加密解密字符串

///

/// 基于 ProtectedData 实现的加密解密字符串&＃xff0c;可以跨windows用户使用&＃xff0c;但是不能跨计算机使用
///

public static class EncryptHelper
{
public static string Encrypt(string stringToEncrypt)
{
byte[] toEncrypt &＃61; UnicodeEncoding.UTF8.GetBytes(stringToEncrypt);
MemoryStream stream &＃61; new MemoryStream();
int bytesWritten &＃61; EncryptDataToStream(toEncrypt, null, DataProtectionScope.LocalMachine, stream);
stream.Close();
return Convert.ToBase64String(stream.ToArray());
}
public static string Decrypt(string encryptedString)
{
byte[] encrypted &＃61; Convert.FromBase64String(encryptedString);
MemoryStream stream &＃61; new MemoryStream(encrypted);
byte[] decryptData &＃61; DecryptDataFromStream(null, DataProtectionScope.LocalMachine, stream, encrypted.Length);
stream.Close();
return UnicodeEncoding.UTF8.GetString(decryptData);
}

private static int EncryptDataToStream(byte[] buffer, byte[] entropy, DataProtectionScope scope, Stream stream)
{
if (buffer &＃61;&＃61; null)
{
throw new ArgumentNullException("buffer");
}
if (buffer.Length <&＃61; 0)
{
throw new ArgumentException("buffer");
}
if (stream &＃61;&＃61; null)
{
throw new ArgumentNullException("stream");
}

int length &＃61; 0;

byte[] encrptedData &＃61; ProtectedData.Protect(buffer, entropy, scope);

if (stream.CanWrite && encrptedData !&＃61; null)
{
stream.Write(encrptedData, 0, encrptedData.Length);

length &＃61; encrptedData.Length;
}

return length;
}
private static byte[] DecryptDataFromStream(byte[] entropy, DataProtectionScope scope, Stream stream, int length)
{
if (stream &＃61;&＃61; null)
{
throw new ArgumentNullException("stream");
}
if (length <&＃61; 0)
{
throw new ArgumentException("length");
}

byte[] inBuffer &＃61; new byte[length];
byte[] outBuffer;

if (stream.CanRead)
{
stream.Read(inBuffer, 0, length);

outBuffer &＃61; ProtectedData.Unprotect(inBuffer, entropy, scope);
}
else
{
throw new IOException("Could not read the stream.");
}

return outBuffer;

}
}