public static byte[] DeriveFromKey(byte[] masterKey, int subKeyLength, ulong subKeyId, byte[] context)
{
var key = new byte[32];
key.Initialize();
Array.Copy(masterKey, 0, key, 0, masterKey.Length > 32 ? 32 : masterKey.Length);
var ctx = new byte[8];
ctx.Initialize();
Array.Copy(context, 0, ctx, 0, context.Length > 8 ? 8 : context.Length);
var subkey = new byte[subKeyLength];
var bin = Marshal.AllocHGlobal(subkey.Length);
var ret = SodiumLibrary.crypto_kdf_derive_from_key(bin, new UIntPtr((uint)subKeyLength), subKeyId, ctx, key);
if (ret != 0)
{
throw new InvalidOperationException($"Error derive sub key from master key. ({ret})");
}
Marshal.Copy(bin, subkey, 0, subKeyLength);
Marshal.FreeHGlobal(bin);
return(subkey);
}