Adds the ability to read and write to amiibo bin files

This introduces the ability to read and write game data and model
information from an Amiibo dump file (BIN format). Note that this
functionality requires the presence of a key_retail.bin file. For the
option to appear and function in the UI, ensure that the key_retail.bin
file is located in the <RyujinxData>/system folder.

src/Ryujinx.HLE/HOS/Services/Nfc/AmiiboDecryption/AmiiboBinReader.cs

@@ -0,0 +1,340 @@
+using Ryujinx.Common.Configuration;
+using Ryujinx.Common.Logging;
+using Ryujinx.HLE.HOS.Services.Nfc.Nfp;
+using Ryujinx.HLE.HOS.Services.Nfc.Nfp.NfpManager;
+using System;
+using System.IO;
+
+namespace Ryujinx.HLE.HOS.Services.Nfc.AmiiboDecryption
+{
+    public class AmiiboBinReader
+    {
+        private static byte CalculateBCC0(byte[] uid)
+        {
+            return (byte)(uid[0] ^ uid[1] ^ uid[2] ^ 0x88);
+        }
+
+        private static byte CalculateBCC1(byte[] uid)
+        {
+            return (byte)(uid[3] ^ uid[4] ^ uid[5] ^ uid[6]);
+        }
+
+        public static VirtualAmiiboFile ReadBinFile(byte[] fileBytes)
+        {
+            string keyRetailBinPath = GetKeyRetailBinPath();
+            if (string.IsNullOrEmpty(keyRetailBinPath))
+            {
+                return new VirtualAmiiboFile();
+            }
+
+            byte[] initialCounter = new byte[16];
+
+            const int totalPages = 135;
+            const int pageSize = 4;
+            const int totalBytes = totalPages * pageSize;
+
+            if (fileBytes.Length < totalBytes)
+            {
+                return new VirtualAmiiboFile();
+            }
+
+            AmiiboDecrypter amiiboDecryptor = new AmiiboDecrypter(keyRetailBinPath);
+            AmiiboDump amiiboDump = amiiboDecryptor.DecryptAmiiboDump(fileBytes);
+
+            byte[] titleId = new byte[8];
+            byte[] usedCharacter = new byte[2];
+            byte[] variation = new byte[2];
+            byte[] amiiboID = new byte[2];
+            byte[] setID = new byte[1];
+            byte[] initDate = new byte[2];
+            byte[] writeDate = new byte[2];
+            byte[] writeCounter = new byte[2];
+            byte[] appId = new byte[8];
+            byte[] settingsBytes = new byte[2];
+            byte formData = 0;
+            byte[] applicationAreas = new byte[216];
+            byte[] dataFull = amiiboDump.GetData();
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Data Full Length: {dataFull.Length}");
+            byte[] uid = new byte[7];
+            Array.Copy(dataFull, 0, uid, 0, 7);
+
+            byte bcc0 = CalculateBCC0(uid);
+            byte bcc1 = CalculateBCC1(uid);
+            LogDebugData(uid, bcc0, bcc1);
+            for (int page = 0; page < 128; page++) // NTAG215 has 128 pages
+            {
+                int pageStartIdx = page * 4; // Each page is 4 bytes
+                byte[] pageData = new byte[4];
+                byte[] sourceBytes = dataFull;
+                Array.Copy(sourceBytes, pageStartIdx, pageData, 0, 4);
+                // Special handling for specific pages
+                switch (page)
+                {
+                    case 0: // Page 0 (UID + BCC0)
+                        Logger.Debug?.Print(LogClass.ServiceNfp, "Page 0: UID and BCC0.");
+                        break;
+                    case 2: // Page 2 (BCC1 + Internal Value)
+                        byte internalValue = pageData[1];
+                        Logger.Debug?.Print(LogClass.ServiceNfp, $"Page 2: BCC1 + Internal Value 0x{internalValue:X2} (Expected 0x48).");
+                        break;
+                    case 6:
+                        // Bytes 0 and 1 are init date, bytes 2 and 3 are write date
+                        Array.Copy(pageData, 0, initDate, 0, 2);
+                        Array.Copy(pageData, 2, writeDate, 0, 2);
+                        break;
+                    case 21:
+                        // Bytes 0 and 1 are used character, bytes 2 and 3 are variation
+                        Array.Copy(pageData, 0, usedCharacter, 0, 2);
+                        Array.Copy(pageData, 2, variation, 0, 2);
+                        break;
+                    case 22:
+                        // Bytes 0 and 1 are amiibo ID, byte 2 is set ID, byte 3 is form data
+                        Array.Copy(pageData, 0, amiiboID, 0, 2);
+                        setID[0] = pageData[2];
+                        formData = pageData[3];
+                        break;
+                    case 64:
+                    case 65:
+                        // Extract title ID
+                        int titleIdOffset = (page - 64) * 4;
+                        Array.Copy(pageData, 0, titleId, titleIdOffset, 4);
+                        break;
+                    case 66:
+                        // Bytes 0 and 1 are write counter
+                        Array.Copy(pageData, 0, writeCounter, 0, 2);
+                        break;
+                    // Pages 76 to 127 are application areas
+                    case >= 76 and <= 127:
+                        int appAreaOffset = (page - 76) * 4;
+                        Array.Copy(pageData, 0, applicationAreas, appAreaOffset, 4);
+                        break;
+                }
+            }
+
+            string usedCharacterStr = BitConverter.ToString(usedCharacter).Replace("-", "");
+            string variationStr = BitConverter.ToString(variation).Replace("-", "");
+            string amiiboIDStr = BitConverter.ToString(amiiboID).Replace("-", "");
+            string setIDStr = BitConverter.ToString(setID).Replace("-", "");
+            string head = usedCharacterStr + variationStr;
+            string tail = amiiboIDStr + setIDStr + "02";
+            string finalID = head + tail;
+
+            ushort settingsValue = BitConverter.ToUInt16(settingsBytes, 0);
+            ushort initDateValue = BitConverter.ToUInt16(initDate, 0);
+            ushort writeDateValue = BitConverter.ToUInt16(writeDate, 0);
+            DateTime initDateTime = DateTimeFromTag(initDateValue);
+            DateTime writeDateTime = DateTimeFromTag(writeDateValue);
+            ushort writeCounterValue = BitConverter.ToUInt16(writeCounter, 0);
+            string nickName = amiiboDump.AmiiboNickname;
+            LogFinalData(titleId, appId, head, tail, finalID, nickName, initDateTime, writeDateTime, settingsValue, writeCounterValue, applicationAreas);
+
+            VirtualAmiiboFile virtualAmiiboFile = new VirtualAmiiboFile
+            {
+                FileVersion = 1,
+                TagUuid = uid,
+                AmiiboId = finalID,
+                NickName = nickName,
+                FirstWriteDate = initDateTime,
+                LastWriteDate = writeDateTime,
+                WriteCounter = writeCounterValue,
+            };
+            if (writeCounterValue > 0)
+            {
+                VirtualAmiibo.ApplicationBytes = applicationAreas;
+            }
+            VirtualAmiibo.NickName = nickName;
+            return virtualAmiiboFile;
+        }
+        public static bool SaveBinFile(string inputFile, byte[] appData)
+        {
+            Logger.Info?.Print(LogClass.ServiceNfp, "Saving bin file.");
+            byte[] readBytes;
+            try
+            {
+                readBytes = File.ReadAllBytes(inputFile);
+            }
+            catch (Exception ex)
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, $"Error reading file: {ex.Message}");
+                return false;
+            }
+            string keyRetailBinPath = GetKeyRetailBinPath();
+            if (string.IsNullOrEmpty(keyRetailBinPath))
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, "Key retail path is empty.");
+                return false;
+            }
+
+            if (appData.Length != 216) // Ensure application area size is valid
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, "Invalid application data length. Expected 216 bytes.");
+                return false;
+            }
+
+            AmiiboDecrypter amiiboDecryptor = new AmiiboDecrypter(keyRetailBinPath);
+            AmiiboDump amiiboDump = amiiboDecryptor.DecryptAmiiboDump(readBytes);
+
+            byte[] oldData = amiiboDump.GetData();
+            if (oldData.Length != 540) // Verify the expected length for NTAG215 tags
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, "Invalid tag data length. Expected 540 bytes.");
+                return false;
+            }
+
+            byte[] newData = new byte[oldData.Length];
+            Array.Copy(oldData, newData, oldData.Length);
+
+            // Replace application area with appData
+            int appAreaOffset = 76 * 4; // Starting page (76) times 4 bytes per page
+            Array.Copy(appData, 0, newData, appAreaOffset, appData.Length);
+
+            AmiiboDump encryptedDump = amiiboDecryptor.EncryptAmiiboDump(newData);
+            byte[] encryptedData = encryptedDump.GetData();
+
+            if (encryptedData == null || encryptedData.Length != readBytes.Length)
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, "Failed to encrypt data correctly.");
+                return false;
+            }
+            inputFile = inputFile.Replace("_modified", string.Empty);
+            // Save the encrypted data to file or return it for saving externally
+            string outputFilePath = Path.Combine(Path.GetDirectoryName(inputFile), Path.GetFileNameWithoutExtension(inputFile) + "_modified.bin");
+            try
+            {
+                File.WriteAllBytes(outputFilePath, encryptedData);
+                Logger.Info?.Print(LogClass.ServiceNfp, $"Modified Amiibo data saved to {outputFilePath}.");
+                return true;
+            }
+            catch (Exception ex)
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, $"Error saving file: {ex.Message}");
+                return false;
+            }
+        }
+        public static bool SaveBinFile(string inputFile, string newNickName)
+        {
+            Logger.Info?.Print(LogClass.ServiceNfp, "Saving bin file.");
+            byte[] readBytes;
+            try
+            {
+                readBytes = File.ReadAllBytes(inputFile);
+            }
+            catch (Exception ex)
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, $"Error reading file: {ex.Message}");
+                return false;
+            }
+            string keyRetailBinPath = GetKeyRetailBinPath();
+            if (string.IsNullOrEmpty(keyRetailBinPath))
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, "Key retail path is empty.");
+                return false;
+            }
+
+            AmiiboDecrypter amiiboDecryptor = new AmiiboDecrypter(keyRetailBinPath);
+            AmiiboDump amiiboDump = amiiboDecryptor.DecryptAmiiboDump(readBytes);
+            amiiboDump.AmiiboNickname = newNickName;
+            byte[] oldData = amiiboDump.GetData();
+            if (oldData.Length != 540) // Verify the expected length for NTAG215 tags
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, "Invalid tag data length. Expected 540 bytes.");
+                return false;
+            }
+            byte[] encryptedData = amiiboDecryptor.EncryptAmiiboDump(oldData).GetData();
+
+            if (encryptedData == null || encryptedData.Length != readBytes.Length)
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, "Failed to encrypt data correctly.");
+                return false;
+            }
+            inputFile = inputFile.Replace("_modified", string.Empty);
+            // Save the encrypted data to file or return it for saving externally
+            string outputFilePath = Path.Combine(Path.GetDirectoryName(inputFile), Path.GetFileNameWithoutExtension(inputFile) + "_modified.bin");
+            try
+            {
+                File.WriteAllBytes(outputFilePath, encryptedData);
+                Logger.Info?.Print(LogClass.ServiceNfp, $"Modified Amiibo data saved to {outputFilePath}.");
+                return true;
+            }
+            catch (Exception ex)
+            {
+                Logger.Error?.Print(LogClass.ServiceNfp, $"Error saving file: {ex.Message}");
+                return false;
+            }
+        }
+        private static void LogDebugData(byte[] uid, byte bcc0, byte bcc1)
+        {
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"UID: {BitConverter.ToString(uid)}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"BCC0: 0x{bcc0:X2}, BCC1: 0x{bcc1:X2}");
+        }
+
+        private static void LogFinalData(byte[] titleId, byte[] appId, string head, string tail, string finalID, string nickName, DateTime initDateTime, DateTime writeDateTime, ushort settingsValue, ushort writeCounterValue, byte[] applicationAreas)
+        {
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Title ID: 0x{BitConverter.ToString(titleId).Replace("-", "")}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Application Program ID: 0x{BitConverter.ToString(appId).Replace("-", "")}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Head: {head}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Tail: {tail}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Final ID: {finalID}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Nickname: {nickName}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Init Date: {initDateTime}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Write Date: {writeDateTime}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Settings: 0x{settingsValue:X4}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, $"Write Counter: {writeCounterValue}");
+            Logger.Debug?.Print(LogClass.ServiceNfp, "Length of Application Areas: " + applicationAreas.Length);
+        }
+
+        private static uint CalculateCRC32(byte[] input)
+        {
+            uint[] table = new uint[256];
+            uint polynomial = 0xEDB88320;
+            for (uint i = 0; i < table.Length; ++i)
+            {
+                uint crc = i;
+                for (int j = 0; j < 8; ++j)
+                {
+                    if ((crc & 1) != 0)
+                        crc = (crc >> 1) ^ polynomial;
+                    else
+                        crc >>= 1;
+                }
+                table[i] = crc;
+            }
+
+            uint result = 0xFFFFFFFF;
+            foreach (byte b in input)
+            {
+                byte index = (byte)((result & 0xFF) ^ b);
+                result = (result >> 8) ^ table[index];
+            }
+            return ~result;
+        }
+
+        private static string GetKeyRetailBinPath()
+        {
+            return Path.Combine(AppDataManager.KeysDirPath, "key_retail.bin");
+        }
+
+        public static bool HasKeyRetailBinPath()
+        {
+            return File.Exists(GetKeyRetailBinPath());
+        }
+        public static DateTime DateTimeFromTag(ushort value)
+        {
+            try
+            {
+                int day = value & 0x1F;
+                int month = (value >> 5) & 0x0F;
+                int year = (value >> 9) & 0x7F;
+
+                if (day == 0 || month == 0 || month > 12 || day > DateTime.DaysInMonth(2000 + year, month))
+                    throw new ArgumentOutOfRangeException();
+
+                return new DateTime(2000 + year, month, day);
+            }
+            catch
+            {
+                return DateTime.Now;
+            }
+        }
+    }
+}

src/Ryujinx.HLE/HOS/Services/Nfc/AmiiboDecryption/AmiiboDecrypter.cs

@@ -0,0 +1,43 @@
+using System.IO;
+
+namespace Ryujinx.HLE.HOS.Services.Nfc.AmiiboDecryption
+{
+    public class AmiiboDecrypter
+    {
+        public AmiiboMasterKey DataKey { get; private set; }
+        public AmiiboMasterKey TagKey { get; private set; }
+
+        public AmiiboDecrypter(string keyRetailBinPath)
+        {
+            var combinedKeys = File.ReadAllBytes(keyRetailBinPath);
+            var keys = AmiiboMasterKey.FromCombinedBin(combinedKeys);
+            DataKey = keys.DataKey;
+            TagKey = keys.TagKey;
+        }
+
+        public AmiiboDump DecryptAmiiboDump(byte[] encryptedDumpData)
+        {
+            // Initialize AmiiboDump with encrypted data
+            AmiiboDump amiiboDump = new AmiiboDump(encryptedDumpData, DataKey, TagKey, isLocked: true);
+
+            // Unlock (decrypt) the dump
+            amiiboDump.Unlock();
+
+            // Optional: Verify HMACs
+            amiiboDump.VerifyHMACs();
+
+            return amiiboDump;
+        }
+
+        public AmiiboDump EncryptAmiiboDump(byte[] decryptedDumpData)
+        {
+            // Initialize AmiiboDump with decrypted data
+            AmiiboDump amiiboDump = new AmiiboDump(decryptedDumpData, DataKey, TagKey, isLocked: false);
+
+            // Lock (encrypt) the dump
+            amiiboDump.Lock();
+
+            return amiiboDump;
+        }
+    }
+}

src/Ryujinx.HLE/HOS/Services/Nfc/AmiiboDecryption/AmiiboDump.cs

@@ -0,0 +1,387 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Cryptography;
+
+namespace Ryujinx.HLE.HOS.Services.Nfc.AmiiboDecryption
+{
+    public class AmiiboDump
+    {
+        private AmiiboMasterKey dataMasterKey;
+        private AmiiboMasterKey tagMasterKey;
+
+        private bool isLocked;
+        private byte[] data;
+        private byte[] hmacTagKey;
+        private byte[] hmacDataKey;
+        private byte[] aesKey;
+        private byte[] aesIv;
+
+        public AmiiboDump(byte[] dumpData, AmiiboMasterKey dataKey, AmiiboMasterKey tagKey, bool isLocked = true)
+        {
+            if (dumpData.Length < 540)
+                throw new ArgumentException("Incomplete dump. Amiibo data is at least 540 bytes.");
+
+            this.data = new byte[540];
+            Array.Copy(dumpData, this.data, dumpData.Length);
+            this.dataMasterKey = dataKey;
+            this.tagMasterKey = tagKey;
+            this.isLocked = isLocked;
+
+            if (!isLocked)
+            {
+                DeriveKeysAndCipher();
+            }
+        }
+
+        private byte[] DeriveKey(AmiiboMasterKey key, bool deriveAes, out byte[] derivedAesKey, out byte[] derivedAesIv)
+        {
+            List<byte> seed = new List<byte>();
+
+            // Start with the type string (14 bytes)
+            seed.AddRange(key.TypeString);
+
+            // Append data based on magic size
+            int append = 16 - key.MagicSize;
+            byte[] extract = new byte[16];
+            Array.Copy(this.data, 0x011, extract, 0, 2); // Extract two bytes from user data section
+            for (int i = 2; i < 16; i++)
+            {
+                extract[i] = 0x00;
+            }
+            seed.AddRange(extract.Take(append));
+
+            // Add the magic bytes
+            seed.AddRange(key.MagicBytes.Take(key.MagicSize));
+
+            // Extract the UID (UID is 8 bytes)
+            byte[] uid = new byte[8];
+            Array.Copy(this.data, 0x000, uid, 0, 8);
+            seed.AddRange(uid);
+            seed.AddRange(uid);
+
+            // Extract some tag data (pages 0x20 - 0x28)
+            byte[] user = new byte[32];
+            Array.Copy(this.data, 0x060, user, 0, 32);
+
+            // XOR it with the key padding (XorPad)
+            byte[] paddedUser = new byte[32];
+            for (int i = 0; i < user.Length; i++)
+            {
+                paddedUser[i] = (byte)(user[i] ^ key.XorPad[i]);
+            }
+            seed.AddRange(paddedUser);
+
+            byte[] seedBytes = seed.ToArray();
+            if (seedBytes.Length != 78)
+            {
+                throw new Exception("Size check for key derived seed failed");
+            }
+
+            byte[] hmacKey;
+            derivedAesKey = null;
+            derivedAesIv = null;
+
+            if (deriveAes)
+            {
+                // Derive AES Key and IV
+                var dataForAes = new byte[2 + seedBytes.Length];
+                dataForAes[0] = 0x00;
+                dataForAes[1] = 0x00; // Counter (0)
+                Array.Copy(seedBytes, 0, dataForAes, 2, seedBytes.Length);
+
+                byte[] derivedBytes;
+                using (var hmac = new HMACSHA256(key.HmacKey))
+                {
+                    derivedBytes = hmac.ComputeHash(dataForAes);
+                }
+
+                derivedAesKey = derivedBytes.Take(16).ToArray();
+                derivedAesIv = derivedBytes.Skip(16).Take(16).ToArray();
+
+                // Derive HMAC Key
+                var dataForHmacKey = new byte[2 + seedBytes.Length];
+                dataForHmacKey[0] = 0x00;
+                dataForHmacKey[1] = 0x01; // Counter (1)
+                Array.Copy(seedBytes, 0, dataForHmacKey, 2, seedBytes.Length);
+
+                using (var hmac = new HMACSHA256(key.HmacKey))
+                {
+                    derivedBytes = hmac.ComputeHash(dataForHmacKey);
+                }
+
+                hmacKey = derivedBytes.Take(16).ToArray();
+            }
+            else
+            {
+                // Derive HMAC Key only
+                var dataForHmacKey = new byte[2 + seedBytes.Length];
+                dataForHmacKey[0] = 0x00;
+                dataForHmacKey[1] = 0x01; // Counter (1)
+                Array.Copy(seedBytes, 0, dataForHmacKey, 2, seedBytes.Length);
+
+                byte[] derivedBytes;
+                using (var hmac = new HMACSHA256(key.HmacKey))
+                {
+                    derivedBytes = hmac.ComputeHash(dataForHmacKey);
+                }
+
+                hmacKey = derivedBytes.Take(16).ToArray();
+            }
+
+            return hmacKey;
+        }
+
+        private void DeriveKeysAndCipher()
+        {
+            byte[] discard;
+            // Derive HMAC Tag Key
+            this.hmacTagKey = DeriveKey(this.tagMasterKey, false, out discard, out discard);
+
+            // Derive HMAC Data Key and AES Key/IV
+            this.hmacDataKey = DeriveKey(this.dataMasterKey, true, out aesKey, out aesIv);
+        }
+
+        private void DecryptData()
+        {
+            byte[] encryptedBlock = new byte[0x020 + 0x168];
+            Array.Copy(data, 0x014, encryptedBlock, 0, 0x020);       // data[0x014:0x034]
+            Array.Copy(data, 0x0A0, encryptedBlock, 0x020, 0x168);   // data[0x0A0:0x208]
+
+            byte[] decryptedBlock = AES_CTR_Transform(encryptedBlock, aesKey, aesIv);
+
+            // Copy decrypted data back
+            Array.Copy(decryptedBlock, 0, data, 0x014, 0x020);
+            Array.Copy(decryptedBlock, 0x020, data, 0x0A0, 0x168);
+        }
+
+        private void EncryptData()
+        {
+            byte[] plainBlock = new byte[0x020 + 0x168];
+            Array.Copy(data, 0x014, plainBlock, 0, 0x020);       // data[0x014:0x034]
+            Array.Copy(data, 0x0A0, plainBlock, 0x020, 0x168);   // data[0x0A0:0x208]
+
+            byte[] encryptedBlock = AES_CTR_Transform(plainBlock, aesKey, aesIv);
+
+            // Copy encrypted data back
+            Array.Copy(encryptedBlock, 0, data, 0x014, 0x020);
+            Array.Copy(encryptedBlock, 0x020, data, 0x0A0, 0x168);
+        }
+
+        private byte[] AES_CTR_Transform(byte[] data, byte[] key, byte[] iv)
+        {
+            byte[] output = new byte[data.Length];
+
+            using (Aes aes = Aes.Create())
+            {
+                aes.Key = key;
+                aes.Mode = CipherMode.ECB;
+                aes.Padding = PaddingMode.None;
+
+                int blockSize = aes.BlockSize / 8; // in bytes, should be 16
+                byte[] counter = new byte[blockSize];
+                Array.Copy(iv, counter, blockSize);
+
+                using (ICryptoTransform encryptor = aes.CreateEncryptor())
+                {
+                    byte[] encryptedCounter = new byte[blockSize];
+
+                    for (int i = 0; i < data.Length; i += blockSize)
+                    {
+                        // Encrypt the counter
+                        encryptor.TransformBlock(counter, 0, blockSize, encryptedCounter, 0);
+
+                        // Determine the number of bytes to process in this block
+                        int blockLength = Math.Min(blockSize, data.Length - i);
+
+                        // XOR the encrypted counter with the plaintext/ciphertext block
+                        for (int j = 0; j < blockLength; j++)
+                        {
+                            output[i + j] = (byte)(data[i + j] ^ encryptedCounter[j]);
+                        }
+
+                        // Increment the counter
+                        IncrementCounter(counter);
+                    }
+                }
+            }
+
+            return output;
+        }
+
+        private void IncrementCounter(byte[] counter)
+        {
+            for (int i = counter.Length - 1; i >= 0; i--)
+            {
+                if (++counter[i] != 0)
+                    break;
+            }
+        }
+
+        private void DeriveHMACs()
+        {
+            if (isLocked)
+                throw new InvalidOperationException("Cannot derive HMACs when data is locked.");
+
+            // Calculate tag HMAC
+            byte[] tagHmacData = new byte[8 + 44];
+            Array.Copy(data, 0x000, tagHmacData, 0, 8);
+            Array.Copy(data, 0x054, tagHmacData, 8, 44);
+
+            byte[] tagHmac;
+            using (var hmac = new HMACSHA256(hmacTagKey))
+            {
+                tagHmac = hmac.ComputeHash(tagHmacData);
+            }
+
+            // Overwrite the stored tag HMAC
+            Array.Copy(tagHmac, 0, data, 0x034, 32);
+
+            // Prepare data for data HMAC
+            int len1 = 0x023; // 0x011 to 0x034 (0x034 - 0x011)
+            int len2 = 0x168; // 0x0A0 to 0x208 (0x208 - 0x0A0)
+            int len3 = tagHmac.Length; // 32 bytes
+            int len4 = 0x008; // 0x000 to 0x008 (0x008 - 0x000)
+            int len5 = 0x02C; // 0x054 to 0x080 (0x080 - 0x054)
+            int totalLength = len1 + len2 + len3 + len4 + len5;
+            byte[] dataHmacData = new byte[totalLength];
+
+            int offset = 0;
+            Array.Copy(data, 0x011, dataHmacData, offset, len1);
+            offset += len1;
+            Array.Copy(data, 0x0A0, dataHmacData, offset, len2);
+            offset += len2;
+            Array.Copy(tagHmac, 0, dataHmacData, offset, len3);
+            offset += len3;
+            Array.Copy(data, 0x000, dataHmacData, offset, len4);
+            offset += len4;
+            Array.Copy(data, 0x054, dataHmacData, offset, len5);
+
+            byte[] dataHmac;
+            using (var hmac = new HMACSHA256(hmacDataKey))
+            {
+                dataHmac = hmac.ComputeHash(dataHmacData);
+            }
+
+            // Overwrite the stored data HMAC
+            Array.Copy(dataHmac, 0, data, 0x080, 32);
+        }
+
+        public void VerifyHMACs()
+        {
+            if (isLocked)
+                throw new InvalidOperationException("Cannot verify HMACs when data is locked.");
+
+            // Calculate tag HMAC
+            byte[] tagHmacData = new byte[8 + 44];
+            Array.Copy(data, 0x000, tagHmacData, 0, 8);
+            Array.Copy(data, 0x054, tagHmacData, 8, 44);
+
+            byte[] calculatedTagHmac;
+            using (var hmac = new HMACSHA256(hmacTagKey))
+            {
+                calculatedTagHmac = hmac.ComputeHash(tagHmacData);
+            }
+
+            byte[] storedTagHmac = new byte[32];
+            Array.Copy(data, 0x034, storedTagHmac, 0, 32);
+
+            if (!calculatedTagHmac.SequenceEqual(storedTagHmac))
+            {
+                throw new Exception("Tag HMAC verification failed.");
+            }
+
+            // Prepare data for data HMAC
+            int len1 = 0x023; // 0x011 to 0x034
+            int len2 = 0x168; // 0x0A0 to 0x208
+            int len3 = calculatedTagHmac.Length; // 32 bytes
+            int len4 = 0x008; // 0x000 to 0x008
+            int len5 = 0x02C; // 0x054 to 0x080
+            int totalLength = len1 + len2 + len3 + len4 + len5;
+            byte[] dataHmacData = new byte[totalLength];
+
+            int offset = 0;
+            Array.Copy(data, 0x011, dataHmacData, offset, len1);
+            offset += len1;
+            Array.Copy(data, 0x0A0, dataHmacData, offset, len2);
+            offset += len2;
+            Array.Copy(calculatedTagHmac, 0, dataHmacData, offset, len3);
+            offset += len3;
+            Array.Copy(data, 0x000, dataHmacData, offset, len4);
+            offset += len4;
+            Array.Copy(data, 0x054, dataHmacData, offset, len5);
+
+            byte[] calculatedDataHmac;
+            using (var hmac = new HMACSHA256(hmacDataKey))
+            {
+                calculatedDataHmac = hmac.ComputeHash(dataHmacData);
+            }
+
+            byte[] storedDataHmac = new byte[32];
+            Array.Copy(data, 0x080, storedDataHmac, 0, 32);
+
+            if (!calculatedDataHmac.SequenceEqual(storedDataHmac))
+            {
+                throw new Exception("Data HMAC verification failed.");
+            }
+        }
+
+        public void Unlock()
+        {
+            if (!isLocked)
+                throw new InvalidOperationException("Data is already unlocked.");
+
+            // Derive keys and cipher
+            DeriveKeysAndCipher();
+
+            // Decrypt the encrypted data
+            DecryptData();
+
+            isLocked = false;
+        }
+
+        public void Lock()
+        {
+            if (isLocked)
+                throw new InvalidOperationException("Data is already locked.");
+
+            // Recalculate HMACs
+            DeriveHMACs();
+
+            // Encrypt the data
+            EncryptData();
+
+            isLocked = true;
+        }
+
+        public byte[] GetData()
+        {
+            return data;
+        }
+
+        // Property to get or set Amiibo nickname
+        public string AmiiboNickname
+        {
+            get
+            {
+                // data[0x020:0x034], big endian UTF-16
+                byte[] nicknameBytes = new byte[0x014];
+                Array.Copy(data, 0x020, nicknameBytes, 0, 0x014);
+                string nickname = System.Text.Encoding.BigEndianUnicode.GetString(nicknameBytes).TrimEnd('\0');
+                return nickname;
+            }
+            set
+            {
+                byte[] nicknameBytes = System.Text.Encoding.BigEndianUnicode.GetBytes(value.PadRight(10, '\0'));
+                if (nicknameBytes.Length > 20)
+                    throw new ArgumentException("Nickname too long.");
+                Array.Copy(nicknameBytes, 0, data, 0x020, nicknameBytes.Length);
+                // Pad remaining bytes with zeros
+                for (int i = 0x020 + nicknameBytes.Length; i < 0x034; i++)
+                {
+                    data[i] = 0x00;
+                }
+            }
+        }
+    }
+}

src/Ryujinx.HLE/HOS/Services/Nfc/AmiiboDecryption/AmiiboMasterKey.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Linq;
+
+namespace Ryujinx.HLE.HOS.Services.Nfc.AmiiboDecryption
+{
+    public class AmiiboMasterKey
+    {
+        public byte[] HmacKey { get; private set; }     // 16 bytes
+        public byte[] TypeString { get; private set; }  // 14 bytes
+        public byte Rfu { get; private set; }           // 1 byte
+        public byte MagicSize { get; private set; }     // 1 byte
+        public byte[] MagicBytes { get; private set; }  // 16 bytes
+        public byte[] XorPad { get; private set; }      // 32 bytes
+
+        public AmiiboMasterKey(byte[] data)
+        {
+            if (data.Length != 80)
+                throw new ArgumentException("Master key data must be 80 bytes.");
+
+            HmacKey = data.Take(16).ToArray();
+            TypeString = data.Skip(16).Take(14).ToArray();
+            Rfu = data[30];
+            MagicSize = data[31];
+            MagicBytes = data.Skip(32).Take(16).ToArray();
+            XorPad = data.Skip(48).Take(32).ToArray();
+        }
+
+        public static (AmiiboMasterKey DataKey, AmiiboMasterKey TagKey) FromCombinedBin(byte[] combinedBin)
+        {
+            if (combinedBin.Length != 160)
+                throw new ArgumentException($"Data is {combinedBin.Length} bytes (should be 160).");
+
+            byte[] dataBin = combinedBin.Take(80).ToArray();
+            byte[] tagBin = combinedBin.Skip(80).Take(80).ToArray();
+
+            AmiiboMasterKey dataKey = new AmiiboMasterKey(dataBin);
+            AmiiboMasterKey tagKey = new AmiiboMasterKey(tagBin);
+
+            return (dataKey, tagKey);
+        }
+    }
+}

src/Ryujinx.HLE/HOS/Services/Nfc/Nfp/NfpManager/INfp.cs

@@ -78,7 +78,6 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
             if (_state == State.Initialized)
             {
                 _cancelTokenSource?.Cancel();
-
                 // NOTE: All events are destroyed here.
                 context.Device.System.NfpDevices.Clear();
 
@@ -146,9 +145,7 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
                     break;
                 }
             }
-
             _cancelTokenSource = new CancellationTokenSource();
-
             Task.Run(() =>
             {
                 while (true)
@@ -199,7 +196,6 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
                     break;
                 }
             }
-
             return ResultCode.Success;
         }
 
@@ -229,7 +225,6 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
             }
 
             // TODO: Found how the MountTarget is handled.
-
             for (int i = 0; i < context.Device.System.NfpDevices.Count; i++)
             {
                 if (context.Device.System.NfpDevices[i].Handle == (PlayerIndex)deviceHandle)
@@ -488,14 +483,12 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
 #pragma warning disable IDE0059 // Remove unnecessary value assignment
             uint deviceHandle = (uint)context.RequestData.ReadUInt64();
 #pragma warning restore IDE0059
-
             if (context.Device.System.NfpDevices.Count == 0)
             {
                 return ResultCode.DeviceNotFound;
             }
 
             // NOTE: Since we handle amiibo through VirtualAmiibo, we don't have to flush anything in our case.
-
             return ResultCode.Success;
         }
 
@@ -884,7 +877,6 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
                     return ResultCode.Success;
                 }
             }
-
             return ResultCode.DeviceNotFound;
         }
 

src/Ryujinx.HLE/HOS/Services/Nfc/Nfp/NfpManager/Types/VirtualAmiiboFile.cs

@@ -3,7 +3,7 @@ using System.Collections.Generic;
 
 namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp.NfpManager
 {
-    struct VirtualAmiiboFile
+    public struct VirtualAmiiboFile
     {
         public uint FileVersion { get; set; }
         public byte[] TagUuid { get; set; }
@@ -15,7 +15,7 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp.NfpManager
         public List<VirtualAmiiboApplicationArea> ApplicationAreas { get; set; }
     }
 
-    struct VirtualAmiiboApplicationArea
+    public struct VirtualAmiiboApplicationArea
     {
         public uint ApplicationAreaId { get; set; }
         public byte[] ApplicationArea { get; set; }

src/Ryujinx.HLE/HOS/Services/Nfc/Nfp/VirtualAmiibo.cs

@@ -4,6 +4,7 @@ using Ryujinx.Common.Utilities;
 using Ryujinx.Cpu;
 using Ryujinx.HLE.HOS.Services.Mii;
 using Ryujinx.HLE.HOS.Services.Mii.Types;
+using Ryujinx.HLE.HOS.Services.Nfc.AmiiboDecryption;
 using Ryujinx.HLE.HOS.Services.Nfc.Nfp.NfpManager;
 using System;
 using System.Collections.Generic;
@@ -14,10 +15,11 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
 {
     static class VirtualAmiibo
     {
-        private static uint _openedApplicationAreaId;
-
+        public static uint OpenedApplicationAreaId;
+        public static byte[] ApplicationBytes = new byte[0];
+        public static string InputBin = string.Empty;
+        public static string NickName = string.Empty;
         private static readonly AmiiboJsonSerializerContext _serializerContext = AmiiboJsonSerializerContext.Default;
-
         public static byte[] GenerateUuid(string amiiboId, bool useRandomUuid)
         {
             if (useRandomUuid)
@@ -69,6 +71,11 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
         {
             VirtualAmiiboFile amiiboFile = LoadAmiiboFile(amiiboId);
             string nickname = amiiboFile.NickName ?? "Ryujinx";
+            if (NickName != string.Empty)
+            {
+                nickname = NickName;
+                NickName = string.Empty;
+            }
             UtilityImpl utilityImpl = new(tickSource);
             CharInfo charInfo = new();
 
@@ -98,16 +105,26 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
         {
             VirtualAmiiboFile virtualAmiiboFile = LoadAmiiboFile(amiiboId);
             virtualAmiiboFile.NickName = newNickName;
+            if (InputBin != string.Empty)
+            {
+                AmiiboBinReader.SaveBinFile(InputBin, virtualAmiiboFile.NickName);
+                return;
+            }
             SaveAmiiboFile(virtualAmiiboFile);
         }
 
         public static bool OpenApplicationArea(string amiiboId, uint applicationAreaId)
         {
             VirtualAmiiboFile virtualAmiiboFile = LoadAmiiboFile(amiiboId);
+            if (ApplicationBytes.Length > 0)
+            {
+                OpenedApplicationAreaId = applicationAreaId;
+                return true;
+            }
 
             if (virtualAmiiboFile.ApplicationAreas.Any(item => item.ApplicationAreaId == applicationAreaId))
             {
-                _openedApplicationAreaId = applicationAreaId;
+                OpenedApplicationAreaId = applicationAreaId;
 
                 return true;
             }
@@ -117,11 +134,17 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
 
         public static byte[] GetApplicationArea(string amiiboId)
         {
+            if (ApplicationBytes.Length > 0)
+            {
+                byte[] bytes = ApplicationBytes;
+                ApplicationBytes = new byte[0];
+                return bytes;
+            }
             VirtualAmiiboFile virtualAmiiboFile = LoadAmiiboFile(amiiboId);
 
             foreach (VirtualAmiiboApplicationArea applicationArea in virtualAmiiboFile.ApplicationAreas)
             {
-                if (applicationArea.ApplicationAreaId == _openedApplicationAreaId)
+                if (applicationArea.ApplicationAreaId == OpenedApplicationAreaId)
                 {
                     return applicationArea.ApplicationArea;
                 }
@@ -152,17 +175,22 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
 
         public static void SetApplicationArea(string amiiboId, byte[] applicationAreaData)
         {
+            if (InputBin != string.Empty)
+            {
+                AmiiboBinReader.SaveBinFile(InputBin, applicationAreaData);
+                return;
+            }
             VirtualAmiiboFile virtualAmiiboFile = LoadAmiiboFile(amiiboId);
 
-            if (virtualAmiiboFile.ApplicationAreas.Any(item => item.ApplicationAreaId == _openedApplicationAreaId))
+            if (virtualAmiiboFile.ApplicationAreas.Any(item => item.ApplicationAreaId == OpenedApplicationAreaId))
             {
                 for (int i = 0; i < virtualAmiiboFile.ApplicationAreas.Count; i++)
                 {
-                    if (virtualAmiiboFile.ApplicationAreas[i].ApplicationAreaId == _openedApplicationAreaId)
+                    if (virtualAmiiboFile.ApplicationAreas[i].ApplicationAreaId == OpenedApplicationAreaId)
                     {
                         virtualAmiiboFile.ApplicationAreas[i] = new VirtualAmiiboApplicationArea()
                         {
-                            ApplicationAreaId = _openedApplicationAreaId,
+                            ApplicationAreaId = OpenedApplicationAreaId,
                             ApplicationArea = applicationAreaData,
                         };
 
@@ -205,10 +233,21 @@ namespace Ryujinx.HLE.HOS.Services.Nfc.Nfp
             return virtualAmiiboFile;
         }
 
-        private static void SaveAmiiboFile(VirtualAmiiboFile virtualAmiiboFile)
+        public static void SaveAmiiboFile(VirtualAmiiboFile virtualAmiiboFile)
         {
             string filePath = Path.Join(AppDataManager.BaseDirPath, "system", "amiibo", $"{virtualAmiiboFile.AmiiboId}.json");
             JsonHelper.SerializeToFile(filePath, virtualAmiiboFile, _serializerContext.VirtualAmiiboFile);
         }
+
+        public static bool SaveFileExists(VirtualAmiiboFile virtualAmiiboFile)
+        {
+            if (InputBin != string.Empty)
+            {
+                SaveAmiiboFile(virtualAmiiboFile);
+                return true;
+
+            }
+            return File.Exists(Path.Join(AppDataManager.BaseDirPath, "system", "amiibo", $"{virtualAmiiboFile.AmiiboId}.json"));
+        }
     }
 }