diff --git a/ArcFormats/ArcNitro.cs b/ArcFormats/ArcNitro.cs
new file mode 100644
index 00000000..0e4a3e84
--- /dev/null
+++ b/ArcFormats/ArcNitro.cs
@@ -0,0 +1,151 @@
+//! \file       ArcNitro.cs
+//! \date       Wed Feb 25 20:28:14 2015
+//! \brief      Nitro+ PAK archives implementation.
+//
+// Copyright (C) 2015 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.IO;
+using System.Text;
+using GameRes.Utility;
+using ZLibNet;
+
+namespace GameRes.Formats.NitroPlus
+{
+    internal class PakEntry : Entry
+    {
+        public uint Key;
+    }
+
+    [Export(typeof(ArchiveFormat))]
+    public class PakOpener : ArchiveFormat
+    {
+        public override string         Tag { get { return "NITRO+/PAK"; } }
+        public override string Description { get { return "Nitro+ resource archive"; } }
+        public override uint     Signature { get { return 0x03; } }
+        public override bool  IsHierarchic { get { return false; } }
+        public override bool     CanCreate { get { return false; } }
+
+        public PakOpener ()
+        {
+            Extensions = new string[] { "pak" };
+        }
+
+        public override ArcFile TryOpen (ArcView file)
+        {
+            byte[] name_buf = new byte[0x100];
+            if (0x110 > file.View.Reserve (4, 0x110))
+                return null;
+
+            uint size_xor = file.View.ReadUInt32 (0x104);
+            if (0x64 != size_xor)
+                return null;
+            file.View.Read (4, name_buf, 0, 0x100);
+            int name_len = 0;
+            for (int i = 0; i < name_buf.Length; ++i)
+            {
+                if (0 == name_buf[i])
+                    break;
+                if (name_buf[i] >= 0x80 || name_buf[i] < 0x20)
+                    return null;
+                ++name_len;
+            }
+            if (0 == name_len || name_len > 0x10)
+                return null;
+
+            uint header_key = GetKey (name_buf, name_len);
+            uint unpacked = file.View.ReadUInt32 (0x108) ^ header_key;
+            int count = (int)(file.View.ReadUInt32 (0x10c) ^ header_key);
+            if (count <= 0 || count > 0xfffff)
+                return null;
+
+            var dir = new List<Entry> (count);
+            uint header_size = file.View.ReadUInt32 (0x110) ^ size_xor;
+            long base_offset = 0x114 + header_size;
+            var input = file.CreateStream (0x114, header_size);
+            using (var header_stream = new ZLibStream (input, CompressionMode.Decompress))
+            using (var header = new BinaryReader (header_stream, Encoding.ASCII, true))
+            {
+                for (int i = 0; i < count; ++i)
+                {
+                    name_len = header.ReadInt32();
+                    if (name_len <= 0 || name_len > name_buf.Length)
+                        return null;
+                    if (name_len != header.Read (name_buf, 0, name_len))
+                        return null;
+                    uint key = GetKey (name_buf, name_len);
+                    uint offset = header.ReadUInt32() ^ key;
+                    uint size = header.ReadUInt32() ^ key;
+                    uint val1 = header.ReadUInt32() ^ key;
+                    uint val2 = header.ReadUInt32() ^ key;
+                    uint val3 = header.ReadUInt32() ^ key;
+
+                    var entry = new PakEntry {
+                        Name        = Encodings.cp932.GetString (name_buf, 0, name_len),
+                        Offset      = base_offset+offset,
+                        Size        = size,
+                        Key         = key,
+                    };
+                    if (!entry.CheckPlacement (file.MaxOffset))
+                        return null;
+                    entry.Type = FormatCatalog.Instance.GetTypeFromName (entry.Name);
+                    dir.Add (entry);
+                }
+                return new ArcFile (file, this, dir);
+            }
+        }
+
+        static uint GetKey (byte[] name, int length)
+        {
+            int key = 0;
+            for (int i = 0; i < length; ++i)
+            {
+                key *= 0x89;
+                key += (sbyte)name[i];
+            }
+            return (uint)key;
+        }
+
+        public override Stream OpenEntry (ArcFile arc, Entry entry)
+        {
+            var pak_entry = entry as PakEntry;
+            if (null == pak_entry)
+                return arc.File.CreateStream (entry.Offset, entry.Size);
+            uint enc_size = Math.Min (entry.Size, 0x10u);
+            if (0 == enc_size)
+                return Stream.Null;
+            var buf = new byte[enc_size];
+            arc.File.View.Read (entry.Offset, buf, 0, enc_size);
+            uint key = pak_entry.Key;
+            for (int i = 0; i < buf.Length; ++i)
+            {
+                buf[i] ^= (byte)key;
+                key = key >> 8 | key << 24;
+            }
+            if (enc_size == entry.Size)
+                return new MemoryStream (buf, false);
+            return new RenPy.RpaStream (buf, arc.File.CreateStream (entry.Offset+enc_size, entry.Size-enc_size));
+        }
+    }
+}