateMultiSigContract(2,
                     new ECPoint[]
@@ -114,8 +121,13 @@ public void FeeIsMultiSigContract()
                         b.GetKey().PublicKey
                     });
 
-                var acc = walletA.CreateAccount(multiSignContract, a.GetKey());
-                acc = walletB.CreateAccount(multiSignContract, b.GetKey());
+                ta = new Task<WalletAccount>(() => walletA.CreateAccount(multiSignContract, a.GetKey()));
+                tb = new Task<WalletAccount>(() => walletB.CreateAccount(multiSignContract, b.GetKey()));
+                ta.Start();
+                tb.Start();
+                Task.WaitAll(ta, tb);
+
+                var acc = tb.Result;
 
                 // Fake balance
 
diff --git a/neo/Cryptography/ECC/ECPoint.cs b/neo/Cryptography/ECC/ECPoint.cs
index 18b1cdab1a..dbd556eb50 100644
--- a/neo/Cryptography/ECC/ECPoint.cs
+++ b/neo/Cryptography/ECC/ECPoint.cs
@@ -112,11 +112,21 @@ public static ECPoint DeserializeFrom(BinaryReader reader, ECCurve curve)
             {
                 case 0x02:
                 case 0x03:
-                    reader.Read(buffer, 1, expectedLength);
-                    return DecodePoint(buffer.Take(1 + expectedLength).ToArray(), curve);
+                    {
+                        if (reader.Read(buffer, 1, expectedLength) != expectedLength)
+                        {
+                            throw new FormatException();
+                        }
+                        return DecodePoint(buffer.Take(1 + expectedLength).ToArray(), curve);
+                    }
                 case 0x04:
-                    reader.Read(buffer, 1, expectedLength * 2);
-                    return DecodePoint(buffer, curve);
+                    {
+                        if (reader.Read(buffer, 1, expectedLength * 2) != expectedLength * 2)
+                        {
+                            throw new FormatException();
+                        }
+                        return DecodePoint(buffer, curve);
+                    }
                 default:
                     throw new FormatException("Invalid point encoding " + buffer[0]);
             }
diff --git a/neo/IO/Caching/FIFOSet.cs b/neo/IO/Caching/FIFOSet.cs
index 6dd52dbccf..7769cb5ad5 100644
--- a/neo/IO/Caching/FIFOSet.cs
+++ b/neo/IO/Caching/FIFOSet.cs
@@ -51,7 +51,7 @@ public void ExceptWith(IEnumerable<UInt256> hashes)
 
         public IEnumerator<T> GetEnumerator()
         {
-            var entries = dictionary.Values.Cast<T>().ToArray();
+            var entries = dictionary.Keys.Cast<T>().ToArray();
             foreach (var entry in entries) yield return entry;
         }
 
diff --git a/neo/Ledger/MemoryPool.cs b/neo/Ledger/MemoryPool.cs
index 94f7ec9e0f..96e17dc34f 100644
--- a/neo/Ledger/MemoryPool.cs
+++ b/neo/Ledger/MemoryPool.cs
@@ -361,7 +361,8 @@ internal void UpdatePoolForBlockPersisted(Block block, Snapshot snapshot)
                 if (policyChanged)
                 {
                     foreach (PoolItem item in _unverifiedSortedTransactions.Reverse())
-                        _system.Blockchain.Tell(item.Tx, ActorRefs.NoSender);
+                        if(item.Tx.FeePerByte >= _feePerByte)
+                            _system.Blockchain.Tell(item.Tx, ActorRefs.NoSender);
                     _unverifiedTransactions.Clear();
                     _unverifiedSortedTransactions.Clear();
                 }
diff --git a/neo/Network/P2P/Payloads/Block.cs b/neo/Network/P2P/Payloads/Block.cs
index f83a3b6093..b5fe689059 100644
--- a/neo/Network/P2P/Payloads/Block.cs
+++ b/neo/Network/P2P/Payloads/Block.cs
@@ -107,10 +107,10 @@ public override JObject ToJson()
             return json;
         }
 
-        public static Block FromJson(JObject json)
+        public new static Block FromJson(JObject json)
         {
             Block block = new Block();
-            block.PraseFromJson(json);
+            (block as BlockBase).FromJson(json);
             block.ConsensusData = ConsensusData.FromJson(json["consensus_data"]);
             block.Transactions = ((JArray)json["tx"]).Select(p => Transaction.FromJson(p)).ToArray();
             return block;
diff --git a/neo/Network/P2P/Payloads/BlockBase.cs b/neo/Network/P2P/Payloads/BlockBase.cs
index 8fe545115c..b2b1bf3d67 100644
--- a/neo/Network/P2P/Payloads/BlockBase.cs
+++ b/neo/Network/P2P/Payloads/BlockBase.cs
@@ -104,7 +104,7 @@ public virtual JObject ToJson()
             return json;
         }
 
-        public void PraseFromJson(JObject json)
+        public void FromJson(JObject json)
         {
             Version = (uint)json["version"].AsNumber();
             PrevHash = UInt256.Parse(json["previousblockhash"].AsString());
diff --git a/neo/Network/P2P/Payloads/Header.cs b/neo/Network/P2P/Payloads/Header.cs
index e32b1a5daa..52639ee1fb 100644
--- a/neo/Network/P2P/Payloads/Header.cs
+++ b/neo/Network/P2P/Payloads/Header.cs
@@ -55,10 +55,10 @@ public TrimmedBlock Trim()
             };
         }
 
-        public static Header FromJson(JObject json)
+        public new static Header FromJson(JObject json)
         {
             Header header = new Header();
-            header.PraseFromJson(json);
+            (header as BlockBase).FromJson(json);
             return header;
         }
 
diff --git a/neo/SDK/RPC/HttpService.cs b/neo/SDK/RPC/HttpService.cs
index 7f5df397a7..6fa7069413 100644
--- a/neo/SDK/RPC/HttpService.cs
+++ b/neo/SDK/RPC/HttpService.cs
@@ -26,22 +26,23 @@ public void Dispose()
             httpClient?.Dispose();
         }
 
-        public async Task<JObject> SendAsync(RPCRequest request)
+        public async Task<RPCResponse> SendAsync(RPCRequest request)
         {
             var requestJson = request.ToJson().ToString();
             var result = await httpClient.PostAsync(httpClient.BaseAddress, new StringContent(requestJson, Encoding.UTF8));
             var content = await result.Content.ReadAsStringAsync();
             var response = RPCResponse.FromJson(JObject.Parse(content));
+            response.RawResponse = content;
 
             if (response.Error != null)
             {
                 throw new NeoSdkException(response.Error.Code, response.Error.Message, response.Error.Data);
             }
 
-            return response.Result;
+            return response;
         }
 
-        public JObject Send(RPCRequest request)
+        public RPCResponse Send(RPCRequest request)
         {
             try
             {
diff --git a/neo/SDK/RPC/IRpcClient.cs b/neo/SDK/RPC/IRpcClient.cs
index f62367cba4..a05afeb362 100644
--- a/neo/SDK/RPC/IRpcClient.cs
+++ b/neo/SDK/RPC/IRpcClient.cs
@@ -114,7 +114,7 @@ public interface IRpcClient
         /// Returns the result after calling a smart contract at scripthash with the given operation and parameters.
         /// This RPC call does not affect the blockchain in any way.
         /// </summary>
-        SDK_InvokeScriptResult InvokeFunction(string address, string function, SDK_StackJson[] stacks);
+        SDK_InvokeScriptResult InvokeFunction(string address, string function, SDK_Stack[] stacks);
 
         /// <summary>
         /// Returns the result after passing a script through the VM.
@@ -141,11 +141,6 @@ public interface IRpcClient
         /// Verifies that the address is a correct NEO address.
         /// </summary>
         SDK_ValidateAddressResult ValidateAddress(string address);
-
-        /// <summary>
-        /// Returns the balance of all NEP-5 assets in the specified address.
-        /// </summary>
-        SDK_Nep5Balances GetNep5Balances(string address);
-
+        
     }
 }
diff --git a/neo/SDK/RPC/Model/RPCResponse.cs b/neo/SDK/RPC/Model/RPCResponse.cs
index 402820f085..972e3bf829 100644
--- a/neo/SDK/RPC/Model/RPCResponse.cs
+++ b/neo/SDK/RPC/Model/RPCResponse.cs
@@ -8,13 +8,15 @@ namespace Neo.SDK.RPC.Model
     public class RPCResponse
     {
         public int? Id { get; set; }
-        
+
         public string Jsonrpc { get; set; }
-        
+
         public RPCResponseError Error { get; set; }
-        
+
         public JObject Result { get; set; }
 
+        public string RawResponse { get; set; }
+
         /// <summary>
         /// Parse from json
         /// </summary>
@@ -49,9 +51,9 @@ public JObject ToJson()
     public class RPCResponseError
     {
         public int Code { get; set; }
-        
+
         public string Message { get; set; }
-        
+
         public JObject Data { get; set; }
 
         /// <summary>
diff --git a/neo/SDK/RPC/Model/SDK_InvokeScriptResult.cs b/neo/SDK/RPC/Model/SDK_InvokeScriptResult.cs
index f24d5f1842..8d7ad87464 100644
--- a/neo/SDK/RPC/Model/SDK_InvokeScriptResult.cs
+++ b/neo/SDK/RPC/Model/SDK_InvokeScriptResult.cs
@@ -16,7 +16,7 @@ public class SDK_InvokeScriptResult
         public string GasConsumed { get; set; }
 
         [JsonProperty(PropertyName = "stack")]
-        public SDK_StackJson[] Stack { get; set; }
+        public SDK_Stack[] Stack { get; set; }
 
         [JsonProperty(PropertyName = "tx")]
         public string Tx { get; set; }
@@ -39,12 +39,12 @@ public static SDK_InvokeScriptResult FromJson(JObject json)
             invokeScriptResult.State = json["state"].AsString();
             invokeScriptResult.GasConsumed = json["gas_consumed"].AsString();
             invokeScriptResult.Tx = json["tx"].AsString();
-            invokeScriptResult.Stack = ((JArray)json["stack"]).Select(p => SDK_StackJson.FromJson(p)).ToArray();
+            invokeScriptResult.Stack = ((JArray)json["stack"]).Select(p => SDK_Stack.FromJson(p)).ToArray();
             return invokeScriptResult;
         }
     }
 
-    public class SDK_StackJson
+    public class SDK_Stack
     {
         public string Type { get; set; }
         
@@ -58,9 +58,9 @@ public JObject ToJson()
             return json;
         }
 
-        public static SDK_StackJson FromJson(JObject json)
+        public static SDK_Stack FromJson(JObject json)
         {
-            SDK_StackJson stackJson = new SDK_StackJson();
+            SDK_Stack stackJson = new SDK_Stack();
             stackJson.Type = json["type"].AsString();
             stackJson.Value = json["value"].AsString();
             return stackJson;
diff --git a/neo/SDK/RPC/RpcClient.cs b/neo/SDK/RPC/RpcClient.cs
index 1d9ef4ef55..ed35c69fb7 100644
--- a/neo/SDK/RPC/RpcClient.cs
+++ b/neo/SDK/RPC/RpcClient.cs
@@ -33,7 +33,7 @@ private JObject RpcSend(string method, params JObject[] paraArgs)
                 Method = method,
                 Params = paraArgs.Select(p => p).ToArray()
             };
-            return rpcHelper.Send(request);
+            return rpcHelper.Send(request).Result;
         }
 
         public string GetBestBlockHash()
@@ -148,7 +148,7 @@ public SDK_Version GetVersion()
             return SDK_Version.FromJson(RpcSend("getversion"));
         }
 
-        public SDK_InvokeScriptResult InvokeFunction(string address, string function, SDK_StackJson[] stacks)
+        public SDK_InvokeScriptResult InvokeFunction(string address, string function, SDK_Stack[] stacks)
         {
             return SDK_InvokeScriptResult.FromJson(RpcSend("invokefunction", address, function, stacks.Select(p => p.ToJson()).ToArray()));
         }
@@ -178,10 +178,5 @@ public SDK_ValidateAddressResult ValidateAddress(string address)
             return SDK_ValidateAddressResult.FromJson(RpcSend("validateaddress", address));
         }
 
-        public SDK_Nep5Balances GetNep5Balances(string address)
-        {
-            return SDK_Nep5Balances.FromJson(RpcSend("getnep5balances", address));
-        }
-
     }
 }
diff --git a/neo/UIntBase.cs b/neo/UIntBase.cs
index 3808001022..22431c4cae 100644
--- a/neo/UIntBase.cs
+++ b/neo/UIntBase.cs
@@ -5,7 +5,6 @@
 
 namespace Neo
 {
-
     /// <summary>
     /// Base class for little-endian unsigned integers. Two classes inherit from this: UInt160 and UInt256.
     /// Only basic comparison/serialization are proposed for these classes. For arithmetic purposes, use BigInteger class.
@@ -15,7 +14,7 @@ public abstract class UIntBase : IEquatable<UIntBase>, ISerializable
         /// <summary>
         /// Storing unsigned int in a little-endian byte array.
         /// </summary>
-        private byte[] data_bytes;
+        private readonly byte[] data_bytes;
 
         /// <summary>
         /// Number of bytes of the unsigned int.
@@ -44,7 +43,10 @@ protected UIntBase(int bytes, byte[] value)
         /// </summary>
         void ISerializable.Deserialize(BinaryReader reader)
         {
-            reader.Read(data_bytes, 0, data_bytes.Length);
+            if (reader.Read(data_bytes, 0, data_bytes.Length) != data_bytes.Length)
+            {
+                throw new FormatException();
+            }
         }
 
         /// <summary>
@@ -53,7 +55,7 @@ void ISerializable.Deserialize(BinaryReader reader)
         /// </summary>
         public bool Equals(UIntBase other)
         {
-            if (ReferenceEquals(other, null))
+            if (other is null)
                 return false;
             if (ReferenceEquals(this, other))
                 return true;
@@ -68,7 +70,7 @@ public bool Equals(UIntBase other)
         /// </summary>
         public override bool Equals(object obj)
         {
-            if (ReferenceEquals(obj, null))
+            if (obj is null)
                 return false;
             if (!(obj is UIntBase))
                 return false;