[转]应用RSACryptoServiceProvider类轻松实现RSA算法

在我们现实当中经常会存在需要对某些数据进行加密保护 然后进行解密的操作,比方,我们需要对某些XML配置信息里面的某些数据进行加密,以防止任何人打开该XML配置信息都能正常的看到该配置信息里面的内容,从而被人家篡改程序,甚至致使系统崩溃.下面我就谈下现在比较常用的RSA算法以及如何在Visual C#中如何实现.
 
1.首先介绍下什么是RSA算法,让大家对RSA算法有个简要的理解.
   RSA算法非常简单，概述如下:
　　找两素数p和q
　　 取n=p*q  如:n=3*7=21
　　 取t=(p-1)*(q-1) 如:t = 2*6 = 12
 　 取任何一个数e,要求满足e
　　取d*e%t==1  如:d=7,e=7,则7*7/12刚好等于1满足要求
　　这样最终得到三个数: n d e,即 n=21,d=7,e=7
　　设消息为数M
　　设c=(M**d)%n就得到了加密后的消息c
　　设m=(c**e)%n则 m == M，从而完成对c的解密。
　　注:**表示次方,上面两式中的d和e可以互换。
 
　　在对称加密中:
　　n d两个数构成公钥，可以告诉别人;
　　n e两个数构成私钥，e自己保留，不让任何人知道。
　　给别人发送的信息使用e加密，只要别人能用d解开就证明信息是由你发送的，构成了签名机制。
　　别人给你发送信息时使用d加密，这样只有拥有e的你能够对其解密。
　　rsa的安全性在于对于一个大数n，没有有效的方法能够将其分解从而在已知n d的情况无法获得e;同样在已知n e的情况下无法求得d。
 
2.上面就是对RSA算法的一个简要概括,该描述在很多书本上都有介绍,这里也就不做过多解释了,下面我们看下在.net 里面如何实现该算法.
   在.net 里面,有一个叫RSACryptoServiceProvider的类,在MSDN中,我们可以了解到该类使用加密服务提供程序 (CSP) 提供的rsa算法的实现,执行不对称加密和解密,从继承关系上我们了解到该类继承自RSA类.通过该类,我们可以导出加密解密所需要的XML信息,并且能够根据我们提供的XML信息进行加密解密计算,下面是对该类的一些具体操作,主要包括如何导出密钥,如何用形成的密钥进行加密和解密,完成我们一般的操作.
   public class Cyh_RSA
    {
        public Cyh_RSA()
        {
           
        }
 
        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="p_inputString">需要加密的字符串信息</param>
        /// <param name="p_strKeyPath">加密用的密钥所在的路径(*.cyh_publickey)</param>
        /// <returns>加密以后的字符串信息</returns>
        public string Encrypt(string p_inputString, string p_strKeyPath)
        {
            string fileString = null;
            string outString = null;
            if (File.Exists(p_strKeyPath))
            {
                StreamReader streamReader = new StreamReader(p_strKeyPath, true);
                fileString = streamReader.ReadToEnd();
                streamReader.Close();
 
            }
 
            if (fileString != null)
            {
                string bitStrengthString = fileString.Substring(0, fileString.IndexOf("</BitStrength>") + 14);
                fileString = fileString.Replace(bitStrengthString, "");
                int bitStrength = Convert.ToInt32(bitStrengthString.Replace("<BitStrength>", "").Replace("</BitStrength>", ""));
                try
                {
                    outString = EncryptString(p_inputString, bitStrength, fileString);
                }
                catch (Exception Ex)
                {
                    MessageBox.Show("出错: \n" + Ex.Message);
                }
 
            }
 
            return outString;
        }
        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="p_inputString">需要解密的字符串信息</param>
        /// <param name="p_strKeyPath">解密用的密钥所在的路径(*.cyh_primarykey)</param>
        /// <returns>解密以后的字符串信息</returns>
        public string Decrypt(string p_inputString, string p_strKeyPath)
        {
            string fileString = null;
            string outString = null;
            if (File.Exists(p_strKeyPath))
            {
                StreamReader streamReader = new StreamReader(p_strKeyPath, true);
                fileString = streamReader.ReadToEnd();
                streamReader.Close();
 
            }
 
            if (fileString != null)
            {
                string bitStrengthString = fileString.Substring(0, fileString.IndexOf("</BitStrength>") + 14);
                fileString = fileString.Replace(bitStrengthString, "");
                int bitStrength = Convert.ToInt32(bitStrengthString.Replace("<BitStrength>", "").Replace("</BitStrength>", ""));
                try
                {
                    outString = DecryptString(p_inputString, bitStrength, fileString);
                }
                catch (Exception Ex)
                {
                    MessageBox.Show("出错: \n" + Ex.Message);
                }
 
            }
 
            return outString;
 
        }
 
        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="p_inputString">需要加密的字符串</param>
        /// <param name="p_dwKeySize">密钥的大小</param>
        /// <param name="p_xmlString">包含密钥的XML文本信息</param>
        /// <returns>加密后的文本信息</returns>
        private string EncryptString(string p_inputString, int p_dwKeySize, string p_xmlString)
        {
            RSACryptoServiceProvider rsaCryptoServiceProvider = new RSACryptoServiceProvider(p_dwKeySize);
            rsaCryptoServiceProvider.FromXmlString(p_xmlString);
            int keySize = p_dwKeySize / 8;
            byte[] bytes = Encoding.UTF32.GetBytes(p_inputString);
            int maxLength = keySize - 42;
            int dataLength = bytes.Length;
            int iterations = dataLength / maxLength;
            StringBuilder stringBuilder = new StringBuilder();
            for (int i = 0; i <= iterations; i++)
            {
                byte[] tempBytes = new byte[(dataLength - maxLength * i > maxLength) ? maxLength : dataLength - maxLength * i];
                Buffer.BlockCopy(bytes, maxLength * i, tempBytes, 0, tempBytes.Length);
                byte[] encryptedBytes = rsaCryptoServiceProvider.Encrypt(tempBytes, true);
                Array.Reverse(encryptedBytes);
                stringBuilder.Append(Convert.ToBase64String(encryptedBytes));
            }
            return stringBuilder.ToString();
        }
 
        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="p_inputString">需要解密的字符串信息</param>
        /// <param name="p_dwKeySize">密钥的大小</param>
        /// <param name="p_xmlString">包含密钥的文本信息</param>
        /// <returns>解密后的文本信息</returns>
        private string DecryptString(string inputString, int dwKeySize, string xmlString)
        {
            RSACryptoServiceProvider rsaCryptoServiceProvider = new RSACryptoServiceProvider(dwKeySize);
            rsaCryptoServiceProvider.FromXmlString(xmlString);
            int base64BlockSize = ((dwKeySize / 8) % 3 != 0) ? (((dwKeySize / 8) / 3) * 4) + 4 : ((dwKeySize / 8) / 3) * 4;
            int iterations = inputString.Length / base64BlockSize;
            ArrayList arrayList = new ArrayList();
            for (int i = 0; i < iterations; i++)
            {
                byte[] encryptedBytes = Convert.FromBase64String(inputString.Substring(base64BlockSize * i, base64BlockSize));
                Array.Reverse(encryptedBytes);
                arrayList.AddRange(rsaCryptoServiceProvider.Decrypt(encryptedBytes, true));
            }
            return Encoding.UTF32.GetString(arrayList.ToArray(Type.GetType("System.Byte")) as byte[]);
        }
 
        /// <summary>
        /// 形成并保存公开密钥和私有密钥
        /// </summary>
        /// <param name="p_currentBitStrength">密钥大小</param>
        public void SaveKey(int p_currentBitStrength)
        {
            RSACryptoServiceProvider RSAProvider = new RSACryptoServiceProvider(p_currentBitStrength);
            string publicAndPrivateKeys = "<BitStrength>" + p_currentBitStrength.ToString() + "</BitStrength>" + RSAProvider.ToXmlString(true);
            string justPublicKey = "<BitStrength>" + p_currentBitStrength.ToString() + "</BitStrength>" + RSAProvider.ToXmlString(false);
            if (saveFile("Save Public/Private Keys As", "Public/Private Keys Document( *.cyh_primarykey )|*.cyh_primarykey", publicAndPrivateKeys))
            { while (!saveFile("Save Public Key As", "Public Key Document( *.cyh_publickey )|*.cyh_publickey", justPublicKey)) { ; } }
        }
 
        /// <summary>
        /// 保存信息
        /// </summary>
        /// <param name="p_title">标题</param>
        /// <param name="p_filterString">过滤条件</param>
        /// <param name="p_outputString">输出内容</param>
        /// <returns>是否成功</returns>
        private bool saveFile(string p_title, string p_filterString, string p_outputString)
        {
            SaveFileDialog saveFileDialog = new SaveFileDialog();
            saveFileDialog.Title = p_title;
            saveFileDialog.Filter = p_filterString;
            saveFileDialog.FileName = "";
            if (saveFileDialog.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    StreamWriter streamWriter = new StreamWriter(saveFileDialog.FileName, false);
                    if (p_outputString != null)
                    { streamWriter.Write(p_outputString); }
                    streamWriter.Close();
                    return true;
                }
                catch (Exception Ex)
                {
                    Console.WriteLine(Ex.Message);
                    return false;
                }
            }
            return false;
        }
    }
这样,您在任何地方都可以使用该类对数据进行加密和解密,并且操作相当方便,如:
生成密钥:
 Cyh_RSA rsa = new Cyh_RSA();
 rsa.SaveKey(1024);
加密:
Cyh_RSA rsa = new Cyh_RSA();
rsa.Encrypt("需要加密的内容", "包含密钥的路径");
解密:
Cyh_RSA rsa = new Cyh_RSA();
rsa.Decrypt("需要解密的内容", "包含密钥的路径");