diff --git a/hactoolnet/Program.cs b/hactoolnet/Program.cs
index f1b2805d..203a1e8f 100644
--- a/hactoolnet/Program.cs
+++ b/hactoolnet/Program.cs
@@ -30,7 +30,7 @@ namespace hactoolnet
         static void ReadNca()
         {
             var keyset = ExternalKeys.ReadKeyFile("keys.txt", "titlekeys.txt");
-            using (var file = new FileStream("bf8b106a2e68df3c3f1694636423585a.nca", FileMode.Open, FileAccess.Read))
+            using (var file = new FileStream("671d172e7993ee033d1be25ee76378e3.nca", FileMode.Open, FileAccess.Read))
             {
                 var nca = new Nca(keyset, file, false);
                 var romfs = nca.OpenSection(0, false);
@@ -107,7 +107,7 @@ namespace hactoolnet
                 {
                     Console.WriteLine($"      {nca.HasRightsId} {nca.NcaId} {nca.Header.ContentType}");
 
-                    foreach (var sect in nca.Sections)
+                    foreach (var sect in nca.Sections.Where(x => x != null))
                     {
                         Console.WriteLine($"        {sect.SectionNum} {sect.Type} {sect.Header.CryptType} {sect.SuperblockHashValidity}");
                     }
diff --git a/libhac/Nca.cs b/libhac/Nca.cs
index 36bea252..0149b0df 100644
--- a/libhac/Nca.cs
+++ b/libhac/Nca.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Generic;
 using System.IO;
 using System.Security.Cryptography;
 using libhac.XTSSharp;
@@ -17,7 +16,7 @@ namespace libhac
         public Stream Stream { get; private set; }
         private bool KeepOpen { get; }
 
-        public List<NcaSection> Sections = new List<NcaSection>();
+        public NcaSection[] Sections { get; } = new NcaSection[4];
 
         public Nca(Keyset keyset, Stream stream, bool keepOpen)
         {
@@ -47,14 +46,14 @@ namespace libhac
             {
                 var section = ParseSection(i);
                 if (section == null) continue;
-                Sections.Add(section);
+                Sections[i] = section;
                 ValidateSuperblockHash(i);
             }
         }
 
         public Stream OpenSection(int index, bool raw)
         {
-            if (index >= Sections.Count) throw new ArgumentOutOfRangeException(nameof(index));
+            if (Sections[index] == null) throw new ArgumentOutOfRangeException(nameof(index));
             var sect = Sections[index];
 
             long offset = sect.Offset;
@@ -83,7 +82,7 @@ namespace libhac
             switch (sect.Header.CryptType)
             {
                 case SectionCryptType.None:
-                    break;
+                    return new SubStream(Stream, offset, size);
                 case SectionCryptType.XTS:
                     break;
                 case SectionCryptType.CTR:
@@ -144,7 +143,7 @@ namespace libhac
 
         private void ValidateSuperblockHash(int index)
         {
-            if (index >= Sections.Count) throw new ArgumentOutOfRangeException(nameof(index));
+            if (Sections[index] == null) throw new ArgumentOutOfRangeException(nameof(index));
             var sect = Sections[index];
             var stream = OpenSection(index, true);
 
@@ -164,6 +163,10 @@ namespace libhac
                     size = pfs0.HashTableSize;
                     break;
                 case SectionType.Romfs:
+                    var ivfc = sect.Header.Romfs.IvfcHeader;
+                    expected = ivfc.MasterHash;
+                    offset = (long)ivfc.LevelHeaders[0].LogicalOffset;
+                    size = 1 << (int)ivfc.LevelHeaders[0].BlockSize;
                     break;
                 case SectionType.Bktr:
                     break;
diff --git a/libhac/NcaStructs.cs b/libhac/NcaStructs.cs
index eafa0666..0b26eae6 100644
--- a/libhac/NcaStructs.cs
+++ b/libhac/NcaStructs.cs
@@ -101,6 +101,7 @@ namespace libhac
 
         public NcaFsHeader(BinaryReader reader)
         {
+            var start = reader.BaseStream.Position;
             Field0 = reader.ReadByte();
             Field1 = reader.ReadByte();
             PartitionType = (SectionPartitionType)reader.ReadByte();
@@ -128,7 +129,7 @@ namespace libhac
             }
 
             Ctr = reader.ReadBytes(8).Reverse().ToArray();
-            reader.BaseStream.Position += 184;
+            reader.BaseStream.Position = start + 512;
         }
     }
 
diff --git a/libhac/Substream.cs b/libhac/Substream.cs
new file mode 100644
index 00000000..a46e8872
--- /dev/null
+++ b/libhac/Substream.cs
@@ -0,0 +1,75 @@
+using System;
+using System.IO;
+
+namespace libhac
+{
+    public class SubStream : Stream
+    {
+        private Stream BaseStream { get; }
+        private long Offset { get; }
+
+        public SubStream(Stream baseStream, long offset, long length)
+        {
+            if (baseStream == null) throw new ArgumentNullException(nameof(baseStream));
+            if (offset < 0) throw new ArgumentOutOfRangeException(nameof(offset));
+            if (!baseStream.CanSeek || !baseStream.CanRead) throw new NotSupportedException();
+
+            BaseStream = baseStream;
+            Length = length;
+            Offset = offset;
+
+            baseStream.Seek(offset, SeekOrigin.Current);
+        }
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            long remaining = Length - Position;
+            if (remaining <= 0) return 0;
+            if (remaining < count) count = (int)remaining;
+            return BaseStream.Read(buffer, offset, count);
+        }
+
+        public override long Length { get; }
+        public override bool CanRead => BaseStream.CanRead;
+        public override bool CanWrite => BaseStream.CanWrite;
+        public override bool CanSeek => BaseStream.CanSeek;
+
+        public override long Position
+        {
+            get => BaseStream.Position - Offset;
+            set
+            {
+                if (value < 0 || value >= Length)
+                    throw new ArgumentOutOfRangeException(nameof(value));
+
+                BaseStream.Position = Offset + value;
+            }
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            switch (origin)
+            {
+                case SeekOrigin.Begin:
+                    Position = offset;
+                    break;
+                case SeekOrigin.Current:
+                    Position += offset;
+                    break;
+                case SeekOrigin.End:
+                    Position = Length - offset;
+                    break;
+            }
+
+            return Position;
+        }
+
+        public override void SetLength(long value) => throw new NotSupportedException();
+
+        public override void Flush() => BaseStream.Flush();
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}