33.NET对加密和解密的支持

  散列运算

mscorlib.dll下的System.Security.Cryptography下：
抽象类HashAlgorithm
    抽象类MD5
        MD5CryptoServiceProvider
    SHA1
        SHA1CryptoServiceProvider密封类：调用Windows Crypto API
        SHA1Managed普通类：用托管代码写的
    SHA256
        SHA256CryptoServiceProvider
        SHA256Managed
    SHA384
    SHA512

 

□ 对字节数组或流散列运算

    class Program 

    { 

        static void Main(string[] args) 

        { 

            string str = "Hello World"; 

            HashAlgorithm hashAlgorithm = HashAlgorithm.Create(HashAlgorithmType.SHA1); 

            byte[] data = Encoding.Default.GetBytes(str); 

            byte[] digest = hashAlgorithm.ComputeHash(data); 

            foreach (byte b in digest) 

            { 

                Console.Write("{0:X}",b); 

            } 

            Console.ReadKey(); 

        } 

    }

    public class HashAlgorithmType 

    { 

        public const string SHA1 = "SHA1"; 

        public const string SHA256 = "SHA256"; 

        public const string SHA384 = "SHA384"; 

        public const string SHA512 = "SHA512"; 

        public const string MD5 = "MD5"; 

    }

 

□ 密匙散列运算       

            string key = "secret key"; 

            byte[] data = Encoding.Default.GetBytes(key); 

            KeyedHashAlgorithm kha = new HMACSHA1(); 

            byte[] digest = kha.ComputeHash(data); 

            foreach (byte b in digest) 

            { 

                Console.Write("{0:x}",b); 

            }

 

  对称加密和解密

SymmetricAlgorithm
    DES
        DESCryptoServiceProvider
    TripleDES
        TripleDESCryptoServiceProvider
    Rijndael
        RijindaelManaged
    RC2  
        RC2CryptoServiceProvider

 

IV:Initialization vector初始化向量：
-为了解决加密字符串加密后仍然有重复部分，引入IV，加密字符串即使有重复，也会被打乱。
-IV值可以随意指定，但长度固定，通常为64位byte类型
-密匙长度也是固定的，通常为128位或196位byte类型

 

使用Encoding类将字符串转换为byte[]：
-如果使用UTF8，会变长编码

 

加密解密方法：
-加密方法：CreateEncryptor()，返回ICryptoTransform接口类型
-解密方法：CreateDecryptor()，返回ICrtyptoTransform接口类型

 

明文流和加密流的转换：

public CryptoStream(Stream stream, ICryptoTransform transform, CryptoStreamMode mode)

    class Program 

    { 

        static void Main(string[] args) 

        { 

            #region 对称加密和解密

            string key = "secret key"; 

            string str = "Hello World";

            //加密 

            string encryptedText = SymmetricCryptoHelper.Encrypt(str, key); 

            Console.WriteLine(encryptedText);

            //解密 

            string clearText = SymmetricCryptoHelper.Decrypt(encryptedText, key); 

            Console.WriteLine(clearText);

            Console.ReadKey();

            #endregion 

        } 

    }

    //对称加密帮助类 

    public class SymmetricCryptoHelper 

    { 

        private ICryptoTransform encryptor;  //加密器对象 

        private ICryptoTransform decryptor; //解密器对象 

        private const int BufferSize = 1024;

        public SymmetricCryptoHelper(string algorithmName, byte[] key) 

        { 

            SymmetricAlgorithm provider = SymmetricAlgorithm.Create(algorithmName); 

            provider.Key = key; 

            provider.IV = new byte[] { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };

            encryptor = provider.CreateEncryptor(); 

            decryptor = provider.CreateDecryptor(); 

        }

        public SymmetricCryptoHelper(byte[] key) : this("TripleDES", key){}

        //加密算法 

        public string Encrypt(string clearText) 

        { 

            //创建明文流 

            byte[] clearBuffer = Encoding.UTF8.GetBytes(clearText); 

            //byte[] clearBuffer = Encoding.Default.GetBytes(clearText); 

            MemoryStream clearStream = new MemoryStream(clearBuffer);

            //创建空的密文流 

            MemoryStream encryptedStream = new MemoryStream();

            //明文流和密文流转换流，准备写到密文流中 

            CryptoStream cryptoStream = new CryptoStream(encryptedStream, encryptor, CryptoStreamMode.Write); 

            int bytesRead = 0; 

            byte[] buffer = new byte[BufferSize]; 

            do 

            { 

                //读取明文流到buffer中 

                bytesRead = clearStream.Read(buffer, 0, BufferSize); 

                //通过CryptoStream将buffer中的明文流字节数组写到明文流中 

                cryptoStream.Write(buffer, 0, bytesRead); 

            } while (bytesRead > 0);

            cryptoStream.FlushFinalBlock();

            //获取加密后的字节数组 

            buffer = encryptedStream.ToArray();

            //将加密后的字节数组转换成字符串 

            string encryptedText = Convert.ToBase64String(buffer); 

            return encryptedText; 

        }

        //解密算法 

        public string Decrypt(string encryptedText) 

        { 

            //把加密字符串转换为加密字节数组 

            byte[] encryptedBuffer = Convert.FromBase64String(encryptedText); 

            //创建密文流 

            Stream encryptedStream = new MemoryStream(encryptedBuffer);

            //创建空的明文流 

            MemoryStream clearStream = new MemoryStream();

            //创建明文流和密文流的转化流，读取密文流 

            CryptoStream cryptoStream = new CryptoStream(encryptedStream, decryptor, CryptoStreamMode.Read);

            int bytesRead = 0; 

            byte[] buffer = new byte[BufferSize];

            do 

            { 

                //通过CryptoStream读取密文流到Buffer 

                bytesRead = cryptoStream.Read(buffer, 0, BufferSize); 

                //把Buffer中的密文流写到明文流中 

                clearStream.Write(buffer, 0, bytesRead); 

            } while (bytesRead > 0);

            //将明文流转换成字节数组 

            buffer = clearStream.GetBuffer();

            string clearText = Encoding.UTF8.GetString(buffer, 0, (int)clearStream.Length); 

            //string clearText = Encoding.Default.GetString(buffer, 0, (int)clearStream.Length); 

            return clearText; 

        }

        //密匙加密 

        public static string Encrypt(string clearText, string key) 

        { 

            byte[] keyData = new byte[16]; //TripleDES密匙固定长度为16个字节

            //把密匙字符串转换成字节数组 

            byte[] sourceData = Encoding.Default.GetBytes(key); 

            int copyBytes = 16; 

            if (sourceData.Length < 16) 

            { 

                copyBytes = sourceData.Length; 

            }

            //把密匙数组复制到keyData字节数组中 

            Array.Copy(sourceData,keyData,copyBytes);

            SymmetricCryptoHelper helper = new SymmetricCryptoHelper(keyData); 

            return helper.Encrypt(clearText); 

        }

        //密匙解密 

        public static string Decrypt(string encryptedText, string key) 

        { 

            byte[] keyData = new byte[16]; 

            byte[] sourceData = Encoding.Default.GetBytes(key); 

            int copyBytes = 16; 

            if (sourceData.Length < 16) 

            { 

                copyBytes = sourceData.Length; 

            } 

            Array.Copy(sourceData,keyData,copyBytes);

            SymmetricCryptoHelper helper = new SymmetricCryptoHelper(keyData); 

            return helper.Decrypt(encryptedText); 

        } 

    }

 

  非对称加密

AsymmetricAlgorithm
    RSA
        RSACryptoServiceProvider
    DSA
        DSACryptoServiceProvider：只能进行认证模式，即数字签名

 

对称加密中的密匙：
密匙为由开发者设定的字符串

 

非对称加密中的密匙：
● 通常是自动生成，不同的算法有不同的密匙格式   
● 在创建RSACryptoServiceProvider实例时，会自动创建一个公/私密匙对。在实例上调用ToXmlString()方法获得。

            RSACryptoServiceProvider provider = new RSACryptoServiceProvider();
            string publicPrivate = provider.ToXmlString(true);//获得公/私匙对
            //string publicOnly = provider.ToXmlString(false); //只获得公匙
            Console.Write(publicPrivate);
            Console.ReadKey();

 

□ 非对称加密帮助类

    //非对称加密帮助类 

    public class RSACryptoHelper 

    { 

        //加密 

        public static string Encrypt(string publicKeyXml, string plainText) 

        { 

            RSACryptoServiceProvider provider = new RSACryptoServiceProvider(); 

            provider.FromXmlString(publicKeyXml); //使用公匙初始化对象 

            byte[] plainData = Encoding.Default.GetBytes(plainText); 

            byte[] encryptedData = provider.Encrypt(plainData, true); 

            return Convert.ToBase64String(encryptedData); 

        }

        //解密 

        public static string Decrypt(string privateKeyXml, string encryptedText) 

        { 

            RSACryptoServiceProvider provider = new RSACryptoServiceProvider(); 

            provider.FromXmlString(privateKeyXml); 

            byte[] encryptedData = Convert.FromBase64String(encryptedText); 

            byte[] plainData = provider.Decrypt(encryptedData, true); 

            string plainText = Encoding.Default.GetString(plainData); 

            return plainText; 

        } 

    }

 

  数字签名

RSACryptoServiceProvider或DSACryptoServiceProvider
SignData()对摘要进行签名，并返回签名后的摘要。
VerifyData()得出本地摘要，并解密传递进来的原始摘要，对比返回bool类型结果。

 

□ 数字签名帮助类

    public class RSACryptoHelper 

    { 

        public static string SignData(string plainText, string privateKeyXml) 

        { 

            RSACryptoServiceProvider provider = new RSACryptoServiceProvider(); 

            provider.FromXmlString(privateKeyXml);

            byte[] plainData = Encoding.Default.GetBytes(plainText); 

            //设置获取摘要的算法 

            HashAlgorithm sha1 = HashAlgorithm.Create("SHA1"); 

            //获取签名过的摘要,是使用私匙加密过的摘要 

            byte[] signedDigest = provider.SignData(plainData, sha1); 

            return Convert.ToBase64String(signedDigest); 

        }

        public static bool VerifyData(string plainText, string signature, string publicKeyXml) 

        { 

            RSACryptoServiceProvider provider = new RSACryptoServiceProvider(); 

            provider.FromXmlString(publicKeyXml);

            byte[] plainData = Encoding.Default.GetBytes(plainText); 

            byte[] signedDigest = Convert.FromBase64String(signature);

            HashAlgorithm sha1 = HashAlgorithm.Create("SHA1"); 

            bool isDataIntact = provider.VerifyData(plainData, sha1, signedDigest); 

            return isDataIntact; 

        }

        //使用SingnHash 

        public static string SignData2(string plainText, string privateKeyXml) 

        { 

            RSACryptoServiceProvider provider = new RSACryptoServiceProvider(); 

            provider.FromXmlString(privateKeyXml); 

            byte[] plainData = Encoding.Default.GetBytes(plainText);

            //设置获取摘要的算法 

            HashAlgorithm sha1 = HashAlgorithm.Create("SHA1"); 

            //获得原始摘要 

            byte[] digestData = sha1.ComputeHash(plainData); 

            //对元素摘要进行签名 

            byte[] signedDigest = provider.SignHash(digestData, "SHA1"); 

            return Convert.ToBase64String(signedDigest); 

        }

        //使用VerifyHash 

        public static bool VerifyData2(string plainText, string signedDigest, string publicKeyXml) 

        { 

            RSACryptoServiceProvider provider = new RSACryptoServiceProvider(); 

            provider.FromXmlString(publicKeyXml);

            byte[] plainData = Encoding.Default.GetBytes("SHA1"); 

            byte[] signedDigestData = Convert.FromBase64String(signedDigest);

            //获得本地摘要 

            HashAlgorithm sha1 = HashAlgorithm.Create("SHA1"); 

            byte[] digest = sha1.ComputeHash(plainData);

            //解密签名 

            bool isDataIntact = provider.VerifyHash(digest, "SHA1", signedDigestData); 

            return isDataIntact; 

        } 

    }

 

参考资料：
※ 《.NET之美》--张子阳,感谢写了这么好的书！