Encryption in .NET Framework is a little tricky… not just create an object and call Encrypt and Decrypt methods, but terms like CryptoServiceProvider, CipherMode, IV and so on…Most of the examples that i found on the internet treats file encryption instead of text encryption (which i’m interested in).
These days i found a very useful article about text encryption written by Chidi C. Ezeukwu. Based on it i wrote a class for encryption/decryption with RC2 algorythm. This class can be used stand-alone in the application or as an assembly.
An archive that contains the VS.NET project for the assembly is available here: .NET rc2 Encryption assembly project
The compiled DLL assembly zipped is available here: .NET rc2 Encryption DLL assembly
The class code is the following:
using System.IO;
using System.Text;
using System.Security.Cryptography;
namespace webxpert
{
public class wx_crypt
{
#region Variables
private string mKey = string.Empty;
private string mSalt = string.Empty;
private SymmetricAlgorithm mCryptoService;
#endregion
#region Properties
public string Key
{
get
{
return mKey;
}
set
{
mKey = value;
}
}
public string Salt
{
// Salt value
get
{
return mSalt;
}
set
{
mSalt = value;
}
}
#endregion
#region Constructor
public wx_crypt()
{
mCryptoService = new RC2CryptoServiceProvider();
mCryptoService.IV = new byte[] {0xf, 0x6f, 0x13, 0x2e, 0x35, 0xc2, 0xcd, 0xf9};
mCryptoService.Mode = CipherMode.CBC;
}
#endregion
#region Methods
public virtual byte[] GetLegalKey()
{
// Adjust key if necessary, and return a valid key
if (mCryptoService.LegalKeySizes.Length > 0)
{
// Key sizes in bits
int keySize = mKey.Length * 8;
int minSize = mCryptoService.LegalKeySizes[0].MinSize;
int maxSize = mCryptoService.LegalKeySizes[0].MaxSize;
int skipSize = mCryptoService.LegalKeySizes[0].SkipSize;
if (keySize > maxSize)
{
// Extract maximum size allowed
mKey = mKey.Substring(0, maxSize / 8);
}
else if (keySize < maxSize)
{
// Set valid size
int validSize = (keySize <= minSize)? minSize : (keySize – keySize % skipSize) + skipSize;
if (keySize < validSize)
{
// Pad the key with asterisk to make up the size
mKey = mKey.PadRight(validSize / 8, ‘*’);
}
}
}
PasswordDeriveBytes key = new PasswordDeriveBytes(mKey, ASCIIEncoding.ASCII.GetBytes(mSalt));
return key.GetBytes(mKey.Length);
}
public virtual string Encrypt(string plainText)
{
byte[] plainByte = ASCIIEncoding.ASCII.GetBytes(plainText);
byte[] keyByte = GetLegalKey();
// Set private key
mCryptoService.Key = keyByte;
// Encryptor object
ICryptoTransform cryptoTransform = mCryptoService.CreateEncryptor();
// Memory stream object
MemoryStream ms = new MemoryStream();
// Crpto stream object
CryptoStream cs = new CryptoStream(ms, cryptoTransform, CryptoStreamMode.Write);
// Write encrypted byte to memory stream
cs.Write(plainByte, 0, plainByte.Length);
cs.FlushFinalBlock();
// Get the encrypted byte length
byte[] cryptoByte = ms.ToArray();
// Convert into base 64 to enable result to be used in Xml
return Convert.ToBase64String(cryptoByte, 0, cryptoByte.GetLength(0));
}
public virtual string Decrypt(string cryptoText)
{
// Convert from base 64 string to bytes
byte[] cryptoByte = Convert.FromBase64String(cryptoText);
byte[] keyByte = GetLegalKey();
// Set private key
mCryptoService.Key = keyByte;
// Decryptor object
ICryptoTransform cryptoTransform = mCryptoService.CreateDecryptor();
try
{
// Memory stream object
MemoryStream ms = new MemoryStream(cryptoByte, 0, cryptoByte.Length);
// Crpto stream object
CryptoStream cs = new CryptoStream(ms, cryptoTransform, CryptoStreamMode.Read);
// Get the result from the Crypto stream
StreamReader sr = new StreamReader(cs);
return sr.ReadToEnd();
}
catch
{
return null;
}
}
#endregion
}
}
Andrei
http://www.webxpert.ro
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