diff --git a/NDecrypt.Core/CommonOperations.cs b/NDecrypt.Core/CommonOperations.cs
index 2ce0d35..231f589 100644
--- a/NDecrypt.Core/CommonOperations.cs
+++ b/NDecrypt.Core/CommonOperations.cs
@@ -134,9 +134,10 @@ namespace NDecrypt.Core
         /// <param name="input">Byte array to add to</param>
         /// <param name="add">Amount to add</param>
         /// <returns>Byte array representing the new value</returns>
-        public static byte[] Add(byte[] input, int add)
+        public static byte[] Add(byte[] input, uint add)
         {
             byte[] addBytes = BitConverter.GetBytes(add);
+            Array.Reverse(addBytes);
             byte[] paddedBytes = new byte[16];
             Array.Copy(addBytes, 0, paddedBytes, 12, 4);
             return Add(input, paddedBytes);
@@ -155,10 +156,10 @@ namespace NDecrypt.Core
 
             byte[] output = new byte[outLength];
 
-            int carry = 0;
+            uint carry = 0;
             for (int i = 0; i < addBytes; i++)
             {
-                int addValue = left[i] + right[i] + carry;
+                uint addValue = (uint)(left[i] + right[i] + carry);
                 output[i] = (byte)addValue;
                 carry = addValue > byte.MaxValue ? byte.MaxValue - addValue : 0;
             }
@@ -195,11 +196,11 @@ namespace NDecrypt.Core
             // Shift by bits
             while (r_bits-- > 0)
             {
-                int carry = 0;
+                uint carry = 0;
                 for (int i = 0; i < val.Length; i++)
                 {
                     byte nextByte = (byte)((val[i] << 1) + carry);
-                    carry = (val[i] << 1) > byte.MaxValue ? byte.MaxValue - (val[i] << 1) : 0;
+                    carry = (uint)((val[i] << 1) > byte.MaxValue ? byte.MaxValue - (val[i] << 1) : 0);
                     val[i] = nextByte;
                 }
 
diff --git a/NDecrypt.Core/NDecrypt.Core.csproj b/NDecrypt.Core/NDecrypt.Core.csproj
index 37130d2..d125dff 100644
--- a/NDecrypt.Core/NDecrypt.Core.csproj
+++ b/NDecrypt.Core/NDecrypt.Core.csproj
@@ -47,7 +47,7 @@
         <PackageReference Include="SabreTools.Hashing" Version="1.4.0" />
         <PackageReference Include="SabreTools.IO" Version="1.5.0" />
         <PackageReference Include="SabreTools.Models" Version="1.5.1" />
-        <PackageReference Include="SabreTools.Serialization" Version="1.7.1" />
+        <PackageReference Include="SabreTools.Serialization" Version="1.7.2" />
     </ItemGroup>
 
 </Project>
\ No newline at end of file
diff --git a/NDecrypt.Core/ThreeDSTool.cs b/NDecrypt.Core/ThreeDSTool.cs
index f6ba6de..4fbf835 100644
--- a/NDecrypt.Core/ThreeDSTool.cs
+++ b/NDecrypt.Core/ThreeDSTool.cs
@@ -282,8 +282,8 @@ namespace NDecrypt.Core
             output.Seek(exeFsOffset, SeekOrigin.Begin);
 
             // Create the ExeFS AES cipher for this partition
-            int ctroffsetE = (int)(cart.MediaUnitSize / 0x10);
-            byte[] exefsIVWithOffset = Add(cart.ExeFSIV(index), ctroffsetE);
+            uint ctroffsetE = cart.MediaUnitSize / 0x10;
+            byte[] exefsIVWithOffset = Add(FlipFirstHalf(cart.ExeFSIV(index)), ctroffsetE);
             var cipher = CreateAESDecryptionCipher(KeysMap[index].NormalKey2C!, exefsIVWithOffset);
 
             // Setup and perform the decryption
@@ -373,7 +373,7 @@ namespace NDecrypt.Core
 
                 // Create the ExeFS AES ciphers for this partition
                 uint ctroffset = (fileHeader.FileOffset + cart.MediaUnitSize) / 0x10;
-                byte[] exefsIVWithOffsetForHeader = Add(cart.ExeFSIV(index), (int)ctroffset);
+                byte[] exefsIVWithOffsetForHeader = Add(FlipFirstHalf(cart.ExeFSIV(index)), ctroffset);
                 var firstCipher = CreateAESDecryptionCipher(KeysMap[index].NormalKey!, exefsIVWithOffsetForHeader);
                 var secondCipher = CreateAESEncryptionCipher(KeysMap[index].NormalKey2C!, exefsIVWithOffsetForHeader);
 
@@ -421,7 +421,7 @@ namespace NDecrypt.Core
             output.Seek(romFsOffset, SeekOrigin.Begin);
 
             // Create the RomFS AES cipher for this partition
-            var cipher = CreateAESDecryptionCipher(KeysMap[index].NormalKey!, cart.RomFSIV(index));
+            var cipher = CreateAESDecryptionCipher(KeysMap[index].NormalKey!, FlipFirstHalf(cart.RomFSIV(index)));
 
             // Setup and perform the decryption
             PerformAESOperation(romFsSize,
@@ -649,8 +649,8 @@ namespace NDecrypt.Core
             output.Seek(exeFsHeaderOffset, SeekOrigin.Begin);
 
             // Create the ExeFS AES cipher for this partition
-            int ctroffsetE = (int)(cart.MediaUnitSize / 0x10);
-            byte[] exefsIVWithOffset = Add(cart.ExeFSIV(index), ctroffsetE);
+            uint ctroffsetE = cart.MediaUnitSize / 0x10;
+            byte[] exefsIVWithOffset = Add(FlipFirstHalf(cart.ExeFSIV(index)), ctroffsetE);
             var cipher = CreateAESEncryptionCipher(KeysMap[index].NormalKey2C!, exefsIVWithOffset);
 
             // Setup and perform the encryption
@@ -743,7 +743,7 @@ namespace NDecrypt.Core
 
                 // Create the ExeFS AES ciphers for this partition
                 uint ctroffset = (fileHeader.FileOffset + cart.MediaUnitSize) / 0x10;
-                byte[] exefsIVWithOffsetForHeader = Add(cart.ExeFSIV(index), (int)ctroffset);
+                byte[] exefsIVWithOffsetForHeader = Add(FlipFirstHalf(cart.ExeFSIV(index)), ctroffset);
                 var firstCipher = CreateAESEncryptionCipher(KeysMap[index].NormalKey!, exefsIVWithOffsetForHeader);
                 var secondCipher = CreateAESDecryptionCipher(KeysMap[index].NormalKey2C!, exefsIVWithOffsetForHeader);
 
@@ -798,7 +798,7 @@ namespace NDecrypt.Core
             }
 
             // Create the RomFS AES cipher for this partition
-            var cipher = CreateAESEncryptionCipher(KeysMap[index].NormalKey!, cart.RomFSIV(index));
+            var cipher = CreateAESEncryptionCipher(KeysMap[index].NormalKey!, FlipFirstHalf(cart.RomFSIV(index)));
 
             // Setup and perform the decryption
             PerformAESOperation(romFsSize,
@@ -846,5 +846,18 @@ namespace NDecrypt.Core
         }
 
         #endregion
+
+        // TODO: REMOVE WHEN SERIALIZATION FIXED
+        private static byte[] FlipFirstHalf(byte[] data)
+        {
+            byte[] toFlip = new byte[8];
+            Array.Copy(data, toFlip, 8);
+            Array.Reverse(toFlip);
+
+            byte[] output = new byte[16];
+            Array.Copy(toFlip, output, 8);
+            Array.Copy(data, 8, output, 8, 8);
+            return output;
+        }
     }
 }