Note: I have added one penalty for restricted OFB modes, i.e., only messages of fixed or limited size were accepted! This is actually an incorrect implementation of OFB as modes of operations should work for arbitrary length message, but I have decided to only penalise those programs and not to consider them as incorrect!
The following is a guideline to how I intend to mark programming exercise 1. However, I reserve the right to changes in particular if some unforeseen problems occur.Submission penalties:
| -20 | No paper submission |
| -20 | No sources (or late submitted sources) |
| -10 | Sources where submitted late but in time on paper |
Output penalties:
| -20 | No intermediate output |
| -10 | No explicit output of round keys or no output after major steps (i.e., matrix multiplication, end of round of the Feistel Cipher, etc.) |
| 0 | Full points for intermediate output after every major step + all round keys or more details (see also section on Aesthetics below) |
Input penalties:
| -10 | If there is no interface (command line, text, or GUI), i.e., I have to input M + K + IV in the source and recompile! |
| -5 | If I have to do some other form of tinkering with the code. |
| 0 | Full points if there is a text interface or GUI to input M + K + IV, or (my preferred option) M + K + IV can be given as command line parameters. |
Correctness:
In addition to the 10 problems requested in the
exercise specification, I will test each implementation with up to 8 special
message-key-IV triples plus 5 message-key-IV triples randomly chosen from a set
of 50 randomly created ones. The plaintext messages are not all of the same length!
| -10 | If OFB mode is not capable of enciphering messages between 64 and 192 bit |
| max 40 | Some ciphertexts are incorrect. |
| max 30 | The majority of ciphertexts are incorrect. |
| max 25 | All but first ciphertext are incorrect. |
Unfinished Implementations:
I will award a maximum of 15 points
for unfinished implementations, depending on the submitted code.
Aesthetics:
I reserve 5 points (in-between 75 and 80 only) for
aesthetics. That is, every submission that does incur no penalties will
automatically be awarded 75 marks; additional marks up to 80 are awarded
depending on the legibility of the intermediate output. This can be seen as a
tiny reward for putting additional effort into producing nicely formatted
output.