Linear block-ciphers Mystery Cache
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This cache is a sequel to Blok-ciffre for begyndere
Some time ago I thought about simple block ciphers. I wanted to find a way to attack the general problem, but then it dawned on me how many ciphers there are. If the block has length n (ie n bits encoded to n other bits), then there are 2n different bit strings to be encoded. If you imagine two tables with all possibilities, you can describe all the possible encodings as connecting one table with the other one line at a time. This can be done in 2n! ways.
A 1-bit block has 2 possible code functions.
A 2-bit block has 24 possible code functions.
A block of 3 bit has 40320, 4 bit gives 16 20922789888000 code features and already 5 bit gives 263130836933693530167218012160000000 possible code functions.
Oops! We need to narrow that down a bit. Let us say that the coding function must be linear: The value of a coded bit can depend on the value of any of the uncoded bit, their negation, and sums (mod 2) of these.
For example for a block size of 3 bits. The first encrypted bit is the sum of the first and second bit and negation of the third. The second encrypted bit is the second bit and the third encrypted bit is the negation of the third bit. All modulo 2.
So for instance 000 → 101, 001 → 000, 111 → 010
Can you crack a general linear block code of size 18? Everything else works as in the previous puzzle.
Delightful_unreserved_impossible_few_estimating_men_favourable_see_entreaties._She__
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The cache can be found at:
The geochecker page has a quotation. Copy-paste is into a write note to claim first-to-solve.
I was intrigued by Hügh solving Muchu's sommerferie 2 with a neural network. What an unusual choice of tool. I tried solving this one the same way, with no luck. I think the search landscape is too flat with too many local minima for a neural network to work, but I am very interested if anyone has success. My best network had 80% correct bits.
The photo has nothing to do with the code, other than it was inspired by Muchu’s code.
Additional Hints
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