/// <summary>
/// Read the protected data and return it protected with a sequence
/// of bytes generated by a random stream. The object's data will be
/// invisible in process memory only if the object has been initialized
/// using a <c>XorredBuffer</c>. If no <c>XorredBuffer</c> has been used
/// or the binary has been read once already (in plain-text), the
/// operation won't be secure and the protected string will be visible
/// in process memory.
/// </summary>
/// <param name="crsRandomSource">Random number source.</param>
/// <returns>Protected data.</returns>
/// <exception cref="System.ArgumentNullException">Thrown if the input
/// parameter is <c>null</c>.</exception>
public byte[] ReadXorredData(CryptoRandomStream crsRandomSource)
{
Debug.Assert(crsRandomSource != null);
if (crsRandomSource == null)
{
throw new ArgumentNullException("crsRandomSource");
}
if (m_xbEncrypted != null)
{
uint uLen = m_xbEncrypted.Length;
byte[] randomPad = crsRandomSource.GetRandomBytes(uLen);
return(m_xbEncrypted.ChangeKey(randomPad));
}
else
{
byte[] pbData = ReadData();
uint uLen = (uint)pbData.Length;
byte[] randomPad = crsRandomSource.GetRandomBytes(uLen);
Debug.Assert(randomPad.Length == uLen);
for (uint i = 0; i < uLen; i++)
{
pbData[i] ^= randomPad[i];
}
return(pbData);
}
}
public void ChangeKey()
{
// arrange
var data = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
var firstPad = new byte[] { 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 };
var protectedData = new byte[data.Length];
for (var i = 0; i < data.Length; i++)
{
protectedData[i] = (byte) (data[i] ^ firstPad[i]);
}
var xb = new XorredBuffer(protectedData, firstPad);
var secondPad = new byte[] { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27 };
// act
var actual = xb.ChangeKey(secondPad);
// assert
Assert.AreEqual(data.Length, actual.Length);
Assert.AreSame(protectedData, actual);
for (var i = 0; i < data.Length; i++ )
{
Assert.AreEqual(0x20, actual[i]);
}
}