Timeline for In perfectly secret scheme, if key and message space are uniformly distributed, is ciphertext space always uniform as well?
Current License: CC BY-SA 4.0
5 events
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| Oct 16, 2018 at 6:30 | comment | added | Shan Chen | @kodlu Well, I don't want to be very insistent on this. But if the ciphertext space can be anything, then you can get a very trivial counterexample by adding a weird string to the ciphertext space as long as that string (or whatever) can never be generated by a perfect secret encryption scheme. | |
| Oct 16, 2018 at 4:31 | comment | added | kodlu | The answer is correct as the question stands. The question asked if any encryption scheme with certain properties on key and message distribution yielded uniform ciphertexts and the answer demontrated a counterexample. | |
| Oct 15, 2018 at 17:23 | comment | added | SEJPM | @ShanChen In general it is not required for encryption schemes to be surjective. Also if you feel better then, you can imagine my counter-example with a random 1% chance of appending a 1 bit instead of a 0 bit. | |
| Oct 15, 2018 at 17:17 | comment | added | Shan Chen | This is not a valid counter example. You cannot assume the ciphertext space consists of all 2-bit strings. Those ciphertexts that never happen should not be counted. | |
| Oct 15, 2018 at 11:46 | history | answered | SEJPM | CC BY-SA 4.0 |