using System.IO;
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using System.Security.Cryptography;
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using System.Text;
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using UnityEngine;
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#if !NETFX_CORE
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namespace Core.Data
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{
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/// <summary>
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/// Encryption extension to Json Saver
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/// </summary>
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public class EncryptedJsonSaver<T> : JsonSaver<T> where T : IDataStore
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{
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/// <summary>
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/// IV for Rijndael defaults to 16 if using its default block size
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/// </summary>
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const int k_InitializationVectorLength = 16;
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/// <summary>
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/// Longest supported key length for Rijndael is 256 bits (32 bytes)
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/// Other supported values are 128 or 192 bits
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/// </summary>
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const int k_KeyLength = 32;
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/// <summary>
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/// Salt for encryption
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/// </summary>
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static readonly byte[] s_Salt =
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{
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0x6b, 0xb0, 0xa1, 0x65, 0x08, 0xf8, 0xe6, 0xe8, 0x4d, 0x9e, 0x2f, 0x19, 0x97, 0xec, 0x0d, 0x6e,
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0xe7, 0xec, 0xe2, 0x0a, 0xd9, 0x47, 0xa7, 0x8d, 0xff, 0x3d, 0xe1, 0x65, 0x4f, 0x46, 0x00, 0x22
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};
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public EncryptedJsonSaver(string filename)
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: base(filename)
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{
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}
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/// <summary>
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/// Get device bytes to prevent copying save file to different device
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/// </summary>
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static byte[] GetUniqueDeviceBytes()
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{
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byte[] deviceIdentifier = Encoding.ASCII.GetBytes(SystemInfo.deviceUniqueIdentifier);
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return deviceIdentifier;
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}
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/// <summary>
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/// Gets encrypted write stream
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/// </summary>
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/// <returns>The write stream.</returns>
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protected override StreamWriter GetWriteStream()
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{
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var underlyingStream = new FileStream(m_Filename, FileMode.Create);
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var byteGenerator = new Rfc2898DeriveBytes(GetUniqueDeviceBytes(), s_Salt, 1000);
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var random = new RNGCryptoServiceProvider();
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byte[] key = byteGenerator.GetBytes(k_KeyLength);
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byte[] iv = new byte[k_InitializationVectorLength];
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random.GetBytes(iv);
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Rijndael rijndael = Rijndael.Create();
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rijndael.Key = key;
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rijndael.IV = iv;
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underlyingStream.Write(iv, 0, k_InitializationVectorLength);
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var encryptedStream = new CryptoStream(underlyingStream, rijndael.CreateEncryptor(), CryptoStreamMode.Write);
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return new StreamWriter(encryptedStream);
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}
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/// <summary>
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/// Gets decrypted read stream
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/// </summary>
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/// <returns>The read stream.</returns>
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protected override StreamReader GetReadStream()
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{
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var underlyingStream = new FileStream(m_Filename, FileMode.Open);
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var byteGenerator = new Rfc2898DeriveBytes(GetUniqueDeviceBytes(), s_Salt, 1000);
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byte[] key = byteGenerator.GetBytes(k_KeyLength);
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byte[] iv = new byte[k_InitializationVectorLength];
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underlyingStream.Read(iv, 0, k_InitializationVectorLength);
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Rijndael rijndael = Rijndael.Create();
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rijndael.Key = key;
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rijndael.IV = iv;
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var encryptedStream = new CryptoStream(underlyingStream, rijndael.CreateDecryptor(), CryptoStreamMode.Read);
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return new StreamReader(encryptedStream);
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}
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}
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}
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#endif
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