Unityでstringまたはシリアライズ可能なクラスをJSONに変換してAES暗号化して保存・読み込みする

FileAESCrypter.cs

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using UnityEngine;

/// <summary>
/// stringまたはシリアライズ可能なクラスをJSONに変換してAES暗号化して保存・読み込みする//
/// 参考: http://qiita.com/tempura/items/ad154d1269882ceda0f4
/// </summary>

public class FileAESCrypter
{
    private static readonly string EncryptKey = "0123456789012345";

    public static void EncryptJsonToFile<T>(T data, string savePath)
    {
        string jsondata = JsonUtility.ToJson(data);
        Debug.Log("jsondata" + jsondata);
        EncryptToFile(jsondata, savePath);
    }

    public static void EncryptToFile(string data, string savePath)
    {
        {
            // 暗号化
            byte[] bytes = Encoding.UTF8.GetBytes(data);

            string initialVector;
            byte[] bodyBytes;

            EncryptAes(bytes, out initialVector, out bodyBytes);

            // 保存
            byte[] initialVectorBytes = Encoding.UTF8.GetBytes(initialVector);

            if (!File.Exists(savePath))
            {
                Debug.Log("can't find file path");
                Directory.CreateDirectory(Path.GetDirectoryName(savePath));
            }

            using (FileStream fs = new FileStream(savePath, FileMode.Create, FileAccess.Write))
            using (BinaryWriter bw = new BinaryWriter(fs))
            {
                bw.Write(initialVectorBytes.Length);
                bw.Write(initialVectorBytes);

                bw.Write(bodyBytes.Length);
                bw.Write(bodyBytes);

                bw.Close();
            }
        }
    }

    public static bool DecryptJsonFromFile<T>(out T data, string savePath)
    {
        string strdata;
        bool value = DecryptFromFile(out strdata, savePath);

        data = value ? JsonUtility.FromJson<T>(strdata) : default(T);

        return value;
    }

    public static bool DecryptFromFile(out string data, string savePath)
    {
        // 読み込み
        byte[] initialVectorBytes = null;
        byte[] bodyBytes = null;

        if (!File.Exists(savePath))
        {
            Debug.LogError("cant find decrpt file path:" + savePath);
            data = string.Empty;
            return false;
        }

        using (FileStream fs = new FileStream(savePath, FileMode.Open, FileAccess.Read))
        using (BinaryReader br = new BinaryReader(fs))
        {
            int length = br.ReadInt32();
            initialVectorBytes = br.ReadBytes(length);

            length = br.ReadInt32();
            bodyBytes = br.ReadBytes(length);
        }

        // 複合化
        byte[] bytes;
        string initialVector = Encoding.UTF8.GetString(initialVectorBytes);
        DecryptAes(bodyBytes, initialVector, out bytes);

        data = Encoding.UTF8.GetString(bytes);
        return true;
    }

    public static void EncryptAes(byte[] src, out string initialVector, out byte[] dst)
    {
        initialVector = Guid.NewGuid().ToString("N").Substring(0, EncryptKey.Length);
        dst = null;
        using (RijndaelManaged rijndael = new RijndaelManaged())
        {
            rijndael.Padding = PaddingMode.PKCS7;
            rijndael.Mode = CipherMode.CBC;
            rijndael.KeySize = 256;
            rijndael.BlockSize = 128;

            byte[] key = Encoding.UTF8.GetBytes(EncryptKey);
            byte[] vec = Encoding.UTF8.GetBytes(initialVector);

            using (ICryptoTransform encryptor = rijndael.CreateEncryptor(key, vec))
            using (MemoryStream ms = new MemoryStream())
            using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
            {
                cs.Write(src, 0, src.Length);
                cs.FlushFinalBlock();
                dst = ms.ToArray();
            }
        }
    }

    public static void DecryptAes(byte[] src, string initialVector, out byte[] dst)
    {
        dst = new byte[src.Length];
        using (RijndaelManaged rijndael = new RijndaelManaged())
        {
            rijndael.Padding = PaddingMode.PKCS7;
            rijndael.Mode = CipherMode.CBC;
            rijndael.KeySize = 256;
            rijndael.BlockSize = 128;

            byte[] key = Encoding.UTF8.GetBytes(EncryptKey);
            byte[] vec = Encoding.UTF8.GetBytes(initialVector);

            using (ICryptoTransform decryptor = rijndael.CreateDecryptor(key, vec))
            using (MemoryStream ms = new MemoryStream(src))
            using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
            {
                cs.Read(dst, 0, dst.Length);
            }
        }
    }
}