自己做数字签名加密解密这就了，对这些东西有一点点懂，可能自己整理的有些错误。
C#在using System.Security.Cryptography下有 DESCryptoServiceProvider RSACryptoServiceProvider
DESCryptoServiceProvider 是用于对称加密 RSACryptoServiceProvider是用于非对称加密
对称加密的意思：有一个密钥 相当于加密算法，加密用它来加密，解密也需要用到它。因为加密解密都是用同一个密钥所以叫对称加密。 对称加密有一个坏处只要拥有密钥的人都可以解密。
非对称加密：就是有2个密钥，一个是公钥，一个是私钥，私钥是自己的，不能随便给人，公钥随便给，无所谓。一般是别人用你的公钥加密，然后把密文给你，你用你的私钥解密，这样一样加密和解密不是同一个密钥，所以叫非对称。 非对称的好处是假如没有私钥别人是无法解密的，就算加密的那个人他把数据加密了他也无法解密，加密者把密文和公钥随便给那个人都无法解密。
数字签名：数字签名的意义就是这些数据与原文数据比对是否修改过，这个解释有点麻烦，当初我也搞了好久才理解！一般是用自己的私钥对数据进行签名，然后用公钥去验证这个数据是否修改过
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现在该说说DESCryptoServiceProvider 和RSACryptoServiceProvider 在C#中的具体怎么用:
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1、用RSACryptoServiceProvider 加密解密
//加密解密用到的公钥与私钥
RSACryptoServiceProvider oRSA = new RSACryptoServiceProvider();
string privatekey=oRSA.ToXmlString(true);//私钥
string publickey=oRSA.ToXmlString(false);//公钥
//这两个密钥需要保存下来
byte[] messagebytes = Encoding.UTF8.GetBytes("luo罗"); //需要加密的数据
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//公钥加密
RSACryptoServiceProvider oRSA1 = new RSACryptoServiceProvider();
oRSA1.FromXmlString(publickey); //加密要用到公钥所以导入公钥
byte[] AOutput = oRSA1.Encrypt(messagebytes ,false); //AOutput 加密以后的数据
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//私钥解密
RSACryptoServiceProvider oRSA2 = new RSACryptoServiceProvider();
oRSA2.FromXmlString(privatekey);
byte[] AInput = oRSA2.Decrypt(AOutput, false);
string reslut=Encoding.ASCII.GetString(AInput)
2、用RSACryptoServiceProvider签名验签
byte[] messagebytes = Encoding.UTF8.GetBytes("luo罗");
RSACryptoServiceProvider oRSA = new RSACryptoServiceProvider();
string privatekey = oRSA.ToXmlString(true);
string publickey = oRSA.ToXmlString(false);
//私钥签名
RSACryptoServiceProvider oRSA3 = new RSACryptoServiceProvider();
oRSA3.FromXmlString(privatekey);
byte[] AOutput = oRSA3.SignData(messagebytes, "SHA1");
//公钥验证
RSACryptoServiceProvider oRSA4 = new RSACryptoServiceProvider();
oRSA4.FromXmlString(publickey);
bool bVerify = oRSA4.VerifyData(messagebytes, "SHA1", AOutput);
3、用证书进行签名
因为一般证书的私钥是不可以导出的所以所以用第2种方法导入私钥的来进行签名行不通
byte[] messagebytes = Encoding.UTF8.GetBytes("luo罗");
string Path = @"D:\Certificate\1.P12";
X509Certificate2 x509 = new X509Certificate2(Path, "12345678");
SHA1 sha1 = new SHA1CryptoServiceProvider();
byte[] hashbytes = sha1.ComputeHash(messagebytes); //对要签名的数据进行哈希
RSAPKCS1SignatureFormatter signe = new RSAPKCS1SignatureFormatter();
signe.SetKey(x509.PrivateKey); //设置签名用到的私钥
signe.SetHashAlgorithm("SHA1"); //设置签名算法
byte[] reslut = signe.CreateSignature(hashbytes);
验签：与第2方法相同
RSACryptoServiceProvider oRSA4 = new RSACryptoServiceProvider();
oRSA4.FromXmlString(x509.PublicKey.Key.ToXmlString(false));
bool bVerify = oRSA4.VerifyData(messagebytes, "SHA1", reslut);
4、用证书加密解密
string Path = @"D:\Certificate\1.P12";
X509Certificate2 x509 = new X509Certificate2(Path, "12345678");
byte[] data = System.Text.Encoding.UTF8.GetBytes("cheshi罗");
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//证书公钥加密
RSACryptoServiceProvider oRSA1 = new RSACryptoServiceProvider();
oRSA1.FromXmlString(x509.PublicKey.Key.ToXmlString(false));
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byte[] AOutput = oRSA1.Encrypt(data, false);
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//证书私钥解密
RSACryptoServiceProvider rsa2 = (RSACryptoServiceProvider)x509.PrivateKey;
byte[] plainbytes = rsa2.Decrypt(AOutput, false);
string reslut = Encoding.UTF8.GetString(plainbytes);
5用证书对文件加密解密，因为文件可能特别大 所以需要用流和buffer的方式来，鄙视把文件全部读到byte[]里进行加密的人，假如文件5G，那全部读到byte[]里崩溃掉
private void Form1_Load(object sender, EventArgs e)
{
x509=new X509Certificate2(Path, "12345678");
RSACryptoServiceProvider oRSA1 = new RSACryptoServiceProvider();
Encrypt();
Decrypt();
}
private void Decrypt()
{
string FilePath = "2.txt";
string OutFile = "3.txt";
System.IO.FileStream picfs = new System.IO.FileStream(FilePath, System.IO.FileMode.Open);
System.IO.FileStream fs = new System.IO.FileStream(OutFile, System.IO.FileMode.OpenOrCreate);
oRSA1 = (RSACryptoServiceProvider)x509.PrivateKey;
int blocksize = oRSA1.KeySize/8;
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byte[] buffer, buffer1, encryblock;
bool Closed = true;
while (Closed)
{
buffer = null;
buffer = new byte[blocksize];
int k = picfs.Read(buffer, 0, buffer.Length);
if (k > 0)
{
if (blocksize == k)
{
encryblock = oRSA1.Decrypt(buffer, false);
fs.Write(encryblock, 0, encryblock.Length);
}
else
{
buffer1 = new byte[k];
for (int i = 0; i < k; i++)
{
buffer1[i] = buffer[i];
}
encryblock = oRSA1.Decrypt(buffer1, false);
fs.Write(encryblock, 0, encryblock.Length);
}
}
else
{
picfs.Close();
fs.Close();
Closed = false;
}
}
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}
private void Encrypt()
{
string FilePath = "1.txt";
string OutFile = "2.txt";
//证书公钥加密
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oRSA1.FromXmlString(x509.PublicKey.Key.ToXmlString(false));
System.IO.FileStream picfs = new System.IO.FileStream(FilePath, System.IO.FileMode.Open);
System.IO.FileStream fs = new System.IO.FileStream(OutFile, System.IO.FileMode.OpenOrCreate);
int blocksize = 0;
if (oRSA1.KeySize == 1024)
{
blocksize = 16;
}
else
{
blocksize = 8;
}
byte[] buffer, buffer1, encryblock;
bool Closed = true;
while (Closed)
{
buffer = null;
buffer = new byte[blocksize];
int k = picfs.Read(buffer, 0, buffer.Length);
if (k > 0)
{
if (blocksize == k)
{
encryblock = oRSA1.Encrypt(buffer, false);
fs.Write(encryblock, 0, encryblock.Length);
}
else
{
buffer1 = new byte[k];
for (int i = 0; i < k; i++)
{
buffer1[i] = buffer[i];
}
encryblock = oRSA1.Encrypt(buffer1, false);
fs.Write(encryblock, 0, encryblock.Length);
}
}
else
{
picfs.Close();
fs.Close();
Closed = false;
}
}
}
6用证书对文件进行签名验签，因为文件可能特别大 所以需要用流和buffer的方式来
private void Form1_Load(object sender, EventArgs e)
{
x509 = new X509Certificate2(Path, "12345678");
SignFile("1.txt", "11.txt");
VerifyFile("1.txt", "11.txt");
}
private bool VerifyFile(string FileName, string SignedFileName)
{
bool reslut = true;
System.IO.StreamReader objread = new System.IO.StreamReader(FileName);
System.IO.StreamReader objreadSigned = new System.IO.StreamReader(SignedFileName);
RSACryptoServiceProvider VeryRsa = new RSACryptoServiceProvider();
VeryRsa.FromXmlString(x509.PublicKey.Key.ToXmlString(false));
int Inblocksize = 0;
int Signedblocksize = 0;
if (VeryRsa.KeySize == 1024)
{
Inblocksize = 16;
}
else
{
Inblocksize = 8;
}
Signedblocksize = VeryRsa.KeySize / 8;
bool Closed = true;
byte[] Buffer; //原文缓存区
byte[] InBuffer;//原文缓存区
byte[] Buffer1;//签名文件缓存区
while (Closed)
{
Buffer = null;
Buffer = new byte[Inblocksize];
int k = objread.BaseStream.Read(Buffer, 0, Buffer.Length);
if (k > 0)
{
if (Inblocksize == k) //读出来的长度和缓存区一样大
{
Buffer1 = new byte[Signedblocksize];
objreadSigned.BaseStream.Read(Buffer1, 0, Buffer1.Length);
reslut = VeryRsa.VerifyData(Buffer,"SHA1",Buffer1);
if (!reslut)
{
Closed = false;
}
}
else
{ //意思是Buffer没满，只有k个字节，k字节后面全是空所以不需要验签
InBuffer = new byte[k];
for (int i = 0; i < k; i++)
{
InBuffer[i] = Buffer[i];
}
Buffer1 = new byte[Signedblocksize];
objreadSigned.BaseStream.Read(Buffer1, 0, Buffer1.Length);
reslut = VeryRsa.VerifyData(InBuffer, "SHA1", Buffer1);
if (!reslut)
{
Closed = false;
}
}
}
else
{
//这里的意思是原文已经读完毕了，并且已经和签名文件对应验签成功，那么
//签名文件也必须读完毕了。
if (objreadSigned.BaseStream.Position!= objreadSigned.BaseStream.Length)
{
reslut = false;
}
objreadSigned.Close();
objread.Close();
Closed = false;
}
}
return reslut;
}
private void SignFile(string InFileName,string OutFileName)
{
RSACryptoServiceProvider SignRsa = (RSACryptoServiceProvider)x509.PrivateKey;
System.IO.StreamReader objread = new System.IO.StreamReader(InFileName);
System.IO.StreamWriter objwrite = new System.IO.StreamWriter(OutFileName, false);
int blocksize = 0;
if (SignRsa.KeySize == 1024)
{
blocksize = 16;
}
else
{
blocksize = 8;
}
bool Closed = true;
byte[] Buffer = new byte[blocksize];
byte[] buffer1, SignBytes;
while (Closed)
{
int k = objread.BaseStream.Read(Buffer, 0, Buffer.Length);
if (k > 0)
{
if (k == blocksize)
{
SignBytes = SignRsa.SignData(Buffer, "SHA1");
objwrite.BaseStream.Write(SignBytes, 0, SignBytes.Length);
}
else
{
buffer1 = new byte[k];
for (int i = 0; i < k; i++)
{
buffer1[i] = Buffer[i];
}
SignBytes = SignRsa.SignData(buffer1, "SHA1");
objwrite.BaseStream.Write(SignBytes, 0, SignBytes.Length);
}
}
else
{
Closed = false;
objread.Close();
objwrite.Close();
}
}
}
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7、用DESCryptoServiceProvider 进行对称加密
byte[] messagebytes = Encoding.UTF8.GetBytes("LUO罗");
//需要用的对称密钥
DESCryptoServiceProvider Des = new DESCryptoServiceProvider();
byte[] key = Des.Key;
//加密
DESCryptoServiceProvider tdesProvider = new DESCryptoServiceProvider();
tdesProvider.Key = key;
tdesProvider.Mode = CipherMode.ECB;
byte[] encrypted = tdesProvider.CreateEncryptor().TransformFinalBlock(messagebytes, 0, messagebytes.Length);
//解密
DESCryptoServiceProvider tdesProvider2 = new DESCryptoServiceProvider();
tdesProvider.Key = key1;
tdesProvider.Mode = CipherMode.ECB;
byte[] outputdata = tdesProvider.CreateDecryptor().TransformFinalBlock(encrypted, 0, encrypted.Length);
string reslut = Encoding.UTF8.GetString(outputdata);
7用DESCryptoServiceProvider 加解密 流
CryptoStream csDecrypt = new CryptoStream(Stream, Des.CreateEncryptor(), CryptoStreamMode.Write);
CryptoStream csDecrypt = new CryptoStream(Stream, Des.CreateDecryptor(), CryptoStreamMode.Write);
摘自红色黑客联盟(www.7747.net) 原文：http://www.7747.net/kf/201007/52626.html