assume for example a crypto system aim to generate a cipher message with exactly the same size of its plain text and also be stateless to be able to decrypt out of order received packets. Of course this crypto system expose some information about the message attributes however if we sacrifice this level of security but not more, is any crypto system that address such issue?
Yes, that's not only possible, but you can try it yourself. Stream ciphers tend to work this way. You XOR each plaintext character with a corresponding key from a keystream, and you end up with the same number of characters as you had in the plaintext message. At the receiving end, the recipient needs to XOR that ciphertext with the same keystream, and the original plaintext comes out.
Try it yourself. Use a PRNG to generate the keystream. If the guy at the other end uses the same PRNG, and the same seed you used to create the keystream in the encryption step, he'll restore the original.
Such methods have been used since antiquity:
https://en.wikipedia.org/wiki/Caesar_cipher
You can create an encryption system that meets any conditions, but the security of messages is usually the priority.
@albert, yes this is possible however stream ciphers are statefull and if you look for a stateless block cipher then stream ciphering is not possible.
- Badges
- Science topic