The official Challenge 10 tips and hints thread

[madness]

@Jake, look online for Lanaki’s course. It was written in the 1990s, before computering was inveted. The four-square cipher is in lesson 17.

Now’s as good a time as any to learn to program.

[PeterTompkin]

10 B… Solved… another fine mess I was in for a while there…

[Crackerjack]

Interestingly, what I found out recently is that white spaces do affect the IOC calculation. So if you do the IOC calculation of the 10A ciphertext WITH spaces, then the result will be closer to that of English (around 0.056). If you do it WITHOUT spaces, then the value will 0.041. Hope this helps!

[yiannis]

Not sure

[Cricket11]

For 10b, I know we do not get any feedback, but do they tell us if it is correct?

[Luke_Garner]

I absolutely love the resolving feeling of everything just falling into place. The challenge of this chapter especially. When all seems lost through the agitation of trying over and over again, my advice would be to just step back a second, look at the bigger picture. Think of when you first started this challenge, and maybe take a few steps back in time from there if necessary.

[Flappyasdf_2023]

Sorry to bother you, but on that front if I haven’t received that communication does that mean that I have no chance of winning overall?

[I am afraid we don’t comment on that at this stage. We asked everyone who completed Challenge 10B in the first couple of days to send us their method by displaying a congrats message on submission. If we don’t hear from them we will send messages on the BOSS messaging system, but hopefully that won’t be needed. If you think you might have missed the request, then keep an eye on messages to see if we get in touch. All the best, Harry]

[Watermelons]

Shouldn’t it be:
14a+3b = 17

14c+3d=*20*

8a+4b =12

8c+4d=16

Sorry if it’s my mistake, I just can’t see why it’s 3 not 20

[Because I am an idiot. Madness also pointed this out and the hint has been corrected! Sorry, Harry]

[madness]

The second equation should be = 20

[kford_academy]

Question regarding the Bletchley awards:
Suppose two teams, A and B, both solve 10B in the same amount of time. Team A uses a hill-climbing algorithm whilst Team B uses an Excel file. All other things being equal, would Team B have a better chance of getting through to Bletchley than Team A, or can you not say (yet)?

[It’s impossible to say I am afraid! We take things “in the round”. Sorry I can’t be more helpful. Harry]

[Nikhilesh]

Hi Harry similarly to Flappyasdf_2023 we had submited Chapter 10B in the “first couple of days” yet our congrats message doesnt contain anything about submitting methods thanks

 

[If you didn’t hear from us yet via the messaging system then you are not likely to be asked to send us an account, and you can put your feet up and relax in the knowledge that your work is done! You might still get an invite to the prize giving, but we can’t say anything with any certainty about that yet, as we need to know how many tickets we are offering to medallists. We hope that even without a prize everyone who took part got something from the competition, and that you really will be able to enjoy having cracked the cipher. With our very best wishes, Harry and Jodie]

[Jake]

> @Jake, look online for Lanaki’s course. It was written in the 1990s, before computering was inveted. The four-square cipher is in lesson 17.

Thank you very much!

> Now’s as good a time as any to learn to program.

I disagree. :p. The summer, maybe.

[Harry]

The final hint for Challenge 10A

 

To start deciphering the message you convert the text to numbers with A->0, B-1 and so on

So the start reads

HHIZR KHHXH

which encodes as

7, 7, 8, 25, 17, 10, 7, 7, 23, 7

Now we group these into vectors

(7,7)

(8,25)

(17,10)

(7,7)

(23,7)

We then multiply these vectors by the 2×2 matrix we found last time, given by the string 2,-1,-1,1)

(7,7)-> (2*7-1*7, -1*7+1*7) = (14-7, -7+7) -> (H,A)

Any guesses what comes next?(8,25) -> (2*8-1*25, -1*8+1*25) = (16-25, -8+25) = (-9, 17) = (17,17) -> (R,R)

We leave it to you to complete the decryption!

Hope you enjoyed it!

Harry and Jodie

[Harry]

The fifth official hint for Challenge 10B

 

[Jasmina]

Is 10B a Polybius cipher?

Also,Hello!

[Author]

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