探讨.NET Core中实现AES加密和解密以及.NET Core为我们提供了什么方便！

前言

对于数据加密和解密每次我都是从网上拷贝一份，无需有太多了解，由于在.net core中对加密和解密目前全部是统一了接口，只是做具体的实现，由于遇到过问题，所以将打算基本了解下其原理，知其然足矣，知其所以然那就达不到了，利用AES加密更加安全，上一篇园友又提出，所以借着这个机会刚好用到加密和解密，同时我也已将项目中DES加密已替换为AES，在这里介绍一下。

AES加密介绍

高级加密标准（英语：Advanced Encryption Standard，缩写：AES），在密码学中又称Rijndael加密法，是美国联邦政府采用的一种区块加密标准。这个标准用来替代原先的DES，已经被多方分析且广为全世界所使用。它要求区块大小必须为128位，而密钥长度则可以为128、196、256位。基于此我们来实现.NET Framework版本和.NET Core版本。

在.NET Framework中实现AES加密和解密

AES加密

        public static string EncryptText(string input, string key)
        {

            byte[] bytesToBeEncrypted = Encoding.UTF8.GetBytes(input);
            byte[] passwordBytes = Encoding.UTF8.GetBytes(key);

            passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

            byte[] bytesEncrypted = AESEncryptBytes(bytesToBeEncrypted, passwordBytes);

            string result = Convert.ToBase64String(bytesEncrypted);

            return result;
        }

        public static byte[] AESEncryptBytes(byte[] bytesToBeEncrypted, byte[] passwordBytes)
        {
            byte[] encryptedBytes = null;

            var saltBytes = new byte[] { , , , , , , ,  ,};

            using (var ms = new MemoryStream())
            {
                using (var AES = new RijndaelManaged())
                {
                    AES.KeySize = ;
                    AES.BlockSize = ;

                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, );
                    AES.Key = key.GetBytes();
                    AES.IV = key.GetBytes();

                    AES.Mode = CipherMode.CBC;

                    using (var cs = new CryptoStream(ms, AES.CreateEncryptor(),
                        CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeEncrypted, , bytesToBeEncrypted.Length);
                        cs.Close();
                    }

                    encryptedBytes = ms.ToArray();
                }
            }

            return encryptedBytes;
        }

上述盐字节必须为至少8个字节，否则报错如下：

AES解密

        public static string DecryptText(string input, string key)
        {
            byte[] bytesToBeDecrypted = Convert.FromBase64String(input);

            byte[] passwordBytes = Encoding.UTF8.GetBytes(key);

            passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

            byte[] bytesDecrypted = AESDecryptBytes(bytesToBeDecrypted, passwordBytes);

            string result = Encoding.UTF8.GetString(bytesDecrypted);

            return result;
        }

        public static byte[] AESDecryptBytes(byte[] bytesToBeDecrypted, byte[] passwordBytes)
        {
            byte[] decryptedBytes = null;

            var saltBytes = new byte[] { , , , , , , ,  ,};

            using (var ms = new MemoryStream())
            {
                using (var AES = new RijndaelManaged())
                {
                    AES.KeySize = ;
                    AES.BlockSize = ;

                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, );
                    AES.Key = key.GetBytes();
                    AES.IV = key.GetBytes();

                    AES.Mode = CipherMode.CBC;

                    using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeDecrypted, , bytesToBeDecrypted.Length);
                        cs.Close();
                    }

                    decryptedBytes = ms.ToArray();
                }
            }

            return decryptedBytes;
        }

测试如下：

            var encrptText = "Jeffcky";
            var key = Guid.NewGuid().ToString("N");
            Console.WriteLine("加密前内容：" + encrptText);
            var input = EncryptText(encrptText,key);
            Console.WriteLine("加密后字符串为：" + input);
            var text = DecryptText(input, key);
            Console.WriteLine("解密后内容：" + text);

上述利用 RijndaelManaged 来实例化AES，最终该类继承自 SymmetricAlgorithm 对称算法类。通过我们实例化一个 Rfc2898DeriveBytes 来对密钥密钥和盐循环迭代1000次从而实现加密，同理解密反向操作。

在.NET Core中实现AES加密和解密

在.NET Core中对于对称加密统一接口不再利用不同类而实现，对于非对称加密当然和对称加密接口就不同了，创建起来格外方便，不再是实例化对应的类，如下

            //对称加密
            var aes = Aes.Create();
            var tripleDES = TripleDES.Create();

            //非对称加密
            var rsa = RSA.Create();

由下可以看出直接定义了一个静态方法来创建加密

    public abstract class Aes : SymmetricAlgorithm
    {
        protected Aes();

        public override KeySizes[] LegalBlockSizes { get; }
        public override KeySizes[] LegalKeySizes { get; }

        public static Aes Create();
    }

    public abstract class RSA : AsymmetricAlgorithm
    {
        protected RSA();

        public static RSA Create();
        ...
    }

当然命名空间依然是 System.Security.Cryptography 。我们直接看实现。

AES加密

        public static string AESEncrypt(string input, string key)
        {
            var encryptKey = Encoding.UTF8.GetBytes(key);

            using (var aesAlg = Aes.Create())
            {
                using (var encryptor = aesAlg.CreateEncryptor(encryptKey, aesAlg.IV))
                {
                    using (var msEncrypt = new MemoryStream())
                    {
                        using (var csEncrypt = new CryptoStream(msEncrypt, encryptor,
                            CryptoStreamMode.Write))

                        using (var swEncrypt = new StreamWriter(csEncrypt))
                        {
                            swEncrypt.Write(input);
                        }

                        var iv = aesAlg.IV;

                        var decryptedContent = msEncrypt.ToArray();

                        var result = new byte[iv.Length + decryptedContent.Length];

                        Buffer.BlockCopy(iv, , result, , iv.Length);
                        Buffer.BlockCopy(decryptedContent, , result,
                            iv.Length, decryptedContent.Length);

                        return Convert.ToBase64String(result);
                    }
                }
            }
        }

AES解密（修改：2019-11-13）

        public static string AESDecrypt(string input, string key)
        {
            var fullCipher = Convert.FromBase64String(input);

            var iv = new byte[];
            var cipher = new byte[fullCipher.Length-iv.Length];

            Buffer.BlockCopy(fullCipher, , iv, , iv.Length);
            Buffer.BlockCopy(fullCipher, iv.Length, cipher, , fullCipher.Length- iv.Length);
            var decryptKey = Encoding.UTF8.GetBytes(key);

            using (var aesAlg = Aes.Create())
            {
                using (var decryptor = aesAlg.CreateDecryptor(decryptKey, iv))
                {
                    string result;
                    using (var msDecrypt = new MemoryStream(cipher))
                    {
                        using (var csDecrypt = new CryptoStream(msDecrypt,
                            decryptor, CryptoStreamMode.Read))
                        {
                            using (var srDecrypt = new StreamReader(csDecrypt))
                            {
                                result = srDecrypt.ReadToEnd();
                            }
                        }
                    }

                    return result;
                }
            }
        }

测试如下：

            var key = Guid.NewGuid().ToString("N");
            var name = "Jeffcky";
            Console.WriteLine($"加密字符串为{name}");
            var encryptStr = AESEncrypt(name, key);
            Console.WriteLine($"加密后结果为：{encryptStr}");
            var decryptStr = AESDecrypt(encryptStr, key);
            Console.WriteLine($"解密后字符串为{decryptStr}");

总结

在.NET Core中实现对称加密和非对称加密无论是实现还是创建都更加简洁，之前也并未去具体了解加密和解密相关内容，借此机会稍微了解下对应的加密所以花了一点时间。对于AES加密还没怎么具体去了解内部原理，只是参照了一点资料，以此作为备忘录，目前.NET Core仅支持AES、TripleDES、RSA。希望对在.NET Core项目中需要实现加密的童鞋提供一点帮助。接下来有时间我们继续巩固下线程基础知识，敬请期待，待我学习完毕再来更新博客和大家一起分享。