/// <summary>
/// MGF1 is a mask generation function, based on a
/// hash function. MGF1 coincides with the mask generation functions
/// defined in IEEE Std 1363-2000 and the draft ANSI X9.44.
/// </summary>
/// <param name="mgfSeed">Seed from which mask is generated, an octet string</param>
/// <param name="maskLen">Intended length in octets of the mask, at most 2^32 hLen</param>
/// <param name="hash">
/// Hash function (hLen denotes the length in octets of the hash
/// function output)
/// </param>
/// <returns>An octet string of length maskLen</returns>
/// <exception cref="MaskTooLongException">
/// Thrown when maskLen > 2^32*hLen
/// </exception>
public byte[] MGF1(byte[] mgfSeed, int maskLen, HashAlgorithm hash)
{
int hLen = hash.HashSize / 8;
if (maskLen > BigInteger.Pow(2, 32) * hLen)
{
throw new MaskTooLongException("Mask too long");
}
byte[] T = new byte[0];
for (BigInteger counter = 0; counter < (maskLen - 1) / hLen + 1; counter++)
{
byte[] C = dataPrimitives.I2OSP(counter, 4);
byte[] H = hash.ComputeHash(ByteArraysUtils.Concat(mgfSeed, C));
T = ByteArraysUtils.Concat(T, H);
}
return(ByteArraysUtils.GetSubArray(T, 0, maskLen));
}
public byte[] Encrypt(byte[] data, string passphrase)
{
// Check arguments.
if (data == null || data.Length <= 0)
{
throw new ArgumentNullException("plainText");
}
if (passphrase == null || passphrase.Length <= 0)
{
throw new ArgumentNullException("Key");
}
byte[] encrypted;
byte[] IV;
string plainText = Encoding.UTF8.GetString(data);
// Create an Aes object
// with the specified key and IV.
using (Aes aesAlg = Aes.Create())
{
aesAlg.Key = CreateKey(passphrase);
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
IV = aesAlg.IV;
// Create the streams used for encryption.
using (MemoryStream msEncrypt = new MemoryStream())
{
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
{
//Write all data to the stream.
swEncrypt.Write(plainText);
}
encrypted = msEncrypt.ToArray();
}
}
}
// Write IV to the encrypted data header
byte[] result = ByteArraysUtils.Concat(IV, encrypted);
// Return the encrypted bytes from the memory stream.
return(result);
}
