These rules are slightly different from what they have been in previous years, so please read them carefully. Marks may be deducted if you don't fully follow the rules.
You may submit solutions (as a plain text file, please) to at most three ciphers (except your own cipher, of course). However, only the BEST TWO will be counted.
Solutions should be uploaded at the link provided on the QMplus page. As before, no Microsoft Word, Richtext, PDF, etc., plain text only. (On Microsoft Windows the Notepad application produces the nearest approximation to plain text.)
Please upload solutions to different ciphers as different files. The files should be named like noohi012345678-xy, where 012345678 is your student number, xy is the number of the ciphertext you are breaking, and "noohi" is replaced by your surname. At the start of each file state your FULL NAME and your STUDENT NUMBER and also state the number of the cipher you are trying to crack.
You are allowed to work in groups. If you do so, you should indicate the name of the people you have collaborated with at the top of your submission file. You will not loose marks for collaboration (but you will if you do not mention it in your submission).
In order to be counted, your solution must contain a FULL EXPLANATION of the method of cryptanalysis. This means a step-by-step guide to each deduction (or guess) you make, and why. This would particularly apply if say nulls have been used, or the letter frequencies are slightly strange.
If you use a computer program, it must be one you’ve written yourself, and the program must be submitted along with your solution. You must also fully document the program to say what each bit is doing.
Please play fair and do not help anyone else to break your own cipher. I expect to be able to spot most cases of collusion.
This part of the cipher challenge counts 5% of your overall mark for the module. You will receive an overall mark out of 100 for this part of the cipher challenge, but you are entitled to get bonus marks, so you may get up to 200.
Each cipher you break will be worth 70 points. But the following rules apply: 1) If you are the only person to break a cipher, you will get an additional 30 points for it; 2) If a cipher is broken by more than three people, it will be worth only 30 points breaking it.
WARNING. It is often easy to catch cheaters; it is only a matter of I having the time to analyse your entries carefully enough. Keep this in mind: if you have not understood the material well enough to break the ciphers on your own, you are likely to leave clues when you copy solutions from somewhere else. If I spot that you have cheated, it counts as an offence and it will be reported. You will get 0 for Part 2 AND Part 1.
Select a cipher from those below. For various reasons it is possible that a “harder” cipher is easier to crack than an “easier” one, so don’t give up on the “harder” ones. As it is hard to decide which ciphers are easier/harder to break than others, I may occasionally change my mind and move some of the ciphers across the "easy", "intermediate" or “hard” sections.
Note. If your cipher does not appear here it is because either: 1) you have violated a Cipher Challenge rule making your cipher wrong or impossibly difficult beyond what was allowed by the rules; or 2) your description of the cipher has been insufficient, making it impossible for me to verify its correctness. The reason for not publishing your cipher is only to be fair to students who will be trying to break your cipher. You will nevertheless get credit for the work you have done (and marks deducted for your errors).
Cipher E11, Cipher E12, Cipher E9, Cipher E2, Cipher E10, Cipher E5, Cipher E7, Cipher E8, Cipher E1, Cipher E13, Cipher E4, Cipher E6, Cipher E14
Note: Some of the ciphers in this part may not be not-so-hard, and may actually be easier than those I have put in the “Easier” section.
Cipher I1, Cipher I2, Cipher I3, Cipher I4, Cipher I5, Cipher I6, Cipher I7, Cipher I8, Cipher I9 href="javascript:document.getElementById('chosencipher').contentWindow.location.replace('intermediate/I10.txt')">Cipher I10
Note: Some of the ciphers in this part may not be not-so-hard, and may actually be easier than those I have put in the “Easier” section.
Cipher H1, Cipher H2, Cipher H3, Cipher H4, Cipher H5, Cipher H6, Cipher H7, Cipher H8, Cipher H9, Cipher H10, Cipher H11, Cipher H12, Cipher H13
This page is maintained by Behrang Noohi.
Last updated: 20 Dec 2017.