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October 11, 2005

HINT 2 FOR CHALLENGE 2B

Frequency analysis gives a good way to attack Challenge 2B but as many of you have discovered, used on its own it does leave a certain ambiguity in that some letters appear so rarely (maybe only once) that it is hard to determine what they stand for among the possible rarely used plaintext characters.

The best way to disambiguate the text is to figure out what sort of cipher the Soviets are using for the message. It isn't just random. You know from your succesful efforts to crack it that it must be some kind of simple monoalphabetic substitution, but it isn't a Caesear shift, so what could it be? I won't tell you which, but it is likely to be either a keyword cipher or perhaps an affine shift as these are the two simplest examples. Look them up! Good luck,

Posted by Harry at October 11, 2005 03:07 PM

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Thank you for the faster feedback! I don't think it's a coincidence the challenges are so well structured with many different pathways and footholds (sorry for the mixed metaphors). So thank you Harry for making such interesting challenges. Can't wait till next week!

Posted by: cecil at October 14, 2005 07:22 AM

Please Harry could you tell us what the timing interval for score decreases is going to be for challenge 3.

Posted by: tom at October 12, 2005 06:42 PM

Shez, if you have a careful look at the letters in the alphabet used for the code, their positions aren't as random as they might first appear... have another look and you might be able to get it!

Posted by: Jess at October 11, 2005 08:40 PM

the thing is there are 3 letters not being used in the alphabet, so how do you actually work the last letter out?

Posted by: shez at October 11, 2005 08:11 PM