Actually, yes. The path you take to stir the fluid would be your key which would be verified by getting back to the initial dye state. The key size would be i

Actually, yes. The path you take to stir the fluid would be your key which would be verified by getting back to the initial dye state. The key size would be ideally infinite dimensional (the dimension of the path space), but practically bandwidth limited by your ability resolve the dye pattern.