We are working on a project in which we will need to encode and encrypt 1 - 1.3 kb worth of data at a time. We need the result of each piece of data to be the same size it was before, or be smaller, or be only slightly bigger. Basically as small as it can be while still being secure and still being able to get the original data back by decrypting and decoding.
If you were doing something like this how would you best approach it? Is there an encryption algorithm that only adds minimal (if any) size compared to the size of the unencrypted data?