/// <summary>Creates a detached Box</summary>
/// <param name="message">The message.</param>
/// <param name="nonce">The 24 byte nonce.</param>
/// <param name="secretKey">The secret key to sign message with.</param>
/// <param name="publicKey">The recipient's public key.</param>
/// <returns>A detached object with a cipher and a mac.</returns>
/// <exception cref="KeyOutOfRangeException"></exception>
/// <exception cref="NonceOutOfRangeException"></exception>
/// <exception cref="CryptographicException"></exception>
public static DetachedBox CreateDetached(byte[] message, byte[] nonce, byte[] secretKey, byte[] publicKey)
{
//validate the length of the secret key
if (secretKey == null || secretKey.Length != SecretKeyBytes)
{
throw new KeyOutOfRangeException("secretKey", (secretKey == null) ? 0 : secretKey.Length,
string.Format("key must be {0} bytes in length.", SecretKeyBytes));
}
//validate the length of the public key
if (publicKey == null || publicKey.Length != PublicKeyBytes)
{
throw new KeyOutOfRangeException("publicKey", (publicKey == null) ? 0 : secretKey.Length,
string.Format("key must be {0} bytes in length.", PublicKeyBytes));
}
//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));
}
var cipher = new byte[message.Length];
var mac = new byte[MAC_BYTES];
var ret = SodiumLibrary.crypto_box_detached(cipher, mac, message, message.Length, nonce, secretKey, publicKey);
if (ret != 0)
{
throw new CryptographicException("Failed to create public detached Box");
}
return(new DetachedBox(cipher, mac));
}
