为数据库中的关键字段进行加密是必不可少的，特别是一些用户密码，银行卡账号等。现在我们来说一下如何在Nhibernate中创建一个加密类来为数据库中的关键字段加密。

1 创建一个接口：IEncryptor

public interface IEncryptor    {        string Encrypt(string plainText);        string Decrypt(string encryptedText);        string EncryptionKey { get; set; }    }

2 再创建一个继承它的子类：SymmetricEncryptorBase

public class SymmetricEncryptorBase : IEncryptor    {        private readonly SymmetricAlgorithm _cryptoProvider;        private byte[] _myBytes;        protected SymmetricEncryptorBase(        SymmetricAlgorithm cryptoProvider)        {            _cryptoProvider = cryptoProvider;        }        #region IEncryptor 成员        public string EncryptionKey { get; set; }              /// 
        /// 加密，利用CryptoStream        /// 
        ///         /// 
             public string Encrypt(string plainText)        {            var bytes = GetEncryptionKeyBytes();            using (var memoryStream = new MemoryStream())            {                ICryptoTransform encryptor = _cryptoProvider                .CreateEncryptor(bytes, bytes);                using (var cryptoStream = new CryptoStream(                memoryStream, encryptor, CryptoStreamMode.Write))                {                    using (var writer = new StreamWriter(cryptoStream))                    {                                               writer.Write(plainText);                        writer.Flush();                        cryptoStream.FlushFinalBlock();                        return Convert.ToBase64String(                        memoryStream.GetBuffer(),                        0,                        (int)memoryStream.Length);                    }                }            }        }        //获取密钥        private byte[] GetEncryptionKeyBytes()        {            if (_myBytes == null)                _myBytes = Encoding.ASCII.GetBytes(EncryptionKey);            return _myBytes;        }        /// 
        /// 解密        /// 
        ///         /// 
             public string Decrypt(string encryptedText)        {            var bytes = GetEncryptionKeyBytes();            using (var memoryStream = new MemoryStream(            Convert.FromBase64String(encryptedText)))            {                ICryptoTransform decryptor = _cryptoProvider                .CreateDecryptor(bytes, bytes);                using (var cryptoStream = new CryptoStream(                memoryStream, decryptor, CryptoStreamMode.Read))                {                    using (var reader = new StreamReader(cryptoStream))                    {                        return reader.ReadToEnd();                    }                }            }        }        #endregion    }

3 再创建一个类：DESEncryptor

public class DESEncryptor : SymmetricEncryptorBase    {        public DESEncryptor()            : base(new DESCryptoServiceProvider())        { }    }

4 再新建一个类：EncryptedString，通过这个类来调用前面的DESEncryptor来加密解密字符串

public class EncryptedString : IUserType, IParameterizedType    {        private IEncryptor _encryptor;        public object NullSafeGet( IDataReader rs, string[] names, object owner)        {            //treat for the posibility of null values            object passwordString =            NHibernateUtil.String.NullSafeGet(rs, names[0]);            if (passwordString != null)            {                return _encryptor.Decrypt((string)passwordString);            }            return null;        }        public void NullSafeSet(IDbCommand cmd,object value,int index)        {            if (value == null)            {                NHibernateUtil.String.NullSafeSet(cmd, null, index);                return;            }            string encryptedValue = _encryptor.Encrypt((string)value);            NHibernateUtil.String.NullSafeSet(            cmd, encryptedValue, index);        }        public object DeepCopy(object value)        {            return value == null ? null :        string.Copy((string)value);        }        public object Replace(object original,        object target, object owner)        {            return original;        }        public object Assemble(object cached, object owner)        {            return DeepCopy(cached);        }        public object Disassemble(object value)        {            return DeepCopy(value);        }        public SqlType[] SqlTypes        {            get            {                return new[] { new SqlType(DbType.String) };            }        }        public Type ReturnedType        {            get { return typeof(string); }        }        public bool IsMutable        {            get { return false; }        }        public new bool Equals(object x, object y)        {            if (ReferenceEquals(x, y))            {                return true;            }            if (x == null || y == null)            {                return false;            }            return x.Equals(y);        }        public int GetHashCode(object x)        {            if (x == null)            {                throw new ArgumentNullException("x");            }            return x.GetHashCode();        }        public void SetParameterValues(        IDictionary
     
       parameters)        {            if (parameters != null)            {                var encryptorTypeName = parameters["encryptor"];                _encryptor = !string.IsNullOrEmpty(encryptorTypeName)                ? (IEncryptor)Instantiate(encryptorTypeName)                : new DESEncryptor();                var encryptionKey = parameters["encryptionKey"];                if (!string.IsNullOrEmpty(encryptionKey))                    _encryptor.EncryptionKey = encryptionKey;            }            else            {                _encryptor = new DESEncryptor();            }        }        private static object Instantiate(string typeName)        {            var type = Type.GetType(typeName);            return Activator.CreateInstance(type);        }    }
     

 OK.这个加密类到此就完成了。现在我们来创建一个Account对象来测试。

public class Account    {        public virtual Guid Id { get; set; }        public virtual string EMail { get; set; }        public virtual string Name { get; set; }        public virtual string CardNumber { get; set; }        public virtual int ExpirationMonth { get; set; }        public virtual int ExpirationYear { get; set; }        public virtual string ZipCode { get; set; }    }

重要的是定义相应的Account.hbm.xml文件：

     
       
          
           
             EncryptedStringExample.DESEncryptor,      EncryptedStringExample        
           
       12345678  
        
          
             
            
           
           
           
           
           
           
           
         
      
     

 在一个新建的控制台应用程序中，我们新建一个Account对象来测试一下：

private static void AddAccount(NHibernate.ISession session)        {            session.Save(new Account() {              CardNumber="45678",             EMail="bb@qq.com",             ExpirationMonth=12,             ExpirationYear=2012,             Name="gyoung",             ZipCode="55555"            });        }

加密的字段为：CardNumber.打开数据库，看到存储在其中的字段已经被加密了.

现在我们从数据库中取出该字段看看。因为只有一条记录，我就只取第一条了。

private static Account GetAccount(NHibernate.ISession session)        {            return session.QueryOver
     
      ().Take(1).SingleOrDefault();        }
     

在Main方法中增加两行代码：

Account account = GetAccount(session);  Console.WriteLine(account.CardNumber);

我们可以看到控制台上显示出来的值为：

 可以看出解密正确。

 源码下载：。项目中的EncryptedStringExample与EncryptedStringTest