Initial version.

LockItShared/Services/BluetoothLock/Crypto/Cipher.cs

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+using System;
+using System.IO;
+using System.Security.Cryptography;
+using TINK.Model.Device;
+
+namespace TINK.Services.BluetoothLock.Crypto
+{
+    public class Cipher : ICipher
+    {
+        /// <summary> Decrypt data. </summary>
+        /// <remarks>
+        /// Further info see:
+        /// https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography.aes?view=netcore-3.1 for further info
+        //  https://docs.microsoft.com/en-us/dotnet/standard/security/cryptographic-services
+        //  https://stackoverflow.com/questions/24903575/how-to-return-byte-when-decrypt-using-cryptostream-descryptoserviceprovider/24903689
+
+        /// </remarks>
+        /// <param name="key">Key to decrypt data with.</param>
+        /// <param name="encrypted">Encrpyted data to decrypt.</param>
+        /// <returns>Decrypted data.</returns>
+        public byte[] Decrypt(byte[] key, byte[] encrypted)
+        {
+            // Check arguments.
+            if (encrypted == null || encrypted.Length <= 0)
+                throw new ArgumentNullException(nameof(encrypted));
+
+            if (key == null || key.Length <= 0)
+                throw new ArgumentNullException(nameof(key));
+
+            using (Aes aesAlg = Aes.Create())
+            {
+                aesAlg.KeySize = 192;
+                aesAlg.Mode = CipherMode.ECB;
+                aesAlg.Padding = PaddingMode.None;
+                aesAlg.Key = key;
+
+                // Create a decryptor to perform the stream transform.
+                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
+
+                // Create the streams used for decryption.
+                using (var msDecrypt = new MemoryStream())
+                {
+                    using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Write))
+                    {
+                        csDecrypt.Write(encrypted, 0, encrypted.Length);
+                        csDecrypt.FlushFinalBlock();
+                        return msDecrypt.ToArray();
+                    }
+                }
+            }
+        }
+
+        public byte[] Encrypt(byte[] key, byte[] clear)
+        {
+            // Check arguments.
+            if (clear == null || clear.Length <= 0)
+                throw new ArgumentNullException("plainText");
+
+            if (key == null || key.Length <= 0)
+                throw new ArgumentNullException("Key");
+
+            // Create an AesCryptoServiceProvider object
+            // with the specified key and IV.
+            using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
+            {
+                aesAlg.KeySize = 192;
+                aesAlg.Mode = CipherMode.ECB;
+                aesAlg.Padding = PaddingMode.None;
+                aesAlg.Key = key;
+
+                // Create an encryptor to perform the stream transform.
+                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
+
+                // Create the streams used for encryption.
+                using (var msEncrypt = new MemoryStream())
+                {
+                    using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
+                    {
+                        csEncrypt.Write(clear, 0, clear.Length);
+                        csEncrypt.FlushFinalBlock();
+                        return msEncrypt.ToArray();
+                    }
+                }
+            }
+
+        }
+    }
+}