/// <summary>Creates a Secret Box</summary>
/// <param name="message">The message.</param>
/// <param name="nonce">The 24 byte nonce.</param>
/// <param name="key">The 32 byte key.</param>
/// <returns>The encrypted message.</returns>
/// <exception cref="KeyOutOfRangeException"></exception>
/// <exception cref="NonceOutOfRangeException"></exception>
/// <exception cref="CryptographicException"></exception>
public static byte[] Create(byte[] message, byte[] nonce, byte[] key)
{
//validate the length of the key
if (key == null || key.Length != KEY_BYTES)
{
throw new KeyOutOfRangeException("key", (key == null) ? 0 : key.Length,
string.Format("key must be {0} bytes in length.", KEY_BYTES));
}
//validate the length of the nonce
if (nonce == null || nonce.Length != NONCE_BYTES)
{
throw new NonceOutOfRangeException("nonce", (nonce == null) ? 0 : nonce.Length,
string.Format("nonce must be {0} bytes in length.", NONCE_BYTES));
}
//pad the message, to start with ZERO_BYTES null bytes
var paddedMessage = new byte[message.Length + ZERO_BYTES];
Array.Copy(message, 0, paddedMessage, ZERO_BYTES, message.Length);
var buffer = new byte[paddedMessage.Length];
var ret = SodiumLibrary.crypto_secretbox(buffer, paddedMessage, paddedMessage.Length, nonce, key);
if (ret != 0)
{
throw new CryptographicException("Failed to create SecretBox");
}
return(buffer);
}