C#中对字符串的加密和解密

/// <summary>
/// 对字符串进行加密
/// </summary>
/// <param name="proclaimText"></param>
/// <returns></returns>
public static string CipherText(string proclaimText)
{
if (proclaimText.IsEmpty()) return proclaimText;

byte[] proclaimBytes = UnicodeEncoding.BigEndianUnicode.GetBytes(proclaimText);
int proclaimBytesCount = proclaimBytes.Length;
byte[] cipherBytes = new byte[proclaimBytesCount * 2];

for (int i = 0; i < proclaimBytesCount; i += 2)
{
byte proclaimByte = proclaimBytes[i];
int upperByte = proclaimByte & 0xf0;
int lowerByte = proclaimByte & 0x0f;
upperByte = upperByte >> 4;
lowerByte = lowerByte << 4;

byte proclaimByte2 = proclaimBytes[i + 1];
int upperByte2 = proclaimByte2 & 0xf0;
int lowerByte2 = proclaimByte2 & 0x0f;
upperByte2 |= upperByte;
lowerByte2 |= lowerByte;

cipherBytes[i * 2] = 0x4e;
cipherBytes[i * 2 + 1] = Convert.ToByte(upperByte2);
cipherBytes[(i + 1) * 2] = 0x4f;
cipherBytes[(i + 1) * 2 + 1] = Convert.ToByte(lowerByte2);
}
return UnicodeEncoding.BigEndianUnicode.GetString(cipherBytes, 0, cipherBytes.Length);
}

/// <summary>
/// 对字符串进行解密
/// </summary>
/// <param name="proclaimText"></param>
/// <returns></returns>
public static string DoProclaimText(string CipherText)
{
if (CipherText.IsEmpty()) return CipherText;

byte[] cipherBytes = UnicodeEncoding.BigEndianUnicode.GetBytes(CipherText);
int cipherBytesCount = cipherBytes.Length;

byte[] proclaimBytes = new byte[cipherBytesCount / 2];

for (int i = 0; i < cipherBytesCount; i += 4)
{
byte cipherByte1 = cipherBytes[i + 1];
byte cipherByte2 = cipherBytes[i + 3];

int lowerByte = (cipherByte1 & 0x0f) << 4;
int upperByte = cipherByte1 & 0xf0;

int lowerByte2 = cipherByte2 & 0x0f;
int upperByte2 = (cipherByte2 & 0xf0) >> 4;

proclaimBytes[i / 2] = Convert.ToByte(lowerByte | upperByte2);
proclaimBytes[i / 2 + 1] = Convert.ToByte(upperByte | lowerByte2);
}
return UnicodeEncoding.BigEndianUnicode.GetString(proclaimBytes, 0, proclaimBytes.Length);
}