一：前言

常用的文件加密算法有：DES、AES、RSA、SHA-1、MD5…..
.Net自带了安全类库，在System.Security.Cryptography下有一些常用的加密算法
其中MD5属于摘要算法，多用于检查文件是否有修改

二：加密算法介绍

——对称加密
对称加密算法有AES、DES、3DES等
在对称加密算法中，密钥只有一个，加密和解密都使用相同的密钥

——非对称加密
非对称加密算法有RSA、DSA、ECC等
在非对称加密算法中，需要两个密钥，一个公钥一个私钥
如果使用公钥对数据进行加密，只有使用对应的私钥才能进行解密，如果使用私钥对数据进行加密，只有使用对应的公钥才能进行解密

——签名加密算法(散列算法)
签名加密算法有SHA1、MD5、HMAC等
签名加密算法不需要密钥，一般不可逆

三：AES算法

需要注意的是加密后获得的bytes千万别用UTF8去获取字符串，不然会有信息损失，导致后面解密失败

using System;
using System.Security.Cryptography;
using System.Text;

/// <summary>
/// AES工具
/// </summary>
public class AESUtils
{
    const string AES_KEY = "dhjkfhskajflwoxj";

    /// <summary>
    /// AES加密
    /// </summary>
    /// <param name="content">明文</param>
    public static string Encrypt(string content)
    {
        if (string.IsNullOrEmpty(content))
        {
            return null;
        }
        byte[] contentBytes = Encoding.UTF8.GetBytes(content);
        byte[] keyBytes = Encoding.UTF8.GetBytes(AES_KEY);
        RijndaelManaged rm = new RijndaelManaged();
        rm.Key = keyBytes;
        rm.Mode = CipherMode.ECB;
        rm.Padding = PaddingMode.PKCS7;
        ICryptoTransform ict = rm.CreateEncryptor();
        byte[] resultBytes = ict.TransformFinalBlock(contentBytes, 0, contentBytes.Length);
        return Convert.ToBase64String(resultBytes, 0, resultBytes.Length);
    }

    /// <summary>
    /// AES解密
    /// </summary>
    /// <param name="str">密文</param>
    public static string Decrypt(string content)
    {
        if (string.IsNullOrEmpty(content))
        {
            return null;
        }
        byte[] contentBytes = Convert.FromBase64String(content);
        byte[] keyBytes = Encoding.UTF8.GetBytes(AES_KEY);
        RijndaelManaged rm = new RijndaelManaged();
        rm.Key = keyBytes;
        rm.Mode = CipherMode.ECB;
        rm.Padding = PaddingMode.PKCS7;
        ICryptoTransform ict = rm.CreateDecryptor();
        byte[] resultBytes = ict.TransformFinalBlock(contentBytes, 0, contentBytes.Length);
        return Encoding.UTF8.GetString(resultBytes);
    }
}

四：DES算法

需要注意的是加密后获得的bytes千万别用UTF8去获取字符串，不然会有信息损失，导致后面解密失败

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

/// <summary>
/// DES工具
/// </summary>
public class DESUtils
{
    public const string DES_KEY = "lhwyjlyy";

    /// <summary>
    /// DES加密
    /// </summary>
    /// <param name="content">明文</param>
    public static string Encrypt(string content)
    {
        if (string.IsNullOrEmpty(content))
        {
            return null;
        }
        byte[] contentBytes = Encoding.UTF8.GetBytes(content);
        byte[] keyBytes = Encoding.UTF8.GetBytes(DES_KEY);
        DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
        provider.Key = keyBytes;
        provider.IV = keyBytes;
        MemoryStream ms = new MemoryStream();
        CryptoStream cs = new CryptoStream(ms, provider.CreateEncryptor(), CryptoStreamMode.Write);
        cs.Write(contentBytes, 0, contentBytes.Length);
        cs.FlushFinalBlock();
        return Convert.ToBase64String(ms.ToArray());
    }

    /// <summary>
    /// DES解密
    /// </summary>
    /// <param name="content">密文</param>
    public static string Decrypt(string content)
    {
        if (string.IsNullOrEmpty(content))
        {
            return null;
        }
        byte[] contentBytes = Convert.FromBase64String(content);
        byte[] keyBytes = Encoding.UTF8.GetBytes(DES_KEY);
        DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
        provider.Key = keyBytes;
        provider.IV = keyBytes;
        MemoryStream ms = new MemoryStream();
        CryptoStream cs = new CryptoStream(ms, provider.CreateDecryptor(), CryptoStreamMode.Write);
        cs.Write(contentBytes, 0, contentBytes.Length);
        cs.FlushFinalBlock();
        return Encoding.UTF8.GetString(ms.ToArray());
    }
}