详解ASP.NET中加密和解密的方法

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;
        }
    }

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