diff --git a/build/CodeGen/results.csv b/build/CodeGen/results.csv
index ef973e5e..f9c257ec 100644
--- a/build/CodeGen/results.csv
+++ b/build/CodeGen/results.csv
@@ -1935,3 +1935,10 @@ Module,DescriptionStart,DescriptionEnd,Flags,Namespace,Name,Summary
 428,1041,,,,InvalidPackage1SectionSize,
 428,1042,,,,InvalidPackage1MarikoBodySize,
 428,1043,,,,InvalidPackage1Pk11Size,
+
+428,2000,2199,,,PreconditionViolation,
+428,2001,2019,,,UnsupportedOperation,
+428,2002,,,,UnsupportedCalculateMacForPackage1,The package1 type doesn't support calculating a MAC over its pk11. Only modern Erista package1s support this.
+
+428,2050,2069,,,KeyNotFound,
+428,2051,,,,Package1MacKeyNotFound,
\ No newline at end of file
diff --git a/src/LibHac/Boot/Package1.cs b/src/LibHac/Boot/Package1.cs
index 58199121..3dab974e 100644
--- a/src/LibHac/Boot/Package1.cs
+++ b/src/LibHac/Boot/Package1.cs
@@ -6,10 +6,12 @@ using System.Runtime.InteropServices;
 using LibHac.Common;
 using LibHac.Common.FixedArrays;
 using LibHac.Common.Keys;
+using LibHac.Crypto;
 using LibHac.Diag;
 using LibHac.Fs;
 using LibHac.Tools.FsSystem;
 using LibHac.Util;
+using AesKey = LibHac.Crypto.AesKey;
 
 namespace LibHac.Boot;
 
@@ -153,6 +155,35 @@ public class Package1
         return Result.Success;
     }
 
+    /// <summary>
+    /// Calculates the MAC for a modern Erista pk11.
+    /// </summary>
+    /// <param name="macBuffer">The buffer where the generated MAC will be placed. Must be at least 16 bytes long.</param>
+    /// <returns><see cref="Result.Success"/>: The operation was successful.<br/>
+    /// <see cref="ResultLibHac.UnsupportedCalculateMacForPackage1"/>: The package1 type does not support calculating
+    /// a MAC over its pk11.<br/>
+    /// <see cref="ResultLibHac.Package1MacKeyNotFound"/>: The key used to calculate the MAC was not found
+    /// in the <see cref="KeySet"/>.</returns>
+    public Result CalculateModernEristaMac(Span<byte> macBuffer)
+    {
+        if (IsMariko || !IsModern)
+            return ResultLibHac.UnsupportedCalculateMacForPackage1.Log();
+
+        AesKey macKey = KeySet.Package1MacKeys[KeyRevision];
+        if (macKey.IsZeros())
+            return ResultLibHac.Package1MacKeyNotFound.Log();
+
+        // Todo: Use a smaller buffer instead of reading the entire thing in at once.
+        byte[] macTarget = new byte[Pk11Size + 0x20];
+
+        Result res = _bodyStorage.Read(0x7000 - 0x20, macTarget);
+        if (res.IsFailure()) return res.Miss();
+
+        Aes.CalculateCmac(macBuffer, macTarget, macKey);
+
+        return Result.Success;
+    }
+
     /// <summary>
     /// Read the encrypted section of a Mariko Package1 and try to decrypt it.
     /// </summary>
@@ -336,7 +367,7 @@ public class Package1
         Assert.SdkRequires(IsDecrypted);
 
         int pk11Size = Unsafe.SizeOf<Package1Pk11Header>() + GetSectionSize(Package1Section.WarmBoot) +
-                GetSectionSize(Package1Section.Bootloader) + GetSectionSize(Package1Section.SecureMonitor);
+                       GetSectionSize(Package1Section.Bootloader) + GetSectionSize(Package1Section.SecureMonitor);
 
         pk11Size = Alignment.AlignUp(pk11Size, 0x10);
 
diff --git a/src/LibHac/Common/Keys/KeyDerivation.cs b/src/LibHac/Common/Keys/KeyDerivation.cs
index b7a017eb..10556fc2 100644
--- a/src/LibHac/Common/Keys/KeyDerivation.cs
+++ b/src/LibHac/Common/Keys/KeyDerivation.cs
@@ -89,7 +89,7 @@ internal static class KeyDerivation
         Encryption,
         Signature,
         Kek,
-        
+
         // TSEC directly uses the value generated by this (no key derivation) to encrypt pk11's AES IV that's found
         // at 0x6FF0 in package1. When decrypting pk11, TSEC will overwrite the unencrypted IV in package1 with the
         // encrypted IV.
diff --git a/src/LibHac/Common/ResultLibHac.cs b/src/LibHac/Common/ResultLibHac.cs
index 78b1e71d..e8d388ad 100644
--- a/src/LibHac/Common/ResultLibHac.cs
+++ b/src/LibHac/Common/ResultLibHac.cs
@@ -92,4 +92,16 @@ public static class ResultLibHac
             public static Result.Base InvalidPackage1MarikoBodySize => new Result.Base(ModuleLibHac, 1042);
             /// <summary>Error code: 2428-1043; Inner value: 0x827ac</summary>
             public static Result.Base InvalidPackage1Pk11Size => new Result.Base(ModuleLibHac, 1043);
+
+    /// <summary>Error code: 2428-2000; Range: 2000-2199; Inner value: 0xfa1ac</summary>
+    public static Result.Base PreconditionViolation { [MethodImpl(MethodImplOptions.AggressiveInlining)] get => new Result.Base(ModuleLibHac, 2000, 2199); }
+        /// <summary>Error code: 2428-2001; Range: 2001-2019; Inner value: 0xfa3ac</summary>
+        public static Result.Base UnsupportedOperation { [MethodImpl(MethodImplOptions.AggressiveInlining)] get => new Result.Base(ModuleLibHac, 2001, 2019); }
+            /// <summary>The package1 type doesn't support calculating a MAC over its pk11. Only modern Erista package1s support this.<br/>Error code: 2428-2002; Inner value: 0xfa5ac</summary>
+            public static Result.Base UnsupportedCalculateMacForPackage1 => new Result.Base(ModuleLibHac, 2002);
+
+        /// <summary>Error code: 2428-2050; Range: 2050-2069; Inner value: 0x1005ac</summary>
+        public static Result.Base KeyNotFound { [MethodImpl(MethodImplOptions.AggressiveInlining)] get => new Result.Base(ModuleLibHac, 2050, 2069); }
+            /// <summary>Error code: 2428-2051; Inner value: 0x1007ac</summary>
+            public static Result.Base Package1MacKeyNotFound => new Result.Base(ModuleLibHac, 2051);
 }
\ No newline at end of file
diff --git a/src/hactoolnet/ProcessPackage.cs b/src/hactoolnet/ProcessPackage.cs
index ca614a67..b39c70a3 100644
--- a/src/hactoolnet/ProcessPackage.cs
+++ b/src/hactoolnet/ProcessPackage.cs
@@ -1,4 +1,5 @@
-using System.IO;
+using System;
+using System.IO;
 using System.Runtime.CompilerServices;
 using System.Text;
 using LibHac;
@@ -82,7 +83,22 @@ internal static class ProcessPackage
 
         if (!package1.IsMariko && package1.IsModern)
         {
-            PrintItem(sb, colLen, "    PK11 MAC:", package1.Pk11Mac.ItemsRo.ToArray());
+            string validity = "";
+
+            Span<byte> mac = stackalloc byte[0x10];
+            Result res = package1.CalculateModernEristaMac(mac);
+
+            if (res.IsFailure())
+            {
+                if (!ResultLibHac.Package1MacKeyNotFound.Includes(res))
+                    res.ThrowIfFailure();
+            }
+            else
+            {
+                validity = mac.SequenceEqual(package1.Pk11Mac) ? " (Valid)" : " (Invalid)";
+            }
+
+            PrintItem(sb, colLen, $"    PK11 MAC:{validity}", package1.Pk11Mac.ItemsRo.ToArray());
         }
 
         if (package1.IsDecrypted)
@@ -91,7 +107,7 @@ internal static class ProcessPackage
 
             if (!package1.IsMariko)
             {
-                PrintItem(sb, colLen, "    Key Revision:", $"{package1.KeyRevision:x2} ({Utilities.GetKeyRevisionSummary(package1.KeyRevision)})");
+                PrintItem(sb, colLen, "    Key Revision:", $"{package1.KeyRevision:x2}");
             }
 
             PrintItem(sb, colLen, "    PK11 Size:", $"{package1.Pk11Size:x8}");