C#实现RSA加密与解密、签名与认证

一、RSA简介

RSA公钥加密算法是1977年由Ron Rivest、Adi Shamirh和LenAdleman在（美国麻省理工学院）开发的。RSA取名来自开发他们三者的名字。RSA是目前最有影响力的公钥加密算法，它能够抵抗到目前为止已知的所有密码攻击，已被ISO推荐为公钥数据加密标准。RSA算法基于一个十分简单的数论事实：将两个大素数相乘十分容易，但那时想要对其乘积进行因式分解却极其困难，因此可以将乘积公开作为加密密钥。RSA算法是第一个能同时用于加密和数字签名的算法，也易于理解和操作。
RSA是被研究得最广泛的公钥算法，从提出到现在已近二十年，经历了各种攻击的考验，逐渐为人们接受，普遍认为是目前最优秀的公钥方案之一。RSA的安全性依赖于大数的因子分解，但并没有从理论上证明破译RSA的难度与大数分解难度等价。即RSA的重大缺陷是无法从理论上把握它的保密性能如何，而且密码学界多数人士倾向于因子分解不是NPC问题。
RSA的缺点主要有：
A)产生密钥很麻烦，受到素数产生技术的限制，因而难以做到一次一密。

B)分组长度太大，为保证安全性，n 至少也要 600bits以上，使运算代价很高，尤其是速度较慢，较对称密码算法慢几个数量级；且随着大数分解技术的发展，这个长度还在增加，不利于数据格式的标准化。目前，SET(Secure Electronic Transaction)协议中要求CA采用2048bits长的密钥，其他实体使用1024比特的密钥。

C)RSA密钥长度随着保密级别提高，增加很快。下表列出了对同一安全级别所对应的密钥长度。

这种算法1978年就出现了，它是第一个既能用于数据加密也能用于数字签名的算法。它易于理解和操作，也很流行。算法的名字以发明者的名字命名：Ron Rivest, 
AdiShamir 和Leonard Adleman。早在1973年，英国国家通信总局的数学家Clifford Cocks就发现了类似的算法。但是他的发现被列为绝密，直到1998年才公诸于世。
RSA算法是一种非对称密码算法，所谓非对称，就是指该算法需要一对密钥，使用其中一个加密，则需要用另一个才能解密。
RSA的算法涉及三个参数，n、e1、e2。
其中，n是两个大质数p、q的积，n的二进制表示时所占用的位数，就是所谓的密钥长度。
e1和e2是一对相关的值，e1可以任意取，但要求e1与(p-1)*(q-1)互质；再选择e2，要求(e2*e1)mod((p-1)*(q-1))=1。
(n及e1),(n及e2)就是密钥对。
RSA加解密的算法完全相同,设A为明文，B为密文，则：A=B^e1 mod n；B=A^e2 mod n；
e1和e2可以互换使用，即：

A=B^e2 mod n；B=A^e1 mod n;

二、MD5加密介绍

参考：http://blog.csdn.net/wonsoft/article/details/5913572
MD5的全称是message-digest algorithm 5(信息-摘要算法，在90年代初由mit laboratory for computer science和rsa data security inc的ronald l. rivest开发出来， 经md2、md3和md4发展而来。
MD5具有很好的安全性(因为它具有不可逆的特征,加过密的密文经过解密后和加密前的东东相同的可能性极小)

public string GetStrMd5(string ConvertString)
       {
           string strBodyBase64 = Convert.ToBase64String(Encoding.UTF8.GetBytes(ConvertString));
           string t2=System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(strBodyBase64, "MD5").ToUpper();
           return t2;
       }

三、C#对PKCS＃8编码的RSA私钥进行签名

 对MD5加密后的长度为32的密文进行PKCS8的RSA签名的方法：

/// <summary>
        /// 对MD5加密后的长度为32的密文进行签名
        /// </summary>
        /// <param name="strPrivateKey">私钥</param>
        /// <param name="strContent">MD5加密后的密文</param>
        /// <returns></returns>
        public string SignatureFormatter(string strPrivateKey, string strContent)
        {
            byte[] btContent = Encoding.UTF8.GetBytes(strContent);
            byte[] hv = MD5.Create().ComputeHash(btContent);
            RSACryptoServiceProvider rsp = new RSACryptoServiceProvider();
            rsp.FromXmlString(strPrivateKey);
            RSAPKCS1SignatureFormatter rf = new RSAPKCS1SignatureFormatter(rsp);
            rf.SetHashAlgorithm("MD5");
            byte[] signature = rf.CreateSignature(hv);
            return Convert.ToBase64String(signature);
        }

四、C#实现RSA加密与解密、签名与认证常用方法

1.RSA加密解密：
　(1)获取密钥，这里是产生密钥，实际应用中可以从各种存储介质上读取密钥 (2)加密 (3)解密
2.RSA签名和验证
　(1)获取密钥，这里是产生密钥，实际应用中可以从各种存储介质上读取密钥 (2)获取待签名的Hash码 (3)获取签名的字符串 (4)验证
3.公钥与私钥的理解：
　(1)私钥用来进行解密和签名，是给自己用的。
　(2)公钥由本人公开，用于加密和验证签名，是给别人用的。
    (3)当该用户发送文件时，用私钥签名，别人用他给的公钥验证签名，可以保证该信息是由他发送的。当该用户接受文件时，别人用他的公钥加密，他用私钥解密，可以保证该信息只能由他接收到。

using System.Security.Cryptography;
class RSACryption
{
    #region RSA 加密解密
    #region RSA 的密钥产生
    /// <summary>
    /// RSA产生密钥
    /// </summary>
    /// <param name="xmlKeys">私钥</param>
    /// <param name="xmlPublicKey">公钥</param>
    public void RSAKey(out string xmlKeys, out string xmlPublicKey)
    {
        try
        {
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            xmlKeys = rsa.ToXmlString(true);
            xmlPublicKey = rsa.ToXmlString(false);
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    #endregion

    #region RSA加密函数
    //##############################################################################
    //RSA 方式加密
    //KEY必须是XML的形式,返回的是字符串
    //该加密方式有长度限制的！
    //##############################################################################

    /// <summary>
    /// RSA的加密函数
    /// </summary>
    /// <param name="xmlPublicKey">公钥</param>
    /// <param name="encryptString">待加密的字符串</param>
    /// <returns></returns>
    public string RSAEncrypt(string xmlPublicKey, string encryptString)
    {
        try
        {
            byte[] PlainTextBArray;
            byte[] CypherTextBArray;
            string Result;
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPublicKey);
            PlainTextBArray = (new UnicodeEncoding()).GetBytes(encryptString);
            CypherTextBArray = rsa.Encrypt(PlainTextBArray, false);
            Result = Convert.ToBase64String(CypherTextBArray);
            return Result;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    /// <summary>
    /// RSA的加密函数
    /// </summary>
    /// <param name="xmlPublicKey">公钥</param>
    /// <param name="EncryptString">待加密的字节数组</param>
    /// <returns></returns>
    public string RSAEncrypt(string xmlPublicKey, byte[] EncryptString)
    {
        try
        {
            byte[] CypherTextBArray;
            string Result;
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPublicKey);
            CypherTextBArray = rsa.Encrypt(EncryptString, false);
            Result = Convert.ToBase64String(CypherTextBArray);
            return Result;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    #endregion

    #region RSA的解密函数
    /// <summary>
    /// RSA的解密函数
    /// </summary>
    /// <param name="xmlPrivateKey">私钥</param>
    /// <param name="decryptString">待解密的字符串</param>
    /// <returns></returns>
    public string RSADecrypt(string xmlPrivateKey, string decryptString)
    {
        try
        {
            byte[] PlainTextBArray;
            byte[] DypherTextBArray;
            string Result;
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPrivateKey);
            PlainTextBArray = Convert.FromBase64String(decryptString);
            DypherTextBArray = rsa.Decrypt(PlainTextBArray, false);
            Result = (new UnicodeEncoding()).GetString(DypherTextBArray);
            return Result;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    /// <summary>
    /// RSA的解密函数
    /// </summary>
    /// <param name="xmlPrivateKey">私钥</param>
    /// <param name="DecryptString">待解密的字节数组</param>
    /// <returns></returns>
    public string RSADecrypt(string xmlPrivateKey, byte[] DecryptString)
    {
        try
        {
            byte[] DypherTextBArray;
            string Result;
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPrivateKey);
            DypherTextBArray = rsa.Decrypt(DecryptString, false);
            Result = (new UnicodeEncoding()).GetString(DypherTextBArray);
            return Result;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    #endregion
    #endregion

    #region RSA数字签名
    #region 获取Hash描述表
    /// <summary>
    /// 获取Hash描述表
    /// </summary>
    /// <param name="strSource">待签名的字符串</param>
    /// <param name="HashData">Hash描述</param>
    /// <returns></returns>
    public bool GetHash(string strSource, ref byte[] HashData)
    {
        try
        {
            byte[] Buffer;
            System.Security.Cryptography.HashAlgorithm MD5 = System.Security.Cryptography.HashAlgorithm.Create("MD5");
            Buffer = System.Text.Encoding.GetEncoding("GB2312").GetBytes(strSource);
            HashData = MD5.ComputeHash(Buffer);
            return true;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    /// <summary>
    /// 获取Hash描述表
    /// </summary>
    /// <param name="strSource">待签名的字符串</param>
    /// <param name="strHashData">Hash描述</param>
    /// <returns></returns>
    public bool GetHash(string strSource, ref string strHashData)
    {
        try
        {
            //从字符串中取得Hash描述
            byte[] Buffer;
            byte[] HashData;
            System.Security.Cryptography.HashAlgorithm MD5 = System.Security.Cryptography.HashAlgorithm.Create("MD5");
            Buffer = System.Text.Encoding.GetEncoding("GB2312").GetBytes(strSource);
            HashData = MD5.ComputeHash(Buffer);
            strHashData = Convert.ToBase64String(HashData);
            return true;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    /// <summary>
    /// 获取Hash描述表
    /// </summary>
    /// <param name="objFile">待签名的文件</param>
    /// <param name="HashData">Hash描述</param>
    /// <returns></returns>
    public bool GetHash(System.IO.FileStream objFile, ref byte[] HashData)
    {
        try
        {
            //从文件中取得Hash描述
            System.Security.Cryptography.HashAlgorithm MD5 = System.Security.Cryptography.HashAlgorithm.Create("MD5");
            HashData = MD5.ComputeHash(objFile);
            objFile.Close();
            return true;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    /// <summary>
    /// 获取Hash描述表
    /// </summary>
    /// <param name="objFile">待签名的文件</param>
    /// <param name="strHashData">Hash描述</param>
    /// <returns></returns>
    public bool GetHash(System.IO.FileStream objFile, ref string strHashData)
    {
        try
        {
            //从文件中取得Hash描述
            byte[] HashData;
            System.Security.Cryptography.HashAlgorithm MD5 = System.Security.Cryptography.HashAlgorithm.Create("MD5");
            HashData = MD5.ComputeHash(objFile);
            objFile.Close();
            strHashData = Convert.ToBase64String(HashData);
            return true;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    #endregion

    #region RSA签名
    /// <summary>
    /// RSA签名
    /// </summary>
    /// <param name="strKeyPrivate">私钥</param>
    /// <param name="HashbyteSignature">待签名Hash描述</param>
    /// <param name="EncryptedSignatureData">签名后的结果</param>
    /// <returns></returns>
    public bool SignatureFormatter(string strKeyPrivate, byte[] HashbyteSignature, ref byte[] EncryptedSignatureData)
    {
        try
        {
            System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

            RSA.FromXmlString(strKeyPrivate);
            System.Security.Cryptography.RSAPKCS1SignatureFormatter RSAFormatter = new System.Security.Cryptography.RSAPKCS1SignatureFormatter

(RSA);
            //设置签名的算法为MD5
            RSAFormatter.SetHashAlgorithm("MD5");
            //执行签名
            EncryptedSignatureData = RSAFormatter.CreateSignature(HashbyteSignature);
            return true;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    /// <summary>
    /// RSA签名
    /// </summary>
    /// <param name="strKeyPrivate">私钥</param>
    /// <param name="HashbyteSignature">待签名Hash描述</param>
    /// <param name="m_strEncryptedSignatureData">签名后的结果</param>
    /// <returns></returns>
    public bool SignatureFormatter(string strKeyPrivate, byte[] HashbyteSignature, ref string strEncryptedSignatureData)
    {
        try
        {
            byte[] EncryptedSignatureData;
            System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();
            RSA.FromXmlString(strKeyPrivate);
            System.Security.Cryptography.RSAPKCS1SignatureFormatter RSAFormatter = new System.Security.Cryptography.RSAPKCS1SignatureFormatter

(RSA);
            //设置签名的算法为MD5
            RSAFormatter.SetHashAlgorithm("MD5");
            //执行签名
            EncryptedSignatureData = RSAFormatter.CreateSignature(HashbyteSignature);
            strEncryptedSignatureData = Convert.ToBase64String(EncryptedSignatureData);
            return true;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    /// <summary>
    /// RSA签名
    /// </summary>
    /// <param name="strKeyPrivate">私钥</param>
    /// <param name="strHashbyteSignature">待签名Hash描述</param>
    /// <param name="EncryptedSignatureData">签名后的结果</param>
    /// <returns></returns>
    public bool SignatureFormatter(string strKeyPrivate, string strHashbyteSignature, ref byte[] EncryptedSignatureData)
    {
        try
        {
            byte[] HashbyteSignature;

            HashbyteSignature = Convert.FromBase64String(strHashbyteSignature);
            System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();


            RSA.FromXmlString(strKeyPrivate);
            System.Security.Cryptography.RSAPKCS1SignatureFormatter RSAFormatter = new System.Security.Cryptography.RSAPKCS1SignatureFormatter

(RSA);
            //设置签名的算法为MD5
            RSAFormatter.SetHashAlgorithm("MD5");
            //执行签名
            EncryptedSignatureData = RSAFormatter.CreateSignature(HashbyteSignature);

            return true;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    /// <summary>
    /// RSA签名
    /// </summary>
    /// <param name="strKeyPrivate">私钥</param>
    /// <param name="strHashbyteSignature">待签名Hash描述</param>
    /// <param name="strEncryptedSignatureData">签名后的结果</param>
    /// <returns></returns>
    public bool SignatureFormatter(string strKeyPrivate, string strHashbyteSignature, ref string strEncryptedSignatureData)
    {
        try
        {
            byte[] HashbyteSignature;
            byte[] EncryptedSignatureData;
            HashbyteSignature = Convert.FromBase64String(strHashbyteSignature);
            System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();
            RSA.FromXmlString(strKeyPrivate);
            System.Security.Cryptography.RSAPKCS1SignatureFormatter RSAFormatter = new System.Security.Cryptography.RSAPKCS1SignatureFormatter

(RSA);
            //设置签名的算法为MD5
            RSAFormatter.SetHashAlgorithm("MD5");
            //执行签名
            EncryptedSignatureData = RSAFormatter.CreateSignature(HashbyteSignature);
            strEncryptedSignatureData = Convert.ToBase64String(EncryptedSignatureData);
            return true;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    #endregion

    #region RSA 签名验证
    /// <summary>
    /// RSA签名验证
    /// </summary>
    /// <param name="strKeyPublic">公钥</param>
    /// <param name="HashbyteDeformatter">Hash描述</param>
    /// <param name="DeformatterData">签名后的结果</param>
    /// <returns></returns>
    public bool SignatureDeformatter(string strKeyPublic, byte[] HashbyteDeformatter, byte[] DeformatterData)
    {
        try
        {
            System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();
            RSA.FromXmlString(strKeyPublic);
            System.Security.Cryptography.RSAPKCS1SignatureDeformatter RSADeformatter = new

System.Security.Cryptography.RSAPKCS1SignatureDeformatter(RSA);
            //指定解密的时候HASH算法为MD5
            RSADeformatter.SetHashAlgorithm("MD5");
            if (RSADeformatter.VerifySignature(HashbyteDeformatter, DeformatterData))
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    /// <summary>
    /// RSA签名验证
    /// </summary>
    /// <param name="strKeyPublic">公钥</param>
    /// <param name="strHashbyteDeformatter">Hash描述</param>
    /// <param name="DeformatterData">签名后的结果</param>
    /// <returns></returns>
    public bool SignatureDeformatter(string strKeyPublic, string strHashbyteDeformatter, byte[] DeformatterData)
    {
        try
        {
            byte[] HashbyteDeformatter;
            HashbyteDeformatter = Convert.FromBase64String(strHashbyteDeformatter);
            System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();
            RSA.FromXmlString(strKeyPublic);
            System.Security.Cryptography.RSAPKCS1SignatureDeformatter RSADeformatter = new

System.Security.Cryptography.RSAPKCS1SignatureDeformatter(RSA);
            //指定解密的时候HASH算法为MD5
            RSADeformatter.SetHashAlgorithm("MD5");
            if (RSADeformatter.VerifySignature(HashbyteDeformatter, DeformatterData))
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    /// <summary>
    /// RSA签名验证
    /// </summary>
    /// <param name="strKeyPublic">公钥</param>
    /// <param name="HashbyteDeformatter">Hash描述</param>
    /// <param name="strDeformatterData">签名后的结果</param>
    /// <returns></returns>
    public bool SignatureDeformatter(string strKeyPublic, byte[] HashbyteDeformatter, string strDeformatterData)
    {
        try
        {
            byte[] DeformatterData;
            System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();
            RSA.FromXmlString(strKeyPublic);
            System.Security.Cryptography.RSAPKCS1SignatureDeformatter RSADeformatter = new

System.Security.Cryptography.RSAPKCS1SignatureDeformatter(RSA);
            //指定解密的时候HASH算法为MD5
            RSADeformatter.SetHashAlgorithm("MD5");
            DeformatterData = Convert.FromBase64String(strDeformatterData);
            if (RSADeformatter.VerifySignature(HashbyteDeformatter, DeformatterData))
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    /// <summary>
    /// RSA签名验证
    /// </summary>
    /// <param name="strKeyPublic">公钥</param>
    /// <param name="strHashbyteDeformatter">Hash描述</param>
    /// <param name="strDeformatterData">签名后的结果</param>
    /// <returns></returns>
    public bool SignatureDeformatter(string strKeyPublic, string strHashbyteDeformatter, string strDeformatterData)
    {
        try
        {
            byte[] DeformatterData;
            byte[] HashbyteDeformatter;
            HashbyteDeformatter = Convert.FromBase64String(strHashbyteDeformatter);
            System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();
            RSA.FromXmlString(strKeyPublic);
            System.Security.Cryptography.RSAPKCS1SignatureDeformatter RSADeformatter = new

System.Security.Cryptography.RSAPKCS1SignatureDeformatter(RSA);
            //指定解密的时候HASH算法为MD5
            RSADeformatter.SetHashAlgorithm("MD5");
            DeformatterData = Convert.FromBase64String(strDeformatterData);
            if (RSADeformatter.VerifySignature(HashbyteDeformatter, DeformatterData))
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    #endregion
    #endregion
}

参考网站：

http://www.cnblogs.com/linzheng/archive/2011/02/20/1959123.html
http://www.cnblogs.com/sydeveloper/archive/2012/08/11/2633624.html
http://codego.net/126956/