2019-07-18 更新:增加RSA文件加密，和修复加密字符串过长
RSA的缺点主要有：
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：
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;
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A:发送文件时，用私钥签名，用户B:用A给的公钥验证签名，可以保证该信息是由A发送的。当该用户A接受文件时，B用A的公钥加密，A用私钥解密，B的公钥是正确的。
核心代码如下，注意加密解密和签名分开，如不懂可以联系我 www.luofenming.com
using System;
using System.Collections;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
namespace RSA
{
class RASCrypion
{
#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
{
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;
StringBuilder result = new StringBuilder();
string temp;
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.FromXmlString(xmlPublicKey);
PlainTextBArray = (new UnicodeEncoding()).GetBytes(encryptString);
double count = Math.Ceiling(PlainTextBArray.Length / 117.0);
for (int i = 0; i < count; i++)
{
//最长117个字节加密后生成一个固定长度128个字节(不管多少位字节都是生成128个字节)
CypherTextBArray = rsa.Encrypt(PlainTextBArray.Skip(i * 117).Take(117).ToArray(), false);
temp = Convert.ToBase64String(CypherTextBArray);
result.Append(temp);
}
return result.ToString(); ;
}
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;
StringBuilder result = new StringBuilder();
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.FromXmlString(xmlPublicKey);
double count = Math.Ceiling(EncryptString.Length / 117.0);
for (int i = 0; i < count; i++)
{
CypherTextBArray = rsa.Encrypt(EncryptString, false);
result.Append(Convert.ToBase64String(CypherTextBArray));
}
return result.ToString();
}
catch (Exception ex)
{
throw ex;
}
}
/// <summary>
/// 加密文件
/// </summary>
/// <param name="filename"></param>
/// <param name="key"></param>
/// <returns></returns>
public bool RSAEncryptFile(string filename, string key)
{
FileStream f;
try
{
f = new FileStream(filename, FileMode.Open, FileAccess.ReadWrite, FileShare.Read);
}
catch
{
return false;
}
Random r = new Random();
Thread.Sleep(10 * r.Next(3, 8));
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(1024);
rsa.FromXmlString(key);
//导入密钥
byte[] data = new byte[117];
ArrayList con = new ArrayList();
while (f.Read(data, 0, 117) != 0)
{
byte[] result = rsa.Encrypt(data, false);
//Thread.Sleep(10 * r.Next(2, 7));
con.Add(result);
}
//加密
f.Seek(0, SeekOrigin.Begin);
foreach (byte[] d in con)
{
f.Write(d, 0, d.Length);
}
f.Close();
return true;
}
#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;
StringBuilder result = new StringBuilder();
string temp = string.Empty;
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.FromXmlString(xmlPrivateKey);
int count = decryptString.Length / 172;
for (int i = 0; i < count; i++)
{
//加密之后为128字节转 Convert.ToBase64String 的长度为固定长度172
PlainTextBArray = Convert.FromBase64String(decryptString.Substring(i * 172, 172));
DypherTextBArray = rsa.Decrypt(PlainTextBArray, false);
temp = (new UnicodeEncoding()).GetString(DypherTextBArray);
result.Append(temp);
}
return result.ToString();
}
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;
StringBuilder result = new StringBuilder();
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.FromXmlString(xmlPrivateKey);
int count = DecryptString.Length / 128;//因为加密的Byte固定长度是128
for (int i = 0; i < count; i++)
{
DypherTextBArray = rsa.Decrypt(DecryptString.Skip(i * 128).Take(128).ToArray(), false);
result.Append((new UnicodeEncoding()).GetString(DypherTextBArray));
}
return result.ToString();
}
catch (Exception ex)
{
throw ex;
}
}
/// <summary>
/// 解密文件
/// </summary>
/// <param name="filename"></param>
/// <param name="key"></param>
/// <returns></returns>
public bool RSADecryptFile(string filename, string key)
{
FileStream f;
try
{
f = new FileStream(filename, FileMode.Open, FileAccess.ReadWrite, FileShare.Read);
}
catch (Exception ex)
{
return false;
}
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(1024);
try
{
rsa.FromXmlString(key);
}
catch
{
return false;
}
byte[] data = new byte[128];
ArrayList con = new ArrayList();
while (f.Read(data, 0, 128) != 0)
{
byte[] result;
try
{
result = rsa.Decrypt(data, false);
}
catch (Exception ex)
{
return false;
}
con.Add(result);
}
//解密
f.SetLength(con.Count * 16);
f.Seek(0, SeekOrigin.Begin);
foreach (byte[] d in con)
{
f.Write(d, 0, d.Length);
}
f.Close();
return true;
}
#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;
HashAlgorithm MD5 = 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;
HashAlgorithm MD5 = 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
HashAlgorithm MD5 = 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;
HashAlgorithm MD5 = 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
{
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSA.FromXmlString(strKeyPrivate);
RSAPKCS1SignatureFormatter RSAFormatter = new 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;
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSA.FromXmlString(strKeyPrivate);
RSAPKCS1SignatureFormatter RSAFormatter = new 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);
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSA.FromXmlString(strKeyPrivate);
RSAPKCS1SignatureFormatter RSAFormatter = new 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);
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSA.FromXmlString(strKeyPrivate);
RSAPKCS1SignatureFormatter RSAFormatter = new 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
{
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSA.FromXmlString(strKeyPublic);
RSAPKCS1SignatureDeformatter RSADeformatter = new 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);
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSA.FromXmlString(strKeyPublic);
RSAPKCS1SignatureDeformatter RSADeformatter = new 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;
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSA.FromXmlString(strKeyPublic);
RSAPKCS1SignatureDeformatter RSADeformatter = new 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);
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSA.FromXmlString(strKeyPublic);
RSAPKCS1SignatureDeformatter RSADeformatter = new 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
}
}