The C encryption algorithm summarizes the of recommendations

Method 1:

// Must be added to System.Web A reference to the  
using System.Web.Security; 
... 
/// <summary> 
/// SHA1 Encrypted string  
/// </summary> 
/// <param name="source"> The source string </param> 
/// <returns> An encrypted string </returns> 
public string SHA1(string source) 
{ 
return FormsAuthentication.HashPasswordForStoringInConfigFile(source, "SHA1"); 
} 
/// <summary> 
/// MD5 Encrypted string  
/// </summary> 
/// <param name="source"> The source string </param> 
/// <returns> An encrypted string </returns> 
public string MD5(string source) 
{ 
return FormsAuthentication.HashPasswordForStoringInConfigFile(source, "MD5");; 
}

Method 2(reversible encryption and decryption) :

using System.Security.Cryptography; 
... 
public string Encode(string data) 
{ 
byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64); 
byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64); 
DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider(); 
int i = cryptoProvider.KeySize; 
MemoryStream ms = new MemoryStream(); 
CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(byKey, byIV), CryptoStreamMode.Write); 
StreamWriter sw = new StreamWriter(cst); 
sw.Write(data); 
sw.Flush(); 
cst.FlushFinalBlock(); 
sw.Flush(); 
return Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length); 
} 
public string Decode(string data) 
{ 
byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64); 
byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64); 
byte[] byEnc; 
try 
{ 
byEnc = Convert.FromBase64String(data); 
} 
catch 
{ 
return null; 
} 
DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider(); 
MemoryStream ms = new MemoryStream(byEnc); 
CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateDecryptor(byKey, byIV), CryptoStreamMode.Read); 
StreamReader sr = new StreamReader(cst); 
return sr.ReadToEnd(); 
}

Method 3(MD5 irreversible) :

using System.Security.Cryptography; 
... 
//MD5 Irreversible encryption  
//32 An encryption  
public string GetMD5_32(string s, string _input_charset) 
{ 
MD5 md5 = new MD5CryptoServiceProvider(); 
byte[] t = md5.ComputeHash(Encoding.GetEncoding(_input_charset).GetBytes(s)); 
StringBuilder sb = new StringBuilder(32); 
for (int i = 0; i < t.Length; i++) 
{ 
sb.Append(t[i].ToString("x").PadLeft(2, '0')); 
} 
return sb.ToString(); 
} 
//16 An encryption  
public static string GetMd5_16(string ConvertString) 
{ 
MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider(); 
string t2 = BitConverter.ToString(md5.ComputeHash(UTF8Encoding.Default.GetBytes(ConvertString)), 4, 8); 
t2 = t2.Replace("-", ""); 
return t2; 
}

Method 4(symmetric encryption) :

using System.IO; 
using System.Security.Cryptography; 
... 
private SymmetricAlgorithm mobjCryptoService; 
private string Key; 
/// <summary> 
///  The constructor of the symmetric encryption class  
/// </summary> 
public SymmetricMethod() 
{ 
mobjCryptoService = new RijndaelManaged(); 
Key = "Guz(%&hj7x89H$yuBI0456FtmaT5&fvHUFCy76*h%(HilJ$lhj!y6&(*jkP87jH7"; 
} 
/// <summary> 
///  Get the key  
/// </summary> 
/// <returns> The key </returns> 
private byte[] GetLegalKey() 
{ 
string sTemp = Key; 
mobjCryptoService.GenerateKey(); 
byte[] bytTemp = mobjCryptoService.Key; 
int KeyLength = bytTemp.Length; 
if (sTemp.Length > KeyLength) 
sTemp = sTemp.Substring(0, KeyLength); 
else if (sTemp.Length < KeyLength) 
sTemp = sTemp.PadRight(KeyLength, ' '); 
return ASCIIEncoding.ASCII.GetBytes(sTemp); 
} 
/// <summary> 
///  Get the initial vector IV 
/// </summary> 
/// <returns> Try a vector IV</returns> 
private byte[] GetLegalIV() 
{ 
string sTemp = "E4ghj*Ghg7!rNIfb&95GUY86GfghUb#er57HBh(u%g6HJ($jhWk7&!hg4ui%$hjk"; 
mobjCryptoService.GenerateIV(); 
byte[] bytTemp = mobjCryptoService.IV; 
int IVLength = bytTemp.Length; 
if (sTemp.Length > IVLength) 
sTemp = sTemp.Substring(0, IVLength); 
else if (sTemp.Length < IVLength) 
sTemp = sTemp.PadRight(IVLength, ' '); 
return ASCIIEncoding.ASCII.GetBytes(sTemp); 
} 
/// <summary> 
///  Encryption methods  
/// </summary> 
/// <param name="Source"> The string to be encrypted </param> 
/// <returns> An encrypted string </returns> 
public string Encrypto(string Source) 
{ 
byte[] bytIn = UTF8Encoding.UTF8.GetBytes(Source); 
MemoryStream ms = new MemoryStream(); 
mobjCryptoService.Key = GetLegalKey(); 
mobjCryptoService.IV = GetLegalIV(); 
ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor(); 
CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write); 
cs.Write(bytIn, 0, bytIn.Length); 
cs.FlushFinalBlock(); 
ms.Close(); 
byte[] bytOut = ms.ToArray(); 
return Convert.ToBase64String(bytOut); 
} 
/// <summary> 
///  Decryption method  
/// </summary> 
/// <param name="Source"> String to be decrypted </param> 
/// <returns> Decrypted string </returns> 
public string Decrypto(string Source) 
{ 
byte[] bytIn = Convert.FromBase64String(Source); 
MemoryStream ms = new MemoryStream(bytIn, 0, bytIn.Length); 
mobjCryptoService.Key = GetLegalKey(); 
mobjCryptoService.IV = GetLegalIV(); 
ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor(); 
CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read); 
StreamReader sr = new StreamReader(cs); 
return sr.ReadToEnd(); 
}

Method 5:

using System.IO; 
using System.Security.Cryptography; 
using System.Text; 
... 
// Default key vector  
private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF }; 
/// <summary> 
/// DES Encrypted string  
/// </summary> 
/// <param name="encryptString"> A string to be encrypted </param> 
/// <param name="encryptKey"> Encryption key , Requirements for 8 position </param> 
/// <returns> Encrypting successfully returns the encrypted string, failing to return the source string </returns> 
public static string EncryptDES(string encryptString, string encryptKey) 
{ 
try 
{ 
byte[] rgbKey = Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8)); 
byte[] rgbIV = Keys; 
byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString); 
DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider(); 
MemoryStream mStream = new MemoryStream(); 
CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write); 
cStream.Write(inputByteArray, 0, inputByteArray.Length); 
cStream.FlushFinalBlock(); 
return Convert.ToBase64String(mStream.ToArray()); 
} 
catch 
{ 
return encryptString; 
} 
} 
/// <summary> 
/// DES Decrypt string  
/// </summary> 
/// <param name="decryptString"> A string to be decrypted </param> 
/// <param name="decryptKey"> The decryption key , Requirements for 8 position , Same as the encryption key </param> 
/// <returns> Decryption successfully returns the decrypted string, failed to return the source string </returns> 
public static string DecryptDES(string decryptString, string decryptKey) 
{ 
try 
{ 
byte[] rgbKey = Encoding.UTF8.GetBytes(decryptKey); 
byte[] rgbIV = Keys; 
byte[] inputByteArray = Convert.FromBase64String(decryptString); 
DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider(); 
MemoryStream mStream = new MemoryStream(); 
CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write); 
cStream.Write(inputByteArray, 0, inputByteArray.Length); 
cStream.FlushFinalBlock(); 
return Encoding.UTF8.GetString(mStream.ToArray()); 
} 
catch 
{ 
return decryptString; 
} 
}

Method 6(file encryption) :

using System.IO; 
using System.Security.Cryptography; 
using System.Text; 
... 
// Encrypted file  
private static void EncryptData(String inName, String outName, byte[] desKey, byte[] desIV) 
{ 
//Create the file streams to handle the input and output files. 
FileStream fin = new FileStream(inName, FileMode.Open, FileAccess.Read); 
FileStream fout = new FileStream(outName, FileMode.OpenOrCreate, FileAccess.Write); 
fout.SetLength(0); 
//Create variables to help with read and write. 
byte[] bin = new byte[100]; //This is intermediate storage for the encryption. 
long rdlen = 0; //This is the total number of bytes written. 
long totlen = fin.Length; //This is the total length of the input file. 
int len; //This is the number of bytes to be written at a time. 
DES des = new DESCryptoServiceProvider(); 
CryptoStream encStream = new CryptoStream(fout, des.CreateEncryptor(desKey, desIV), CryptoStreamMode.Write); 
//Read from the input file, then encrypt and write to the output file. 
while (rdlen < totlen) 
{ 
len = fin.Read(bin, 0, 100); 
encStream.Write(bin, 0, len); 
rdlen = rdlen + len; 
} 
encStream.Close(); 
fout.Close(); 
fin.Close(); 
} 
// Declassified documents  
private static void DecryptData(String inName, String outName, byte[] desKey, byte[] desIV) 
{ 
//Create the file streams to handle the input and output files. 
FileStream fin = new FileStream(inName, FileMode.Open, FileAccess.Read); 
FileStream fout = new FileStream(outName, FileMode.OpenOrCreate, FileAccess.Write); 
fout.SetLength(0); 
//Create variables to help with read and write. 
byte[] bin = new byte[100]; //This is intermediate storage for the encryption. 
long rdlen = 0; //This is the total number of bytes written. 
long totlen = fin.Length; //This is the total length of the input file. 
int len; //This is the number of bytes to be written at a time. 
DES des = new DESCryptoServiceProvider(); 
CryptoStream encStream = new CryptoStream(fout, des.CreateDecryptor(desKey, desIV), CryptoStreamMode.Write); 
//Read from the input file, then encrypt and write to the output file. 
while (rdlen < totlen) 
{ 
len = fin.Read(bin, 0, 100); 
encStream.Write(bin, 0, len); 
rdlen = rdlen + len; 
} 
encStream.Close(); 
fout.Close(); 
fin.Close(); 
}

using System; 
using System.Security.Cryptography;// This is the premise for processing word coding  
using System.Text; 
using System.IO; 
/// <summary> 
/// DES Encryption methods  
/// </summary> 
/// <param name="strPlain"> clear </param> 
/// <param name="strDESKey"> The key </param> 
/// <param name="strDESIV"> vector </param> 
/// <returns> cipher </returns> 
public string DESEncrypt(string strPlain,string strDESKey,string strDESIV) 
{ 
// Converts the key into a byte array  
byte[] bytesDESKey=ASCIIEncoding.ASCII.GetBytes(strDESKey); 
// Converts a vector into a byte array  
byte[] bytesDESIV=ASCIIEncoding.ASCII.GetBytes(strDESIV); 
// The statement 1 A new one DES object  
DESCryptoServiceProvider desEncrypt=new DESCryptoServiceProvider(); 
// Open up 1 Block of memory stream  
MemoryStream msEncrypt=new MemoryStream(); 
// The memory stream object is wrapped as an encrypted stream object  
CryptoStream csEncrypt=new CryptoStream(msEncrypt,desEncrypt.CreateEncryptor(bytesDESKey,bytesDESIV),CryptoStreamMode.Write); 
// The encrypted stream object is wrapped as a write into stream object  
StreamWriter swEncrypt=new StreamWriter(csEncrypt); 
// Write the incoming object to write the plaintext  
swEncrypt.WriteLine(strPlain); 
// Write in stream closed  
swEncrypt.Close(); 
// Encrypted stream shutdown  
csEncrypt.Close(); 
// Replace the memory stream with a byte array, and the memory stream is now ciphertext  
byte[] bytesCipher=msEncrypt.ToArray(); 
// Memory stream shutdown  
msEncrypt.Close(); 
// Converts the ciphertext byte array to a string and returns  
return UnicodeEncoding.Unicode.GetString(bytesCipher); 
} 
/// <summary> 
/// DES Decryption method  
/// </summary> 
/// <param name="strCipher"> cipher </param> 
/// <param name="strDESKey"> The key </param> 
/// <param name="strDESIV"> vector </param> 
/// <returns> clear </returns> 
public string DESDecrypt(string strCipher,string strDESKey,string strDESIV) 
{ 
// Converts the key into a byte array  
byte[] bytesDESKey=ASCIIEncoding.ASCII.GetBytes(strDESKey); 
// Converts a vector into a byte array  
byte[] bytesDESIV=ASCIIEncoding.ASCII.GetBytes(strDESIV); 
// Converts the ciphertext into a byte array  
byte[] bytesCipher=UnicodeEncoding.Unicode.GetBytes(strCipher); 
// The statement 1 A new one DES object  
DESCryptoServiceProvider desDecrypt=new DESCryptoServiceProvider(); 
// Open up 1 Block memory stream and store an array of ciphertext bytes  
MemoryStream msDecrypt=new MemoryStream(bytesCipher); 
// Wrap the memory flow object into a decrypted flow object  
CryptoStream csDecrypt=new CryptoStream(msDecrypt,desDecrypt.CreateDecryptor(bytesDESKey,bytesDESIV),CryptoStreamMode.Read); 
// The decrypted stream object is wrapped as a read stream object  
StreamReader srDecrypt=new StreamReader(csDecrypt); 
// clear = The read content of the read stream  
string strPlainText=srDecrypt.ReadLine(); 
// Read off flow  
srDecrypt.Close(); 
// Decryption stream closed  
csDecrypt.Close(); 
// Memory stream shutdown  
msDecrypt.Close(); 
// Return to clear  
return strPlainText; 
}