/// <summary>
/// Adds padding to the input data and returns the padded data.
/// </summary>
/// <param name="dataBytes">Data to be padded prior to encryption</param>
/// <param name="params">RSA Parameters used for padding computation</param>
/// <returns>Padded message</returns>
public byte[] EncodeMessage(byte[] dataBytes, RSAParameters @params)
{
//Determine if we can add padding.
if (dataBytes.Length > GetMaxMessageLength(@params))
{
throw new CryptographicException("Data length is too long. Increase your key size or consider encrypting less data.");
}
int padLength = @params.N.Length - dataBytes.Length - 3;
BigInteger biRnd = new BigInteger();
biRnd.genRandomBits(padLength * 8, new Random(DateTime.Now.Millisecond));
byte[] bytRandom = null;
bytRandom = biRnd.getBytes();
int z1 = bytRandom.Length;
//Make sure the bytes are all > 0.
for (int i = 0; i <= bytRandom.Length - 1; i++)
{
if (bytRandom[i] == 0x00)
{
bytRandom[i] = 0x01;
}
}
byte[] result = new byte[@params.N.Length];
//Add the starting 0x00 byte
result[0] = 0x00;
//Add the version code 0x02 byte
result[1] = 0x02;
for (int i = 0; i <= bytRandom.Length - 1; i++)
{
z1 = i + 2;
result[z1] = bytRandom[i];
}
//Add the trailing 0 byte after the padding.
result[bytRandom.Length + 2] = 0x00;
//This starting index for the unpadded data.
int idx = bytRandom.Length + 3;
//Copy the unpadded data to the padded byte array.
dataBytes.CopyTo(result, idx);
return result;
}
