Could you not also just throw in 1-2kb of random data with your short data? Your app can then just disregard all text after a null bye or something similar. I'

Could you not also just throw in 1-2kb of random data with your short data? Your app can then just disregard all text after a null bye or something similar. I'm not a cryptographer but that sounds like a good strategy when encrypting very short strings to resist cryptanalysis.